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#### Table of Contents
[Required Parts](#Required-Parts)
[Required Tools](#Required-Tools)
[Build Instrcutions](#Required-Parts)
# Required Parts
The DIY Particle Detector comes in two variants.
The circuit board is the same for both, but the diodes and few resistor/capacitor values differ (D1-4,R3-5,R8,C4,C6,C9).
* **electron-detector** - easier to build and operate for beginners, more sensitive to radioactivity than the alpha-spectrometer
* using 4 very low-cost BPW34F diodes as sensor and 21 other parts
* [get parts & circuit board easier via kitspace.org](https://kitspace.org/boards/github.com/ozel/diy_particle_detector/diy%20electron%20detector/) or buy a [**complete kit**](https://shop.kitspace.org/buy/electron-detector/)
* [**parts overview & assembly guide PDF**](https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/hardware/V1.2/documentation/DIY%20detector%20-%20parts%20overview%20v1-2%20electron%20version.pdf),
[German version](https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/hardware/V1.2/documentation/DIY%20detector%20-%20parts%20overview%20v1-2%20electron%20version%20DE.pdf)
<!-- * [*interactive* assembly guide on kitspace.org](https://kitspace.org/interactive_bom/?github.com/ozel/DIY_particle_detector/electron-detector) -->
* **alpha-spectrometer** - measures the characteristic energy of alpha particles (as well as detecting electrons)
* using 1 rather expensive BPX61 diode as sensor and 23 other parts
* [get parts & circuit board easier via kitspace.org](https://kitspace.org/boards/github.com/ozel/diy_particle_detector/diy%20alpha%20spectrometer/)
* [**parts overview & assembly guide PDF**](https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/hardware/V1.2/documentation/DIY%20detector%20-%20parts%20overview%20v1-2%20alphaspectrometer%20version.pdf)
<!-- * [*interactive* assembly guide on kitspace.org](https://kitspace.org/interactive_bom/?github.com/ozel/DIY_particle_detector/alpha-spectrometer) -->
* chose a suitable [[metal enclosure|Enclosures]]
*minimum size* housing the circuit board, batterie, switch and connector:
* 8 x 4.5 x 3 cm³ (9V battery upright)
or
* 8 x 5.5 x 2 cm³ (9V battery flat)
* few centimeters of flexible electrical wire to connect the signal output connector and on/off switch
* the right [[cable|Cables]], connecting the signal output with an oscilloscope or computer/smartphone/tablet
* a [[9 V battery|Batteries]]
* depending on the enclosure, addititional screws for fixing the detector inside the enclosure
* M3 [distance bolts](https://www.google.com/search?q=m3+distance+screw) or ['PCB standoff'/hex spacers](https://uk.rs-online.com/web/p/standoffs/1613631/) and a pair of corresponding M3 nuts and screws is recommended (made from metal instead of plastic)
Both variants of the detector require the same circuit board, but with different sets of electronic parts, the [schematic drawing](https://github.com/ozel/DIY_particle_detector/blob/master/hardware/V1.2/documentation/DIY%20particle%20detector%20schematic%20v1-2.pdf) features both sets of parts in an overview.
### Tips for ordering parts
Please use the two kitspace links above to find the right order codes for each variant from several different electronic part suppliers.
There are no additional costs if you use its '1-click BOM' functionality, it merely copies the right amount of parts and their order codes into the respective shopping carts of supported suppliers. www.kitspace.org is community-run and intends to simplify the uptake and distribution of open hardware projects.
Unfortunately, not every electronic part supplier ships to private individuals in all countries. Mouser and Digikey are currently the more universal ones from the suppliers supported on kitspace. Both offer free shipping if a minimum threshold of ~50 USD/EUR is reached.
If you want to order as a private person, please check first which of the listed supplier supports this in your country. Then create your own account at the supplier's website, log in with your account and finally use one of the two kitspace project links (see above) to populate your shopping cart with the correct order codes for all required parts. Please open a new question in [Discussions](https://github.com/ozel/DIY_particle_detector/discussions) if you have problems with certain parts.
# Required Tools
* solder iron
* solder wire
* sharp pliers (preferably of the "side cutting" or "electronic" type)
* small screwdriver
* for creating holes in the metal case:
* either hole punchers and a hammer: 2, 5 & 9 mm diameter, for [[candy tin boxes|Enclosures#candy-tin-boxes]]
(punching tools require smaller diameters than the final hole size)
* or a drilling machine: 3, 6 & 10 mm drill size, for [[thick-walled metal enclosures|Enclosures#diecast-aluminum-enclosures]]
* either a hardware oscilloscope or a [software oscilloscope/python scripts](https://github.com/ozel/DIY_particle_detector#software) and a [[soundcard/headset input|Soundcards]] together with a computer/smartphone/tablet
Optional tools, but handy:
* tweezers
* a simple multimeter for measuring resistance (useful for finding problems and distinguishing the resistor values)
# Build Instructions
Before you start soldering, make up your mind about how and where you want to mount the detector inside the [[metal case|Enclosures]] (please consider all the remarks on that page!).
If the enclosure is quite small, you may want to put the large capacitor C8 and/or the diodes D1-D4 on the opposite side as they are marked on the circuit board. For example, the detector is more sensitive if the diodes are very closely placed in front of a [[radiation window|Enclosures#creating-a-radiation-window]]. C8 could be rather mounted on the opposite side of the board in such cases.
If the enclosure is rather large and radioactive objects will fit inside easily, the default position of all components on the board can be kept as marked.
_Always use one of the two parts overview PDFs linked at the very top as an assembly guide._
Solder the components as they are listed on those sheets, top-bottom, left column followed by the right column.
General note: The small capacitors and resistors can be mounted either way.
Only C8, the diodes D1-D4 and U1 must be mounted exactly in the correct orientation since these are components with a specific polarity.
1. solder the resistors in the correct places as marked on the board, carefully checking for their color bands
2. cut all residual and protruding resistor leads off as close a possible to the board
3. solder the small (yellow) capacitors in the correct places as marked on the board
- C5 should be mounted as flat as possible if the selected [[enclosure is very small|Enclosures#diecast-aluminum-tin-boxes]] and if the battery will be directly on top of it
4. cut the residual and protruding capacitor leads off as close a possible to the board
- the leads of C5 must be cut as short as possible such that U1 can fit closely on top of them
5. solder the large capacitor C8 on that side of the board that fits better to the available space in your enclosure
- if unsure about the best position, keep 2-3 mm of free space between C8 and the board - this extra lead length provides an option to later bend C8 horizontally/flat if necessary
6. solder the diodes, 4 x BPW34F or 1 x ***[[modified BPX61|Diodes#preparation-of-the-bpx61-diode-for-alpha-spectroscopy]]***, respecting their polarity (anode vs. cathode)
- _the cathode pins must point to the board center, marked with the letter 'K'_ (see images below)
- Electron-detector: the BPW34F's _cathode_pin_ is marked with a notch
- Alpha-Spectrometer: the BPX61's _anode_pin_ marked with a notch, which must point away from the board
7. solder the black amplifier chip U1, respecting its polarity: pin 1 is marked with a circle on the board & chip
- double-check that the pins from C5 are cut short enough and do not touch each other
8. check all solder points on the board for possible short circuits, cut them short/flat if required
- optionally measure the resistance on the +/- 9 V battery connector holes, it must be much higher than zero: 9 to 10 kilo Ohms
9. make sure the chosen [[enclosure|Enclosures]] has all the required holes in the correct size for (c.f. [[Required Tools|Assembly-Instructions#required-tools]])
- signal output connector (BNC or audio), check if it fits in place and mount it
- on/off switch, check if it fits in place and mount it
- optionally, create a [[radiation window|Enclosures#creating-a-radiation-window]] in front of the diodes
10. solder the black ground wire of the 9 V battery clip into the hole labelled '-', next to '+9V' and C8
11. solder the red wire of the 9 V battery clip to the middle pin of the on/off switch
12. strip the insulation from 3 short pieces of electrical wire at the ends
13. solder one short piece of electrical wire between the on/off switch and the hole labelled '+9V' on the board
14. solder a pair of short pieces of electrical wire between the board and the signal output BNC connector
- solder two wires into the holes marked with 'signal' and '-' on the board
- solder the other end of the 'signal' wire to the BNC connector's inner pin
- solder the other end of the '-' wire to the outer part of the BNC connector, usually surrounded by an extra connection ring
Alternatively, the '-' wire can be soldered directly on tin box walls next to the connector (does not work with aluminum cases).
- if an [[audio connector|Cables#connection-with-a-headset-socket]] is used instead of the BNC connector, tip/sleeve should be connected respectively
15. check all wire connections for possible short circuits, correct them if required
- optionally measure the resistance on the +/- 9 V battery clip connector, it must change when switching on/off
16. fix the circuit board in place with screws, either via the _two_ metalized board edges or via _one to two_ of the 3 metalized holes
17. connect a full [[9 V battery|Batteries]], place it inside the metal enclosure
18. close the lid of the enclosure
- light must not reach inside, even the tiniest holes and slits must be covered with sticky tape from the inside
Top sides of the **electron-detector** variant on the left, the **alpha-spectrometer** varaint on the right:
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.2/documentation/3D_top_electron.png" width="350"><img src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.2/documentation/3D_top_alpha.png" width="350">
The central label 'K' between the diodes D1-D4 marks the position of the cathode pins.
('K' was derived from the Greek word 'kathodos' - it also looks like the electronic diode symbol)
Bottom sides of the **electron-detector** variant on the left, the **alpha-spectrometer** varaint on the right:
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.2/documentation/3D_bottom_electron.png" width="350"><img src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.2/documentation/3D_bottom_alpha.png" width="350">
# Troubleshooting
Moved to [[Troubleshooting]].

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The detectors work with both, single-use 9 V batteries and rechargeable 9 V accumulators. Designated as [_PP3_ or _E-Block_](https://en.wikipedia.org/wiki/Nine-volt_battery).
The power consumption is very low, only a few milliamperes, see notes on [[runtime|Batteries#runtime-on-batteries]] below.
*Rechargeable 9V NIMH accumulators and chargers are quite cheap these days, it is recommended to use them - they'll pay for themselves quickly in comparison to the price of single-use batteries.*
### Recommended rechargeable 9 V NIMH accumulators
- [GP17R9H => 9.6 V version](https://ind.gpbatteries.com/pub/media/uploads/pdf/rechargeable_NiMH/by_series/standard_series_cylindrical/GP17R9H.pdf) (recommended for the alpha-spectrometer, resulting in a slightly larger bias voltage)
- [GP17R8H => 8.4 V version](https://www.gpbmindustry.com/product-page/gp17r8h)
Those accumulators are rather thin (about 15.5 mm) in comparison to single-use 9 V batteries (around 17 mm thick).
These thin accumulators have a particular advantage when using small [[diecast aluminum enclusres|Enclosures#diecast-aluminum-enclosures]] where the available space is very tight.
**Reichelt.de** is at the moment one of the best-price suppliers for the [9.6 V NIMH accumulator](https://www.reichelt.de/gp-nimh-industry-cell-9-v-block-9-6-v-170-mah-gp-17-r9h-p199776.html) shipping worldwide. They also sell a [cheap charger](https://www.reichelt.de/ch/en/akku-charger-for-aa-aaa-9v-ni-mh-ni-cd-logilink-pa0168-p225265.html?&trstct=pol_2&nbc=1) and a [faster double-charger](https://www.reichelt.de/ch/en/microcontroller-regulated-plug-in-charger-powerline-2-p30664.html?&nbc=1&trstct=lsbght_sldr::225265).
### Runtime on batteries
Both detector variants, the alpha-spectrometer and the electron-detector, consume about 4.4 mA of current (measured at 11.5 V = a freshly charged 9.6V NIMH accumulator).
With the accumulators recommended above providing a nominal value of 170 mA*hour capacity, the minimum practically observed runtime is between 30 hours with old & used accumulators and somewhat above 40 hours for brand new accumulators.
Single-use batteries can provide longer run-times, up to 100 hours, largely depending on their discharge characteristic and nominal capacity.
### Note on using power supplies instead of batteries
The two detector circuits are both extremely sensitive to noise and wire-bound coupling of electromagnetic interference radiation introduced by a regular, mains-connected power supply. It is in principle possible to use something else than batteries or accumulators, but only if you know precisely what you are doing (additional filtering is required etc.). Personally, I am exclusively using rechargeable accumulators for reasons of simplicity.
### Note on using external batteries
If you want to connect batteries externally, outside of the [[metal enclosure|Enclosures]], be aware that this may as well introduce considerable electromagnetic noise (wires acting as an antenna).
Personally, I put the 9V battery always within the metal case for that very reason. It could work using a shielded cable (e.g. BNC style) but unshielded simple pairs of wires, connecting plus and minus, will almost certainly lead to problems.

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### BNC vs. Audio Cables
The cable attached to the signal output should be shielded and not too long, about 1 meter works well.
A BNC socket is easy to install in candy tin boxes and very robust, but smaller 3.5 mm audio sockets can be used as well.
BNC at the detector also allows the use of standard BNC cables for direct attaching to regular oscilloscope inputs.
Standard stereo/3-pin 3.5 mm jack to 3.5 mm jack audio cables can be used, but they should be short and _shielded_ which is rare. Look for high-quality cables from a music/audio equipment store, e.g. microphone cables.
### Ready-made Cables
* BNC to 3-pin/stereo jack (TRS) cable [from Ebay](https://www.ebay.com/itm/BNC-Male-to-3-5mm-Stereo-1-8-TRS-Plug-Monitor-Decoder-DVR-Audio-Cable-4-16FT/274552805003)
* BNC to 4-pin/headset jack (TRRS) cable [from Ebay](https://www.ebay.com/itm/363206939958)
***ATTENTION:
Please read the [[overiew below|Cables#audio-jack-connector-overview-35-mm-trstrrs]] carefullty for deciding which 3.5 mm audio jack connector you need: 3-pin or 4-pin, TRS or TRRS!***
### Audio Jack Connector Overview (3.5 mm TRS/TRRS)
***3-pin*** versus ***4-pin***, ***TRS*** versus ***TRRS:***
A ***3-pin 'TRS jack'*** is required for regular mono or stereo sound inputs (like on USB soundcards, certain desktop computers or old laptops).
A ***4-pin 'TRRS jack'*** is required for most integrated headset sockets of smartphones, tablets and modern laptops.
![TRS_TRRS_input_wiring](https://user-images.githubusercontent.com/653212/91208896-351d7180-e70b-11ea-8e30-507c9cef8450.png)
MIC = microphone input => connect with detector ouput (marked as 'signal' on the board)
GROUND = connect with the outer shield of the cable (marked as '-' on the board)
**Important Note**:
*Certain systems, like all Apple hardware, switch only automatically from headphones mode (=output only) into a headset mode (=simultaneous audio output and input) if the detector is powered before plugging it in.*
Few non-Apple PCs and laptops have flexible 4-pin sockets that could be configured in different modes, e.g.: headset mode (TRRS-style) or microphone mode (TRS-like, using only the tip and sleeve connections for the 4-pin socket).
Please check your audio system settings of Windows or Linux very carefully in order to find out and decide which mode you want to use.
Further [pinout drawings](https://components101.com/connectors/35mm-audio-jack) of typical TRS and TRRS connectors.
### Part Suggestions for Making Your Own Cables
Since the crimping of BNC connectors onto shielded coaxial cables can be annoying, the easiest way for a BNC-based connection is to cut a pre-configured, 2-3 meters long, BNC-to-BNC (male/male type) cable in half. Then solder a 3-pin/stereo 3.5 mm jack onto the cut end of the coax cable. RG-174 coax cables have a rather thin outer diameter below 3 mm which makes them easier to attach and solder to the 3.5 mm jack connectors in comparison with more common and thicker RG-5x cables.
Recommended parts:
* RG-174 coaxial cable with BNC-BNC male connectors: [Pomona Electronics, 2249-K-120](https://octopart.com/search?q=2249-K-120&currency=EUR&specs=0&in_stock_only=1&sort=median_price_1000&sort-dir=asc) (_3 meters to be cut in 2 halves => allows for making 2 cables_)
* 3.5 mm 3-pin/stereo jack connector (TRS): [Neutrik, NYS231BG](https://octopart.com/search?q=NYS231BG&currency=EUR&specs=0&in_stock_only=1&sort=median_price_1000&sort-dir=asc)
* Alternatively: 3.5 mm 4-pin/headset jack connector (TRRS): [Cliff FC68124](https://octopart.com/search?q=FC68124&currency=EUR&specs=0&in_stock_only=1) ([[instructions below|Cables#connection-with-a-headset-socket]])
### Connection with a Headset Socket
Smartphones, tablets, and modern laptops (e.g. Macbooks from 2013 and later) usually have a socket for 4-pin TRRS connectors, the one that headsets use. They use 4 pins to connect stereo earphones as output, one (mono) microphone as input, and a shared ground connection.
This requires a 4-pin 3.5 mm audio jack connector, where the second ring (counted _after_ the tip) serves as ground and the sleeve/shaft at the connector base is the signal input. See the "TRRS Jack" drawing in the image at the bottom.
Some old 4-pin headset sockets may require a reversed polarity. If the pulses are upwards instead of downwards pointing, simply swap the ground and signal connection at the second rind and the sleeve.
The circuit board must be powered in case of certain smartphones and laptops (Macbooks/iPhones/iPads) __before__ plugging the TRRS audio jack into the headset socket. If the detector is not recognized as an external microphone, please check the values of R8, R9, C9, and C10. Those values must be exactly as specified and differ depending on which variant is built (electron-detector vs. alpha-spectrometer).
Soldering 4-pin TRRS audio jack connectors to BNC cables is not recommended for electronic beginners. Please consider buying [ready-made cables](Cables#ready-made-cables) instead.
### Connection with a Mono or Stereo Microphone Socket
Soldering a cable with a 3-pin/stereo jack connector (TRS):
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/images/RG174_coax_cable-audio_jack.jpeg" width=512>
Note how the *center of the coax cable* connects to the tip of the stereo/3-ping TRS audio jack (that is usually the left channel in case of stereo inputs). The middle ring is skipped but better to be present instead of using a mono/2-pin audio jack. Certain microphone input sockets, like the ones of CM108 USB [[Soundcards]], apply a small bias voltage to the middle ring. This would be shorted to ground if using only a mono/2-pin audio jack and could affect the measurements.
The *shield of the coax cable* connects the ground of the detector circuit with the sleeve of a stereo/3-pin TRS audio connector.
See the "TRS Jack" drawing in the image at the bottom.
Readily configured cables are rare but can be found online. Search for "BNC 3.5 mm".
Make sure to check for the required polarity at the 3.5 mm audio jack connector or modify it if need. Metal-cased 3.5 mm audio jack connectors are usually easy to open.

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## Depletion Profiles
C-V curves of several diodes of the BPW34 series and BXP61 type have been taken to characterize the thickness of the sensitive layer under reverse bias conditions.
With about 8 V on the cathode, the typical sensitive layer thickness is about 50 um which corresponds well with the recorded energy spectra.
Based on the C-V curves, the following doping profiles are derived:
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/images/Neff_10diodes_HR.png" width="550">
The effective charge carrier concentration 'Neff' is on average about half of the value reported in 2008 by [Ravotti et al.](http://cds.cern.ch/record/1169276/files/04636908.pdf) which can be explained by manufacturing process variations. The similarity of the curve shapes confirms that all of the investigated diodes use either the same or at least very similar silicon chips. The regular micropattern visible in the doping profile curves is a measurement artifact that is caused by internal rounding errors of the C-V measurement device. The thin double lines indicate the error range of the instrument as stated by its manufacturer (Keysight B1500A with the MFCMU module).
In comparison to the BPW34F depletion plot in figure 5 ([Ravotti 2008](http://cds.cern.ch/record/1169276/files/04636908.pdf)), the depletion plots shown here do not probe as well the shallow and deep ends of the depletion profile depth. This is caused by a smaller voltage range (25 V max. vs. ~180 V) and larger incremental step size (smaller step sizes would resolve the shallow depletion depths better) in the measurements above.
Further discussion of the CV measurements can be found in [corresponding article](https://doi.org/10.3390/s19194264).
The folder [data_analysis_and_reference_measurements/diode_detector/diode_characterisation_and_simulation_plots](https://github.com/ozel/DIY_particle_detector/tree/master/data_analysis_and_reference_measurements/diode_detector/diode_characterisation_and_simulation_plots) provides the scripts to reproduce the corresponding plots.
The raw C-V measurement data is available in [data_analysis_and_reference_measurements/diode_detector/data/high_resolution_CV](https://github.com/ozel/DIY_particle_detector/tree/master/data_analysis_and_reference_measurements/diode_detector/data/high_resolution_CV).

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### PIN Diodes
The image below shows several PIN photodiodes of the BPW34 family and BPX61 diodes on a black piece of foam:
<img width=512 src="https://github.com/ozel/DIY_particle_detector/blob/master/images/PIN_photodiodes_and_metal_foil.jpeg">
Both kinds of diodes, the BPW34 series in different plastic cases and the BPX61 with metal/glass encasing, have the same sensitive area (~7 mm^2) and contain a very similar silicon chip - [[if not the same|Diode-Characterisation]]. The physics of these semiconducting solid-state silicon sensors when used with ionizing radiation is explained in detail in the [article corresponding to this repository](https://doi.org/10.3390/s19194264). The section about figure 1 discusses why their general efficiency for detecting gamma photons is quite low.
#### Diode Packaging
Considering the original packaging of the diodes, alpha particles from natural sources of radioactivity (up to 8 MeV energy) are not able to cross the passive plastic or glass windows without being fully absorbed before reaching the actual sensitive area.
Removing the BPW34's plastic casing is quite difficult without destroying the tiny bond wire connecting the anode of the diode.
For enabling alpha-spectrometry, the glass window of the BPX61 diode can be easily removed as explained [[below|Diodes#preparation-of-the-bpx61-diode-for-alpha-spectroscopy]].
### Blocking of Unwanted Radiation
The easiest way to operate the detector is to put everything in one large and ___dark___ metal box:
- the circuit board with its mounted diode(s)
- the battery
- the object to be measured
The metal box must be absolutely light-tight. Otherwise, the photodiodes will measure what they are supposed to do. If the oscilloscope shows regular 50 or 100 Hz sinus waveforms, it is most likely artificial stray light from fluorescent neon tubes or LED lamps. If stray light is not the problem (put additionally thick black cloth on top of the detector case to be sure) 50 Hz and higher frequencies can disturb the signals because of electromagnetic interferences from household appliances, for example, nearby mains connected refrigerators or machinery consisting of electronic motors. Changing the room may help if indoors.
#### Blocking of radio waves
The detector circuit is extremely sensitive to electromagnetic interferences (EMI) from radio waves/RF radiation and must be operated within a metal case acting as a Faraday cage.
A metal case completely blocks alpha particles from outside (apart from radon gas potentially sneaking inside) while other types of ionizing radiation like electrons/beta particles will be only partially absorbed which leads to reduced detection rates (additionally affected by an increased distance between detector and specimen).
#### Blocking of light using thin foils
The rightmost BPX61 diode in the picture at the top is covered with a piece of very thin metal foil using superglue. This metal foil stems from an old broken down foil capacitor shown next to the diodes on the very right in the same picture. This is an advanced technique that can be used to protect the diode partially from light (100% light blocking cannot be achieved this way) and have it peek through a hole of the detector's metal case into the outside. If used in this way, the diode should be still operated by facing downwards on the specimen and not within a bright light environment. Some further light-shielding methods like a ring of dark foam or a towel/dark piece of cloth covering everything can be applied.
Pictures from [[@Matthias32|https://github.com/matthias32]] showing how foil capacitors can be opened with enough force and the help of strong pliers or cutters:
<img width=256 src="https://user-images.githubusercontent.com/26323856/95664714-b5c4ef80-0b4a-11eb-96ae-a4ff08719d7a.JPEG">
<img width=256 src="https://user-images.githubusercontent.com/26323856/95664718-beb5c100-0b4a-11eb-8a62-5f1702e3101b.JPEG">
<img width=516 src="https://user-images.githubusercontent.com/26323856/95664724-d12ffa80-0b4a-11eb-9f2f-ab6e64e1f599.JPEG">
### Preparation of the BPX61 diode for alpha-spectroscopy
Microscope image of Osram BPX61 diode below on the left, the green scale indicates 2 mm. The sensitive area of the silicon chip is 2.65 x 2.65 mm^2. A bond wire from the anode pin on the right connects the top of the chip (this side is also marked with a notch in the metal case, lower right corner).
*In order to detect alpha particles, the glass window of the diode must be removed.*
Care must be taken such that the bond wire stays in place when the glass window is removed: The right picture shows the mounted BPX61 diode after its glass window was removed: cutting small dents into the border of the TO metal case with small pliers easily crack the glass. *Tipp: keep the diode upside down above a trash can during this procedure such that the glass pieces fall immediately down and away from the silicon chip!*
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.2/documentation/BXP61_mircoscope.png" height="300"><img src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.2/documentation/BPX61_onboard.jpg" height="300">
Another view of a BPX61 diode without glass window here mounted on the backside of the circuit board:
<img src="https://github.com/ozel/DIY_particle_detector/blob/master/images/BPX61_window_glass_removed.jpg" width=600>
Four small dents, carefully cut using small pliers is enough to crack the glass window completely. Turning the diode upside down afterwards and hitting it with or against a piece of hard metal/tool on the corner/side will remove the glass bit by bit. Poking inside the diode with tweezers is not advised since that can easily destroy the tiny wirebond. Loose chips of the glass can be carefully removed with some canned air, although too much pressure might as well impact the bond wire. As long as none of the glass chips or too much glass dust rests on top of the silicon chip, it will work fine.

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## General Recommendations
***The detector enclosure must be made from metal***, acting as a Faraday cage.
Important aspects when choosing a metal case:
- large enough to house a [[9 V battery|Batteries]], the circuit board, signal output connector and on/off switch
*minimum size recommendation*:
* 8 x 4.5 x 3 cm³ (9V battery upright)
or
* 8 x 5.5 x 2 cm³ (9V battery flat)
- measuring objects inside the box (easier; proximity to the diodes is useful) or outside (more advanced)
_For measuring the energy spectra of alpha particles_ with the **alpha-spectrometer variant**, using a larger box with everything inside, including the radioactive object, is the recommended method!
- the circuit board should be firmly fixed in place with at least one screw
- mobile or stationary usage of the detector?
**_For beginners building the DIY particle detectors, a [[candy tin box|Enclosures#candy-tin-boxes]] and rather stationary usage on a table_** is generally advised - the case can be easily upgraded later.
Tin boxes are easy to work with since the metal is typically very flexible and soft, but this can be also a downside. The larger the tin box, the more it is sensitive towards picking up vibrations (["microphony effect"](https://en.wikipedia.org/wiki/Microphonics)).
Therefore, if the detector is enclosed in a candy tin box, it should not be touched or moved during measurements.
In particular, the alpha-spectrometer variant may be disturbed even in loud environments due to its larger amplification factor.
If choosing instead sturdy and thick-walled metal enclosures like [[diecast aluminum|Enclosures#diecast-aluminum-enclosures]], the detectors will be immune to vibrations.
**_The enclosure must block all light completely from reaching inside._** In case of doubt about light-tightness, put a thick and dark towel or piece of cloth on top of the enclosure during measurements. Further context in the [[Diodes|Diodes#blocking-of-unwanted-radiation]] section.
#### Creating a "radiation window"
If you choose a small enclosure where radioactive objects cannot fit inside, it is a good idea to add a "window for radiation" in front of the diodes. This allows more particles to directly reach the diodes with less interaction/absorption in the dense metal walls of the enclosure. See below for some examples where holes have been added opposite to the diodes. In order to keep light still blocked, those holes must be covered again with thin layers of tape. A good combination is one layer for sticky metal tape (copper or aluminum) plus one layer of black electrical insulation/gaffa tape. If metal tape is not at hand, 2-3 layers of electrical tape may be required - depending on the tape and intensity of the surrounding light. Note thin invisible cracks may occur in the metal tape if it is being touched, the additional layer of plastic tape helps to prevent that.
### Candy Tin Boxes
Some tin box enclosure examples below. More in the picture [[Gallery]].
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.1/documentation/DIY_Particle_Detector_in_candy-tin-box.jpg" height="370"><img src="https://github.com/ozel/DIY_particle_detector/raw/master/images/Alpha-spectrometer_with_ceramics_in_chocolate_box.jpeg" height="370">
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.2/documentation/Alpha_spectrometer_in_candy_box_open.jpg" height="282"><img src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.2/documentation/Alpha_spectrometer_in_candy_box_closed.jpg" height="282">
Use a 9 mm [hole puncher](https://www.hoffmann-group.com/US/en/hus/Hand-and-assembly-tools/Hole-punches-deburrers-scrapers/Steel-wad-punch/p/832001-9?tId=504) to quickly and safely create a hole for the signal output BNC connector. Use a smaller hole puncher for the on/off switch and a bigger one to create a [[radiation window|Enclosures#creating-a-radiation-window]] if desired. Note that the hole will be always bigger than the nominal diameter of the hole puncher as tin box walls are usually quite soft. Put a piece of hard wood below the tin box when punching holes. If physical access with the puncher is diffcult because the tin box is small, bend the tin box metal outwards, punch the hole and bend the metal back inwards when finished.
### Diecast Aluminum Enclosures
Two small enclosures that are just big enough for housing everything (besides most specimens):
- [Multicomp G102MF](https://octopart.com/search?q=Multicomp+G102MF&currency=EUR&specs=0&in_stock_only=1&sort=median_price_1000&sort-dir=asc), fits the circuit board precisely using edge mount screws, BUT very tight fit together with the [[battery|Batteries]] (shown below on the left)
- [Deltron 480-0010](https://octopart.com/search?q=Deltron+480-0010&currency=EUR&specs=0&in_stock_only=1&sort=median_price_1000&sort-dir=asc), more available space but no existing mounting holes for the board (shown below on the right)
These diecast aluminum cases are so small that only tiny objects like a small stone or piece of uranium glass (e.g. a marble) will fit inside. If you want to measure barely radioactive objects, larger metal cases are much better. For measuring objects of low radioactive intensity, the diodes should be in direct contact with the specimens' surface which is possible if the metal case is large enough to house everything - including the specimen.
Alternatively, consider adding a [[radiation window|Enclosures#creating-a-radiation-window]] in order to improve the sensitivity of the detector.
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/images/aluminum%20die-cast%20enclosures.jpeg" width="900">
(Note: The hole drilled into the lid on the left is a [[radiation window|Enclosures#creating-a-radiation-window]] covered with metal tape.)
An example of mounting the diodes on the backside of the PCB and adding a [[radiation window|Enclosures#creating-a-radiation-window]] to the underside:
<img width=400 src=https://user-images.githubusercontent.com/26323856/86839223-72696980-c0a1-11ea-9b91-ab077a0ccf31.JPEG>
<img width=400 src=https://user-images.githubusercontent.com/26323856/86839227-739a9680-c0a1-11ea-8c79-271bf4ea06d0.JPEG>
This is the best method to get the detector as sensitive as possible (since the diodes are very close to the windows this way).
It may be a bit more difficult to create a hole in the underside of those small die-cast cases, but it doesn't have to be square-shaped - it can be round as well, drilled with a larger diameter drill bit.
<img width=400 src=https://user-images.githubusercontent.com/26323856/86839219-709fa600-c0a1-11ea-848e-94c4675af830.JPEG>
<img width=400 src=https://user-images.githubusercontent.com/26323856/86839230-739a9680-c0a1-11ea-83c4-500694a403fa.JPEG>
The switch is optional and just fits into the free space next to the battery.
<br><br>
Left side: diodes facing down towards [[radiation window|Enclosures#creating-a-radiation-window]], right side: diodes facing up (radiation window in the lid):
<img width=400 src=https://user-images.githubusercontent.com/26323856/86839222-71d0d300-c0a1-11ea-912d-722952c6ea9f.JPEG>
<img width=400 src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.1/documentation/DIY_Particle_Detector_in_cast-aluminium-case.jpg">
(Note: The right picture is featuring a previous version of the circuit board, V1.1, where the capacitor below U1 was called C6 instead of C5.)
#### Important remarks when using one of these two very small cases:
- consider ordering thinner circuit boards than the standard 1.6 mm PCB thickness,
better 1 or 0.8 mm as the available space is very tight.
- use thin [[9 V rechargeable NIMH accumulators|Batteries]] that come in plastic housings
- cut the component traces, also the ones of the amplifier chip U1, as short as possible and orient the capacitor C5 flat on the board as shown below (or use an SMD version).
- if the 9 V battery has itself a metal enclosure, make sure to prevent short circuits from the sharply cut pins.
e.g. apply enough insulation tape around the battery or add a thin sheet of plastic between board and battery.
- it is no problem if the lid of the enclosure doesn't close completely as long as no light reaches inside. About 1 mm of a slit between the lid and main part of the enclosure is tolerable. Put the soft white or black rubber seal in place, it helps with blocking all light. If all 4 screws are in place, that is enough for the metal case acting as a Faraday cage and provide electromagnetic shielding (blocking EMI) - a thin remaining slit between the lid and main part doesn't matter.
- route the connection wires along the edges/walls of the enclosure (they can pass along the curved edges of the battery)
- the on/off switch can be mounted on the second short side of the main case, on the opposite side to the signal output connector. It will be somewhat in the way above the diodes, but that does not matter when building the **electron-detector variant**.
- In the case of the **alpha-spectrometer variant**, the BPX61 diode should be mounted on the opposite side of the circuit board, facing downwards. A hole with the outer diameter of the diode's metal case should be drilled into the bottom, serving as the [[radiation window|Enclosures#creating-a-radiation-window]]. Instead of covering that hole with sticky metal tape, consider shielding the BPX61 diode directly using an even thinner foil as explained [[here|Diodes#blocking-of-light-using-thin-foils]]. This is the most difficult build - using a bigger case that can fit the radioactive object is much easier.

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## Alpha Particle Spectra
Radioactive elements can be identified based on their individual and characteristic alpha particle energies.
Since alpha particles are very heavy (they are in fact Helium nuclei or positively charged Helium ions: 2 neutrons + 2 protons) in comparison with other sources of ionizing radiation, they interact strongly with matter.
That means they may have lost considerable amounts of energy before reaching the detector depending on the properties of the source material and the surrounding air.
Alpha-spectra can be difficult to interpret because of this. A Simulation of the measurement helps to identify the radioactive elements and can compensate for specific effects - a very common method in nuclear and particle physics. A good, free simulation program is described [[here|Software#simulation-of-alpha-spectra]].
It's important to approach the specimen as close as possible with the diode. If the BPX61 is in touch with the surface, the remaining air gap is about 2 mm. The [density of air](https://en.wikipedia.org/wiki/Density_of_air) - depending on temperature, atmospheric pressure and humidity - should be estimated as precisely as possible for best results. In professional settings, vacuum pumps are used in order to reduce the air density which shrinks the width of the peaks considerable and reduces overlaps in a spectrum (especially on the left-hand sides of peaks).
### Energy Calibration
The following linear equation is used to map the arbitrary pulse amplitudes, as measured by a [[CM108 USB Soundcard|Soundcards]], to the corresponding particle energy given in keV:
```
y [in keV] = m*x + t (simple linear equation)
m = 0.4958436 (slope)
t = -116.40845593 (offset)
x = maximum pulse amplitude (absolute value of the downward facing portion)
x is usually called 'channel number' in MCA software (Multi Channel Analyzer)
```
In combination with this calibration, *the minimum trigger level or threshold for recorded pulses must be set at -300* (c.f. [[pulse_recorder.py line 33 | https://github.com/ozel/DIY_particle_detector/blob/53a7770a66fe0209b38a826d560bc8a4b6b56a0d/data_recording_software/pulse_recorder.py#L33]]; the same level must be used in the web browser application or any other pulse recorder). Pulses with an amplitude of -300 represent the minimum energy threshold of 33 keV. Everything smaller than that is considered spurious electronic noise an not a real pulse from a particle.
***Note:*** **this formula can be quite different for other soundcards and headset inputs as input sensitivity varies a lot**.
It applies to the low-cost CM108 USB [[Soundcards]] only if set at 100% input volume, recording at 16-bit/48.000 Hz and with gain boost enabled - please read these [[operating system specific notes|Soundcards#operating-system-specific-tips]] carefully.
For further context, please refer to the discussions of figures 4, 5, 9, and 10 in the [paper](https://www.mdpi.com/1424-8220/19/19/4264/htm).
### Electron Energies
Beta decays produce electrons with continuous energy distributions.
The total decay energy is isotope specific but always shared between an anti-neutrino and an electron in each disintegration. As a consequence, characteristic electron energy lines do not occur like in measurements of alpha decays.
Furthermore, with thin silicon diodes, most electrons from natural sources of radioactivity are only partially absorbed within the sensitive layer and are even capable to leave the relatively thin diode.
### Gamma/X-ray Photon Spectra
Thin layers of silicon, like the approximately 50 micrometers deep depleted region of a BPX61 diode when biased with about 8 V, absorb only a small fraction of gamma or X-ray photons. Above an energy of 100 keV, the detection probability is already below 0.5% (C.f. figure 1 in the [paper](https://www.mdpi.com/1424-8220/19/19/4264/htm))
Therefore, characteristic gamma and x-ray energy lines may be only identified in the spectrum, if the radioactive object does not emit alpha and/or beta radiation else which is rarely the case.
Characteristic energy lines from X-ray photons may be observed if high enough. The lower/minimum detection threshold of the alpha-spectrometer was verified at about 33 keV using an X-ray machine.

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# Project Outline
The DIY Particle Detector project was supported by the [Fellow FreiesWissen 2020](https://de.wikiversity.org/wiki/Wikiversity:Fellow-Programm_Freies_Wissen/Fellows2020) grant program, hosted by Wikimedia Germany, from October 2020 through June 2021.
This drawing summarises the main purpose of the project:
![main sources of environmental radioactivity](https://upload.wikimedia.org/wikipedia/commons/e/e6/Main_sources_of_environmental_radioactivity.png)
***Students and curious humans*** (like the stick figure in the middle) need modern low-cost & ***open science hardware instruments*** that enable the exploration and a better understanding of natural radioactivity. **#CitizenScience**
My original fellowship application can be found in German on the [Fellow FreiesWissen program page of 2020](https://de.wikiversity.org/wiki/Wikiversity:Fellow-Programm_Freies_Wissen/Einreichungen/Nat%C3%BCrliche_Radioaktivit%C3%A4t_entdecken_und_verstehen_mit_offenen,_g%C3%BCnstigen_%26_selbstgebauten_Messinstrumenten) together with the early version of the logbook which was moved here.
## Main Project Goals & Milestones
The following initial goals were set after the first meeting with all program mentors and the other fellows in October 2020.
### Hardware & Software Development
* improve the [web-based measurement software](https://ozel.github.io/DIY_particle_detector/data_recording_software/webGui/)
* develop the detector more towards a smartphone accessory => improve ease of use
* increase detector sensitivity (e.g. cosmic rays) with a redesign of the electronics
Milestones:
* new hardware revision by June 2021
* incremental software updates throughout the year
### Documentation
* select easier to access multi-language capable web site service than the existing GitHub Wiki
* translate English project docs into German, support others to do the same in their native languages
* start blogging about it
* produce video material
* more build instructions based on 3D models
Milestones:
* blog and first article: January 2020
* dedicated project website: March 2020
* wiki & documentation updates, translations etc.: throughout the year
### Workshops & Talks
* run 3 or more workshops
* 1 workshop in a community living close to a Uranium/Thorium or rare earth mine
* do an open online talk (e.g. apply for CCC's annual congress RC3 call for proposals)
Milestones:
throughout the year (hands-on DIY workshops difficult to plan due to COVID-19)
# Logbook
## June 2021
On June 16, I was invited by Rafael Ballabriga, detector chip designer from CERN, to give an ***online seminar*** within the framework of the Spanish ADMIRA education project. About ***25 high-school students and physics teachers from Barcelona*** participated.
One student did a short presentation about his school project: he built the DIY Particle Detector, designed his own metal enclosure in the 3D CAD program SolidWorks and created CNC manufacturing files for it. He also took several measurements of different sources of radioactivity and compared them with more advanced pixel detectors (which in principle, operate very similar to the low-cost diodes).
Short [Twitter thread](https://twitter.com/0zelot/status/1405197413657219075?s=20) about the students' talk.
On 18/19. June, the final presentation of the Fellow FreiesWissen Program 2020 is happening.
A wrap-up and summary of my whole program experience will follow soon after. *TBD*
## May 2021
In collaboration with a local Fablab/maker space [Oberlab](http://www.oberlab.de), another ***DIY workshop took place on 20/21. May in Gmund***, while the COVID-19 cases were declining quickly thanks to the warm spring weather.
This time it was divided into an online introduction by me on the first day, followed by a DIY workshop from the following morning until noon.
In total ***16 high-school students (age 16-17) built their own detector*** inside a tin box. As guides were present their physics teacher Frederik, Alexander and Heinz from Oberlab, and myself.
![IMG_4263](https://user-images.githubusercontent.com/653212/122480477-35a23400-cfcd-11eb-9758-02e06204f007.JPG)
![IMG_4267](https://user-images.githubusercontent.com/653212/122480502-405cc900-cfcd-11eb-88f1-c20c5428fe92.JPG)
![IMG_4274](https://user-images.githubusercontent.com/653212/122480514-45217d00-cfcd-11eb-9f29-b374033e51ef.JPG)
![IMG_4284](https://user-images.githubusercontent.com/653212/122480572-61251e80-cfcd-11eb-8f13-da42721f2a3b.JPG)
## March 2021
A _**new version of the detector hardware**_ was designed in KiCAD and submitted to JLCPCB where five new circuit boards were manufactured. [Sneak peek tweet](https://twitter.com/0zelot/status/1377578361556504576?s=20).
The new board can host more than six times the number of diodes, compared to the original detector version, and they are still arranged in a compact rectangular matrix (2x2 versus 5x5). This will make the detector more sensitive to weaker sources of radioactivity. A new special feature, for detecting cosmic rays, has been introduced as well together with several circuit options that hopefully reduce the always present electronic noise of the charge-sensitive amplifier further.
Picture of the new hardware:
![image](https://user-images.githubusercontent.com/653212/122523514-6313cf80-d017-11eb-8dad-4f780bf469bd.png)
The tiny black rectangle in the bottom left corner is one diode, next to it the amplifier chip, both in SMD version. The new circuit board prototype (front and back pictured) is optimized for automated low-cost manufacturing in the future, complementing the current DIY version of the detector. The grey square with 3 buttons and display is an M5 stack core module that is extended with a custom bottom module, hosting the new detector. The ESP32 inside the core module will communicate radioactivity measurements over Bluetooth to smartphones/laptops, turning the current DIY particle detector into a gadget-like device with a simplified and more streamlined user experience.
## February 2021
On 13/14.2., the _**Winter School**_ of the fellow program took place with the **_topic of science communication_**.
My personal highlight was the session run by Kerstin Göpfrich & Étienne Serbe who both presented their own science communication projects.
Kerstin talked about her platform [Ring-A-Scientist](https://www.ring-a-scientist.org) that allows school teachers to contact and 'hire' real scientists who are interested in giving classroom talks in front of students.
Étinenne reported experiences about his citizen science project called [Hirnkastl](hirnkastl.science) where they do workshops for students with low-cost EEG devices. Since these devices are also quite sensitive and not always easy to operate, there are some similar challenges with the DIY particle detector units.
## December 2020
**Presentation of the whole project at the RC3 conference**_ on 31.12.2020, the first online version of the annual [CCC](www.ccc.org) Congress in Germany:
* [original recording on youtube](https://www.youtube.com/watch?v=1uoUGNa_g_E)
* [simultaneous translation in german on youtube](https://www.youtube.com/watch?v=bdjcy4tITYw)
* [CCC media server with all versions and subtitles](https://media.ccc.de/v/rc3-11546-measuring_radioactivity_using_low-cost_silicon_sensors)
* [PDF slides](https://cernbox.cern.ch/index.php/s/hiP1wHxpBtw2OmF)
From 30.11 through 7.12., **_12 high-school students in Bonn_** built detectors together with their physics teacher. After the usual project introduction by myself, the physics teacher re-purposed three of his regular physics lessons during which I was present remotely in a video call for any kind of remote support and questions while the students built particle detectors.
Pictures from the workshop:
![8E17B6D1-E1A7-4FCE-8B22-E973F7F2BC6C](https://user-images.githubusercontent.com/653212/122479538-8a44af80-cfcb-11eb-8282-6cea3b60b1fa.jpeg)
![IMG_0297](https://user-images.githubusercontent.com/653212/122479604-a9434180-cfcb-11eb-96f3-43c5ce46ae28.JPG)
![IMG_0287](https://user-images.githubusercontent.com/653212/122479618-b06a4f80-cfcb-11eb-9ec0-69ce2fdb150d.JPG)
![IMG_0288](https://user-images.githubusercontent.com/653212/122479667-c37d1f80-cfcb-11eb-8dc5-562d0e947e7c.JPG)
## November 2020
### Preparation and Hosting of First Online DIY Workshops
This was a trial of a novel workshop format part of the [Science Days Digital 2020](https://2020.science-days.digital), to make the best out of COVID-19 related social distancing requirements.
Participants were gathering locally in small groups and were then guided by me remotely via several video calls.
The preparation was quite time-consuming and involved in terms of necessary communication and organization with teachers and FabLabs.
However, the success was worth the effort and the fellowship supported me to handle certain aspects more pragmatic than otherwise possible. For example, several hardware components had to be shipped quickly to several international destinations, which I paid myself in favor of fast shipping and easier procedures.
The open hardware community platform [www.Kitspace.org](http://www.Kitspace.org) supported these workshops and took this as an opportunity to offer its **first complete hardware kits***:
https://shop.kitspace.org/buy/electron-detector/
The two-page [assembly guide PDF](https://github.com/ozel/DIY_particle_detector/blob/master/hardware/V1.2/documentation/DIY%20detector%20-%20parts%20overview%20v1-2%20electron%20version.pdf) was improved and translated into [German](https://github.com/ozel/DIY_particle_detector/blob/master/hardware/V1.2/documentation/DIY%20detector%20-%20parts%20overview%20v1-2%20electron%20version%20DE.pdf).
Also due to this occasion, corresponding software, a [browser-based oscilloscope](https://ozel.github.io/DIY_particle_detector/data_recording_software/webGui/) for recording detector data, was also [updated and improved](https://github.com/ozel/DIY_particle_detector/tree/master/data_recording_software/webGui).
***Documentation updates*** in the Wiki can be followed [here](https://github.com/ozel/DIY_particle_detector/wiki/_history).
In total, **_30 teachers, students, makers, and enthusiasts took part and built the electron-detector variant_** of my open science hardware instrument during these online workshops.
Pictures from the DIY particle detector online workshop hosted at FabLab Munich, 24. November:
* https://twitter.com/0zelot/status/1331557681186926596
* https://twitter.com/FabLabMuc/status/1331571033053212674
![](https://user-images.githubusercontent.com/653212/100475561-b9eda200-30e3-11eb-8fff-1473c4e54d90.JPG)
![](https://user-images.githubusercontent.com/653212/100475089-82322a80-30e2-11eb-9a2e-6159bc160ac0.JPG)
![](https://user-images.githubusercontent.com/653212/100475096-865e4800-30e2-11eb-9e6e-67bc027c6af0.jpg)
## October 2020
Participation in the [Fellow FreiesWissen 2020 program kick-off event](https://blog.wikimedia.de/2020/10/29/fellows-programm-freies-wissen-2020-21-startete-mit-einem-digitalen-auftakt/) on 16./17. October.
First dedicated meeting with co-mentee [Ludmilla Figueiredo](https://de.wikiversity.org/wiki/Wikiversity:Fellow-Programm_Freies_Wissen/Einreichungen/Computational_notebooks_as_a_tool_for_productivity,_transparency,_and_reproducibility) and our common mentor [Johanna Havemann](https://access2perspectives.com/) on 29. October.
Both events lead to the project planning listed at the top of this page.

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### A collection of DIY particle detector builds done by others on _the Internet_
(please send me a link to yours, or upload pictures yourself [here](https://github.com/ozel/DIY_particle_detector/issues/4) :-)
In collaboration with the Fablab/maker space [Oberlab](http://www.oberlab.de), another COVID-compliant hands-on workshop took place in May 2021 in Gmund. In total 16 high-school students (age 16-17) built their own detector inside a tin box within the physics/technology lecture.
<img width=400 src="https://user-images.githubusercontent.com/653212/122480477-35a23400-cfcd-11eb-9758-02e06204f007.JPG">
<img width=400 src="https://user-images.githubusercontent.com/653212/122480502-405cc900-cfcd-11eb-88f1-c20c5428fe92.JPG">
<img height=400 src="https://user-images.githubusercontent.com/653212/122480514-45217d00-cfcd-11eb-9f29-b374033e51ef.JPG">
<img height=400 src="https://user-images.githubusercontent.com/653212/122480572-61251e80-cfcd-11eb-8f13-da42721f2a3b.JPG">
From 30.11 through 7.12.2020, 12 high-school students in Bonn built detectors together with their physics teacher.
<img width=400 src="https://user-images.githubusercontent.com/653212/122479538-8a44af80-cfcb-11eb-8282-6cea3b60b1fa.jpeg">
<img width=400 src="https://user-images.githubusercontent.com/653212/122479604-a9434180-cfcb-11eb-96f3-43c5ce46ae28.JPG">
<img width=400 src="https://user-images.githubusercontent.com/653212/122479618-b06a4f80-cfcb-11eb-9ec0-69ce2fdb150d.JPG">
<img width=400 src="https://user-images.githubusercontent.com/653212/122479667-c37d1f80-cfcb-11eb-8dc5-562d0e947e7c.JPG">
From the Science Days Digital 2020 online workshop in collaboration with CERN and [@FabLabMuc](https://twitter.com/FabLabMuc/status/1331571033053212674), pictures taken by [@GigaBecquerel](https://twitter.com/GigaBecquerel/status/1331544404465770498):
<img width=400 src=https://user-images.githubusercontent.com/653212/100475096-865e4800-30e2-11eb-9e6e-67bc027c6af0.jpg>
<img width=400 src=https://user-images.githubusercontent.com/653212/100475102-89593880-30e2-11eb-8849-9d89dd598c94.jpg>
<img width=400 src=https://user-images.githubusercontent.com/653212/100475089-82322a80-30e2-11eb-9a2e-6159bc160ac0.JPG>
<img width=400 src=https://user-images.githubusercontent.com/653212/100475561-b9eda200-30e3-11eb-8fff-1473c4e54d90.JPG>
Steve and his son wrote a very [detailed blog post](https://clanhouse.com/cern-at-home-building-a-particle-detector) about their experiences.
<img width=400 src="https://clanhouse.com/wp-content/uploads/2020/09/IMG_0948.jpeg">
<img width=400 src="https://clanhouse.com/wp-content/uploads/2020/09/IMG_0947.jpeg">
Kendra: https://twitter.com/ksibbern/status/1282865224748380162
<img width=400 src="https://pbs.twimg.com/media/Ec2nHSUWkAo-Sio?format=jpg&name=large">
<img width=400 src="https://pbs.twimg.com/media/Ec2nHSUX0AcrO0W?format=jpg&name=large">
<img width=400 src="https://pbs.twimg.com/media/Ec5aA0qXoAE1eV_?format=jpg&name=large">
<br>
[@Matthias32](https://github.com/ozel/DIY_particle_detector/issues/4#issue-652618441):
<img width=400 src=https://user-images.githubusercontent.com/26323856/93909918-a3505680-fd00-11ea-96ba-a92540f5a23c.JPEG>
<img width=400 src=https://user-images.githubusercontent.com/26323856/86839219-709fa600-c0a1-11ea-848e-94c4675af830.JPEG>
<img width=400 src=https://user-images.githubusercontent.com/26323856/86839223-72696980-c0a1-11ea-9b91-ab077a0ccf31.JPEG>
<img width=400 src=https://user-images.githubusercontent.com/26323856/86839230-739a9680-c0a1-11ea-83c4-500694a403fa.JPEG>
<img width=400 src=https://user-images.githubusercontent.com/26323856/86839227-739a9680-c0a1-11ea-8c79-271bf4ea06d0.JPEG>
<br>
[Malte, mikrocontroller.net](https://www.mikrocontroller.net/topic/495968#6327455):
<img width=400 src="https://user-images.githubusercontent.com/653212/87235154-15d7b880-c3d9-11ea-987e-3fc4223cff35.jpg">
<br>
[physicsopenlab.org](https://physicsopenlab.org/2020/06/15/cern-diy-particle-detector/):
<img width=400 src="https://physicsopenlab.org/wp-content/uploads/2020/06/CERNDet-824x1024.jpg">
<br>
Stuart: https://twitter.com/xc0nradx/status/1268354112233582599
<img width=400 src="https://pbs.twimg.com/media/EZoZVjgWoAwDVQ4?format=jpg&name=large">
<br>
Paul: https://twitter.com/nearsys/status/1273462111197229056
<img width=400 src="https://pbs.twimg.com/media/EaxDe_UUwAEHU6Y?format=jpg&name=large">

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For a short **general overview** please refer to the [main readme](https://github.com/ozel/DIY_particle_detector/blob/master/README.md).
There are two detector versions based on the same circuit board using similar components:
- **Electron-Detector** variant which is easier to build, use and more sensitive (more sensor volume than the Alpha-Spectro.)
- **Alpha-Spectrometer** variant which can measure characteristic energy spectra of alpha decays (and also count electrons)
For **scientific context** on the physics of the diode sensors and how it works, please have a look at the [corresponding paper](https://www.mdpi.com/1424-8220/19/19/4264/htm). It explains for example why the sensitivity to gamma radiation is rather low for both detector variants.
_Please post your own builds in the [Discussions](https://github.com/ozel/DIY_particle_detector/discussions) such that I can add them to the [[Gallery]]!_ :grinning:
#### Project introduction talk at rC3, remote CCC Congress, December 2020:
[youtube english](https://www.youtube.com/watch?v=1uoUGNa_g_E),
[youtube german translation](https://www.youtube.com/watch?v=bdjcy4tITYw),
[CCC media server with all versions](https://media.ccc.de/v/rc3-11546-measuring_radioactivity_using_low-cost_silicon_sensors),
[PDF slides](https://cernbox.cern.ch/index.php/s/hiP1wHxpBtw2OmF)
### Wiki Overview
* Hardware/Electronics
* **[[Assembly Instructions|Assembly-Instructions]]** - parts, tools, build instructions and troubleshooting
* [[Batteries]] - rechargeable 9 V NIMH accumulators are recommended
* [[Cables]] - connecting the signal output to a soundcard or a smartphone's/laptop's headset socket
* [[Diodes]] - different types of PIN photodiodes, blocking of radiation/light etc.
* [[Enclosures]] - chose the right kind of metal box for your DIY particle detector
* [[Soundcards]] - recommended low-cost USB soundcards, recording settings
* **[[Troubleshooting]]** - debugging the detector after assembly
* Taking detector data, recording and analysing measurements
* [[Energy Spectra|Energy-Spectra]] particle energy spectra and reference energy calibration
* [[Oscilloscope Measurements]] great for checking if the detector works well
* **[[Software]]** different kinds of freely available recording, analysing and simulation software
* Supplementary material (mostly related to the paper)
* [[Diode Characterisation]] (C-V measurements revealing physical properties of the [[diodes|Diodes]])
* [[Pixel Detectors]] (comparison of the diodes with pixel detectors from CERN)
* Workshops
* [[Science Days Digital 2020]] (Online-Workshop, in German)
* [Gathering of Open Science Hardware 2018 in Shenzhen China](http://openhardware.science/gatherings/gosh-2018-2/), [workshop documentation](https://forum.openhardware.science/t/day-3-build-your-own-particle-detector-discover-natural-radioactivity/1468)
* [S'Cool LAB Summer Camp 2018](https://indico.cern.ch/event/726779/timetable/) at CERN, [poster presentation, page 3](https://indico.cern.ch/event/726779/contributions/2991390/attachments/1697186/2732121/pdfjoiner.pdf)
* [Student Summer School of Barcelona Technoweek 2017](http://icc.ub.edu/congress/TechnoWeek2018/outreach_EN.php), [CERN news](https://home.cern/news/news/knowledge-sharing/summer-school-secondary-students-spain)
* [S'Cool LAB Summer Camp 2017](https://indico.cern.ch/event/570855/timetable/) at CERN, [poster presentation](https://indico.cern.ch/event/570855/contributions/2616929/attachments/1504724/2344411/RG3_DIY_Detector.pdf)
* Project Support
* The project received funding and support from the Fellow FreiesWissen program which is documented [here](https://github.com/ozel/DIY_particle_detector/wiki/Fellow-FreiesWissen-Project).
* Online Coverage
* Steve Foster, UK, September 2020: [[CERN at Home: Building a Particle Detector|https://clanhouse.com/cern-at-home-building-a-particle-detector]]
* Gigazine, Japan, September 2020: [[自宅で作れるCERN公式「素粒子検出器レシピ」が公開中、DIYするとこんな感じ|https://gigazine.net/news/20200911-particle-detector-diy/]]
* Physics Open Lab, June 2020: [[CERN DIY Particle Detector|http://physicsopenlab.org/2020/06/15/cern-diy-particle-detector]]
* Electronics Lab, Mai 2020: [[DIY Silicon Photodiode Particle Detector directly from CERN|https://www.electronics-lab.com/diy-silicon-photodiode-particle-detector-directly-cern/]]
* Hacker News, May 2020: [[DIY Particle Detector (cern.ch)|https://news.ycombinator.com/item?id=23196177]]
***In case of questions or ideas, please make a new post in [Discussions](https://github.com/ozel/DIY_particle_detector/discussions).***
If you read German, another thread is also ongoing on the [mikrocontroller.net forum](https://www.mikrocontroller.net/topic/495968#6265722).
---
_Copyright Oliver Keller 2019-2020._
This documentation describes Open Hardware and is licensed under the CERN OHL v. 1.2.
You may redistribute and modify this documentation under the terms of the CERN OHL v. 1.2. (http://ohwr.org/cernohl).
This documentation is distributed WITHOUT ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING OF MERCHANTABILITY, SATISFACTORY QUALITY AND FITNESS FOR A PARTICULAR PURPOSE.

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# Detector Signals of Radioactivity on an Oscilloscope
The screenshots below show typical output signals from both detector variants with arrows highlighting the signal and noise properties. The blue lines represent signals from individual particles, the grey lines are superpositions of earlier particle signals which triggered the oscilloscope as well.
For a better comparison between the two detector variants, **the same beta & gamma radiation source (potassium salt, KCl) was used in both measurements below** - it does not emit alpha particles.
The negative pulse with its steep downward edge is the main signal and is larger than the electronic noise. The trigger level must be set well below the noise range, which depends on the intensity of surrounding *electromagnetic interference* (EMI) radiation and stray light reaching into the shielding case of the detector. The short negative main signal pulse is followed by a wider positive overshoot which is proportional in size to the amplitude of the main signal. The overshoot is an effect of the amplifier circuit and also depends on the impedance matching from the detector output to the input of the measurement device. The employed oscilloscope features a default input impedance of 1 megaohm. Microphone and line-in inputs of sound cards (as described above) have considerably lower input impedances and pulse measurements will therefore show a larger signal overshoot. The alpha-spectrometer circuit was intentionally designed to produce this kind of a bipolar signal with a lot of overshoot in order to mimic actual audio waves.
*If the detector signals do not look similar to the ones below, please follow the [[Troubleshooting]] guide!*
## Electron-Detector
<img width=600 src=https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/images/oscilloscope_pulse_electron-detector.png>
**Time Scale:** 50 Microseconds per division, **Voltage Scale:** 50 Millivolt per division
Real pulses from particles can be typically well distinguished from electronic noise at trigger level of about -50 mV (and lower) if the detector is well shielded against surrounding light and not exposed to electromagnetic interferences, e.g. from a cell phone, power supply or electromotor close by. The negative pulses are about 50 to 75 us wide with this circuit.
## Alpha-Spectrometer
<img width=600 src=https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/images/oscilloscope_pulse_alpha-spectro.png>
**Time Scale:** 1 Millisecond per division, **Voltage Scale:** 1 Millivolt per division
Typical signal amplitudes of particles from the same beta/gamma radiation source are much lower compared to the electron-detector variant. The electronic noise is much smaller as well and the width of pulses is between 1 and 2 ms. This circuit is optimised for large pulses from alpha particles which is heavy-ionizing radiation and therefore produces a lot more free charges in the sensor.
The amplitude threshold which allows distinguishing between electrons (=smaller signal amplitude) and alpha particles (=larger signal amplitude) is at **-8 mV** in case of a typical oscilloscope with an input impedance of **1 megaohm**. This threshold is lower in case of a sound card due to their lower input impedances. Please refer to [the scientific article](https://doi.org/10.3390/s19194264) and the [[energy calibration function| Energy-Spectra#energy-calibration]] for detailed information.

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## Comparison with pixel detectors from high-energy physics
For comparison, two measurements have been made with the [iPadPix](https://github.com/ozel/iPadPix) mobile device that is based on the 1.4 x 1.4 cm^2 hybrid pixel detector Timepix. Its silicon sensor chip area is 28 times larger and the sensitive volume is about 6 times bigger (300 um vs. 50 um) than a single BPW34 or BPX61 diode.
Due to its larger area, it is well suited for measuring less concentrated sources of radioactivity such as airborne radon progeny collected with an electrostatically charged party balloon.
The diode-based detector can be regarded as a functional model for one pixel of pixel detectors. The physics behind signal formation and subsequent signal processing methods that amplify, characterize, and digitize the pulses are the same.
For further details please consult the scripts provided in [data_analysis_and_reference_measurements/pixel_detector](https://github.com/ozel/DIY_particle_detector/tree/master/data_analysis_and_reference_measurements/pixel_detector) and refer to the [corresponding article](https://doi.org/10.3390/s19194264).

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*This page contains additional info for a DIY online workshop part of the Science Days Digital 2020, in German.*
Hier geht um es einen Online-Workshop vom CERN im Rahmen der Science Days Digital 2020:
https://science-days.digital/cern/pages/teilchendetektor
**Alle Gruppenleiter\*innen müssen sich dort bis Freitag, 30. Oktober 12:00 Uhr, online registrieren!**
Gebaut werden DIY Teilchendetektorn, die auf diesen Seiten beschrieben sind.
Fotos von aufgebauten Detektoren finden sich in der [[Bildergallery| Gallery]].
Am ersten Tag erhalten alle Teilnehmer\*innen eine Online-Einführung in das Prokjekt und den Kontext zu den Detektoren in der Teilchenphysik am CERN.
Anschliessend werden unabhänging voneinander in den unterschiedlichen Gruppen mehrere Detektoren in Schulen/Fab-Labs oder Maker-spaces aufgebaut. Die Betreuer\*innen der Gruppen brauchen dazu grundlegede Lötkenntnisse um den Teilnehmern beim Aufbau helfen zu können. Generell kann das Projekt von Elektronik-Anfängern leicht zusammengebaut werden (mehrfach erprobt, u.a. mit Schülern).
### Zielgruppen:
- ab 16 Jahre bis 60+
- Schülergruppen mit Lehrer*innen, Studentengruppen, citizen science Enthusiasten in Fab-Labs/Makerspaces
- Die Gruppenleiter\*innen benötigen Löterfahrung um den übrigen Teilnehmer\*innen in den Gruppen beim Zusammenbauen der Detektoren zu helfen.
### Termine:
Die folgenden Termine gehören zusammen, der Workshop geht insgesammt über vier Tage, Montag bis Donnerstag.
*Nach Absprache (o.keller@cern.ch) zusätzliche Termine bzw. andere Uhrzeiten am Nachmittag oder Abend möglich.*
- 23\. November | 10:30 – 12 Uhr, Einführung für Schülergruppen per Zoom, ab 16 Jahren/Oberstufe
- 24\. November | 19:00 - 20 Uhr, Alternative kurze Einführung per Zoom, geeignet für Erwachsene
- 24\. und 25. November, ganztags: Online-Support/Troubleshooting per Zoom nach Absprache
- 26\. November | 10:00 Uhr, Abschlusspräsentation per Zoom. Informelles „show & tell“ Format:
Jede Gruppe zeigt was sie gebaut und welche Messungen sie gemacht haben.
### Dauer:
Ungefähr 3-6 Stunden online (flexibel, je nach Support-Bedarf der Gruppen).
Die Detektoren selbst werden *zwischen den Online-Terminen* innerhalb der Gruppen in Eigenregie vor Ort gebaut und anschliessend zum Messen von natürlicher Radioaktivität in der eigenen Umgebung verwendet. Die selbstgebauten Detektoren, gesammelten Erfahrungen & Messergebnisse werden am letzten Tag gezeigt/besprochen und von allen Teilnehmer\*innen untereinander online präsentiert.
### Beschaffung der Materialien:
- Der Detektor besteht aus unterschiedlichen Elektronikbauteilen und einer kleinen Elektronikplatine welche von Hand zusammengelötet werden müssen. Ausserdem wird zum Betrieb ein 9V Block und ein passendes Kabel benötigt. Siehe [[Materialien | Science-Days-Digital-2020#materialien]]-Liste unten.
- Das CERN stellt die benötigte Anzahl von Platinen kostenlos zur Verfügung.
- Als Metallgehäuse dient z.B. eine handelsübliche Blechdose die ebenfalls besorgt werden muss, siehe [[Materialien | Science-Days-Digital-2020#materialien]]-Liste unten unten.
- Die elektronischen Bauteile sowie das Metallgehäuse müssen von den einzelnen Gruppenleiter\*innen selbst vorab besorgt werden: Kosten ca. 10-15 EUR pro Detektor, plus ca. 5-10 Euro für ein Anschlusskabel und eventuelle Adapter - details siehe [[Materialien | Science-Days-Digital-2020#materialien]]-Liste unten. Die Preise variieren stark je nach Bestellmenge und Versandhändler
- Bauteile-Bestelllisten für diverse Elektronik-Versandhändler auf [[kitspace.org|https://kitspace.org/boards/github.com/ozel/diy_particle_detector/electron-detector/]], details unten unter [[Materialien | Science-Days-Digital-2020#materialien]].
- ***Neu:*** komplettes Bauteile-Kit inkl. Kabel, speziell für diesen Workshop: https://shop.kitspace.org/buy/electron-detector-parts-only/
- Gebaut wird die Elektronen-Detektor Variante dieses Projekts. Geübte Bastler können sich nach Absprache auch an die Alpha-Detektor Variante wagen, [[Übersicht zu beiden Detektor-Varianten | https://github.com/ozel/DIY_particle_detector/wiki/Assembly-Instructions#required-parts]].
### Workshop-Vorbereitung
***Alle registrierten Gruppenleiter\*innen stimmen ab 1. November sämtliche Materialien und benötigtes Werkzeug mit Oliver Keller (o.keller@cern.ch) per eMail ab.***
#### Benötigte Werkzeuge
- Lötkolben & Lötzinn
- Entlötlitze (empfohlen) oder manuelle Entlötpumpe
- Elektronik-Seitenschneider (= Seitenschneider mit dünnen Schneidekanten)
- Löcher in's Metallgehäuse via:
- Stanzeisen (mit 2, 5 & 9 mm Lochdruchmesser) und Hammer => geht sehr gut bei dünnen Blechdosen
- z.B. günstige [Henkel-Locheisen](https://www.amazon.de/MATADOR-Henkellocheisen-7200-0713-0050/dp/B00PLLPQP2), gibt's auch im Baumarkt
- möglichst schwerer Hammer
- kleine Holzplatte zum unterlegen
- oder Metallbohrer (3, 6 & 10 mm) und Bohrmaschine => bei dickenwandigen Alu-Gehäusen
- Durchmesser von Stanzeisen sollten immer eine Stufe kleiner gewählt werden als nötig, da die Löcher im weichen Zinnblech automatisch etwas grösser werden als der Normduchmesser eines Stanz-Werkzeuges
- Schraubendreher für M3 Befestigungsschrauben
- 2 Zangen (z.B. Kombizange & Flachzange) zur Befestigung der BNC-Buchse und des Schalters in der Wand des Metallgehäuses (oder eine Zange plus passender Gabelschlüssel)
#### Materialien
- die Platinen werden kostenlos zur Verfügung gestellt
- Elektronik-Bauteile:
- [[Bauteileübersicht | https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/hardware/V1.2/documentation/DIY%20detector%20-%20parts%20overview%20v1-2%20electron%20version.pdf]]
- ***Komplettes Kit inkl. passendem Kabel und Headset-Adapter*** für Messung per Handy/Laptop: https://shop.kitspace.org/buy/electron-detector-parts-only/
- Alternativ: [[Bestellnummern & Warenkorb management|https://kitspace.org/boards/github.com/ozel/diy_particle_detector/electron-detector/]] für Mouser/Farnell/RS-Online via kitspace.org (vorher [1-click BOM browser plugin](https://kitspace.org/1-click-bom/) installieren!)
- Empfehlung für Selbstbesteller: **www.Mouser.de** / [**.ch**](http://www.mouser.ch)/ [**.at**](http://www.mouser.at) (kostenloser Versand ab 50 EUR/ 54 CHF)
- ein Metallgehäuse, entweder aus dünnem Zinn-Blech (z.B. für [[Bonbons/Kekse/Schokolade | https://github.com/ozel/DIY_particle_detector/wiki/Enclosures#candy-tin-boxes]]) oder [[dickwandigem Aluminium | https://github.com/ozel/DIY_particle_detector/wiki/Enclosures#diecast-aluminum-enclosures]].
*Mindestgröße des Metallgehäuses:*
- 8 x 4.5 x 3 cm³ (Batterie hochkant)
oder
- 8 x 5.5 x 2 cm³ (Batterie flach)
- ein 9 V Block pro Detektor (idealerweise [[9 V Akku & Ladegerät|Batteries]])
- dünnes, isoliertes Elektronik-Kabel zum Anschluss des Ein/Aus-Schalters (1-2 mm Aussendurchmesser)
- 1 bis 2 sets von M3 Schrauben, M3 Abstandsbolzen (Sockelschrauben) und M3 Muttern: zur Befestigung der Detektor-Platine im Metalllgehäuse
- ein [[passendes Kabel|Cables]] zum Anschluss an **Oszilloskop, Soundkarte oder Smartphone/Laptop Headset-Anschluss**
- ein Oszilloskop (*sehr empfohlen zum testen*) oder [[USB-Soundkarte | Soundcards]] oder Smartphone/Laptop mit [[Headset-Anschluss | https://github.com/ozel/DIY_particle_detector/wiki/Cables#connection-with-a-headset-socket]]
- schwarzes Isolierklebeband
### Anleitungen
- Vorder & Rückseite der bestückten Platine (Elektronen-Detektor Variante):
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.2/documentation/3D_top_electron.png" width="450"><img src="https://github.com/ozel/DIY_particle_detector/raw/master/hardware/V1.2/documentation/3D_bottom_electron.png" width="450">
- [[zweiseitige Bauanleitung auf Deutsch als PDF | https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/hardware/V1.2/documentation/DIY%20detector%20-%20parts%20overview%20v1-2%20electron%20version%20DE.pdf]] (funktioniert gut als Handout zum Aufbauen)
- [[detailierte Bauanleitung auf Englisch | https://github.com/ozel/DIY_particle_detector/wiki/Assembly-Instructions#build-instructions]]

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The following software can be used to record pulses from the detector and measure radioactivity.
**Overview:**
* [[Signal Display & Pulse Counting|Software#signal-display--pulse-counting]]
* [[Desktop Software|Software#desktop-software]]
* [[Processing-based Audio Oscilloscope|Software#processing-based-audio-oscilloscope]]
* [[Browser Application|Software#browser-application]]
* [[Mobile Apps|Software#mobile-apps]]
* [[Energy Spectra from Alpha Particles|Software#energy-spectra-from-alpha-particles]]
* [[Graphical Software|Software#graphical-software]]
* [[Phython Scripts|Software#python-scripts]]
* [[Simulation of Alpha Spectra|Software#simulation-of-alpha-spectra]]
# Signal Display & Pulse Counting
Oscilloscope-style software for [[desktop/laptop computers|Software#desktop-software]] and [[mobile devices|Software#mobile-apps]] (smartphones/tablets) using either a dedicated [[soundcard|Soundcards]] or [[headset/microphone inputs|Cables#connection-with-a-headset-socket]] to record signals from the detector (Yes, the detectors 'imitate' microphone signals!):
## Desktop Software
The following desktop software programs have been tested to work with Windows, Mac, and Linux.
***Important note:***
Depending on your setup, the correct microphone/sound channel input must be enabled in your operating system settings as _default sound input device_. For example, if you want to use the headset connector with your detector, make sure the system is using that as default input instead of the built-in microphone. If you whistle gently and see sine waves although the detector is plugged in, the wrong sound input is selected.
***First check your sound input configuration:***
* Certain systems, like all Apple devices, require that the detector is powered on before being plugged into the headset socket! Otherwise, external microphone signals are not recorded from the headset connector.
* The microphone sound input volume should be generally set has high as possible.
* When using the **alpha-spectrometer**, *turn on additional boost/gain options* if available (check advanced sound device properties).
* For the **electron-detetcor**, too much extra amplification can hide the signal within the electronic noise. Please try different input volume settings and match the amplitudes of the signal pulse and noise range roughly to the example pulse recordings shown in the screenshots below. With certain headset inputs, *disabling of boost/gain settings* may improve the signal clarity considerably.
* The audio sampling frequency should be set as high as possible, typically 48.000 Hz. Sample resolution: 16-bit.
* In case of problems, pleases read further notes on [[Soundcards]] and [[Cables]] very carefully.
### Processing-based Audio Oscilloscope
Processing is a really nice and open-source environment geared at learning how to program.
A program file ends with .pde extension and is called 'a sketch'. Sketches can be directly run equally well under Windows, Mac OS and Linux without differences.
WaveWatch sketch for Processing screenshot, showing a typical *small electron-detector pulse*, recorded from a regular soundcard/headset input:
<img src=https://user-images.githubusercontent.com/653212/92630407-1a80f600-f2d0-11ea-903c-e01e9b5fbeb0.png width="600">
1. Download the Processing Version 3 from www.processing.org
2. Extract the zip file and double-click on the Processing(.exe) executable inside the extracted folder
3. Inside the Processing window, install the Minim library via the 'Sketch' menu / 'Import Library...' -> 'Add Library...'.
* type 'Minim' into the search field on the top, select and install the library, close the dialog window once finished
4. Select, download and extract the zip files of one of these two oscilloscope programs:
* [WaveWatch oscilloscope for Processing](https://github.com/ozel/WaveWatch/archive/master.zip): Full oscilloscope functionality, flexible zooming & triggering.
5. Open the corresponding .pde program file inside Processing and hit the big play button to start the program.
### Browser Application
Based on the Web Audio API of modern browsers: compatible with recent versions of Chrome and Firefox.
See notes below for use with [[mobile devices|Software#mobile-apps]].
***Try different microphone input volume/gain settings in your operating system***, a good range is 50% to 100%.
Depending on your particular computer audio hardware, 100% is not always the best and may hide pusles in too much noise.
* [Web browser application](https://ozel.github.io/DIY_particle_detector/data_recording_software/webGui/), screenshot of a typical large **alpha-spectrometer pulse** from a high-energy alpha particle:
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/images/webGui_screenshot.png" alt="A single pulse recorded by the web browser GUI." width="600">
***Move the red trigger level up/down with the corresponding arrow buttons*** (or cursor keys), it should be somewhat below the noise level but not too far.
Signals from the alpha-spectrometer produce broader pulses (~1 ms) like in the picture above, the shorter pulses from the **electron-detector** variant (~50 us) appear as narrow needles like in the following screenshot:
<img src="https://user-images.githubusercontent.com/653212/102107670-43b2a480-3e32-11eb-8bed-e6d58cc27efb.png" width="600">
***Update:*** There is a new mode setting! Select either "Electron-Detector" or "Alpha-Spectrometer" from the pull-down list according to your detector variant. The Electron-Detector pulses are now drawn larger and better visible in this dedicated mode.
Main source code with notes in [pulse_recorder.js](https://github.com/ozel/DIY_particle_detector/blob/master/data_recording_software/webGui/js/pulse_recorder.js).
## Mobile Apps
These apps have been tested on recent smartphones and tablets, connecting the detector with its headset socket.
*Please make sure to use the correct cable with a **4-pin** 3.5 mm jack as described [[here|Cables#connection-with-a-headset-socket]].*
Note if your mobile device is too modern and does not have a 3.5 mm headset socket anymore, adapters like [Apple's Lightning to 3.5 mm jack headset adapter](https://www.apple.com/shop/product/MMX62AM/A/lightning-to-35-mm-headphone-jack-adapter) and similar ones for micro-USB or USB-C will work as well.
In combination with a USB adapter like [Apple's Lightning to USB adapter](https://www.apple.com/shop/product/MK0W2AM/A/lightning-to-usb-3-camera-adapter), it is even possible to use the low-cost USB soundcard described in [[Soundcards]].
For Android devices and modern laptops, such adapter cables are sold as "USB On-The-Go (OTG) adapter" featuring micro-USB or USB-C connector.
* [Web browser application](https://ozel.github.io/DIY_particle_detector/data_recording_software/webGui/)
Works in recent versions of Android (in the Chrome or Firefox browser) as well as Apple iOS/iPadOS (*only* in Safari).
***Move the red trigger level up/down with the corresponding arrow buttons***, it should be somewhat below the noise level but not too far.
See the [[screenshots above|Software#browser-application]]. Some headset inputs are very sensitive and produce short oscillations for large pulses. Below is a larger Electron-Detetcor pulse recorded on an iPad using its built-in headset socket:
<img src="https://user-images.githubusercontent.com/653212/102107882-85434f80-3e32-11eb-8e6c-f4cb3436e554.png" width=600>
* The app "Smart Geiger EX" from FTLab/Technonia is compatible and can be used for counting particles. Links: [Google Play Store](https://play.google.com/store/apps/details?id=com.technonia.geiger), [Apple App Store](https://apps.apple.com/us/app/smart-geiger-ex/id921489719)
The wrong dose value given in uS/h must be ignored, only the "Count" and "CPM" ("Counts per Minute") numbers are useful and correct. The detector must be powered on before opening the app!
* Search for generic "sound oscilloscope" applications on Android's Google Play Store or Apple's App Store.
E.g. the "Oscilloscope" iOS app from [Onyx Apps](https://onyx3.com/Oscilloscope/) is rather costly but provides very good triggering functionality, which can be great for debugging the detector and if no other oscilloscope is available. Oscilloscope apps without a trigger functionality will not be useful.
# Energy Spectra from Alpha Particles
The following programs can be used to record characteristic energy spectra of alpha particles with the **alpha-spectrometer variant** of the DIY Particle Detector such as the following spectrum:
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/images/Alpha_spectrum_Majolika_ceramic.png" width="400">
This kind of software is often called MCA, which stands for 'Multi-Channel Analyzer' and dates back to former times when the modern and less abstract term analog-to-digital converter (ADC) was not yet common.
## Record and Display Alpha Spectra
### Graphical Software
There are three programs popular among hobbyists and enthusiasts for recording gamma spectrometer measurements using regular sound/microphone inputs. They can be used as well for recording alpha spectra:
* Theremino MCA: [website](https://www.theremino.com/en/downloads/radioactivity) (mulitple languages supported, open source and regular updates - always use the latest version!)
* BecqMoni (Becquerel Monitor): [website](http://blog.livedoor.jp/kabuworkman-becqmoni/) is in Japanese, but the program itself is in English. Direct [download](http://www.tradelog.biz/download/download.php/archive/BecquerelMonitor-1.0.zip). (it has not been updated in a long time but still works well)
* PRA (Pulse Recorder and Analyser): [website](https://www.gammaspectacular.com/marek/pra/index.html)
All three are freely available and written for Windows but can be used on Mac OS and Linux using the open source [Windows emulator Wine](https://www.winehq.org/).
**Using a preexisting alpha energy calibration:**
* In case of using one of the low-cost [[CM108 USB Soundcards|Soundcards]], the linear energy calibration coefficients usually called `b or m (slope)` and `c or t (offset)` can be simply copied [[from here|Energy-Spectra#energy-calibration]]. Some programs like BecqMoni ask for a third coefficient for a quadratic equation in the form of `a*x² + b*x + c`. The quadratic component `a` should be set to zero in this case.
### Python Scripts
The following two scripts have been developed in conjunction with the scientific article.
* Pulse recording with [pulse_recorder.py](https://github.com/ozel/DIY_particle_detector/blob/master/data_recording_software/pulse_recorder.py).
This program must be started from a terminal window as `python3 pulse_recorder.py` and opens an oscilloscope-style window showing the trigger level as a red line and detector pulses in yellow. The green line represents the energy threshold value at around 0.5 MeV that distinguishes between pulses from electrons (smaller) and alpha particles (larger).
It is ideal for longer, unattended measurements, e.g. overnight. All reference measurements in the paper have been recorded with this.
More notes inside the script.
* Pulse analysis with [analyse_and_plot_pulses.py](https://github.com/ozel/DIY_particle_detector/blob/master/data_analysis_and_reference_measurements/diode_detector/analyse_and_plot_pulses.py)
The raw detector pulses recorded from the python script above or the web browser application, are loaded from the raw data files (stored in Python's Pickle or the MessagePack format). This script analyses all recorded detector pulses and converts the measurement data into convenient time series histograms and generates calibrated energy spectra.
**This script is only intended for the alpha-spectrometer variant.** Measuring [[energy spectra|Energy-Spectra]] with the electron-detector variant is not very useful and would also require adaptions in the analysing algorithm.
## Simulation of Alpha Spectra
Since the energy spectra of alpha particles can be difficult to interpret, especially when recorded in normal ambient air conditions, it can be helpful to simulate certain characteristic alpha spectra. See further notes in [[Energy-Spectra|Energy-Spectra#alpha-particle-spectra]].
A freely available program for simulating alpha spectra is AASI (Advanced Alpha-spectrometric SImulation), [download link](https://www.stuk.fi/web/en/services/aasi-program-for-simulating-energy-spectra-in-alpha-spectrometry/thank-you-for-your-registration-download-the-aasi-program).
Simulation steps:
1. Load the [detector settings file](https://github.com/ozel/DIY_particle_detector/blob/master/data_analysis_and_reference_measurements/diode_detector/sim/AASI_simulation_files/BPX61.det) from the repo, representing the BPX61 diode and properties of this particular amplifier circuit.
2. Define the source with a certain activity and select a radioactive element or a specific alpha particle energy.
3. Define any additional passive layers between source and detector: depth/width and _density_ of the surrounding air and for example guess the density and thickness of protective paint layers (in case of uranium glaze, the orange/red paint is usually covered by a thin transparent glaze).
4. Run the simulation
5. Compare the simulated energy spectrum with your measurement
6. Repeat and adapt steps 2.-5. until the shapes and positions of the peaks roughly match

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### Low-cost USB Soundcards (CM108)
For high precision and better reproducibility of alpha particle measurements, a dedicated small USB soundcard (3 - 10 EUR, depending on the [distributor](http://www.aliexpress.com)) is recommended:
<img src="https://github.com/ozel/DIY_particle_detector/raw/master/images/low-cost_usb_audio_interfaces.jpg" width="300">
The ICY-BOX IB-AC527 on the left and the K&ouml;nig Electronic CMP-SOUNDUSB12 on the right ("3D Sound Controller 5.1") use both a chip series from C-Media Electronics Inc: [CM108 datasheet](https://www.cmedia.com.tw/products/USB20_FULL_SPEED/CM108B).
It's microphone input well specified with a flat frequency response in the required 1-5 kHz range and good signal to noise ratio. As standard USB Audio Class devices, no drivers are required and they are recognized as a regular audio input in many operating systems, including Android & iOS.
The effective input impedance of the CM108's microphone input is about 210 k Ohm according to this [report](https://dalmura.com.au/static/Soundcard%20mods.pdf). _Please note that none of the modifications described in that report are necessary in order to operate the alpha-spectrometer with the shown energy resolution._
I have personally not tried any modifications to the stock CM108 USB soundcards. It would certainly impact the alpha energy calibration and require a new one.
Since the original input impedance of those soundcards is rather low compared to a standard oscilloscope input with 1 Mega Ohm input impedance (directly at the BNC socket), the measured signal pulses are quite smaller when recorded with soundcards.
#### Recording settings
All reference measurements have been taken with one of the blue C-Media CM108-based K&ouml;nig Electronic USB soundcards using the following settings:
- 48 kHz sampling rate
- 16-bit sample resolution
- *100% microphone input volume level*
- *gain boost enabled*
#### Operating system specific tips
The CM1018 USB devices usually appear in the system as "USB PnP Sound Device".
*The CM108 chip has a gain boost setting of 22.5 dB which* ***must be enabled*** *when reusing the [energy calibration](https://github.com/ozel/DIY_particle_detector/wiki/Energy-Spectra#energy-calibration).*
On Mac OS X, there is no option for enabling the gain boost, it seems on by default. In "Audio MIDI Setup", the input device may show up as 2-channel although it is actually mono only. Adjust the resolution, sampling rate, and input level there (level of 1.0 = 100%).
Then make sure it is selected as the current audio input device in "System Preferences / Sound".
On Windows, a 3-letter option called "AGC", "CGA" or "CAG" ("Adaptive/Auto Gain Control") is present in the advanced sound device settings. This is rather wrongly labelled as there is no adaptive gain feature in the chip. It represents the gain boost feature and should be therefore turned on. Also, set the input level to 100%, try to make sure that no additional/hidden software amplification is enabled.
On Linux, the graphical command-line tool `alsamixer` can be used to adjust the microphone input settings of all attached soundcards. Select the external USB device with the hotkey "F6" followed by "F5" to show all controls. Turn up the levels on all channels called "Mic" to 100 (there are two-channel controls labelled as "Mic" in my case). Enable the "Auto Gain Control" setting (representing a static gain boost) by hitting the "m" key for that channel (un-muted = On, muted = Off). This control setting should then show "00" instead of "MM".

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If the detector does not work properly or you are not sure about it:
1. compare again the *correct position of each component* with the parts overview sheets:
[electron-detector](https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/hardware/V1.2/documentation/DIY%20detector%20-%20parts%20overview%20v1-2%20electron%20version.pdf) ([German version](https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/hardware/V1.2/documentation/DIY%20detector%20-%20parts%20overview%20v1-2%20electron%20version%20DE.pdf))
or [alpha-spectrometer](https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/hardware/V1.2/documentation/DIY%20detector%20-%20parts%20overview%20v1-2%20alphaspectrometer%20version.pdf)
- doublecheck the *orientation* of the [[Diodes]] D1-D4 (where is the anode/cathode pin?)
- doublecheck the *orientation* of the black amplifier chip U1 (where is pin 1?)
- doublecheck the *orientation* of the large electrolytic capacitor C8 (where is its negative/minus pin?)
1. connect the detector to a real hardware oscilloscope
- debugging the detector directly on a microphone/headset input by using a software oscilloscope is likely to introduce additional sources of problems
- test those audio inputs at least with a real headset or microphone before attaching the detector
- make sure that the software oscilloscope is recording from the correct channel
- increase the microphone input volume/gain settings of the operating system, a good range is 50% to 100%
- try different gain settings while always adjusting the trigger level accordingly, a setting of 100% may produce too much noise and can hide signal pulses completely
- be sure to use the correct [[Cables]] with the detector
1. if you disconnect the battery and measure across the battery connector with an ohmmeter/multi-meter, it should read about 9-10 kilo Ohm
- if the resistance is close to zero or zero Ohm, there is a short-circuit (e.g "a bridge") between two connections that must be found and removed
- if the resistance is much higher or not measurable, some solder joints might be bad and should be resoldered
1. the signal line on the oscilloscope screen must change briefly every time when you switch the detector on/off or re-connect the battery
- if you see no reaction, re-check all the wire connections, solder joints
- make sure that the [[battery|Batteries]] is *not empty* and delivers at least 8.5 V when disconnected
- *as long as this issue is not solved, it makes no sense advancing to the other points below*
1. try to measure something that is proven to be considerably radioactive
- a vintage piece of uranium glass from the flew market that produces at least 1 count per second with a Geiger-Müller counter
- a big bag of potassium salt = KCl. Sold as "No-Salt", "Lo-Salt" or "sodium-free dietary table salt" or simply as pure KCl from a pharmacy.
1. put the object as close as possible in front of the diodes, if possible inside the **metal eclosure** surrounding the detector!
1. put a thick black piece of cloth or towel on top of the [[detector case|Enclosures]] to make sure that all residual light is blocked!
- consider a darker room and avoid bright sunlight during the first tests
1. do not touch the detector or the table during the measurement (important with thin-walled candy tin boxes)
- if you hit the detector hard and quick with a finger, the vibration should appear as a short sine-like wave
1. compare the signals of your detector on a real oscilloscope with my reference screenshots
- ***Electron-detector reference pulses from KCl:***
<img width=600 src=https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/images/oscilloscope_pulse_electron-detector.png>
- ***Alpha-Spectrometer reference pulses from KCl:***
<img width=600 src=https://raw.githubusercontent.com/ozel/DIY_particle_detector/master/images/oscilloscope_pulse_alpha-spectro.png>
(These pulses are only from electrons, alpha pulses would be even larger!)
Please refer to [[Oscilloscope Measurements]] for further details.
- if the noise range of your signal is much small or larger than the shown ones:
- there is most likely **still too much light reaching inside the case**
- or another electromagnetic source of radiation closeby and interfering
- there could be still a problem with how the components are soldered. Please re-check according to 1.
- make sure the switch and output connector are both firmly fixed to the metal walls.
- it will not work inside a plastic box, **the [[enclosure|Enclosures]] must be made from metal** (Faraday cage)
- if you see continuous 50 Hz, 100 Hz, or much higher frequency sine waves:
- most likely some fluorescent neon-tube or LED light is still reaching inside the detector enclosure
- a high-power electronic appliance or machine (electromotor, fridge compressor etc.) could create too much electromagnetic interference radiation (EMI) - try changing the room or even the building
- if the signal changes when the opened detector enclosure is exposed to light, that is generally a good sign and positive test result. but the shown reference signal pulses and noise range can be only observed if the *closed enclosure is completely blocking any form of light*.
- when accidentally swapping the ground and output signal connection or with certain soundcards/headset inputs, *the pulses may appear inverted and go upwards instead of downwards*:
- check for pulses above the noise level (instead of below it) by moving the trigger level of the oscilloscope upwards
Please start a new thread in the [GitHub Discussions](https://github.com/ozel/DIY_particle_detector/discussions) if none of those tips did the trick.
Also, consider asking a local maker space or fab-lab for support, they'll be likely glad to help. :-)

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The hardware design and documentation in this Wiki are licensed under the [CERN Open Hardware License v1.2](https://github.com/ozel/DIY_particle_detector/blob/master/hardware/V1.2/CERN_OPEN_HARDWARE_LICENSE_OHL_v_1_2.txt). Please refer to the [usage guidelines](https://ohwr.org/project/cernohl/wikis/Documents/CERN-OHL-version-1.2) of the license for further details. The software is provided under the terms of the [BSD license](https://github.com/ozel/DIY_particle_detector/blob/master/LICENSE).
General project overview in [main readme](https://github.com/ozel/DIY_particle_detector/blob/master/README.md), scientific background in [corresponding paper](https://www.mdpi.com/1424-8220/19/19/4264/htm).

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* [[Overview|Home]]
* Hardware/Electronics
* **[[Assembly Instructions|Assembly-Instructions]]**
* [[Batteries]]
* [[Cables]]
* [[Diodes]]
* [[Enclosures]]
* [[Soundcards]]
* **[[Troubleshooting]]**
* Measurements
* [[Oscilloscope Measurements]]
* [[Energy Spectra]]
* **[[Software]]**
* Supplementary Material
* [[Diode Characterisation]]
* [[Pixel Detectors]]
* **[[Picture Gallery | Gallery]]**
* Workshops
* [[Science Days Digital 2020]]
* Project Support
* [[Fellow FreiesWissen Project]]