Improved "Geiger" counter using a Pico

[NuclearPhoenix]

I built a so-called "scintillation counter" with a Raspberry Pi Pico. It's a much more powerful and sensitive device than a conventional Geiger counter to detect gamma radiation. It uses a scintillator crystal to convert the gamma-rays to visible light, a silicon photomultiplier (SiPM) to convert the light into current pulses and the Mini SiD board, a front-end signal processing board for SiPMs. The digital signal going from the Mini SiD is then fed into a digital pin on the Raspberry Pi Pico. The Pico essentially counts the pulses produced by the gamma radiation and displays the current count rate on a standard SSD1306 OLED.

As you can see, the count rate with this small 10 x 2.5 cm board is typically at around 25 counts per second (just natural background) with my setup here, whereas you typically display in counts per minute with Geiger counters.

Test Setup

8895491681331074814.jpg (192.12 KiB) Viewed 1742 times

Mini SiPM driver board (Mini SiD) with attached scintillator crystal

img2.jpg (123.53 KiB) Viewed 1742 times

If you want to learn more about the project, this is all part of the Mini SiD project that I've been working on the past couple of months. Everything is fully open source and I have a Hackaday project page, as well as a GitHub repo with complementary documentation. It's fully certified as open hardware by the OSHWA

https://github.com/OpenGammaProject/Mini-SiD
https://hackaday.io/project/188090-mini ... iver-board

There is already somebody who built himself a nice little device using a very similar approach to me here. The Mini SiD board he is using there is already outdated by now, but the form factor and principle of operation remain the exact same. Thanks to RD-Gammaspectra for the neat example!

https://rd-gammaspectra.xyz/?p=255

Complete 3D printed enclosure with OLED

example.jpg (54.14 KiB) Viewed 1742 times

Let me know if you have any questions or suggestions!

[OAvKart]

Very cool.
Have you tested it against a known source?
I have an old Civil Defense Geiger counter whose CMP meter doesn't work anymore. Definitely just a few clicks per minute, unless the tube is near the check source or some pre-1940 uranium glass that I have.

[NuclearPhoenix]

Sorry for the late reply, I didn't get any notifications.

Yes, I have a couple of samples here that I can test. It's mainly all the other samples that I use to test my spectrometer (also built using a Pico). Lu-176, Am-241 as well as some N.O.R.M.s for example. I can detect <4 g of Lu-176 with almost double the background activity close to the scintillator. A 0.8 µCi ionization smoke detector close to the scintillator yields about 200 cps. That's with an 18 x 30 mm NaI scintillator (the one you can see in all the pictures).

It's pretty easy to set up. You just need to set the SiPM voltage (~29.6V or so), turn the gain to the maximum, connect the digital output of the board to an interrupt pin on the Pico and then play around with the threshold until you get a reasonable value for the background radiation (in my case, with this scintillator, around 25 cps). If you wanna do spectrometry, it's not as easy, but the driver board will still make it a lot less of a pain to deal with the SiPM in general.

[NuclearPhoenix]

Here is a short demo video of the Mini SiD board with the scintillator and SiPM. I'm using an Arduino Uno here, but it works pretty much the same with a Raspberry Pi Pico.

https://youtu.be/oyNexoNbS_0

[NuclearPhoenix]

Here is a great video on a DIY scintillation counter build:

https://youtu.be/t7-f01MC4a4

This is the same user with the blog post and the image from above, but this time it's sort of a guide on how to build one yourself

You don't even need to use a Raspberry Pi Pico anymore. As I've shown on Hackaday and in my previous video, you can use a standard Arduino UNO or even less, something like an ATTiny...

[NuclearPhoenix]

By the way, if you want to get your hands on one of the Mini SiD boards or if you want to support this project, feel free to have a look at my Tindie store. I have fully-assembled boards in stock there, so it makes it much easier to get started without having to worry about (soldering) all the SMD parts. There is also an option to use Kitspace, of course, if you want to DIY everything on your own.

https://www.tindie.com/products/29487/

Beginning from tomorrow, 05/06/2023 there will also be a week-long discount of -33% of the price on Tindie, so it's very cheap currently.

I'm also trying to do more showcasing and some tutorial videos on Youtube at the moment, so stay tuned.

[kip_the_elder]

That's a really cool project.

[NuclearPhoenix]

Thank you!

[NuclearPhoenix]

Another very intriguing build, this time by user dc1rdb, who described some of the build detail on GitHub: https://github.com/OpenGammaProject/Min ... cussions/9

It's a mini SiD connected to a microcontroller that works like a voltage controlled oscillator with a buzzer! It'll change it's output tone frequency with the measured activity. There is a really cool video on GitHub (link above), that I can't really show you here, where he demonstrates the device packaged in a tube with a 3D printed handle. The samples he has collected here are pretty impressive, especially since he's got no problem detecting the rocks already from a couple of meters away.

img.jpg (90.44 KiB) Viewed 539 times