I saw this neat particle spectrometer (also works as a detector) published under CERN’s open hardware license: https://scoollab.web.cern.ch/diy-particle-detector

I used to design these in grad school for fun, but I was making boards by hand in those days, so I didn’t have any convenient Gerber files to send off to the local factory. I wanted to add a nuclear/quantum/modern physics component to a STEM course, so thought this would be pretty great!

There are a few things I would do differently on the board – I’d go SMT (especially for capacitor C5), but I get that it’s done this way for ease-of-assembly. I’d also maybe increase the trace width on some traces, to make sure the factory ships fewer bad boards. I also moved capacitor C8 to the other side of the board, so the distance between the radiation window and the board would be smaller.

All of these things really amount to personal preference, and overall the board is really nicely done! I might redesign the whole thing as SMT later though to reduce size and cost.

As configured, this board detects moderately penetrating particle radiation, like beta radiation. I could have configured it to detect alpha particles, but I’ve already built a few alpha spectrometers, so figured this would be more interesting.

The component that handles the actual ‘detecting’ is the array of 4 PIN photodiodes:

These are a common choice for low cost solid-state particle detectors. Incident radiation causes a tiny voltage on one end of the diode, which is amplified tremendously by the operational amplifier. The extremely high amplification required, means an extremely stable power supply (e.g. a battery) is required, and the entire device should be in a light-proof Faraday cage (e.g. a metal box).

I made 2 units, because the minimum order quantity for the boards was 5, and I’m sure I’ll think of more than one use for the device. Hopefully I’ll be able to detect muon radiation to demonstrate time dilation, beta particles from K-40, and perhaps even detect antimatter via rare K-40 β+ decays.

I’ll try a banana as an antimatter source first, but a banana doesn’t produce very much antimatter (…wow, this is an unusual sentence). Probably I’ll need to go order some pure KCl, and even then low detector efficiency and the rarity of that decay mode will be a (possibly insurmountable) challenge.