GammaFreak: An Affordable, Homemade Gamma Ray Spectrometer and Geiger Counter

I built this spectrometer from scratch for less than $150 USD. It can reliably identify radioactive samples and their constituents, and doubles as a Geiger counter for surveying. The circuit schematic can be found here: drive.google.c...
Thanks for watching, part 2 coming soon!

[@Neptunium]

Pretty cool. Maybe add another cheap CsI to compensate for the low resolution and wire it in anti coincidence? Just for fun! Great job!

[@polt3rgeist407]

This is a great project for 150 USD

[@DolezalPetr]

Ok, this is awesome, would be nice to make a proper pcb for it, I will try to find a suitable photomultiplier tube and recreate the project.

[@GeigerCounterVirtualMuseum]

You know your stuff. Very interesting.

[@membola]

cool,, thanks for uploading this video!

[@project-326]

what scintillation crystal is used in front of the PMT? The PMT only detects visible photons by itself, not gamma ray photons...

[@dg0mg]

It a CsI(Tl) Crystal, Volume ~5cm3, already coupled to the Mini-PMT. The shown complete unit comes out of the "Radiation Pager STE mini" (google for it).

[@poloniopi5579]

The tube is a R7400U and being previously used for gamma radiation detection so according to datasheet it should be CsTe or CsI i think

[@xenotimeyt]

@@poloniopi5579 He says in the video, it's a CsI(Tl) scintillation crystal

[@poloniopi5579]

Good video! I'm looking forward to build one of this. I'm curious about what this would show, if you leave this running several hours ( is that posible?) with a sample of common sand , rocks or even concrete .... Would it detect traces of tiny quantities of radiactive isotopes ?

[@patsauber4843]

Thanks for showing schematic. I think I have the same small PMT + scintillator off ebay, couldn't resist for the price. It's got a bunch of short colored wires where it was hacked out of some other assembly. How do you tell which wire is which?

[@dancevideo2]

One puzzle about the schematic: don't you need constant, fixed DC voltages on the photocathode and all the dynodes to get any decent energy resolution for your spectrum? I see the HV diode D3 to turn the HV AC voltage from T1 || C6 into DC, but I don't see any capacitors on the DC side of the diode, except for intrinsic diode capacitance and stray circuit capacitance, which I would guess is maybe just a few pF? Given that diode is not perfect- there will be some leakage, also there is some variable photocurrent dependent on gamma activity, and there is always 84.7 megohms of bias resistor loading, I would expect there to be significant voltage ripple. But apparently that bias stability is good enough, in this case? What is the actual HV bias voltage in operation?

[@dancevideo2]

OK, at 1:40 I see a pair of blue ceramic HV capacitors in parallel connected to the white wire coming from the large rectangular 20 kV diode, while the transformer connects to the other terminal on the diode, through a black wire. From those capacitors, there are red and white wires going to the board holding the bias chain resistors and PMT assy. So the possibility exists that the schematic shown at 6:53 showing no capacitor on the DC side of the diode, does not precisely represent the actual build.

[@guytech7310]

Yeah. It going to be a very noisy HV power supply. Its not how I would do it!

[@guytech7310]

Very noise HV power supply. Ideally a very low noise HV power supply is required for good results.

[@Desertprophet83]

Nice video !! How nbig is the crystal?

[@Wtfinc]

How much was ur tube? Will it detect alpha and beta too or just gamma?

[@poloniopi5579]

Well...I bought 3 of this PMTs and any of them is working. 😢...I feed it with 800V taken from a cheap clasic Marx generator power supply that can deliver 800V at 0.8mA (more than enough) using about 15V. I filter the high voltage with 4 capacitors of 10nf and 4 20kohm resistors. That leaves some ripple maybe in the 10v range over the 800V high voltage. And that''s all i see in the output at pin 9 ( white cable). No jumps or signal when i put a thorium welding rod or uranium mineral near the pmt. No matter if i take the signal through a cap or resistor. The pmt uses the 330kohm resistors recomended in datasheet.Tested with 10Mohm at first try i see no difference. In this video, ripple must be much bigger and it seems it has no influence, so i think the pmts are dead.I have checked and rechecked voltages at each dynode and connections and it should work!!...I don't know what more could i check.

[@guytech7310]

You need a scintillator like NaI(th) or CsI(Th) coupled to the PMT. PMT alone will not detect gamma radiations (well perhaps at something like 0.00001%). If you want to test your PMT tube, than use a foil over the PMT with a pin hole, and use a LED in a dark box to see if the PMT output produces anything. Sorry if have a Scintillator coupled to the PMT (I cannot gauge from your comment).

[@poloniopi5579]

@@guytech7310 Yes, this PMTs have the scintillator inside. In the video here you can see there si just a PMT.

[@charliemopps4926]

Given its been almost a year and no part 2, I'm assuming you're dead? likely due to gamma rays?

[@andrew_z_012]

nice

[@wzup77ify]

And I thought I was bad at soldering

[@spectrofreak9988]

Hey man I've got a degree in chemistry, not EE 😂. To be fair the shitty connections you see have been desoldered and resoldered 10+ times since I'm testing new parts of the design, but you're not wrong lmao

[@Desertprophet83]

Did you calibrate the spectrometer?