Club Jameco

Large area about 10mmx10mm PIN photodiodes with Scintillator coating on top can sense Cosmic Radiation and also man made radiation. However, electronics is not easy as charge or bunch of electrons that form pulse are very low and thermal noise at room temperature is high, and diode leakage current run into 100s of pA which makes it very difficult. I think people already having good electronics background can try such idea. Sources for such PIN diodes are companies like Hamamatsu Japan, Detection Technology Finland, IRD Inc USA (www.ird-inc.com). etc. You can't pick up some photodiode and get results. It is very tricky business and highly professional companies manufacture these items. I will say good luck if you wish to try these.. PIN Detectors cost about US$100 plus. and then sensitive electronics may also cost that much and one also requires some kind of metering device. like pulse counter with displayor count rate meter etc. It should be expensive project and chances of success depends on material and how you make it. I am in this line and have about 1000 such detectors that work well but they are expensive. Working with GM Tubes is simple but they require high voltage 400-500V and are bit unsafe as they can give shock. One can purchase from LND Inc USA or Philips etc.

Need to see more, can we move forward, how many votes are needed?

A few suggestions that I learned building one of these myself: Use a well-soldered metal shield to entirely enclose the photodiode (array) and transimpedance amplifier to avoid swamping the signal with noise. Make sure the PCB is thoroughly cleaned after soldering, since any residue near the TIA will leak current and mask your signal. Use a guard ring around the high-impedance node to further shield it. Use three or more resistors in series rather than one for the large TIA feedback, to reduce parasitic capacitance which will otherwise limit your bandwidth and TIA gain. Buy a check source (United nuclear sells a bunch) for testing. Cs-137, Eu-152, and Co-60 work pretty well. Am-241 from a smoke detector produces a very low energy gamma which is close to the noise floor of the circuit, and challenging to detect. You can significantly increase bandwidth and the active volume in the detector by reverse biasing the diode by 30V or more. If you do a good job, you'll even be able to estimate the energy of the particle by measuring the height of the output pulse. Good luck! It's a fun project.

The mantle from a white gas lantern (e.g. Coleman) usually contains Thorium, an alpha emitter.

Aluminum foil is too thick/dense to let alpha's through. You'd need something like radfilm which is expensive and hard to find. You'll likely need something conductive to shield the diode to keep hum pickup down. I had to build mine in a Altoids box and use Al foil over a hole to keep hum down so the circuit would work. Also, unless the diode has no covering over the bare silicon surface, it will filter out the alpha's anyway... Also, I wouldn't recommend using the Am241 pit from a smoke detector for any testing. You can do it, but it's very, very illegal to do. If you put that into your instructions, I'm quite sure you'd get unwanted attention from the authority's ! A piece of uranium ore would work quite well and is inexpensive and legal.

Is this the one that uses the BPW34 or 61? I've tried to breadboard this one but I think the interlead capacitance around the LM358 kills it... Looking forward to seeing if we're working from similar schematics. I may just have to go ahead and PCB this one.

Does the photodiode get a cover? If so what is it? Is it transparent to Alpha, beta, and Gamma rays yet opaque to near IR and visible light? Or do you just use it in a dark room?

I built one about 35-40 years ago. Worked well; very compact. Large-area photodiode was expensive and hard to find, and required risky modifications to the TO-5? package, to be capable of detecting alpha radiation. I still have the schematic, etc. somewhere in my files.

Are you going to make this project available in a schematic?