detector projects using Philips XP5312/SN ?

[jbeale]

I was interested to read about the "Prutchi paint-can scintillator" from 2013 described at https://www.diyphysics.com/wp-content/u ... llator.pdf which uses a Philips XP5312/SN PMT with a plastic scintillator block, and reportedly measures 1000 CPM in an area with a 5 uR/hr (0.05 uSv/hr) background.

Now I see ebay listings from The Rad Lab (iRad Inc, Stuart FL) for items including "3 inch Scintillation Detector Kit - Includes most everything you need & instructions", a slightly cheaper "3 inch Scintillation Detector BASIC KIT Includes PMT Scintillator Electronics & BNC", and also a complete assembled unit "3 inch Diameter GAMMA SCINTILLATION DETECTOR w/ Bicron BC412 Organic Scintillator", the latter with a reported 2000 CPM at an unspecified background level.

I'm just curious if anyone could confirm if the kits correspond to the detector part of the Prutchi paint can project, and if anyone here has tried using them to build a detector with useful results. Thanks for any info!

[Rob Tayloe]

I have purchased a number of items from Tom Hall (aka iradinc on ebay). I find his stuff to be a good value and works as advertised. I used to teach a nuclear lab class to engineering and physics students; students were required to complete some small project as part of the lab class. Some students chose to build detectors. It was interesting to observe the number of electrical engineering students that had never soldered anything prior to building a radiation detector kit.

The "Prutchi paint-can scintillator" mentioned was one of several experiments that David Prutchi (whose profession was developing medical devices) conducted with his then 14 year old daughter. I found this to be an interesting experiment and obtained several of the iradinc kits (and new paint cans from a local paint store). There are several kits available. One kit has the PMT and components to make the voltage divider (resistors and one or two caps). One would need to separately obtain a scintillation crystal. It should be noted that the plastic scintillator is not suitable for obtaining gamma ray spectra where one could identify notable photo peaks. The plastic scintillator does make a very sensitive gamma detector (and betas if one uses a very thin "window".) There is another kit that includes a cylindrical plastic scintillator. The Prutchi instructions show how one should couple the scintillator to the PMT and then place the crystal / PMT into a paint can. I have attached a photo of this kit.

I have also purchased some ready-made plastic scintillators. It will be necessary to couple the detector (crystal / PMT) to some device to provide the needed high voltage (around 900 volts) and to count the pulses. I have used a variety of surplus devices for this task.

If the objective is to begin doing gamma spectroscopy, an inexpensive approach is to obtain a good, restored NaI detector (these are available on the iradinc ebay store) and something like the gamma spectatacular MCA device (also available from iradinc or directly from this website). One would then need software to obtain the gamma spectrum (e.g., theremino, PRA, or the new Impulse program). Links to this software can be found on this website.

Software to obtain gamma spectrum from GammaSpectacular MCA
https://www.gammaspectacular.com/blue/s ... -downloads

Kit with plastic scintillator
https://www.ebay.com/itm/263250251252?h ... Swxu1Z2Bxo

s-l1600.jpg

Kit with PMT (need to obtain crystal)
https://www.ebay.com/itm/261918290241?h ... SwEeFVTQGS

s-l1600 (1).jpg

Assembled 3-inch plastic scintillator
https://www.ebay.com/itm/262488549964?h ... SwGvhT4pKF

s-l1600 (2).jpg

Refurbished NaI detector -
https://www.ebay.com/itm/252158579203?h ... Sw4GVYJ4At

s-l1600 (3).jpg

[jbeale]

Thank you for that very informative post! So far I have a few consumer spectrometers (Radiacode 102 and Measall KC761), and I have a surplus NaI(Tl) crystal on order. However at the moment I was curious about simply counting gammas to observe background variations, vs any sort of spectroscopy. The small scintillators within my budget give me a certain count rate and therefore sqrt(N) uncertainty vs time, but I was looking for higher rates to achieve lower fractional uncertainty.

I already got some material, a 7" long Bicron BC412 block and some scraps of BC408, from iradinc on ebay. I used the BC412 block with a 6x6 mm SiPM to make a DIY gamma counter, making a crudely prototyped circuit based on the OpenGamma project by Matthias (NuclearPhoenix) at https://github.com/OpenGammaProject/Open-Gamma-Detector
Just an hour ago, for example, it showed a dramatic increase in counts, from 200 cps up to 1039 cps at the same time there was a light rain sprinkle outside. So maybe I have measured a background change due to a radon washout event. However, I notice my SiPM + opamp + threshold detector circuit is highly sensitive to the SiPM bias voltage. For example, going from +29.1 V bias to +29.3 V bias more than doubles my count rate. I expect higher bias voltage increases my multiplication factor, so my comparator threshold reaches lower-energy gamma events, but maybe also more thermal noise current from the SiPM itself. So my cheap adjustable DC-DC stepup converter from ebay, that I'm using for the bias voltage until I build a better one, may not be stable enough to have great confidence in quantitative measurements.
So at any rate I already have something, but I was curious to try a PMT-based detector to compare it with.

[jbeale]

...and lest anyone be left in suspense, I confirmed my casual lightproofing job around the scintillator block was inadequate. Using a flashlight, I found I could make the count rate jump up when illuminating specific corners, just as it apparently had when the sun broke through the clouds yesterday, making the peaks on the plot shown.