| Geiger tubes are click counters - number of gamma ray events within a large window, but was that click from Potassium by products, Uranium decaying, or Thorium falling apart?? Or, shock, horror, something "radioactive" from atomic fallout!! You'll never know. If you want to identify stuff, you'll be looking for an energy spectrum. If you're after an actual spectrum and you're thinking DIY then a starting point is a thalium doped sodium iodine cyrstal and electronics https://alphaspectra.com/scintillation-detector-manufacturin... https://www.alibaba.com/product-detail/2-inches-NaI-Scintill... Alibaba is listing a single 50mm round x 50mm thick crystal plus electronics at 3K USD each (less than 10) which seems steep to me given years back we used 42 litre crystal packs (with CSIRO grown crystals and in house PhD electronics engineers, etc - so YMMV). Now your problem is sampling the output levels several thousand times a second, binning the counts, and having a calibration source and compensating for tempreture drift. You can buy a box that'll do that for you or you can <cough> DIY that with reference to radiometric survey field guides (there's one from AGSO - probably Bob Minty has his name on it). A good all in one handheld is probably something like https://www.radiationsolutions.ca/wp-content/uploads/2020/03... which is one of those "contact us and get a quote" jobs from a Canadian company of good repute with Jens Hovgaard, a Finn, as the Tech CEO | President. He knows his stuff and has an industry algorithm named after him .. although others did similar work elsewhere about the globe. |