I had a BGO detector that I really didn't like. Yesterday I disassembled it and found out why, The crystal was more a fragment than an actual crystal. I dissolved the epoxy that was used to mount it to the PMT (a Hamamatsu R6095). When it came time to remove the crystal, it either pulled up a chip of glass off the head of the PMT or it uncovered an existing chip. I was pretty disappointed with the damage, but figured I might get some use out of it yet. I used silicone grease to couple a 23x60mm NaI crystal with integrated .4 nCi 137Cs stabilization source to the PMT. After a few tests, I was happy with the results so I made something a bit more sturdy than black tape. After soldering a mu metal shield to the tube, I put heat shrink over the tube. My new shield only allows for head on measurements, so I went ahead and wrapped the side of the crystal with 2 mm of copper. The crystal was then mounted with silicone grease, black tape and heat shrink.
I collected a background spectrum for a few hours inside the shield and was pleased with the results. I'm still waiting for my pewter sheet and copper sheet to arrive by mail to finish up the shield, but it seems to be working great.
Scintillation crystals, PMTs, voltage dividers etc...
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