I was able to finish putting together a nice 2X2 CsI(Tl) detector this weekend using one of Luuk’s fine crystals. I have been trying to complete the project for the last month, but very happy with the final results.
I built the detector extra rugged for field use, and included a Ludlum style C connector since I will make this one of my primary companions for use with a good Ludlum analog meter. I spun the crystals can from 6061 Aluminum rod on my lathe and used some very thin aluminum flashing material for the front window that was epoxied into place. The flashing material is very strong, but only .25mm thick, so it should give me very good low energy response. The sides of the can I worked down to 1mm thickness on the lathe, tapering thicker where it attached to the main mu-shield body of the probe. The mu-shield was taken and cut down shorter from another Hamamatsu detector assembly. I used an 8-stage Hamamatsu R6231 with VD wired directly to the pins to keep the probe dimensions short. Overall length of the probe is just over 7.5 inches including the connector.
CsI(Tl) is much denser than NaI(Tl), so this 2” probe should perform more like a good 3” NaI probe only much more compact. Although the crystal itself is not very hygroscopic, I sealed it up very well and made the housing watertight to withstand the rigors of outdoor use. CsI(Tl) is also much less resistant to thermal shock and cracking from bumps and drops, making this probe ideal for use in the field.