Looking for some CZT sensors and detectors to buy, we found images and schematics of the CdZnTe probes of the URSA-II gamma spectrometer.
EV CZT CdZnTe modules - These probes could sometimes be bought on eBay.
Look at the picture and the schematics: http://groups.yahoo.com/group/GammaSpectrometry/attachments/folder/1224057931/item/1517826320/view?picmode=original&mode=tn&order=ordinal&start=1&dir=asc
A lot of times the sensor is Ok but the electronics is failed. However we only need the sensor because the HV and the preamp/conditioner is already into the #theremino PMT_Adapter.
However I read that:
- The electronics is usually broken:
> If anyone's module isn't working, my first guess is that the FET is kaputt.
- The HV has to be very carefully set:
The bias voltage should be increased from zero very slowly in order to avoid a sudden HV transient input on the FET gate due to capacitive feed through via the CZT element. This goes for all preamps (FET and bipolar), using all sensors (PMT included) when there are no protection diodes on the input. I am not so sure I would take the bias voltage past 500 VDC, but I am not really certain of that. The easiest (and perhaps the safest) way to determine an unknown bias voltage is to start low and slowly increase the HV until noise begins to dominate the signal, then back off to a lower voltage.
- The handling of the sensor is problematic:
If you open it up and look inside there is a superfine gold wire from the top of the semiconductor to the board, and if this wire is damaged the unit has had it.
It worked for me with a 60V bias. If you look at the cables, you can see that it is not designed for 1000V, the cable insulation just isn't rated for this kind of voltage. Unlike a PMT the signal does not become stronger with higher bias voltage.
Faster sampling is the way to go, I was using an E-MU sampling at 192 Khz
- This sensor is sensible to the low energy Gamma and X-rays, maybe it is useful to do XRF - X Ray Fluorescence:
Remember these are not going to pick up high energy gamma, but they have a great resolution in the X-Ray region. I think they would make a good XRF.