I need help with broken HPGe Princeton gamma detector

[Vojislav]

Hello,

I have HPGe Princeton gamma detector. I connected it and cooled it but when I try to record standard or background radiation I get specter that is populated in front. I tried to change gain and coarse but I always get the same specter like in the picture below.
Does anybody know what could be wrong with detector or in what direction I should go to repair it.

Thank you in advance.

[jneilson]

I've seen spectra like this from a couple of failed detectors - seems to often be the way the spectrum goes when there's something really wrong. Vacuum failure, crystal warming and HV bias shutdown or preamp electronics issues would be my first inclinations. I'd try a few simple diagnostics, but with my lab experience I typically turn to the experience of the manufacturer/supplier for diagnostics and repair rather than doing too much myself, so am no expert in hardware diagnostics.
I'd first try a few simple tests of the HV, bias shutdown/inhibit links, and check what the pulses look like with a 'scope, make sure your electronics and acquisition chain is behaving as expected.
For vacuum issues, look to whether the detector capsule is "sweating" or gathering condensation or ice - that would be a sign that there's an issue with thermal isolation.
Next step is probably some electronics diagnostics of the preamp circuitry - look for blown components and probe various points with a multimeter - a blown FET is a problem I've heard of and is worth checking.
Beyond a few simple diagnostics like that, I'm afraid I hand over to the manufacturers so would be out of my depth, but there are a couple of hobbyists out there that have done more in-depth HPGe repairs, so hopefully someone else has more pointers for you.

[Vojislav]

Thank you for reply. I will try to check some of this solutions. I think it is something electrical. Vacuum is fine because there is no "sweating".