Hello there!
Recently I got an old planar HPGe with a dead frontend fet from a friend of mine.
I am going to attempt a repair of the detector, by opening it, replacing the fet and pumping it back down.
Sadly there seems to be no data on the cryostat (7600P), not even Orren Tench from http://canberra-industries-50years.com/ could help me here.
At least he could confirm that it's HPGe, not Ge(Li).
Preparing for the operation I decided to take a few x-ray pictures of the detector:
You can see the Disk on the bottom, as well as its holder and wires going to it.
From the Disk you see a single wire going up to some part mounted on a ceramic holder, this is where I expect to find the fet.
Right now I have replacement fets, indium wire to replace the gasket and the pumping adapter, only thing missing is a clean space in my workshop to do the operation.
Once I managed to clear that I'll start the repair and keep you updated!
Lukas
A look inside an old Planar HPGe
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GigaBecquerel
- Posts: 172
- Joined: 04 Jul 2020, 07:34
A look inside an old Planar HPGe
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Sesselmann
- Posts: 1398
- Joined: 27 Apr 2015, 11:40
Re: A look inside an old Planar HPGe
Lukas,
This looks like a fun project, I look forward to see how you go and what you learn along the way. These non working detectors come up on eBay from time to time and often the fix is less complicated than you expect.
Steven
This looks like a fun project, I look forward to see how you go and what you learn along the way. These non working detectors come up on eBay from time to time and often the fix is less complicated than you expect.
Steven
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GigaBecquerel
- Posts: 172
- Joined: 04 Jul 2020, 07:34
Re: A look inside an old Planar HPGe
Hello Steven,
Technically the fix is not very complicated, but it isn't easy either.
The crystal must not be in the air for too long or the lithium contact will corrode to death, from what I've been told 5-10 minutes is a safe time.
Soldering is not an issue, cleaning the joints might be, I've been recommended to use pure ethanol (without bitrex) for that, as it is less hygroscopic than isopropanol and evaporates without a residue.
The high vacuum stuff is another point, the cryostat has to reach e-5 to -6 mbar before closing and must be absolutely leak free. I have a helium leak detector that will help a lot with that.
My working HPGe is blind below ~50 keV, and this planar one will be a great addition to that!
I am not sure what the lower energy limit of it is, but I have a feeling that below that you might get into the regieme of UV spectrometers rather than x-ray detectors ;-)
Technically the fix is not very complicated, but it isn't easy either.
The crystal must not be in the air for too long or the lithium contact will corrode to death, from what I've been told 5-10 minutes is a safe time.
Soldering is not an issue, cleaning the joints might be, I've been recommended to use pure ethanol (without bitrex) for that, as it is less hygroscopic than isopropanol and evaporates without a residue.
The high vacuum stuff is another point, the cryostat has to reach e-5 to -6 mbar before closing and must be absolutely leak free. I have a helium leak detector that will help a lot with that.
My working HPGe is blind below ~50 keV, and this planar one will be a great addition to that!
I am not sure what the lower energy limit of it is, but I have a feeling that below that you might get into the regieme of UV spectrometers rather than x-ray detectors ;-)
