Search found 163 matches

by GigaBecquerel
04 Mar 2022, 20:04
Forum: Detectors
Topic: 2*pi vs 4*pi
Replies: 7
Views: 150

Re: 2*pi vs 4*pi

Yes, exactly, every source can be approximated as a point source and therefore follows the r² law if it's small enough, and / or far enough away. A good rule of thumb is to be more than 10 times the sources diameter away from the source, at this point your errors due to the finite volume will be abs...
by GigaBecquerel
03 Mar 2022, 21:00
Forum: Detectors
Topic: 2*pi vs 4*pi
Replies: 7
Views: 150

Re: 2*pi vs 4*pi

Hello glhansen, There are two "different" detector efficiencies, and I think you might be mixing them up a bit here. One is the 2pi / 4pi you're talking about, which just says how much of the sphere is covered by your detector. The other one is your detectors "response spectrum",...
by GigaBecquerel
31 Jan 2022, 19:15
Forum: Software
Topic: Gamma spectrometer Theremino or PRA
Replies: 3
Views: 157

Re: Gamma spectrometer Theremino or PRA

Hello Pawel, Welcome to the forum! CdWO4 generally isn't great for spectroscopy, especially of it's that small, but you should get more than one peak. Your signal looks fairly noisy, what's the mVpp on the baseline vs mean signal height? Also, I recommend using BecqMoni, which gave me the best resul...
by GigaBecquerel
21 Jan 2022, 19:24
Forum: Detectors
Topic: HPGe Repair And Fet Swap
Replies: 8
Views: 252

Re: HPGe Repair And Fet Swap

Hi Luuk,

All the new detectors use O-Rings, I guess both due to advances in the materials, as well as cost.
The O-Ring sealed ones also have to be pumped more often, which is another source for money...
One could also argue to keep the detectors neutron cross section as small as possible.

Lukas
by GigaBecquerel
19 Jan 2022, 08:12
Forum: Detectors
Topic: HPGe Repair And Fet Swap
Replies: 8
Views: 252

Re: HPGe Repair And Fet Swap

Hi Luuk,

Thank you for the FET Names!
I am never sure what exactly to use, but those are a good number of canidates.
I have heard of some fets working well at room temperature, but not working when cooled, have you made that experience at all?

Best Regards
Lukas
by GigaBecquerel
15 Jan 2022, 20:15
Forum: Detectors
Topic: HPGe Repair And Fet Swap
Replies: 8
Views: 252

Re: HPGe Repair And Fet Swap

The O-Ring needs to be compressed, and if that's done right it seals well. It obviously works here, and as far as I know canberra has not changed their cryostat design in over 20 years. While the proprietary valves are very annoying to work with I am glad that they don't use common flanges and easil...
by GigaBecquerel
14 Jan 2022, 19:12
Forum: Detectors
Topic: HPGe Repair And Fet Swap
Replies: 8
Views: 252

Re: HPGe Repair And Fet Swap

Hello Steven, Thanks, I'm glad you like it! The O-Ring and Cap are exactly what's holding the vacuum. The crystal, fet and all are inside the vacuum, and the FR4 structure keeps it centered, as well as keeping the temperature gradient between the outside at room temperature, and the cold finger down...
by GigaBecquerel
11 Jan 2022, 02:08
Forum: Detectors
Topic: HPGe Repair And Fet Swap
Replies: 8
Views: 252

HPGe Repair And Fet Swap

Hi Guys, It’s time for a HPGe repair! This one was broken and needed a new JFET. The detector itself is not mine, but a friends Canberra GC1520 on a portable Big MAC Dewar. It came from eBay, that’s all we know about it. It looks to be in good condition, but the endcap was bent inwards, like it got ...
by GigaBecquerel
04 Jan 2022, 01:45
Forum: General discussion
Topic: Activity Calculation Issues
Replies: 4
Views: 161

Re: Activity Calculation Issues

Did you have the same measurement geometry every time? Not only position, but also source shape etc. Also, I heard that Eu152 is unfavorable as an efficiency calibration source, as it tends to have summing peaks. But I don't have any, so I never looked further into that, it might just be something t...
by GigaBecquerel
01 Dec 2021, 20:55
Forum: Software
Topic: Idea for MCA algorithm
Replies: 3
Views: 101

Re: Idea for MCA algorithm

How would the "Artificial Intelligence" know that the spectrum is shifting, and not decaying into something that's emitting gammas at a slightly lower energy? In my experience software like this will always fail at some edge case, and those edge cases are way more common that you'd think! ...