Gamma Spectrometry Forum

Good Morning Steven, Thank you! I got very lucky with this castle, and I have been collecting materials for it for the last 5-10 years. The lead is from a nuclear medicine department that closed down, I bought it for around 1€ per kg. The copper is cut from offcuts by a company that does contract la...

Hello Guys! Long time no see. Things have changed and thanks to a few friends, Luuk among them, my gamma spectrometer got a real upgrade! From Luuks retirement sale I got a perfect 3x3" NaI Detector, complete assembly with PMT and Crystal. He tested it to be 5.8% @ 662 keV, and who am I to doub...

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...

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",...

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...

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

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

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...

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...

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 ...