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Uranium Ore Gamma Spec

Posted: Tue Sep 15, 2020 12:00 am
by Joe Gayo
I've been working on refining my gamma spectroscopy set up and took the following measurement with the following items:

Bicron 2x2 NaI Detector @ 900V
Ortec 113 PreAmp (1000p)
Canberra 3202 HV Power Supply
Canberra 2020 Spec Amp (x100, 4usec Shaping time, w/ PUR on)
Canberra 35+ (1000 sec count)

Ore sample from Colorado.

Re: Uranium Ore Gamma Spec

Posted: Sat Oct 10, 2020 10:03 pm
by ChristofferBraestrup
That's a very nice spectrum, I don't think it will get much better with a 2x2 NaI crystal!
Linearity is drifting a tiny bit, I assume the orange dots are table values?

If I may ask - why are you lading down your detector so much at the preamp side? You're putting lots of attenuation at the preamp and then most of your gain at the spec. amp.

For the ortec 113 amp, the RC is shunted across the input of the amplifier, so the C effectively acts as a 'charge divider' against Cfeedback.

Re: Uranium Ore Gamma Spec

Posted: Sun Oct 11, 2020 1:36 am
by Richard Hull
There is always non-linearity and drift in a gamma spec using stock PMT xtals with various older spectro systems. This is why you tend to calibrate usisng the Canberra's gain controls for specific regions using test source radionuclides. What's a little drift and shift among amateur scientists. PMT's are at best, only moderately efficient. Close peaks just disappear. Its just part of the game.

Great work Joe. Try presenting the data outside of log mode in linear mode limited to the 605kev peak. Goldie Locks and the three bears are obvious in the extreme.

Richard Hull