NaI temperature changes during long counts

[Jim Kovalchick]

I use a two in NaI crystal to collect gamma specs fairly often. I use a Canberra PMT 2007 base for a preamp, a 2025 spec amplifier, and a 8706 ADC. I gather the data from the ADC with a home brew microcontroller board that I programmed to bin the peaks as they come. I usually run at 512 channels but can go to 16k.


Many of spectra are short, but often I do long counts of low activity samples. I noticed huge shifts and loss of resolution over these long counts because of what I assume is temperature changes. My lab is in my home, and generally the air temperature only changes by a few degrees. My counting cave is a foot from an exterior wall and maybe that's a problem. I cant really change that but maybe I can insulate.


Has anyone tried to address temperature changes over long counts where it is impractical to tweak parameters? I wonder if I can bring temperature into my microcontroller and make adjustments automatically.


Thanks for any ideas.
Jim K

[Sesselmann]

Jim,

Temperature changes are the main source of drift, it affects the PMT, the Crystal and the electronics.

This is why our range of ATOM and MAX digital spectrometers have built in temperature compensation, we calibrate them in a temperature controlled chamber from -20˚C to +50˚C

Steven