Re: Peak shift in NaI spectrum of an Oxford Instrument MCA

[Thomas M Lashley <lashleyt@dteenergy.com>]

Check the high voltage power supply to the the detector.

Tom Lashley
LashleyTDTEenergy.com

LAM HOI CHING wrote:

> Ask for advice for an old piece of MCA:
> I'm puzzled what problem is inside my Oxford Instrument MCA (version PCA3).
> Every time when I check the spectrum energy with Cs137(662keV) , the energy
> reads 600~630keV, the same percentage drop happens with channel readings
> too. When the hardware fine gain is increased by 5% to 10%. The peak
> becomes 662keV again but after 2 hours, the peak raises to 680keV. This
> pattern has repeated for many weeks. I have excluded the room temperature
> effect to the device. This MCA does not have any abnormalities in FWHM
> shapes and efficiency counts. What could possibly be the problem inside the
> hardware ?
>
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