Gamma Spectrometry Forum

Just an observation from running the GS-1100A thru the gears.

The attached file shows 5 Americium peaks, each at a different voltage to the probe provided by the GS-1100A.

The far right is at 900v and each one moving left is at a reduction of 50v down to 700v.

Daryl,

Nice simple experiment, seems to show a non linear relationship.

There are no hard rules, but as a general rule I suggest running the detector at the manufacturers recommended voltage and adjusting the line in voltage to a level which gives you a suitable range. K40 at 50 arb.u works well.

Often better resolution is achieved with lower voltage, this is something you can easily check with the above experiment.

Steven

Steven,

It does look logarithmic. It seems like higher probe voltage reduces bandwidth observed and shows more lower energy detail.

I finally got a K40 picture by lowering the probe voltage to 650v! and it's mid scale!

Since K40 rarely decays via positron emission, shouldn't we see something at 511Kev? I wouldn't think that positron would get very far with that cloud of electrons from which it has to escape.

Thanks for the encouragement.

Daryl

Daryl,

With a very good detector and long recording I have seen a small 511 keV peak in the background, it is usually clearer to see in log mode with the gaussian correlation switched on.

Note, for the gaussian to display correctly you have to carry out the calibration properly and enter the SD.

Steven