MCA front end

Linear and non linear

Re: MCA front end

Postby Doug Coulter » Wed Dec 10, 2014 10:09 pm

Well, here ya go, first light 1x1" detector with Cs137 taped to the end. Gain on the low side for this, lots of compton scattering. I have a hardware issue as the NPN causes the hold cap to drift up if there's a long time between counts and the cap has stopped drawing much of any current. I'll need compensation for that to catch the lower line of the Cs137 at all. Getting there, though. Most of the width of the high line is simply due to that and the random amount of time between pulses for this source and the size of the hold capacitor (eg how long does it take to charge up an extra 200 mv or so more than the BE drop of the PNP vs random timing between the pulses, which averaged about 1.6 khz.
Could be better, but now I know where the errors are.

At least I know where the problems are now... A bit more work to be done on this one. It gives a near perfect one bin with a lab pulse generator with random timed pulses, well, not quite random spacing - 50-1000 us between them it's good. Truly random is another story...
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Doug Coulter
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Location: Floyd county, VA, USA


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