Hi
I am attaching a positron lifetime spectrum showing the main peak at ~ 750 #. there is a small peak at ~350 #. I was wondering what is causing it. The setup is - two BaF2 scintillators attached to Hamamatsu R3377 PMT. the detectors are from Scionix. Electronics is - ORTEC CFDD to TAC to MCA. Allen mills talks about it (i think!) in one of his paper saying that its due to the ionization of hydrogen atoms in the PMT. So, one gets a delayed peak. surprisingly, We can move the satellite peak to right of the main peak by swapping CFDD. Any suggestions on the origin of this peak will be welcome
Sometimes the time-lag between the main peak and the small peak corresponds to the length of one of the gate signals used for the coincidence. If so, the small peak is due to noise created at a discriminator or at a gate-stretcher.
Dear Kengo
You could be right that one of the CFDD's is faulty. But when I look at the CF monitor and the timing outputs, they all look alright. I will try to repeat this with another detector or trigger both the CFDD's using the same detector.
saurabh
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