AIDA
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BRIKEN
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ISOLDE
CIRCE
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DTAS
EDI_PSA
179Ta
CARME
StellarModelling
DCF
K40
BRIKEN
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Optimization of ADC thresholds In order to try to reduce the grass-like background we make a finer adjustment of individual ADC thresholds. We make first a control measurement putting the 252Cf source in the center of the detector (AIDA removed) Start: - Stop: 23:55 File: 161009_2355_252Cf_control.root We then make an adjustment of thresholds one ADC at a time. We adjusted the threshold so that the very low amplitude noise height in the spectrum is only a small fraction of the pulser. New configuration file: 160718Conf_BrikenFull_test02_thr.xlsx A verification measurement with 252Cf Start: 01:55 Stop: 02:09 File: 161010_0209_252Cf_newthr.root And the leave a background measurement overnight: Start: 02:12 Stop: 07:12 File: 161010_0712_bck_newthr.root We compare the grass-noise rates now with the rates before threshold adjustment For that we integrate the BRIKEN spectrum between 900keV and 1.5MeV The rate before was 0.085 counts per second per MeV The rate now is 0.039 counts per second per MeV So the improvement was only a factor 2. One can try to set the thresholds higher however with this rate the probability of having a noise signal in a 0.5ms window after a beta signal will be about 1E-5. The plots below show the situation before and after.
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