Threshold & HV study

Overview

A series of triggered CF-252 runs are conducted at various detector PMT high voltages and discriminator thresholds. A TDC spectrum is acquired using daq2 so that a neutron cut can be applied. These data provides us with a relationship between neutron detection rate and PMT HV/threshold.

Setup

A CF-252 source along with a trigger scintillator is placed at the geometric center of the array of neutron detectors. The source discriminator threshold is kept constant throughout the study at 100 mV.

Pulses from the source trigger are delayed by 1500 ns and serve as the common stop time for the TDC.

An event is considered a neutron detection if both PMT top and bottom saw a hit, and the resulting ToF also lies in the neutron range.

results

Detector	[math]n_{0}[/math] rate	noise	run #	PMT threshold	HV
D30	?	??	r5242	25	1700
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5239	30
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5240	35
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5241	40
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5243	25	1650
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5244	30
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5245	35
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5246	40
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5247	25	1600
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5248	30
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5249	35
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5250	40
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5251	25	1550
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5252	30
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5253	35
D90	?	??
D150	?	??
D225	?	??
D30	?	??	r5254	40
D90	?	??
D150	?	??
D225	?	??