Threshold & HV study

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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 ? ??