HM 2014

9/18/14

Determine best Cahtode HV that produces the largest separation of the source ON/OFF signal.

Then perform a set of measurements (shutter open/closed and source ON/OFF) to establish reproduceability. Make sure you record the scaler count rates.

9/17/14

Measure the charge for several values of the Cathode HV keeping the GEM preamplifier voltage and gas flow rate constant.

CATH 3.2 KV

CATH 3.1 KV

All the runs have the same duration 20 min.

CATH 3.4 KV

Try to take scope picture to show difference between source on and off signal that are being measured by the QDC.

9/16/14

Condition of above results

Shutter is Open

Red is Cf-252 source ON Run 7724

Green is Cf-252 source OFF run 7726

HV_GEM= -2930 Volts HV_Cathode=-3400 Volts

Gas Flow rate = 0.1 ft^3/hr

Goal

Can the Cf-252 source ON signal be changed?

Change the Cathode voltage to try and turn off the signal when the source is on.

Result

Yes, when the cathode voltage is decreased to -3200V, QDC histogram does not show any difference in the collected charge as the shutter is open with the source on it, and when the shutter is open without the source.

Neutron_TGEM_Detector_Abdel