August 16, 2007 - Cosmic Telescope

Today we are continuing our plateauing of the scintillators. For this next test, we are replateauing the bottom scintillator but with its threshold at 225 mV instead of 275 like before while keeping the top scintillator at 275 mV. We are decreasing the threshold because we are still not seeing the count rate that we expect, which is about 8 coincidence counts per minute. Since the count rate in our past experiments is too low, it can be deduced that the threshold is too high and therefore we are not reading some of the cosmic rays that pass through.

Plateau of Bottom Scintillator
Time	HV on top scint.	HV on bottom scint.	Singles Count (on top)	Coinc. Counts	Coinc. per minute
30 min	1300	1450	2831	111	3.7
30 min	1300	1400	2880	104	3.47
30 min	1300	1350	3000	101	3.37
30 min	1300	1300	3164	68	2.27
90 min	1300	1250	3121	77	2.57
30 min	1300	1200	3182	47	1.57
30 min	1300	1150	3100	16	0.533
30 min	1300	1100	3141	3	0.1

This next data set is from the replateau of the top scintillator with both scinitillators thresholds set at 225 mV.

Plateau of Top Scintillator
Time	HV on top scint.	HV on bottom scint.	Singles Count (on top)	Coinc. Counts	Coinc. per minute
30 min	1300	1450
30 min	1300	1400
30 min	1300	1350	4088	87	2.9
30 min	1300	1300	4397	93	3.1
90 min	1300	1250	2120	75	2.5
30 min	1300	1200	1737	81	2.67
30 min	1300	1150	893	70	2.33
30 min	1300	1100	347	40	1.33