05/13/2011 coincidence test

Set up like that:

The voltages, thresholds and widths are as below. Note: I increased my thresholds for PS1 and PS2 from 80 mV up to 100 mV according to my previous calibration threshold line.

	PMT voltage, V	threshold, mV	discr. width, ns
PS1	-1000	-100	50
PS1	-1000	-100	50
n's	-1500	-200	10

First let's do the PS1+PS2 coincidence test. The distance between PS and n's PMT is about 80 cm

The distance between PS and n's PMT is about 80 cm

	counts	time	counts/sec
PS1	[math]2823\pm53.1[/math]	20 min	[math]2.35\pm0.04[/math]
PS2	[math]3091\pm55.6[/math]	20 min	[math]2.58\pm0.05[/math]
PS1+PS2	[math]93\pm9.6[/math]	20 min	[math](7.7\pm0.8)\cdot 10^{-2}[/math]

The distance between PS and n's PMT is about 50 cm

	counts	time	counts/sec
PS1	[math]7513\pm86.5[/math]	60 min	[math]2.09\pm0.02[/math]
PS2	[math]9036\pm95.1[/math]	60 min	[math]2.51\pm0.03[/math]
PS1+PS2	[math]251\pm15.8[/math]	60 min	[math](6.9\pm0.4)\cdot 10^{-2}[/math]

The scope picture of PS1+PS2 coincidence event like:

Second tet's do the PS1+PS2+n's coincidence test

	counts	time	counts/sec
PS1	[math]3229\pm56.8[/math]	20 min	[math]2.69\pm0.05[/math]
PS2	[math]3192\pm56.5[/math]	20 min	[math]2.66\pm0.05[/math]
PS1+PS2+n's	[math]59\pm7.7[/math]	20 min	[math](4.9\pm0.6)\cdot 10^{-2}[/math]

The scope picture of PS1+PS2 coincidence event like:

The ratio of (PS+PS2) rate to (PS+PS2+n's) rate is

[math]\frac{7.7}{4.9} = 1.6[/math]