05/13/2011 timing test

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Set up like that:

The voltages and thresholds are:

	PMT voltage, V	threshold, mV	discr. width, ns
PS1	-1000	-80	100
PS1	-1000	-80	100
n's	-1500	-200	10

Let's do the timing test. The distances are between PS1+PS2 and n's PMT. The time is time difference between PS1(PS2) and n's detector signals

N	80 cm	70 cm	60 cm	50 cm	40 cm	30 cm	20 cm	15 cm	10 cm	0 cm
1	17.6 ns	16.8 ns	16.4 ns	12.8 ns	14.0 ns	12.8 ns	14.4 ns	12.4 ns	11.2 ns
2	17.6 ns	16.8 ns	16.8 ns	19.2 ns	14.2 ns	14.4 ns	13.6 ns	12.0 ns
3	18.4 ns	17.6 ns	18.4 ns	17.6 ns	15.2 ns	16.8 ns	13.2 ns	11.2 ns
4	17.6 ns	17.0 ns	17.6 ns	16.8 ns	18.6 ns	14.4 ns	14.4 ns	10.0 ns
5	17.6 ns	17.0 ns	17.6 ns	16.8 ns	16.0 ns	14.0 ns	13.6 ns	10.0 ns
6	17.6 ns	17.2 ns	16.4 ns	16.8 ns	17.6 ns	15.2 ns	12.4 ns	11.2 ns
7	18.0 ns	18.4 ns	17.6 ns	16.0 ns	15.2 ns	13.2 ns	12.8 ns	12.0 ns
8	16.8 ns	20.8 ns	16.0 ns	17.2 ns	17.2 ns	14.4 ns	12.8 ns	12.8 ns
9	9.6 ns	17.6 ns	16.4 ns	17.2 ns	18.4 ns	17.2 ns	15.2 ns	14.6 ns
10	17.2 ns	22.4 ns	18.4 ns	17.2 ns	16.0 ns	16.4 ns	12.8 ns	12.0 ns
avg, ns	(16.8 ± 2.6)	(18.2 ± 1.9)	(17.2 ± 0.9)	(16.8 ± 1.6)	(16.2 ± 1.6)	(14.9 ± 1.5)	(13.5 ± 0.9)	(11.8 ± 1.4)

As the distance becomes 10 cm and less the coincidence rate becomes very low. I have:

▫ 1 coincidence for 10 min

▫ 0 coincidence for 10 min

Below is the plot of measured time as function of distances: