05/10/2011

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continue...the same set up as before, the distances are the same:

First I change the power supply for HAMAMATSU PMT to the new 2 channel one C.A.E.N N471

The powers are:

PS1 and PS2:  -1000 V (the old 2-channel TENNELEC TC952)
n's: -1100 V (the new 2-channel C.A.E.N N471)

The thresholds were:

PS1 and PS2:  -80 mV
n's: -60 mV

Let see what we have. First he CF-243 source is far far away (sealed in the safe):

	counts/min (1 min test)	counts/min (1 min test)	counts/min (5 min test)	counts/min (5 min test)	avg counts/min
PS1	187	160	166	160.8	168.4
PS2	187	170	180.4	184.4	180.4
PS1+PS2
n's	205	204	201.2	202.4	203.2

Interesting. The same power for HAMAMATSU PMT, but different counts result.

Now I increased the power supply for HAMAMATSU PMT and adjusted the threshold.

The powers are:

PS1 and PS2:  -1000 V (the old 2-channel TENNELEC TC952)
n's: -1500 V (the new 2-channel C.A.E.N N471)

The thresholds were:

PS1 and PS2:  -80 mV 
n's: -500 mV

Let see what we have. First he CF-243 source is far far away (sealed in the safe):

	counts/min (1 min test)	counts/min (1 min test)	counts/min (5 min test)	counts/min (5 min test)	avg counts/min
PS1	187	160	166	160.8	168.4
PS2	187	170	180.4	184.4	180.4
PS1+PS2
n's	205	204	201.2	202.4	203.2