05/19/2011 n's detector threshold calibration source/(w/source)

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Below are my counts rate measurements as function of threshold voltage for n's detector. The source was CF252. The distance between source and n's PMT was about 50 cm. It was 1 PMT set up detector and experiment was hold in LDS on May 19 2011.

First the counts rate was calculated as: 

[math]\mbox{Rate} = \frac{N_{\mbox{source}} - N_{\mbox{w/source}}}{\mbox{Time}}[/math]


First I did my calibration for power supply voltage -1250 V:

Det1 calibraton source 1250V.png Det1 calibraton source 1250 log.png


Second I did my calibration for power supply voltage -1500 V:

Det1 calibraton source 1500V.png Det1 calibraton source 1500 log.png


And bellow I overlay both cases (-1250 V and -1500 V)

Det1 calibraton source 1250 1500.png Det1 calibraton source 1250 1500 log.png


There are no any plateaus, so what is the threshold should be?. Or maybe we are need to look at something different.


Let's recalculate all data using the formula: 

[math]\mbox{Ratio} = \frac{R_s - R_{w/s}}{R_{w/s}}[/math]

Below my data and calculations for the case of -1500 V power supply voltage:

Table 1500V.png

Below my data and calculations for the case of -1250 V power supply voltage:

Table 1250V.png


And below I overlay my results (linear scale):

Det ratio lin.png

and for log scale:

Det ratio log.png


There are two important conclusion at least for this type of PMT was used:

  1. The desirable threshold is about -50 mV
  2. The power supply voltage is as expected -1500 V (there are no plateau for -1250 V)

And there are some discrepancy with Jason's measurements which he did at different place and time and with different PMT and looks like:

Jasons callibration.png

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