Threshold(R27) and Gain(R22) potentiometers (at side of the ESP-2) are adjusted to the maximum position in clockwise direction. However, I am not aware of the output values of both Threshold(R27) and Gain(R22). The nominal threshold value for both SPA-3 and LEG-1 detectors is 10mV which is given in the manual.
HV is changed from 700V to 1200V with a step size of 50V. The nominal HV for both detectors is 1000V which is given in the manual. However, the maximum HV which can be given for the detectors is not mentioned in the manual.
The following plots are made by reading the # of counts per minutes for different HV values. In fact, # of count per minute is calculated by taking counts for 10 minutes.
In the above plot it can be clearly found a plateau region. Hence, 1100V is selected as a suitable HV for LEG-1 detector.
In the above plot there is no plateau region. Since we don’t know the maximum HV for the detector, it is not suitable to increase the HV furthermore. However, 1100V is selected as a suitable HV for SPA-3 detector.
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