Editing Scintillator Preparation (section)

== PMT Adjustments ==

=== Gain Matching ===

In order to gain match the scintillator setup, tests had to be run on each photo multiplier tube. By starting the high voltage at 1200 volts and increasing in 50 volt increments until reaching 2000 volts, the maximum voltage required to get at least one pulse was found at each interval. At each interval, the maximum voltage varied and was found using a series of steps. The first step was to see the pulses and determine where the majority of the peaks were hitting. Then, by using the trigger (which was the line that a pulse had to cross in order to show up on the screen), the area where the maximum voltage was kept could be found. After moving the trigger level down, the pulses would occur less frequently until finally reaching the point where a pulse would happen about once every second. This point was recorded as the maximum voltage. This test was done for each of the intervals on each of the four photo multiplier tubes. The graph below shows each of the four tubes and the voltage (on the x-axis) versus the maximum voltage to get at least one pulse (on the y-axis). 
 

[[File:pmtOut_voltage.png|center|frame|Graph of PMT Output Voltage vs. Voltage Level]]


As expected, the maximum voltage to get at least one pulse increases as the voltage level increases. Three of the four tubes gave relatively close maximum voltages throughout each interval, but one of the tubes displayed maximum voltages significantly less than the other three.