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→Test and Calibration
== Background/Consistency Tests ==
== Background/Consistency Tests ==
The chamber was checked for leaks using a long exposure digital camera. Minute leakage through seams in the back access port was fixed to the extent that sensors were no longer sensitive to that level of background. The box was tested with SiPM measurements performed with room lights on and off (which should provide order of magnitude difference of ambient light.)
The chamber was checked for leaks using long-exposure photography. It was able to detect minute leakage through seams in the back access port. This problem was fixed to the extent that sensors were no longer sensitive to that level of background. The box was tested with SiPM measurements performed with room lights on and off (which should provide order of magnitude difference of ambient light.)
Although the temperature of the sensor is stabilized (using techniques described above) other sources of of systematic errors were a source of concern. These include changes in pulser input function, pulser LED light output variations etc, amplifier gain and bias voltage shifts etc. To test for these effects, a run of several days was performed and signal histograms of half our slices were compared. Two methods of detection rate measurement yielded only ~2.5% variation. It is interesting to note that a similar such run conducted by accident without temperature control of the sensor yielded ~8.3% variation in detection rate.
Although the temperature of the sensor is stabilized (using techniques described above) other sources of of systematic errors were a source of concern. These include changes in pulser input function, pulser LED light output variations etc, amplifier gain and bias voltage shifts etc. To test for these effects, a run of several days was performed and signal histograms of half our slices were compared. Two methods of detection rate measurement yielded only ~2.5% variation. It is interesting to note that a similar such run conducted by accident without temperature control of the sensor yielded ~8.3% variation in detection rate.