JMU Dark Current Tests By: Kevin Nash

JMU Dark Current Tests 1. Our setup and data taking procedure 2. Current progress report 3. Data analysis Full comparison Precision and slot comparison Warm up characteristics High voltage curve 4. What’s next

JMU Dark Current Setup (fig.1) To expedite the rate of testing progress, bar codes are applied to all tubes which lets the user enter the PMT serial code instantly. (fig.2-fig.3) Photomultiplier tubes are inserted into the housing, taped closed, and covered with a sheet prior to testing. (fig.4) After warm up, the tubes are tested with the use of a Labview program that monitors the Picoammeter. After testing, the values are recorded into the MySQL database for future analysis.

Progress Report Currently the JMU team has completed dark current tests on seven out of the ten total batches. 749 tubes have been tested and recorded out of the total 1200 Based on the current rate of progress of approximately 100 tubes per week, all tubes will be tested by early April

All Dark Current Comparison Average JMU dark current was 0.199nA Average Hamamatsu measured dark current was 0.486nA. JMU dark current values are measured an average of 0.291nA lower than the manufacturers tests JMU dark current values range from 0.0062nA to 0.951nA for a total range of 0.945nA compared to the manufacturers range of 3.07nA The chi-square from the mean was 8.96 for JMU tests and 43.66 for the manufacturer tests This would suggest that the JMU tests are more precise

A Closer Look The discrepancy is systematic.

All Dark Current Comparison Both Hamamatsu and JMU dark current tests appear to follow a poisson distribution Clearly, the JMU tests are more precise

Slot Comparison This is a comparison of the five testing slots used in the JMU dark current tests using the same pmt: serial CS2860 and six data points per slot. The average dark current for this PMT was 0.171nA The random error for these tests was +/- 0.045nA There is little or no systematic error from slot to slot This would suggest a maximum random error of 26.3%. Fitting a Gaussian to the data approximates a standard deviation of 0.032 nA

Warm up Behavior Test of all 5 slots during 30 min warm up (fig.1) consists of 7 data points per PMT Test of a single PMT during 30 min warm up (fig.2) consists of 60 data points Both suggest relatively standard operating conditions after 15-20 minutes of warm up Both JMU and Hamamasu measured dark current values are tested after 30 minutes of warm up .

Dark Current HV Curve A comparison of the typical high voltage dark current variation versus the JMU measured dark current variation. Conclusion: The voltage range for the dark current tests is generally not highly effected by ohmic leakage or regenerative effects, and is mainly due to thermionic emission.

The Future Base soldering for all 1200 tubes (fig.1-fig.2) Base to be soldered to socket, using the spring and PVC tube for pressure and spacing within the PMT housing. Base testing (fig.3) This apparatus will be used to test the uniformity of the voltage between the dynode stages. Gain testing through high voltage curve (fig.4) Design and implementation of an even light source and fiber optic network.