For the third vacuum test, I tested the system with the addition of the high-voltage port. For the high voltage feedthrough, I will be using a Bosch spark plug threaded through a 1/2'' thick aluminum plate, J-B welded to the side of the chamber. The schematic on the right is of the aluminum plate that was epoxied to the side of the chamber. In order to connect the spark plug, Anatol and I wrapped the threads in Teflon tape and used a wrench to screw the plug into the threaded hole in the aluminum plate. In addition to making sure that the system could still hold a vacuum after the feedthrough had been attached, we found another (newer) vacuum gauge that fit the plug for the sensor in Dr. Bulman's chamber, and compared the readings of both gauges.
It appears that the third test was a success, as no audible leaks were detected when the pump was first turned on, and the chamber got down to a pressure of about 200 microns on the old gauge. However, when we swapped the old gauge for the new one, we recorded a pressure of 34 microns! As we have no way of calibrating the gauges at this time, it is impossible to decisively say which gauge is the "correct" one, or even if either of the gauges are correct. However, at this point, Anatol and I agreed that the newer gauge was probably more accurate just on the account of it being new, so we will use that one for the time being.
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