In order to protect the vacuum system in the event of a confining fluid leak, low positive pressure (0.1–0.2 MPa), high-vacuum relief valves, and a high-vacuum fluid expansion trap designed to accommodate the decompression of the confining fluid from the maximum confining pressure to 0.1 MPA were included in the vacuum system. Helium leak rate standards were used to blackcalibrate the leak detector, and atmosphere was used as a standard to calibrate the mixing fractions for the quadrupole mass spectrometer.