At the tail end of the GS5-3 run, we did some additional tests suggested by Ecco. We pumped out the cell at ~500 C (core), reaching ~40 microns. This is the typical limit of the vacuum system and cell plumbing in many previous cycles. Then we added H2 from a bottle to 1 bar. After a 30 minute dwell, we pumped the cell out again and found it reached 5 microns of vacuum.
This test was repeated several times, at 600 C and 700 C in the core, with the same result. A final test cycle at 850 C (core) reached a vacuum level of just 2 microns, far better than the vacuum system can achieve even with a closed manifold (typically 25 microns).
I find these results among the most startling and unexpected in my 2 years of Glowstick experiments, and I can't think of a physical explanation for what we measured. I'd appreciate comments on how this can be explained by ordinary physical and chemical phenomena. Tom Clarke's insight would be especially welcome, since he has a demonstrated skill at suggesting plausible explanations for unusual measurements.
The vacuum pump is a Welch Duoseal 4000 with a Pirani vacuum gauge mounted on the manifold. It's connected to the cell with about 40 cm of Tygon tubing with Swagelok valves. The vacuum gauge is battery powered and hasn't shown any unusual behavior in the past. The cell heater was powered from a Variac during these tests, so no EMI above 60 Hz was present.