[Jeff, Daniel]

I connected the Stanford Research Systems Residual Gas Analyzer 100 (SRS 100) RS232 cable (9 pin D-Sub) to a RS232 (male) to USB-A (male) adapter and plugged it into the USB hub in the mobile clean room. I also connected the same adapter from the turbo controller to the hub. I turned on the RGA and took some spectra around 3:30 today. I've attached the graphs from the data. The y-axis is Torr. The total pressure is the sum of the partial pressures; these graphs imply a pressure of around 1E-5 Torr, even though the Agilent pressure gauge had a reading around 1E-7 Torr, two orders of magnitude different. Jeff and I came in around 11 PM tonight and took another RGA reading; H2 and N2 levels were higher than at 3 PM, up to 3E-5 Torr. We then found out the pressure is 1E-3 Torr on the Agilent pressure gauge and the ion pump was off. I don't know if the ion pump going off is a cause or an effect of the high pressure. If the 6E-10 Torr/s rate of rise measurement is accurate, then the pressure after ~12 hours would be ~3E-5 Torr. This seems to indicate the high pressure caused the ion pump to go off. If the helium from the helium leak check were in the system, it would be easily visibile with the RGA (and shouldn't cause such a huge pressure rise). The up-to-air valve and the gate valve to the turbo pump were closed and tight.

If the pressure is this high, this explains the RGA measurments being so high (it's not rated above 1E-4 Torr, so a little discrepancy there makes sense). There is a big mystery for why the pressure is 1.2E-3 Torr after being stable for days. To test the agilent pressure gauge, I rotated and moved the magnet's z-axis (it's a cylinder and on another cylinder). This lowered the pressure to ~7E-4 Torr, half as low. A factor of 2 in pressure isn't a big deal for these issues.

The H2 levels on the RGA also seem quite high.