Fil C., Richard M., Kyle R.

We are temporarily utilizing a contact closure provided by the 10 L/s ion pump controller (local to the newly installed RGA assembly) as an interium solution for the high voltage pressure interlock in HAM6.  Normally, this contact closure is provided by PT110.  However, PT110 is out of service until further notice. 

Details:

It was noted, while PT110 was still working, that an indicated pressure of 9 x 10-7 torr given by PT110 corresponded to a pump current-converted pressure of 4 x 10-7 torr at the 10 L/s ion pump.  9/4 = 2.25:1 ratio.  This is as expected due to the conductances resulting from the physical configuration.  As such, I programmed the 10 L/s ion pump controller's relay contact (P1 pins 10 and 12) to open for any pump current-converted pressures exceeding 1 x 10-6 torr.  This value, (1 x 10-6 torr) x (2.25) ~ 2 x 10-6 torr, is ~ 1/5 the nominal interlock setpoint of 1 x 10-5 torr, i.e., we are now expecting a safety margin of 5 for this unproven setup. 

While not able to test this setup using actual measured pressure changes, I was able to simulate the functionality via programming the setpoint below and above the measured current-converted pressure and observe the as expected behavior from the relay contact using an ohm meter.