Procedure to purge the helium line

If the helium lamp is not used for long time, or the chamber was opened, or there was a bake-out, we need to purge the helium line.

In order to do that we can use the primary/fore pump of the buffer. Here are the steps.

1. Close all the pumping lines, SPIN, MONO, PREP, and two for the cryo-pump
2. Stop the turbo by pressing stop in the PCU pump controller
3. Wait for turbo speed to slow down below 200 hz
4. Start the pump
5. Pump out the helium line by opening the valve
6. Close the valve, and fill line with helium, and pump helium out

Repeat the process a few times.