Formerly Holometer Ion Pump Standard Operating Procedure

Written by Daniel Grass from an emial exchange with Chris Stoughton

Initial Startup

1. Attach the ion pump's CF 2.75" flange to some sort of valve which is connected to the main vacuum inside.

2. If it is not attached, attach the (black and silver colored) permanent magnet around the (matte gold colored) ion pump

3. With the controller unplugged from the wall outlet, plug in the ends of the SHV cable to the ion pump and ion pump controller

4. Plug in a BNC cable from the front of the ion pump controller to an voltmeter (or digital multimeter). The voltage output, monitors the current once the ion pump is on. See this post and below.

5. Plug in the ion pump controller to the wall outlet. The light above "off" should turn on and the output voltage from the front BNC should be 9V. The wall outlet draws 0.03A.

6. Hit the "enable" button so that the controller is ready to supply voltage. Note that this button cannot be turned off, but it will go off if the ion pump trips.

7. While the turbo is still running, hit the "on" button to supply voltage to the ion pump. The voltage from the BNC should drop to 2V and the pressure should spike to ~1E-4 Torr before quickly dropping and the voltage quickly rising to 3-4 V.

8. The light above the "on" button might briefly light up and then click off. The inside of the ion pump is dirty/has water. Initial power on heats up the elements, releases the water, which forces the ion pump to draw too much current and trip. This gas release is why we keep the turbo on; there might be a brief pressure increase. After the pressure goes a little back down (doesn't need to be all the way), hit "on" again. Repeat this process until the light above "on" stays on. It might go off after a few minutes but it should eventually stay on indefinitely.

9. Once the light above "on" stays on indefinitely (give it at least an hour), if the turbo pump and the rest of the vacuum chamber can be independently vented, close the valve to the turbo pump.

10. Turn off the turbo pump.

11. Once the turbo is done spinning down, turn off the scroll pump

12. Monitor the pressure. If the outgassing/leaking is too much, the ion pump will eventaully trip. If there is a leak causing the trip, it has to be fixed. If it is outgassing, then additional pumping with the turbo on (and valve open) might be needed before the ion pump can pump out alone. The target stable pressure for the ion pump is ~10^-7 Torr.

Temporary Shut Down

Follow these instructions when you want to open up the vacuum system, say to adjust the optics inside.

Main Method, to be tested:

1. Shut the valve to the ion pump. DO NOT OPEN THE VALVE UNLESS THE SIDES HAVE ROUGHTLY EQUAL PRESSURE.

The voltage on the ion pump will act as a pressure reference. The voltage should be around 5V.

Alternative #1:

1. Hit the "off" button on the ion pump controller.

2. Make note of the pressure in the vacuum chamber.

3. Shut the valve to the ion pump. DO NOT OPEN THE VALVE UNLESS THE SIDES HAVE ROUGHTLY EQUAL PRESSURE.

Alternative #2:

1. Hit the "off" button on the ion pump controller.

2. Make note of the pressure in the vacuum chamber.

3. Vent with dry nitrogen. This will allow for the ion pump to start up easier next time.

Start up after initial sucess

Assuming everything is plugged in and the turbo gets the pressure down to ~10^-7 Torr.

After "main" shut down:

1. Try to match the pressure on the main body of the chamber to the implied pressure on the ion pump. If the ion pump has tripped/was disconnected, keep the ion pump off and open the gate valve when the main body is around 1E-2 Torr (I think this is appropriate. A test with the interferometer could tell us the actual pressure after a trip). To achieve 1E-2 Torr, pump on the scroll for a while with the turbo pump off or briefly turn on the turbo and very slowly vent.

2. With the pressures matched and the valve to the turbo open, slowly open the valve to the ion pump and monitor the pressure

3. After at least 1 hour of pumping with both pumps, if the turbo pump and the rest of the vacuum chamber can be independently vented, close the valve to the turbo pump.

4. Turn off the turbo pump

5. Once the turbo is done spinning down, turn off the scroll pump

After Alternative #1 shut down:

1. Try to match the pressure on the main body of the chamber to the last pressure noted on the ion pump (or maybe a bit tigher due to small leaks/outgassing)

2. With the pressures matched and the valve to the turbo open, slowly open the valve to the ion pump and monitor the pressure

3. Now with valves to the turbo and ion pump open, press the "enable" and then the "on" button

4. After at least 1 hour of pumping with both pumps, if the turbo pump and the rest of the vacuum chamber can be independently vented, close the valve to the turbo pump.

5. Turn off the turbo pump

6. Once the turbo is done spinning down, turn off the scroll pump

After Alternative #2 shut down:

Start at step 6 of the initial startup

Perminant Shut Down

1. With the valve to the ion pump open, hit the "off" button on the ion pump controller.

2. Make note of the pressure in the vacuum chamber.

3. Vent the entire vacuum chamber to atmospheric pressure

4. Close the valve to prevent contamination

5. Unplug the ion pump controller from the wall outlet

6. Disconnect the ends of the SHV cable

7. Remove the perminant magnet if needed

8. Remove the pump on the CF Flange