Power failure procedure: molecular beam setup US 4.1

This walkthrough will help you re-start the pumps in the molecular beam instrument at US 4.1 after either a planned or an unplanned power outage.

Normal pressures. NB: the TOF pressure will reach the 10E-8 mbar range only after some time. Directly after the pumps have reached maximum speed the pressure is likely to be about 1E-7 mbar. Exact pressure gauge readouts may differ from the ones pictured here. The order of magnitude, however, should be the same as in the figure.

Planned power outage

Preliminary remarks

This walkthrough applies only when there is no nitrogen flow available during the power outage. The turbopumps will be pre-set to ‘Venting mode: 1 = no venting’. The setup must not be vented as the detectors should not be exposed to air.

Shutdown procedure (before the power is out)

1. Close the valves between the two forepumps and the remainder of the vacuum system (see pictures below).
2. Switch off the pressure gauges. This can be done by selecting the gauge by pressing the 'Sensor' button on the control panel until the corresponding number is highlighted and pressing 'sensor off' (see pressure overview above). The FSRC and MEMB gauges will not switch off but it is not an issue as they are full range gauges.
3. Turn off the forepumps. The power buttons are located on the side of the pumps.
4. Turn off the turbopumps. For instructions, see here.
5. Check the pressure gauges to make sure the setup has not vented.

Forepump valve to be closed (1/2).

Forepump valve to be closed (2/2).

Start-up procedure

1. Turn on the forepumps.
2. Open the forepump valves.
3. Once the FSRC and MEMB pressures reach 1 mbar or less, turn on the turbopumps.
4. Wait for all the turbopumps to spin up to full speed and check the pressures.

Unplanned power outage

When the power is out

Should a power outage occur and the setup vents, please open the nitrogen valve [pictured below]. Call/message Olga at +31 627168702.

Nitrogen valve (closed) located at the back of the setup.

When the power is back up

When the power is back, please follow this procedure:

1. Close the nitrogen valve.
2. Make sure the forepumps are on and the pump valves are open (see picture). The forepumps pumps should automatically turn on when the power comes back and they were not turned off.
3. Wait until FSRC and MEMB pressures reach 1E-1 mbar.
4. Turn on the turbopumps.

Turning on the turbopumps

To turn on the Pfeiffer pumps (DCU 600 and the bottom left DCU), press the rightmost button (see picture). For the Edwards pump (bottom right) open the system control menu and change TURBO: OFF to TURBO: ON. All the turbo pumps should be pre-programmed and there should be no need to change any of the settings. The set rotation speed for the pumps is 660 Hz for the big turbo (DCU 600) and 1000 Hz for the small turbos.

Turbopumps at US 4.1