Operation of the pumping cart
 

1. Attach KF25 baffle to whatever you are pumping down. Make sure the pump vent KF10 flange on the turbo molecular pump is closed and sealed. The valve at the top of the turbo pump should be closed.

2. Start the mechanical pump (by turning on cart power strip), it should initially sound like it is pulling hard but it should quiet down, if it does not then check for an open valve or a major leak. Watch and record the time the diaphragm ashcroft gauge on top takes to go down (it usually takes 3 to 4 seconds immediately after you turn the pump on).

3. Turn on the thermocouple gauge controller[1] TC 1(the big black box at the bottom) and the Pirani gauge controller (the yellow box in the middle at the right side). Use the chart on the thermocouple gauge to convert the reading of microamperes to pressure. You should see the pressure drop to between 70 and 100 milliTorr (microns of mercury)

4. Pump down at a rate of 10kPa per minute.

5. Once the pressure is below 0.5 mBar, start water flowing through the turbo pump. The ideal water rate should be between 10ml/s and 20ml/s.

6. Once the water is flowing and the fan is on, start the turbo pump by switching on the "pumping unit" button of the controller (grey box, bottom right).
   You should see a pressure drop on the Pirani gauge and a slight rise in the pressure on the bottom thermocouple gauge.

7. Once the pressure in the thermocouple has bottomed out turn on the ion gauge. For the ion gauge controller (the long silver box on top), first turn on the power then the filament. Keep the Emission on 1 (increse it when the pressure gets really low).

8. Unlike the thermocouple gauges, the ion gauge should not stay on for a long period of time. Turn the ion gauge, wait a couple of minutes for the signal to level out, then turn it off

9. TURNING OFF THE VACUUM SYSTEM: Once the pressure has reached a desirable level, close the valve on the system. Turn the turbo pump off by pressing the "pumping unit" switch on the box. Check the pirani gauge to make sure the pressure is increasing (may take a minute or two). Turn off the water. Turn off power to the entire unit (which turns off mechanical pump - which at this point may be very hot if it was running for a while) by switching off the power strip.

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[1] The current suerving the termocouple gauge should be 0.62A. The current is 0.6A and because the gauge is numbered “2” on its nipple it should be 0.62A, which means the number on the gauge is the second digit after the decimal point.
[2] Under zero load (not pumping on any chamber), it takes about 4 minutes for the Pirani gauge to reach 0.03 Torr, about 5 minutes for the Ion gauge to reach 0.00004 Torr and the thermocouple gauge stays at 65 mTorr from the beginning.


This page is reserved for pumpdown procedures and things associated with the 2 stage pumping/vacuum cart