Maintenance
9. Connect the cold head cable to the cold head. Be sure the other end of the cable is
connected to the compressor.
10. Open the vent valve on the adapter fitting installed on the return coupling of the cold head.
11. Open the charge valve on the supply coupling of the cold head.
12. Start the compressor. The cold head valve motor will also run, allowing the gas to circulate
through the cold head and discharge through the vent valve.
13. After running 30 to 45 seconds, close off the helium supply with the gas cylinder valve (not
the regulator). Watch the regulator pressure gauge. When the pressure falls to 35 to 70
kPa (5 to
10 psig), open the gas cylinder valve to increase the pressure to 690 kPa (100 psig).
14. Repeat Step 13 ten-(10) times.
15. Close the vent valve.
16. With the gas cylinder valve open and the cold head operating, remove the adapter fitting
from
the cold head return coupling.
17. Press the compressor power switch to stop the compressor and the cold head valve motor.
18. Adjust the gas cylinder regulator to charge the cold head to the system equalization
pressure
specified for the compressor being used in this system.
19. Close the charge valve on the adapter fitting.
20. Close the gas cylinder valve.
21. Disconnect the charge line from the adapter fitting. Store the charge line to keep it clean.
22. Remove the adapter fittings from the cold head supply and return couplings.
23. Disconnect the cold head cable from the cold head.
24. Reinstall the cold head in the cryopump. Refer to Cold Head Installation into the Cryopump
in the System manual.
This completes the procedure for gas cleanup and recharging of the cold head (or cryopump). It
is now ready to be connected to the system if the compressor and gas lines do not need to be
cleaned. See the Installation section of the System manual.
Gas Cleanup of the Compressor
Refer to Gas Cleanup in the Maintenance section of the Compressor manual.
Leak Check the Refrigeration System
In addition to identifying suspected leaks, check the gas-charged component for helium leaks
each time it has undergone any amount of disassembly. Use a helium mass spectrometer leak
detector if available. Follow its manufacturer's instructions.
If a leak detector is not available, use a commercial leak detection solution. However, small
leaks may not be detected. Also, it is important to:
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