Update instructions, replacing Section III-V of Appendix A of the 405 Advanced Lab Manual

Last updated 03/13/01

 

  1. Operating procedure to achieve high vacuum in the e/m apparatus
    1. Warming up the system
      1. Make sure all of the valves are closed (turned clockwise). Little force is needed for these valves to seal, and over-tightening can destroy them.
      2. Turn on the mechanical pump. (The switch located on the pump station control panel)
      3. Open the foreline valve. (Turn the valve knob counter-clockwise 2 or 3 turns)
      4. Turn on the Granville-Phillips Ionization Gauge Controller by toggling the power switch to "ON"
      5. Observe the TC-1 meter - this measures vacuum in the diffusion pump.
      6. When the meter for TC-1 reads 10-2 or less, turn on the diffusion pump (switch is located on the pump station control panel). The diffusion pump will take about 30 minutes to heat up and reach operating temperatures. If the system has been contaminated, the diffusion pump will need to run for several hours before use.
      7. After the diffusion pump has been on for a minimum of 30 minutes, turn on the ionization gauge tube by toggling the "filament" switch to "ON". Make sure the autoscale switch is set to "ON".

    2. Roughing out the upper chamber
      1. Before proceeding, DOUBLE CHECK:
        1. the mechanical is running
        2. the foreline valve is the only valve that is open
        3. the upper chamber is secured tightly with the wingnuts/screws
      2. Close the foreline valve. (NEVER leave this valve closed for more than 5 minutes when the diffusion pump is operating)
      3. Open the roughing valve. (Normally when the mechanical pump is removing air from the system, it will make a gurgling noise)
      4. Notice the TC-2 meter. This meter is measuring the vacuum in the upper chamber.
      5. When the TC-2 meter for reads 10-2 or less, close the roughing valve.
      6. Open the foreline valve. (Remember this valve should not be closed for more than 5 minutes)

    3. Pumping with the complete system to achieve high vacuum
      1. Before proceeding, DOUBLE CHECK:
        1. the upper chamber has roughed out (TC-2 meter reads 10- 2 or less)
        2. the foreline valve is open
        3. the roughing valve is closed
      2. Open the high vacuum valve.
      3. Turn "ON" the ionization gauge tube by toggling the switch to "ON". .
      4. Pour liquid nitrogen into the cold trap. (the technician will do this for you; please notify technician when you are ready to have the liquid nitrogen added)

  2. Opening the upper chamber
    1. Close the high vacuum valve
    2. Open the air inlet valve
    3. When the hissing stops, close the air inlet valve
    4. Remove the upper chamber flange by loosening the 6 wingnuts

  3. After you have finished

    4. Vacuum systems should not just turned off. The diffusion pump needs time to cool
    down before the mechanical pump can be turned off. This is accomplished by:

    1. Close the high vacuum valve
    2. Turn off the ion gauge tube by flipping the filament switch to "OFF"
    3. Turn off the diffusion pump
    4. Turn off the Ionization Gauge Tube Controller
    5. The mechanical pump should run for 45 minutes as the diffusion pump cools down. You do not have to wait for the diffusion pump to cool; simply inform the lab technician that you have completed the experiment.