Methyl Halide Trap Removal/Installation
Removal of trap
  1. Turn of cryo-cooler and let warm to room temperature, usually a full day.
  2. Turn off power to GC
  3. Lower the side panel and hold in place with wire or string.  This will allow for easier access to the fittings on the trap inside the GC.
  4. Disconnect fittings to trap, one is inside the GC and one is on the exterior.
  5. Disconnect thermocouple connection and Winchester connection.  It is easier to cut the Winchester off and solder it back after new trap is installed.
  6. Cut the tubing on the trap behind the nut that is inside the GC.  Also cut wire off close to trap tubing.
  7. Pull trap out of the cold block from exterior side of GC.

Installation of new trap

  1. Clear any debris from inside the cold block where the trap will be inserted.  Also dry the hole as best as possible.
  2. Slide new trap through the hole, taking care not to force it through.  The trap should be snug but be careful not to damage it.
  3. Remove tape from trap end and connect 1/16" Valco nut and ferrule fitting to trap on inside of GC.
  4. Now connect trap to tubing inside GC.
  5. Solder Winchester connector back onto trap leads and reconnect to proper mate.
  6. Reconnect thermocouple connection.
  7. Align trap to alignment marks with outside of cold block (usually a pen mark or tape).
  8. Close side panel of GC.
  9. Turn down the duty cycle of the transformer to about half of the current value.
  10. Turn on GC power and check to see if thermocouple is reading appropriate room temperature (on Omega controller) and let the GC come to temperature.
  11. Turn on cryo-cooler and let chill to its lowest point.
  12. Turn the computer on.  Once on, open a shell and run labdoit.
  13. From labdoit you can test the response of the trap.  First heat the trap by typing "heater 2 on" while on the “chroms” screen.  Note you can also type "heater 2 off" to stop heating.  You should see the trap heat immediately.  The Omega temperature controller will try to hold the temp at 130 C.  If the trap heats to 130 C faster than about 5 seconds, the transformer duty cycle is set too high.  Also watch the maximum temperature reached.  If the trap is heating to 150+ C then the variac is set too high. Toggle the trap heater several times and slowly adjust the variac setting to heat the trap to 130 C in about 5 seconds.
  14. With the transformer set, quit the labdoit program (type "quit" in the chroms screen).
  15. Start the run sequence (type: "rungc" on the command line).
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