| Removal of trap
- Turn of cryo-cooler and let
warm to room temperature, usually a full day.
- Turn off power to GC
- 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.
- Disconnect fittings to trap,
one is inside the GC and one is on the exterior.
- Disconnect thermocouple connection
and Winchester connection. It is easier to cut the Winchester
off and solder it back after new trap is installed.
- Cut the tubing on the trap
behind the nut that is inside the GC. Also cut wire off close
to trap tubing.
- Pull trap out of the cold
block from exterior side of GC.
Installation of new
- Clear any debris from inside
the cold block where the trap will be inserted. Also dry the hole
as best as possible.
- 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.
- Remove tape from trap end
and connect 1/16" Valco nut and ferrule fitting to trap on inside
- Now connect trap to tubing
- Solder Winchester connector
back onto trap leads and reconnect to proper mate.
- Reconnect thermocouple connection.
- Align trap to alignment marks
with outside of cold block (usually a pen mark or tape).
- Close side panel of GC.
- Turn down the duty cycle of
the transformer to about half of the current value.
- 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.
- Turn on cryo-cooler and let
chill to its lowest point.
- Turn the computer on.
Once on, open a shell and run labdoit.
- 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.
- With the transformer set,
quit the labdoit program (type "quit" in the chroms
- Start the run sequence (type:
"rungc" on the command line).