2000 MS Hardware Maintenance
72
Chemical Ionization Options
15. Do not turn on the filament or multiplier for about 2-3 minutes after opening the
CI valves. A convenient way to verify that air and water have been removed
sufficiently is to check the ion gauge pressure with the CI valves open. Verify
that the pressure has returned to less than 35 x 10
-6
Torr before turning on the
Filament and Multiplier.
Changing a Channel from Gas to Liquid Operation
To change a channel from gas to liquid operation, the lower restrictor (03-
930596-01) must be replaced by a higher flow rate restrictor (03-930596-02), and
a reservoir bulb must replace the inlet plumbing. The free ends of all restrictors
and tubes should be capped to prevent contamination and plugging during
storage. When finished with the switchover, all ports of the MCI Module must be
connected or plugged.
1. Turn off all relays to the MCI Module.
2. If you have a
turbo pump system
, skip this step. If you have a
diffusion pump
system:
For each channel that will be worked on, close the associated needle
valve by turning the knob clockwise. Monitor the foreline pressure. Do not allow
it to exceed 500 mTorr for more than 20 seconds. This will reduce the inrush of
air into the vacuum system when the channels are reactivated.
3. Remove the MCI cover by loosening the thumbscrew on the front cover.
4. Using a Phillips-head screwdriver, loosen (but do not remove) the four screws
located between the solenoid valves on top of the module.
5. Remove the gas adapter fitting with the long gas line restrictor (28-695138-00
and 03-930597-00, respectively) from the ¼ inch port. Gently twist and pull the
adapter out, from under the manifold.
6. Remove the lower restrictor (03-930596-01) installed in the two 1/8-inch ports
underneath the manifold block and save it in the MCI Module Accessory Kit.
7. Insert the short lower restrictor (03-930596-02) in these ports.
Hazardous chemicals may be present. Avoid contact, especially when
replenishing reservoirs. Use proper eye and skin protection.
8. Using the 5 mL syringe supplied in the Accessory Kit, fill a liquid CI reagent
reservoir halfway with 3 mL of the chosen CI reagent liquid.
9. Insert the reservoir neck into the ¼ inch inlet port of the channel.
10. Tighten the 4 screws on top of the module. The liquid CI reagent reservoir and
restrictor lines will be held firmly by the O-ring seal after the screws are tight.
11. Replace the MCI cover and tighten the thumbscrew to hold it in place. Make sure
that all of the lines are free and clear of the cover before tightening the
thumbscrew.
12. After installing CI reagent liquids, and each time a reagent liquid or gas is
installed, always use care when first opening the CI needle valves.
13.
If you have a
turbo pump
system
, skip this step.
If you have a diffusion
pump
system
, first turn on the relays. For each channel worked on, open the
needle valve slowly by turning the knob fully counterclockwise to clear out the air
in the lines. Monitor the foreline pressure. Do not allow it to exceed 500 mTorr
