937B Controller Instruction Manual
pg. 94
The cathode and anode assemblies are attached to the flange. Disassem bl y
should proceed f rom the bot tom to the top of the internal assembl y d raw ing .
6. To remove the cathode (23), release the two integral, spring-loaded ears that are hooked over the
shoulder of the ceramic insulating support (19).
7. Gently pull up on the ear until it just clears the outer diameter of the ceramic insulating
support (19).
Note the small Elgiloy
®
leaf
(18)
used to connect the ion current feed-through
(17)
to
the cathode and its position. The rotational position of the cathode with respect to the leaf
is not critical, however, be careful not to bend the leaf.
8. Slide the cathode (23) and washer (23) off the insulating support.
9. The insulating support is captured by the guard bolt (21). Remove this using a spanner wrench
(see accessory section) and unscrew the guard bolt from the flange (13).
There is a small curved spring washer
(20)
under the head of the guard bolt. This
spring washer holds the insulating support tight, preloads the guard bolt to resist
unscrewing due to possible vibration, and provides compliance for differential thermal
expansion during bakeout.
11.2.2 Cleaning the Series 431/422 Sensor
Depending on the degree of contamination and application of the sensor, the internal parts may be
cleaned
— either ultrasonically, with mild abrasives, or chemically.
Do not touch any vacuum exposed part after cleaning unless wearing gloves.
Ultrasonic cleaning should use only high-quality detergents compatible with aluminum (e. g.
ALCONOX®). Scrub surfaces with a mild abrasive to remove most contamination. Scotch-
Brite™ or fine
emery cloth may be effective. Rinse with alcohol.
Clean aluminum and ceramic parts chemically in a wash (not recommended for semiconductor
processing), such as a 5 to 20% sodium hydroxide solution, at room temperature (20°C) for one minute.
Follow with a preliminary rinse of deionized water. Remove smut (the black residue left on aluminum
parts) in a 50 to 70% nitric acid dip for about 5 minutes.
Each of the cleaning methods described above should be followed with multiple rinses of deionized water.
Dry all internal components in a clean oven set at 150°C. The ceramic parts
are slightly porous and will
require longer drying time in the oven to drive off the absorbed water.
11.2.3 Assemble the Series 431/422 Sensor
To reassemble the sensor, reverse the order of procedures used during disassembly. Note the following
tightening procedure for the guard bolt. The bolt has a 3/8-40 thread design that is delicate.
1. Finger tighten the guard bolt to compress the spring washer and then back off one turn.
Do not over tighten as this will remove all compliance from the spring washer and
possibly damage the aluminum 3/8-40 thread.
2. Verify that the anode (14) is well-centered within the bore of the guard bolt.
3. If it is off center, carefully bend it back into position and continue with the assembly.