937B Controller Instruction Manual
pg. 97
11.3.2 Clean the I-Mag Sensor
Depending on the degree of contamination and the 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.
Ultrasonically clean surfaces using only high-quality detergents compatible with aluminum (i.e.
ALCONOX®).
Scrub 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 the black residue left on aluminum parts in a
50 to 70% nitric acid dip for about 5 minutes.
Chemical cleaning should not be used to clean the anode; mild abrasives or
ultrasonic cleaning are acceptable.
Do not damage the leaf spring (1) while cleaning or assembling the sensor.
Each of the cleaning methods described above should be followed with multiple rinses of deionized water.
Dry all internal components and the sensor body (9) in a clean oven set at 150°C. The two ceramic
spacers, (4) and (7), are slightly porous and will require longer drying time in the oven to drive off the
absorbed water.
11.3.3 Assemble the I-Mag Sensor
Wear gloves and assemble with clean tools.
1. Roll the sensor body (9) on a flat surface and, looking down the port, check the anode (10) for
any radial runout motion. It should be straight and centered with the sensor body (9) for proper
operation.
2. Install the ground shield (8) using tweezers. Make sure that the ground shield (8) drops into the
locating collar (11).
3. Slide the small ceramic spacer (7) over the small end of the ground
shield (8).
4. Check that the leaf spring (1) will contact the base of the cathode (6),
as shown to the right. If not, remove the small ceramic spacer (7)
and the ground shield (8), and gently bend the leaf spring (1)
towards the anode (10) and then replace the ground shield (8) and
ceramic spacer (7).
5. Slide the cathode (6), the grid washer (5), and the large ceramic
spacer (4) into place. The grid washer (5) has a concave shape.
Refer to the figures to see its installation orientation.
6. Insert the small end of the compression spring (3) into the sensor
body (9).