INFICON Crystal 12 Sensor - Manual (Page 32)

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Crystal12 Sensor Operating Manual
Build the Sensor/Feedthrough Assembly. Remove the sensor and the feedthrough,
cut the water cooling tubes and air tubes to the proper length and connect them
directly to the feedthrough or use vacuum rated couplings.
CAUTION
To prevent damage to the feedthrough or sensor during
welding or brazing, insure that at least one inch of water
tube is left between the sensor and the feedthrough.
After cutting the water and air tubes, verify that they are clear of metal particles by
forcing compressed air through the tubing. Heliarc welding is recommended (torch
brazing may also be acceptable) for connecting the sensor to the feedthrough
water tube.
Vacuum rated connectors such as CAJON® are recommended for use between
the sensor and the feedthrough to speed maintenance. If brazing adapters are to
be used, attach them to the sensor water-cooling tubes prior to connection to the
feedthrough. Make connections as follows:
1 Clean the water tube and adapter surfaces with solvent if necessary.
2 Apply brazing flux to surfaces being joined.
3 Braze the connections using a flame temperature appropriate for the brazing
material being used.
CAUTION
Excessive application of brazing material, or excessive
heat due to brazing, may result in blockage of the water
tube.
4 Verify that each joint is not blocked by blowing compressed air through the
cooling tubes.
5 Thoroughly clean the braze joint and helium leak test before installing the
sensor and feedthrough into the process chamber.
Once all water and air tube connections are fabricated, install the sensor and
feedthrough assembly into the process system and secure all retaining hardware.
Shield the coax cable from heat radiating from the evaporant source or the
substrate heater. You can do this very simply, if your process allows, by wrapping
aluminum foil around the cable and water tubes. Connect the external water tubes
from the feedthrough to your water supply system and flow controller. We
recommend using detachable couples (Swagelok® or equivalent) for external
water tube connections. Apply water pressure to verify flow and tightness.