INFICON TM-400 Thin Film Deposition Monitor - Manual (Page 45)

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TM-350/400 Operating Manual
Chapter 5
Sensor, Feedthrough and Oscillator
5.1 Sensor Head Description
The Sensor head is designed for simple installation and easy crystal replacement.
It consists of two parts: a water-cooled 304 stainless steel housing which is
permanently positioned in the vacuum system, and a quickly removable gold plated
304 stainless steel crystal holder which snaps into the housing. The crystal holder
accommodates an industry standard 0.550” diameter crystal.
This design provides several convenient features in performance and use. The
crystal holder is thermally shielded by the water-cooled housing insuring excellent
crystal performance in temperature environments up to 300 °C.
The exposed crystal electrode is fully grounded to effectively eliminate problems
due to free electrons and RF interference.
The crystal holder is easily removed and installed even in awkward location in the
vacuum system. Once removed from the housing, the crystal is still retained in the
crystal holder by a snap on retainer. The crystal can be easily replaced without
tools at a more convenient place, such as a clean bench.
The housing is provided with four tapped (4-40) holes for convenient mounting, 1/8”
diameter × 30” long inlet and outlet water-cooling tubes, and a coaxial connector.
The electrical connection to an instrumentation feedthrough is made with a 30”
coaxial cable. Both ends of the cable terminate with standard Microdot® S-50 type
connectors. Cable lengths up to 60” are available upon request with a
factory-modified oscillator.
5.2 Sensor Head Installation
The sensor head can be installed in any appropriate location in the vacuum
chamber, preferably more than 10 inches from the evaporation source. It can be
supported by its integral mounting bracket furnished with two #4-40 tapped holes.
The internal (vacuum) cable, supplied with the sensor kit, connects the sensor
head to the dual water/electrical feedthrough, to which the oscillator is attached.
The cable length from the sensor head to feedthrough connection should not
exceed 60 inches. Cable lengths in excess of 30 inches require a factory-modified
oscillator. Shield the sensor cable in the most expedient way possible to protect it
from radiation heat released from the evaporation source or the substrate heater.