Agilent Technologies UHV-24, Инструкция по эксплуатации

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UHV-24/UHV-24p Ionization Gauge
16
DRAF
T
❑
Ground loops can be formed because the chambers are grounded and the controllers
are grounded. For safety reasons, never float any controllers that can be touched
during operation. Because of the low magnitude of ion currents being measured, it is
possible for a ground loop current to overcome the ion gauge signal, sometimes
resulting in a current flowing into the gauge collector. This often happens when the
ion pumps are running on one phase of the AC power system and the
instrumentation is operating off another phase. Experimentation is usually the only
answer to find and fix this kind of problem.
Degas
All UHV-24 and UHV24p gauges are operated and degassed at the factory before shipment.
Whether to degas the gauge after installation depends upon the application. In large systems
that take a long time to pump down, such as several days, or will be baked for an extended
period of time, degassing the gauge has a negligible affect. Considering that the e-beam
degas system used runs at a high emission current, it may not be worth the theoretical
reduction in filament life that results from the small reduction in gas load. In small systems,
where the gauge is a larger percentage of the system surface area and gas load, there may be
benefits to using degas after installation.Gauge degassing is not generally needed unless the
goal is to reach pressures below 1x10
-8
Torr. Degas is not intended to clean tube
contamination.
If using degas, a 15 minute e-beam degas duration, using Agilent Multi-Gauge and senTorr
controllers, is all that is needed. Extending the degas interval only serves to heat up the
surrounding chamber walls and increases the out-gassing rate from those surfaces. Bakeout
is a better way to degas the chamber walls.
Bakeout
A temperature of +450 °C is a safe maximum for repeated or extended bakeout of the nude
gauge.
Do not:
❑
450 °C
❑
Expose the gauge to thermal shock