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Subject: Re: slightly OT: Cold Cathode Ion Gauge
Date: Jan 17, 0:23 am
Poster: Richard Hull
On Jan 17, 0:23 am, Richard Hull wrote:
>Can any of the vacuum practioners here tell me anything about cold cathode discharge gauges? They seem to be a type of ion gauge, and are listed on the duniway site as being good from 10^-2 torr down to 10^-10 torr. They are fantastically cheaper than an ion gauge -- a package including both tube and controller for the cold cathode gauge is $900, while an ion controller alone is $1600. Thoughts?
The cold cathode gauge is indeed an ion pump of sorts and is often touted or used as an "appendage pump" of .5 to 1 liter/sec pump speed. The problem is they really have a useful range of 1micron to about 10e-7 max. On etiher side of these limits the ranges start to crunch. Just like the TC and ION gauges, the cold cathode gauge is gas dependent and is usually cal'd for air. Also, they crude up rapidly if used in the 10-1 micron range for any period. Most folks opt for a TC gauge in addition to the CC gauge or ion type.
The pros rarely spec these systems anymore the capacitive manometer is now the gauge of choice. Many larger ion pumps also include a pressure gauge based on the pump action. The appendage pumps are quite often just an excuse to gauge with them.