In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.
Subject: Re: Glow cleaning/Ion Pumps
Date: Dec 17, 10:29 pm
Poster: Richard Hester
On Dec 17, 10:29 pm, Richard Hester wrote:
It sounds like an auxiliary chamber made of titanium tubing with a central wire electrode of tantalum or some refractory might be just the thing to drink up fusor crud without being too badly fouled in the process, especially if the residual geses are mostly hydrogen.
>Afer a few operations of this sort, one might be able to sort out leaks from outgassing of the chamber walls. Can anyone with ion pump experience (Tom Ligon perhaps) comment on the feasibility of using one at fusor pressures?
>> Richard Hester
>Ion pumps should never be even turned on until about 10e-6 torr if you don't want to be replacing elements on a regular basis. Thisis standard practice. They can work under extreme load at 10e-3 or 1 micron, but they foul up overnight. They are really meant to work in the region of 10e-5 to 10e-9 range....Or at the point where most diff pumps start to slow down.
>When we glow clean, we are using the fusor AS an ion pump and the crap is, indeed, buried in the walls. It is out of the way for this run and will slowly outgas during idle periods if held under vacuum. If one has a real crappy ion pump which is easy to clean or replace elements in, then Richard Hester's idea is great and you would ultimately have a thoroughly clean system. unfortunately at 1 micron a lot of what we are burying are the D2 and hydrogen gases in the chamber. Most of the moisture over time has disociated and been pumped out. Note...This takes a long time and many pumpings with never a bring up to air.