Fusion Message Board

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 20, 9:27 pm
Poster: Tom Ligon

On Dec 20, 9:27 pm, Tom Ligon wrote:

>Richard Hull's post on glow cleaning was interesting. I suspect that the glow cleaning process re-buries crap in the walls that had outgasssed during the time the fusor was idle. Perhaps another way of removing this crud would be to use a small ion pump which will tuck away the garbage into a space where it can be valved off. 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


We have a Perkin Elmer 220 L/sec 8-section ion pump that can pull 1e-9 torr. It is a DI pump, i.e. it has both titanium and tantalum plates.

An ion pump operating at 1e-3 torr is expected to have a useful life of minutes, and may produce as much gas as they pump. They are intended for 1e-6 torr and below.

When we added a Residual Gas Analyzer to our system we found that the ion pump is a poor choice when you are adding a gas load to the system. The fresh gas impacting the plates causes old gas to be regurgitated, and all sorts of interesting chemistry occurs.

I would be more inclined to try some sort of regeneratable sorbtion pump trap. (The MicroMaze can work this way when freshly baked).