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: Equipment issues (was Fusion reaction rates)
Date: Dec 23, 10:19 am
Poster: Jim Lux

On Dec 23, 10:19 am, Jim Lux wrote:

> Yep. The diffusion pump is now a poor man's toy. Few pros will accept them in a system anymore and few in their right professional mind will spec them for any serious new installation.

Except in production systems. I've seen some fairly large diff pumps in vacuum metalization systems (where they evaporate a thin layer of metal onto, for instance, sunglass lenses). They just don't build turbo pumps big enough (24 inch throat), and for that application, you don't need killer vacuum, just a decent mean free path.

Also, BIG BIG diff pumps are used in space simulators. I was recently reading the specs on the big chamber at JPL (20+ feet in diameter and 50+ feet high) which can be pumped down to 1E-7 in 40 minutes....

However, in the small (2-8 inch size) pump area, I'd say that turbos and cryopumps rule the day right now... which is good for us, since it puts all those "obsolete" but perfectly functional diff pump stacks on the market cheap.