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: A heretical thought
Date: Mar 24, 10:17 am
Poster: Jim Lux

On Mar 24, 10:17 am, Jim Lux wrote:

>>>BTW is creating a hard vaccum in a large sphere more difficult compared to a smaller sphere?.
>What about sealing difficulties?. e.g if you made a chamber out of 2 half spheres for instance. Does the greater distance you have to seal over present any extra difficulties as you increase the size of the chamber?

In theory, if you've used conflat type flanges and a deformable gasket bewteen knife edges, the gasket doesn't leak appreciably. (the knife edges make sure you don't have a virtual leak, as would be the likely situation with a flat gasket between flat surfaces).

However, the bigger the system, the more likely you have more feedthroughs, access plates, etc., all of which are an opportunity for screwup. Once you've got all those done right, though, outgassing from the chamber wall will be the major contributor. (And a dominant one, by the way... typical number of 1E-8 torr liter/sec/sq cm for stainless steel after pumpdown for a day)...