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: HV Feed through
Date: Nov 19, 6:24 pm
Poster: Joshua Resnick

On Nov 19, 6:24 pm, Joshua Resnick wrote:

I have started building a HV feed for my new chamber. One of my professors used to design HV power feed through devices and was a wealth of information. My design is based on the fact that the electric field between the conductors in a coaxial cable can be minimized if the ratio of outer diameter to inner diameter is e. So Do/Di = e. This formula is not trivial to derive but you don't have to be a rocket scientist either. My design incorporates this fact. Basically I have radius cut 1 9/16" hole in the center of my baseplate. There is a two halved 3" diameter Teflon "sandwich" that fits on either side of my .5" aluminum baseplate. Through the Teflon piece is an aluminum shaft cut to .575", roughly Do/e. This will act to minimize the E field around the feed through. RTV silicone is used to seal any possible air gaps next to the Teflon and the metal, as to avoid ionization by stress amplification. The theoretical upper limit to this design is over 300,000 volts. However, I'm sure that imperfections would cause a breakdown at a lower voltage, but thanks to Teflon, its pretty close. This bushing then mates with an Alumina shaft leading to the inner electrode.