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: Incremental Steps
Date: Oct 29, 1:29 am
Poster: Richard Hester

On Oct 29, 1:29 am, Richard Hester wrote:

I've been dividing my time between my first demo fusor and an experimental metal halide laser. Important steps/acquisitions:
1) I recently got my hands on a small diffusion pump stack consisting of a Welch 1400 belt drive pump amd a mini CVC air cooled diffusion pump w/fan. The package is small and convenient (albeit heavy), and should serve to pull down my first chamber once I have both pumps cleaned out. The diffusion pump has a simple 1.125" tube inlet, and the former owners must not have needed much of a vacuum, as they used heavy wall vinyl tubing on the diffusion pump inlet. I purchased a proper compression port to KF40 adapter for the inlet at Duniway which probably set me back almost as much as the whole pump stack did.(Yeah, I probably could have silver soldered a compression port fitting to a KF40 flange after a bit of lathe work, but the difference between this and the ready made product was only about $25 anyway)

2) I've finished winding and varnishing a large toroidal pulse transformer and PFN inductor to build a spot welder. My little dental spot welder doesn't have the umph needed for large diameter wire. I've also located some decent 1400V SCRs on the surplus market, and I already have a few 60uF/1000V caps for the capacitive part of the PFN. I'm using a PFN instead of a straight capacitive setup to stretch out the welding pulse, the object being to melt the work piece rather than blow a hole in it... A small high voltage XFMR + rectifier, teeny variac, and trigger circuit should complete the electroncs part of the deal. I plan to gin up a set of spring-loaded jaws out of 1/4" thick phenolic laminate.

3) I've located a source that can laser cut alumina hybrid substrate material. If they are reasonably priced, I'll use alumina as a directly heated dispenser cathode support for the fusor. If not, I'll use mica and take my chances with the initial outgassing.

The object of this little clambake is to build a small (4" diameter)cylindrical demo fusor with dispenser cathode, operate somewhere between 0.1 and 1 micron, and juggle parameters to be able to set current more or less independently of operating pressure. We'll see...

Richard Hester