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: vacuum setups
Date: Feb 04, 09:25 am
Poster: Richard Hull

On Feb 04, 09:25 am, Richard Hull wrote:


In studying Scott Little's and others fusor photos on line, one gets an idea about the level of vacuum materials available to those experimenters.

Most would-be fusorites are like me, struggling to get good stuff and assemble some sort of minimal, but clean system.

Scott is very fortunate as I note a beautiful 2.75 conflat right angle valve ($400 new, 250.00 used)
The 2.75 "X" looks mint! (Another $100.00)
The view port is good for an additional $200.00. The real indicator of super stuff is the pro quality silver plated 12 point bolts.

I muse over the fortunate ones who have access to a college or professsional lab's resources. They can avoid a minimum of $1,000 worth of just very basic infrastructure costs over what we poor slobs clawing our way up the vacuum ladder are forced to shell out.

Most of my stuff is .............make that 100% of my stuff is vomitis from other labs junk piles complete with caked on crude, bakeout burns, dents, etc. I often have to spend hours refurbishing stuff, and if I costed out my labor at even a burger flipper's wage I could have bought the piece new! Alas.......

Still, where there is a will, there is a way.

I am now postioned to actually run a truely clean system with final pressures in the 10-6mm range allowing me to back fill with deuterium gas to working pressures of 1 to 0.1 microns.

A TC gauge, which I once considered a luxury is now rated by me as a must have - absolute minimum level instrument! I am considering a penning or "cold cathode" gauge which can read as low as 10-6mm but can span the highly valued and often missed range of 10-3mm to 10-4mm. Ion gauges are really not all that happy or linear at 10-4mm. Their filaments are strained and lives shorted if one hovers in the 1-.1micron range, which is just where most real neutron work will be done. The venerable and valuable thermocouple gauge is bottomed out at 1 micron. The best TC gauge to use is a DV-6M or better still a 1518 TC gauge tube. These at least have an expanded low end.

I currently know that I am in the promised land when my TC gauge needle dips below zero. But just how far into submicron land I am is a mystery. Most of this wonderful adventure is due to the high current ion pumping action of the fusor itself as errant molecules of crude are buried in the walls. The ultra clean and babied mechanical pump in my system is normally limited to an honest 2 microns.

MY best move thus far has been adopting an all stainless system. This is something few can afford or assemble. Scott, Joshua, and others are fortunate to have good materials and equipment available.

Richard Hull