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 technology and costs
Date: Mar 11, 10:40 am
Poster: Richard Hull

On Mar 11, 10:40 am, Richard Hull wrote:

My work with the fusor is on hold for warmer weather as the lab is a bit cold just now. I have taken most of the winter to work up my neutron detector and secure better vacuum fittings.

I find that the mechanics of securing a good vacuum which can hold without any leaks, is not easy. Even though 1 micron (10-3mm or torr) is not considered more than a moderate vacuum by true "vacuum heads", it is still a dificult task to bring in all the components and connections into the fusor chamber and have it truly air tight.

Vacuum HV insulators, fittings, valves, etc. are very, very expensive. Simple store bought ball valves can work OK, but just aren't up to the task over the long haul.

My third fusor will use a mixture of professional "Conflat" and "Quick Flange" High Vacuum fittings. The rotatable Conflats are the ultimate vacuum fitting but run about $50.00 per connection with no plumbing included!!

The "QF" flange fittings allow for quick disassembly at lower relative cost. (about $20.00 per connection - no plumbing included).

A good stainless bellows vacuum valve in a brass body with solder sockets (lowest priced vacuum valve) is about $120.00.

While a basic fusor can be made up with a single valve, a proper system would require a minimum of 2 valves. A lower pumping system (diffusion pump version) might be better served with 3 valves.

As I am an electronics engineer, the electrical/electronic bothers are actually a snap. It is the vacuum area that I am struggling with.

Now that I have a good handle on all expenses, I would imagine a listing of costs would fall as below:

1. Total neophyte, no equipment, no skills in the multiple technologies involved.

A. Vacuum system cost for crude demo system. with all equipment brand new...... $800.00

As above with used pump.... $300.00

B. Vacuum system for a good, working, neutron producing fusor with all new equipment..$2000.00

As above with used and lucky finds on the most expensive items................$700.00

C. Electronics for demo system version of fusor purchased new but hand made......$300.00

As above but with used or scrounged parts...$50.00

D. Electronics for complete working, neutron producing fusor with neutron detection system. made up by hand from all new parts and components.

as above, but with all lucky finds, hamfest buys and used components...............$600.00

E. Gas delivery system includes 20 liter deuterium cyclinder and lines, regulators and simple leak or bleed valve. new ............$400.00

As can be seen a hapless neophyte with no skills and a desire to build a demo fusor might be out as much as $1000 and a working, neutron producing model might cost $4500!

If the same person is a good scrounger and knows folks who might help him assemble parts of the system (ham radio operators, etc) a demo system can cost as little as $600.00

A neutron producer can cost as little as $1500.00

The neophyte will have to immerse himself into the study of a lot of disciplines and this means a lot of books and time spent in libraries.


Costs can plunge to around 50% of the above costs based on what someone already has on hand. I consider myself exceptional, having been an experimenter for 45 years with associated accumulation of STUFF. I had a vacuum pump on hand (doesn't everyone?) All of the electronics components was on hand. I have built one demo fusor and one demo/neutron test bed fusor and am working on a third deep pumped fusor. I figure I am out about $1000.00 with little needed to purchase inorder to continue to make fusors for a while.

I know of only 3 other amateurs who have or are working on assembling fusors.

Good luck to anyone who attempts a fusor.

Richard Hull