Hello From Rural Dorset

Please take a moment to introduce yourself in this forum and tell us about your interest. You must use your full real name. We do not allow the used of "handles" and pseudonyms on this site.
Post Reply
fabian bunbury
Posts: 4
Joined: Sat Jul 28, 2018 12:21 am
Real name: Fabian Bunbury

Hello From Rural Dorset

Post by fabian bunbury » Sun Jul 29, 2018 3:01 pm

Hello everybody,

I'm a mechanical engineer from rural Dorset and am excited to get into basic fusion. I'm lucky to have access to a fully kitted out workshop (at work) so I can build most things. I have already built most of my first fusor, but am still ironing out some of the bugs and so have lots of questions for you guys. I'm mostly struggling with the vacuum technology because I really want to build my fusor so that it can maintain the vacuum even when the pump is turned off.

I look forward to getting to know all of you exciting and inspired people!
-Fabian Bunbury

User avatar
Richard Hull
Site Admin
Posts: 10918
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Hello From Rural Dorset

Post by Richard Hull » Sun Jul 29, 2018 4:23 pm

Welcome. It is great you are equipped to handle the build. Vacuum technology is, indeed, critical to the operation of the fusor. Your feeling that you would like to have a "pumps-off" vacuum hold at working pressure is admirable. You will come to appreciate the statement, "nature abhors a vacuum".

All the best in your efforts.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

User avatar
Dennis P Brown
Posts: 1529
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: Hello From Rural Dorset

Post by Dennis P Brown » Mon Jul 30, 2018 12:23 pm

Hello but do read the FAQ section on operation of fusors - they require active flow of deuterium gas so these devices are not exactly a 'sealed' system. But certainly, eliminating leaks and reducing 'virtual' leaks (out gassing) pays off in a clean system.

Dan Knapp
Posts: 205
Joined: Wed Aug 06, 2008 12:34 pm
Real name: Dan Knapp

Re: Hello From Rural Dorset

Post by Dan Knapp » Mon Jul 30, 2018 12:43 pm

Fusors don’t “require” flowing deuterium. It’s easiest to adjust pressure with a flowing system, but some fusors operate in sealed mode. One just needs a very good vacuum system to hold vacuum for any useful period of time. I was just reading Doug Coulter’s posts. He does not use flowing deuterium. Also, commercial IEC based neutron generators are sealed systems (e.g. NSD).
Last edited by Dan Knapp on Tue Jul 31, 2018 2:57 pm, edited 1 time in total.

User avatar
Richard Hull
Site Admin
Posts: 10918
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Hello From Rural Dorset

Post by Richard Hull » Mon Jul 30, 2018 7:22 pm

The key to a sealed fusion or neutron producing system is all about gas loading the system and its components such that the system re-gases itself as it buries more and more gas within the system. (nearly impossible). No sealed neutron system lasts...Period! The pre-loaded target unloads over time and complete replacement of the tube or reloading of the target is necessary. In the amateur fusor, continuous flow against what is termed "differential pumping" is the only way to reach a significant, repeatable level of fusion.

In any sealed system, any gas ions are buried and the pressure drops, it is a given. This assumes a perfectly sealed system. Old cold cathode x-ray tubes got "hard" and would no longer function. A Technician would bombard heat a loaded palladium electrode in one arm of the tube to re-gas it and restore it to operational status. With the advent of the Coolidge tube in the 20's with a heated cathode, the hard vacuum was needed. The technicians were soon out of work.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Dan Knapp
Posts: 205
Joined: Wed Aug 06, 2008 12:34 pm
Real name: Dan Knapp

Re: Hello From Rural Dorset

Post by Dan Knapp » Tue Jul 31, 2018 2:57 pm

I erroneously said "NRD" in my post above. It should have read "NSD" (http://www.nsd-fusion.com) (original post has been edited). They claim 20,000 hour lifetime for their sealed tube system. It's not exactly IEC in the usual sense. Instead of a grid, they use a solid cylinder target surface in a cylindrical geometry electrostatic acceleration system. Thermo sells a similar system with similar claimed lifetime. As Richard stated, the secret lies in gas loading. These systems tend to store fuel gas (either deuterium or tritium) in a getter so it can be released as needed.

User avatar
Dennis P Brown
Posts: 1529
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: Hello From Rural Dorset

Post by Dennis P Brown » Wed Aug 01, 2018 12:58 pm

A few words but I feel this topic is off track a bit to what the poster said and what they need to know. Since none of us create commercial systems this whole point is not exactly something most of us (certainly myself) could build - a working sealed fusor. In reality, we amateurs that even struggle with micron level vacuum systems require a flowing deuterium system to have a good chance to make a viable fusor; and that is what anyone building a first fusor should aim for. Frankly, the vast majority of posts and all the FAQ's on the subject deal with flowing systems.

For exactness, sealed systems can be built but that is an unlikely project for most here and new posters should build the 'easiest' system; for truthfully speaking, very, very few will ever achieve fusion (detectable) using even a simple flowing system. Speaking of exactness, I should mention that in my fusor I use fine deuterium gas flow rate to control my current (to first order), not system pressure (though overall system voltage is strongly controlled by ultimate pressure.) I use the DP gate valve to control gross system pressure (and my working voltage.)

Post Reply