Page 1 of 1

The world's largest fusor

Posted: Sat Jul 26, 2014 8:41 pm
by Dan Knapp
The 51st Culham Plasma Physics Summer School was held the past two weeks at the Culham Centre for Fusion Energy, the home of JET (the Joint European Torus) the world’s largest currently operating tokamak. In one of the lectures, it was discussed how the JET plasma is heated by injecting up to 100 KeV deuteron beams, produced by electrostatic acceleration of deuterium ions (as in inertial electrostatic confinement) prior to charge exchange and injection as a neutral beam. In response to the question of what part of the total fusion in JET results directly from collisions of these electrostatically accelerated energetic deuterons, the answer was “most of it,” with only a very small fraction of the total fusion occurring in the thermal plasma when operating with deuterium. This means that JET is actually now operating primarily as a huge doughnut-shaped fusor! It is expected that with the start of the planned deuterium-tritium operation, thermal plasma fusion will predominate; but as of now, JET as it currently operates is actually the world’s largest fusor! Who said IEC wasn’t at the forefront of fusion energy research?

Re: The world's largest fusor

Posted: Sun Jul 27, 2014 3:48 am
by Richard Hull
In spite of what you might say or feel to be the case, I can't find it credible that JET is an electrostatic device, in the end. Claims referencing its output in some runs have been made for JET that just can't be accomplished using an electrostatically focused machine.

Richard Hull

Re: The world's largest fusor

Posted: Sun Jul 27, 2014 10:46 am
by Dan Knapp
JET is clearly a magnetic confinement device designed to do fusion in a Maxwellian thermal plasma. The point was that the majority of the fusion in present operation is from collisions of the non-Maxwellian injected beam as occurs in a fusor. The record energy production in JET was when they did shots with low levels of tritium years ago. The planned tritium campaign will use higher levels of tritium.

Re: The world's largest fusor

Posted: Sun Jul 27, 2014 11:07 am
by Chris Bradley
I have also delved into this topic and the figures of merit I found (combination of discussion with researchers, and papers) the beam-fusion energy component of JET's highest output runs using DT was around ~2 MW fusion power of 22 MW peak total, and ~2 MJ of the 18 MJ of the run. That being said, I believe the 'beam fusion' was added to the fusion output, rather than regarded as a 'power input', so the total thermonuclear fusion power was around 18 MW, 14 MJ, the beam fusion element therefore being in excess of 10%.

Re: The world's largest fusor

Posted: Sun Jul 27, 2014 5:41 pm
by Dan Knapp
The 1997 JET experiments with DT achieved the still current record of 16 MW of fusion power using low levels of tritium. This was about two thirds of the power used to heat the plasma. The planned tritium campaign will use higher tritium levels and could achieve the first breakeven, or even net energy production. Given that the fusion power resulting from the direct collisions of the injected, electrostatically accelerated heating beams still account for a significant part of the total fusion power generated in DT experiments, it could well be that this fraction of "IEC type" fusion will be what finally pushes the total past the breakeven point. Given this, it is surprising that many (if not most) of the magnetic fusion people have never even heard of inertial electrostatic confinement fusion, or, if they have, regard it as an irrelevant thing that kids do in science fair projects.
I don't believe it is correct to count the beam fusion power as input. The power used to produce the beam is clearly input, but the direct fusion power generated from the beam collisions is still part of the total fusion power generated.

Re: The world's largest fusor

Posted: Sun Jul 27, 2014 9:02 pm
by Chris Bradley
It is a neutral beam injection, so bears little in common with a fusor.