http://www.physorg.com/news/2011-03-fus ... lasma.html
quote:
Researchers working on an advanced experimental fusion machine are readying experiments that will investigate a host of scientific puzzles, including how heat escapes as hot magnetized plasma, and what materials are best for handling intense plasma powers.
Scientists conducting research on the National Spherical Torus Experiment (NSTX) at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) have mapped out a list of experiments to start in July and run for eight months. The experimental machine is designed to deepen understanding of how plasmas can be mined for energy.
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Fusion scientists gear up to learn to harness plasma energy
Exactly the same text could have been written 30 years ago.
A vacuously empty press piece, presumably written to meet some committee-lead target for 'dissemination'. But as tokamaks have had nothing much new to disseminate for several years, that is a tough call!
The tokamak world appears to be trapped within their own study of the utter minutiae of capricious plasmas, without any clear, substantial, vision of 'why the darned thing doesn't work'.
The analogy I draw often is with a tap. The tap drips and they study each and every drop that emerges for its shape, speed, consistency, periodicity, turbulence within the drop, surface tension, optical properties, volatility, &c., &c., but all they really need to learn is how to turn the damned valve open!
A vacuously empty press piece, presumably written to meet some committee-lead target for 'dissemination'. But as tokamaks have had nothing much new to disseminate for several years, that is a tough call!
The tokamak world appears to be trapped within their own study of the utter minutiae of capricious plasmas, without any clear, substantial, vision of 'why the darned thing doesn't work'.
The analogy I draw often is with a tap. The tap drips and they study each and every drop that emerges for its shape, speed, consistency, periodicity, turbulence within the drop, surface tension, optical properties, volatility, &c., &c., but all they really need to learn is how to turn the damned valve open!
I'm not so sure studying the 'drip' in Tokamak like machines is inappropriate. The valve wide open aspects of scaling to breakeven size is reasonable, the edge instabilities issues might depend on both levels of approach, but the 'dripping valve' considerations applied to the diverter may be essential if a working machine is contemplated without operation in brief (a few seconds) pulsed modes with similar or longer intervals necessary to drain, refill and setup necessary for the next pulse. If everything else works, the diverter and it's possible modes of operation may be the final roadblock.
The diverter (as I understand it) is a valved drain that allows for the slightly different fusion ions to leave the system preferentially over the fuel ions and electrons. Or like in an internal combustion engine, the valve used to exhaust all of the burnt plasma, befor the next cycle. In a Polywell the fusion ions are claimed to leave the system naturally- a wide open valve equivalence, due to their huge difference in KE compared to the fuel ions and excess energy over the potential well, plus the cusp nature of the confinement that provides an escape path. In the Tokamak (and other cuspless magnetic confinement schemes) the fusion ions reside long enough to transfer most of their excess energy to the plasma (which serves to maintain the heat of the plasma against losses-ie: ignition). Once that happens the KE of the fusion ions is similar to the KE of the rest of the plasma (within the limits of Maxwellian thermalization of the combined ions) so any method that might have the ability to separate the fusion ions has to deal with the subtle differences of He4 and and He3 and H1 ions from the fuel H2 and H3 fuel ions. To do this , and to avoid quickly melting will be a matter of finesse.
Bussard's Polywell has been described as being something like a jet engine. Fuel goes in and products flow out naturally. A Tokamak is more like an internal combustion engine. Valves, intake, combustion and exaust cycles have to be organized in order to produce sustained useful output. Efforts with different valve technology, engine designs (like Sterling engines), and other fine optimizations have been incorporated to maximize the possibilities.
Having said that, the demonstration of the potential capabilities of the internal combustion engine was accomplished before all of these optimizations. Though still, I recall Tom Ligion's comparison to early I. C. engines,that there were fine details (carburation) that had to be figured out in the early I.C. engines before they were accepted as viable.
Dan Tibbets
The diverter (as I understand it) is a valved drain that allows for the slightly different fusion ions to leave the system preferentially over the fuel ions and electrons. Or like in an internal combustion engine, the valve used to exhaust all of the burnt plasma, befor the next cycle. In a Polywell the fusion ions are claimed to leave the system naturally- a wide open valve equivalence, due to their huge difference in KE compared to the fuel ions and excess energy over the potential well, plus the cusp nature of the confinement that provides an escape path. In the Tokamak (and other cuspless magnetic confinement schemes) the fusion ions reside long enough to transfer most of their excess energy to the plasma (which serves to maintain the heat of the plasma against losses-ie: ignition). Once that happens the KE of the fusion ions is similar to the KE of the rest of the plasma (within the limits of Maxwellian thermalization of the combined ions) so any method that might have the ability to separate the fusion ions has to deal with the subtle differences of He4 and and He3 and H1 ions from the fuel H2 and H3 fuel ions. To do this , and to avoid quickly melting will be a matter of finesse.
Bussard's Polywell has been described as being something like a jet engine. Fuel goes in and products flow out naturally. A Tokamak is more like an internal combustion engine. Valves, intake, combustion and exaust cycles have to be organized in order to produce sustained useful output. Efforts with different valve technology, engine designs (like Sterling engines), and other fine optimizations have been incorporated to maximize the possibilities.
Having said that, the demonstration of the potential capabilities of the internal combustion engine was accomplished before all of these optimizations. Though still, I recall Tom Ligion's comparison to early I. C. engines,that there were fine details (carburation) that had to be figured out in the early I.C. engines before they were accepted as viable.
Dan Tibbets
To error is human... and I'm very human.
http://powerandcontrol.blogspot.com/200 ... rview.html
Actually, , Bussard responded to the interviewer's comment that the Polywell was like a jet engine. Bussard conceeded the point in the sense that fuel and energy goes in and fusion power comes out as a natural consequence of how the system works. In this regard a Tokamak is more like an internal combustion engine. The fuel is injected/ compressed, ignited, and then dedicated efforts have to be employed to remove the spent fuel/ fusion products. The Polywell is not nearly the contained internal combustion analogy of the Tokamak, due to the leaky cusps and no need for a distinct exhaust cycle. The Polywell's electron recirculation could be compared to the efficient turbine blades in the combustion zone of a jet engine, they recover enough energy to run the compressor, while the excess energy from fuel burning provides the thrust (perhaps a rocket engine might be a better analogy). A Polywell with direct conversion might be considered like a turbofan as it more efficiently converts the fusion energy to useful power.
Of course these analogies have little to do with what is going on in the machines, but they do serve to illustrate that the nature of Polywells (with their cusps, recirculation, IEC effects, etc). are much different from the cuspless magnetic confinement schemes, both in how they operate and the power density differences potentially achievable.
In this regard I wonder if a DPF could be considered as like a pulse jet (Buzz Bomb). I'm not sure how a FRC would fit in this loose analogy.
Dan Tibbets
Actually, , Bussard responded to the interviewer's comment that the Polywell was like a jet engine. Bussard conceeded the point in the sense that fuel and energy goes in and fusion power comes out as a natural consequence of how the system works. In this regard a Tokamak is more like an internal combustion engine. The fuel is injected/ compressed, ignited, and then dedicated efforts have to be employed to remove the spent fuel/ fusion products. The Polywell is not nearly the contained internal combustion analogy of the Tokamak, due to the leaky cusps and no need for a distinct exhaust cycle. The Polywell's electron recirculation could be compared to the efficient turbine blades in the combustion zone of a jet engine, they recover enough energy to run the compressor, while the excess energy from fuel burning provides the thrust (perhaps a rocket engine might be a better analogy). A Polywell with direct conversion might be considered like a turbofan as it more efficiently converts the fusion energy to useful power.
Of course these analogies have little to do with what is going on in the machines, but they do serve to illustrate that the nature of Polywells (with their cusps, recirculation, IEC effects, etc). are much different from the cuspless magnetic confinement schemes, both in how they operate and the power density differences potentially achievable.
In this regard I wonder if a DPF could be considered as like a pulse jet (Buzz Bomb). I'm not sure how a FRC would fit in this loose analogy.
Dan Tibbets
To error is human... and I'm very human.
I'll bet on that horse. I think it can make a go of it. Race results should be in soon. By the end of summer I reckon.KitemanSA wrote:I was thinking maybe a horse, a dark one!chrismb wrote:You mean, a bit like an elephant... maybe a big white one..?Bussard's Polywell has been described as being something like a jet engine. Fuel goes in and products flow out naturally.
"Brayton Fusion"
