Anyone can go to his lab and ask him to show his results. If I understand it right, Art Carlson did it (former critic of FRCs, who wrote his thesis on them and then was convinced by a visit to Helion that they do indeed have something). Rostoker and Monkhorst have had positive results of their own, independently of Slough. They have subsequently worked with him as well. He is not operating in some vacuum.
FRCs are pretty well understood, there is lots of research on the matter. Slough merely expanded on already existing work and did some tweaks with positive results. He also did fluid dynamic simulations that also confirmed most of his experimental results, with small differences that Slough explains with the 2D- nature of the simulation versus the 3D nature of the actual aparatus, if I remember correctly (been a while since I read it in all detail). This is all very credible. I am not saying that his thing 100% sure to work, but the likelyhood that it will result in an economic reactor is infinitely higher than it is for Toks, which have a likelyhood of 0.
If so, some claims were confirmed and some were not. Which claims were not confirmed?
Read the very next sentence where I write:
All he has to do with the next bigger reactor is confirm the scaling to Q>1.
He cant confirm scaling laws and ability to reach a Q>1 with a single, subscale reactor, dont you agree with that?
Anyone can go to his lab and ask him to show his results. If I understand it right, Art Carlson did it (former critic of FRCs, who wrote his thesis on them and then was convinced by a visit to Helion that they do indeed have something). Rostoker and Monkhorst have had positive results of their own, independently of Slough. They have subsequently worked with him as well. He is not operating in some vacuum.
FRCs are pretty well understood, there is lots of research on the matter. Slough merely expanded on already existing work and did some tweaks with positive results. He also did fluid dynamic simulations that also confirmed most of his experimental results, with small differences that Slough explains with the 2D- nature of the simulation versus the 3D nature of the actual aparatus, if I remember correctly (been a while since I read it in all detail). This is all very credible. I am not saying that his thing 100% sure to work, but the likelyhood that it will result in an economic reactor is infinitely higher than it is for Toks, which have a likelyhood of 0.
If so, some claims were confirmed and some were not. Which claims were not confirmed?
Read the very next sentence where I write:
All he has to do with the next bigger reactor is confirm the scaling to Q>1.
He cant confirm scaling laws and ability to reach a Q>1 with a single, subscale reactor, dont you agree with that?
FRC is quite well understood. But collision and further stopping of two FRC is not. At least for me. But reading bolded by me
The distinct difference between merging and the simple passage of the FRC unopposed is clearly demonstrated
in the article linked by you, I see that I am not asking the trivial question. And you do not know what Art Karlson has confirmed and what has not. FRC forming or/and their collision too.
Here I am only speaking that do not believe that stopping of two FRC is possible via their collision like two equal mass solids stop each other colliding non-elastically.
And I never have seen equations describing forces allowing this stopping.
Skipjack wrote:Yes, but they will have to replace the very expensive components of ITER and future Tok- reactors frequently thanks to neutron damage. Sloughs FRC only has to replace the small burn chamber every now and then which is far enough away from the more expensive parts of the reactor. That makes it much more economic to operate.
And if they have neutron damage they have neutron losses. How much? Well that is the question.
For fission reactors ~2.2neutrons are created to enable 1 to start the next fission. The problems are different (no "escape losses" of significance for the Tok), still - it does give you some idea of what you are up against.
And every penetration is a loss point.
Engineering is the art of making what you want from what you can get at a profit.
But collision and further stopping of two FRC is not. At least for me.
Go ask Slough!
I see that I am not asking the trivial question.
I never said that you were.
Here I am only speaking that do not believe that stopping of two FRC is possible via their collision like two equal mass solids stop each other colliding non-elastically.
And I never have seen equations describing forces allowing this stopping.
You should go and talk to the people that are spending their entire day working on this, not to me. As I said, from what I understand John Slough is rather open about his work. At least from what I understand and remember about him. I am sure that if you went and asked him your questions, he will answer them to you.
But collision and further stopping of two FRC is not. At least for me.
Go ask Slough!
I see that I am not asking the trivial question.
I never said that you were.
Here I am only speaking that do not believe that stopping of two FRC is possible via their collision like two equal mass solids stop each other colliding non-elastically.
And I never have seen equations describing forces allowing this stopping.
You should go and talk to the people that are spending their entire day working on this, not to me. As I said, from what I understand John Slough is rather open about his work. At least from what I understand and remember about him. I am sure that if you went and asked him your questions, he will answer them to you.
I should nothing. But doubt that two clouds of smoke moving at 300 km/s velocity and then colliding can effectively stop and thermalize each other. I do not remember numbers but why you won’t understand that merging means that two plasmoids should convert into one common plasmoid. This means that one plasmoid should be braked at a distance not exceeded linear dimension of another. So, for estimation of required deceleration (negative acceleration) and then required braking force we came to trivial mechanic exercise: given braking distance, initial velocity and we should calculate a. Then F=ma
By my estimation F should have 10^4 N order (1 tonforce!)
Not me but developer should provide evidence that his FRC able create such strong forces.
Another way is to consider MHD model considering two colliding viscosius drops. Drops should merge and that means that after touching each other the continuity then shouldn't be broken. Yes, combination of poloidal and toroidal fields frozen in FRCs provides something like viscosity. But will that viscosity be enough for keeping continuity for the matter initially moving with 300 km/s velocity? How thermalization affects viscosity? Doesn't reduce? And what's goal? Not thermalization till about 100 millions K?
Skipjack wrote:Yes, but they will have to replace the very expensive components of ITER and future Tok- reactors frequently thanks to neutron damage. Sloughs FRC only has to replace the small burn chamber every now and then which is far enough away from the more expensive parts of the reactor. That makes it much more economic to operate.
And if they have neutron damage they have neutron losses. How much? Well that is the question.
For fission reactors ~2.2neutrons are created to enable 1 to start the next fission. The problems are different (no "escape losses" of significance for the Tok), still - it does give you some idea of what you are up against.
And every penetration is a loss point.
The Reproduction Factor can vary greatly. For further understanding read pages 6 & 7 here:
By the way: Page 8 also touches on the definition of "Critical" which is a function of Keff. I know we have discussed that point before a couple of times. Critical means neutron population is self-sustaining stable (not changing).
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
D Tibbets wrote: he may have considered both thermalized plasma and mono energetic plasma, he did not consider the energy distribution of the electrons.
Dan Tibbets
Dan if I may, in laymans terms, Rider showed us scenarios why Polywell wont work, he did not show us scenarios why Polywell would work...
No?
Indeed, if Riders conclusions are correct. There has been some discussion that his models were not adequate. Fokker Plank (sp?)modeling such as done by Chacon may be more predictive.
And barriers predicted under certain assumptions only have validity within those assumptions. They serve as a useful tool in planning, or abandoning an approach. Planning if you can challenge the assumptions, or abandonment if you accept the assumptions and the validity of the results.
I understand the accepted physics of FRC prevented positive Q's, until experiments caused a retreat from this prevalent view (as per A. Carlsons evolving comments on this site a few years ago).. I'm not sure if this would fall under false assumptions or invalid results, or both.
Sorry, I didn't see that someone had started a thread on this!
Here is some feedback:
1. We may be able to reflect the x-rays back into the center - recycling the losses. Gold or lead will do it but they melt at 1337 and 600 K respectively. If the reactor temperature is to high, that idea becomes less likely. We will need a curved chamber to reflect the x-rays back in.
2. Reactor temperature: Rider made a strong case the biggest variation in temperature would be 5%. In his 95 paper, he uses general volumetric equations to do this. He never measured the actual temperature inside a Polywell. He estimated from theory. It is not clear he used the right equations.
3. Rider argues the cloud will randomize in particle energies - going to a bell curve, fine. But he never examined in randomization in space. There is a chance the plasma has some kind of structure. His idea for the cloud in the center: a core, a mantle and an edge, may be flawed. People have suggested that the electron cloud has its own magnetic field, rejecting the externally applied field, and pinching off the loss points. The electron cloud may go diamagnetic. This phenomena may generate a structure. People argue that this, forms a clump of ions in the center. The counter is that the charge separation will form a plasma instability, swirling around, destroying the structure. The relative importance of each of this phenomenon is unknown. These are all open questions.
4. The new polywell designs emphasize electron recirculation. Lots of space, no metal surfaces. Rider commented in his thesis abstract that efficient recirculation was key for this device to work. How efficient will be needed and, how efficient we can achieve, are still unknown.
5. The Polywell may have a resonance condition. It is a complex system. The parameters include: the ions in the center, the rate of ion injection, the electrons in the center, the rate of electron injection, the charge on the ion, the magnetic field strength, the energy of injection for the ions and the geometry. Raise one rate and you may get more X-rays, but more fusion. Lower another and you get a smaller plasma cloud in the center, but more efficient recirculation. The system probably has dimensionless numbers, so we can vary the variables in tandem and simplify analysis.
=======
The hidden assumption in Rider's work is that you must go big to get fusion. If we are locked onto the big expensive machine route, we will never get there. Over the past 50 years, there have been 177 tokomaks either, built, planned or decommissioned, worldwide. If the idea was good, you would have expected success by now. The "big" assumption is also embedded in the Lawson criteria. John Lawson assumed that you had to contain plasma and heat it up for fusion. He estimated 30 million degrees for DT and 150 million for DD. The Fusor can do fusion at room temperature, with cheap equipment. Of course, the Fusor did not exist when Lawson came up with his ideas. If Lawson is right, then we are either containing for a long time (Tokomak), or compressing to a high pressure (ICF). The goal of the National Ignition Facility is to get the average plasma temperature above 10 KeV. Meanwhile the Polywell can get ions to 10 KeV, using a 10 Kv well. It would not take many electrons to reach that voltage and I bet you a million dollars that will require far less energy than firing giant lasers.
Compare this to the early attempts to fly. In his book: "Progress in Flying Machines" (1894), Chanute, shows us that modern attempts to fly went back more than 60 years before the Wright brothers. There were dozens of distinctly different designs attempted, by lots of different people. Goofy, even silly ideas, were tried. The public barely noticed this and generally assumed that it was impossible. Right now, fusion is viewed as impossible and the public barely notices our efforts. The reality is, the fusion machine must get smaller, simpler and cheaper if we are to succeed. Look at the development of the computer. The early computers were the size of whole rooms. The computer needed to get smaller, simpler and cheaper to advance. Smaller and cheaper means more people can try different ideas and innovations can happen faster.
Last edited by mattman on Mon Mar 05, 2012 2:49 pm, edited 2 times in total.
We should take this discussion to Reddit. There are a bunch of undergrad physic majors on there. They have to know that there are possibilities outside of conventional wisdom. We need to inspire some young minds here to take an interest. This is really important.
Dan, ladajo, Joseph, Skipjack you can add your input and ideas to the discussion on Reddit, it might spark a debate. Debates make people think. MIT grad students may not have given Riders work a second look.
Not me but developer should provide evidence that his FRC able create such strong forces.
I did not say that you should provide evidence for your points of critizism, I simply told you to ask your (quite good and relevant) questions to John Slough. I am not a plasma physicist and I only spend about 5 minutes a day on this matter while people whose job this actually is, spend maybe 10 hours a day with it(or more). So it would be much more efficient, if you could just write an email to John Slough and ask him what he has to say about that. Maybe you are right or maybe you are wrong, or maybe you are right and his concept is solving the problem somehow.
I still dont see what is wrong with asking him. You are a professional, he is too. Nothing wrong with you two talking (if he can and wants to talk, not wanting to speak for him there), right?
Mattman, I don't know what efficiency in X ray reflection may be possible, but it is undesired any way. With ignition, and thermalized machines, feflecting x- rays might be desirable. But it is not wanted in a Polywell. The 'heat' in a Polywell or fusor comes from electrostatic acceleration. The waste heat from escaped electrons, ions, x-rays, or fusion ions or neutrons deposit their energies in structures (or direct conversion grids) and heat them up. Ignoring direct conversion, this heat produces electricity through a steam cycle. Not very efficient, but that is about the only way to harvest the heat.
In a Tokamak a portion of this heat is directly recycled in the machine- mosstly through thermalization of very hot/ energetic fusion ions. A Polywell is not an ignition machine, the hot fusion ions mostly escape the machine, and smack into walls or a conversion grid. Any x-rays produced in the Polywell deposite little of their energy in the plasma. They hit walls or penetrate into them. To harvest and recycle this energy, it has to be captured through a steam cycle or something like the direct 'onion skin converter' proposed by Eric Learner with the DPF. The DPF is a small machine, with possibly a beryllium anode that allows a large percentage of the x- rays to harvest the machine pro[per and enter a surrounding direct converter. With a different structure, and dynamics, I don't know if a Polywell could perform nearly as well in this X-ray direct conversion scheme.
Discussing clouds of ions in the center makes me wonder if you are taking too much of a static view. The electrons and ions are both moving all over the place. The important point is that their speeds change in this roughly spherical geometry depending on their radius from the center. The inverse relationship between the ions and electrons and the dynamic consequenses plays a hugh role in the Bremsstruhlung (hopefully spelled right this time) issue. Dwell time, local density changes, and even annealing plays a role. Especially if there is any convergence of the ions towards the center. This results in effective greater densities of ions in the center. This applies to electrons also. If the electrons were at high energies in these increased density areas, the Bremsstruhlung radiation is amplified. But since the electrons are low energy (low KE) in this region the Bremsstruhlung is much less. On the edge and in between the situation tends to reverse, but the ion density is now lesser in these regions. If there is no ion confluence (focus towards the center) or if the electron population is less radial/ more thermalized, this effect may be minimized. Thus the need for diluting the high Z Boron.
Also, referring to Fusors as operating at room temperature is extremely inaccurate. Ignoring the neutral background gas that may not be heated much, the actual fusing ions (or ion- neutral collisions) have very high center of mass KE/ temperatures. If the potential on the central cathode grid is ~ 10,000 volts, then the ions are accelerated to ~ 10,000 eV. This is equivalent to a temperature of ~ 110 million degrees C.
I don't know what efficiency in X ray reflection may be possible
Materials advancements this past year suggest very high levels can be reflected.
In any event, the core question is when are we worried about Bremsstrahlung?
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
Skipjack wrote:I did not say that you should provide evidence for your points of critizism, I simply told you to ask your (quite good and relevant) questions to John Slough.
I only shared you my doubts that Slough’s approach allows to buld commercial reactor in near 10 years. I have not a goal to go in depth of this approach. Especially when I do not believe in its viability. I only tried to explain to you and to others the basis of my doubts.
Skipjack wrote:You are a professional, he is too. Nothing wrong with you two talking (if he can and wants to talk, not wanting to speak for him there), right?
I have not classical plasma physics education. Yes, I have my own idea how to make fusion reactor. Yes, I have very good basis in basic physics. Here my father’s role is high and also the library that he has left to me. Unlike me he was plasma physicist. worked with theta pinch in Sokhumi Nuclear Research Institute and then led Physics Department in Kutaisi Polytechnic University. His teacher was e.g. Petr Kapica, his fellow Lev Landau, etc.
But I am positioning myself as engineer and not physicist. About 25 years ago I told him my fusion idea. He thought and then said: “This should work.” He dead in 1991.
Yes, I am working on my idea but also work for feeding my family. Yes I read a lot. But my knowledge in plasma physics is too eclectic. Like you I am not an expert.
that Slough’s approach allows to buld commercial reactor in near 10 years.
I never said that. I said it has a MUCH HIGHER CHANCE than Tokamaks to result in an economic reactor within the next 10 years.
I have not classical plasma physics education.
I dont even have your background. I am more interested in the potential applications of the technology when it is available, than how exactly to make it work, which is way beyond what I can afford investing myself in.
I have not a goal to go in depth of this approach.
Still no excuse for not sending Slough a quick email with your concerns. The time you wasted discussing this with me here, would have been enough to do that. If you can formulate your exact question and the equation that you mentioned earlier here, I can try forwarding it to John Slough in your place, but that would be silly, no?