If sometimes I tend to be rude it happens only with people with whom (after long and fruitless attempts) I lost any hope of a scientific and/or meaningful discussion. I can't obviously place you in such a category.
Having (hopefully) cleared the misunderstanding let me reply to your arguments:
Robthebob wrote:1. "The absence of a net plasma current leads to an inherent steady-state operation." This doesnt matter, because neutral injections in Tokamaks have "fixed" the steady-state operation problem, but none of it matters, cus neutral injections can be done in Stellarators, (mainly to bring it to H-mode, something something)
2. "No need to input power to keep a stable magnetic configuration means that the Plasma can actually burn continuously." No man, they need neutral injections to bring the machine to H-mode; even if somehow Stellarators doesnt require H-mode, there's likely to be beta limiting factors, which means you need H-mode, something something.
In the Tokamak the Poloidal Magnetic Field is generated by a strong current parallel to the Toroidal Field. This strong current is induced by the central transformer that can only be active for a limited time, hence the Tokamak cannot be steady state.
Neutral Beam Injection, have partially solved this issue in Tokamak, but at the expenses of more complex system and a bigger consumption of auxiliary power. This makes the system more prone to Aux System Failures, Mechanical Failures (cyclic environment for magnetic and thermal stress over almost any component of the machine), and to a lower general electrical efficiency of the whole system.
In the Stellarator the Poloidal Field is created by the special coils wound around the torus, hence NO need for secondary system to generate it like in the Tokamak.
Additionally, because the the current is in the external coils, it does not suffer from the limit of a central transformer (that can only work for a limited time like the Tokamak Poloidal Generator) and it allows the Stellarator to work in a "Poloidal" Steady State.
Also, in the last few years of research on different types of Stellarators it has been realized that out of the various systems available to heat the Plasma in a Commercial Stellarator like the HSR4/18i, it is the Electron Cyclotron Resonant Heating system (ECRH) that is best suited for the Job, and not the Neutral Beam Injection (NBI).
The ECRH emits microwaves that are at the same frequency as the Electron Gyration frequency in the Plasma, this allows the waves to be absorbed by the electrons and thermalized by collision, thus heating the plasma.
Once the Fusion reaction starts the Apha particles from fusion will take over the task to heat the plasma in a self heating situation. Carefully removing the heat from the Plasma will make the reactor reach an equilibrium point allowing it to work in a "Thermal" Steady State.
The W7-X experiment is equipped with both, NBI and ECRH to test also these important issue.
I have a lot of recent and old papers on the above points. If you (or anyone else) are interested to read them just let me know and I will manage to post them here.
Robthebob wrote:Giorgio wrote:"I Really can't think anything that is part of a Tokamak that would improve the already elegant physics and strong stability present inside a Stellarator plasma. But I am always open for suggestions and discussions."
I dont disagree, I'm saying, it's a Tokamak world out there, and if what needs to be demonstrated is that Stellarators can essentially do anything a Tokamak can do, so people can get on the "right train".
Ok, I understand what you mean now and I agree on this. In the first post you made I thought you wanted to point out that an hybrid Stellarator/Tokamak system would have been more efficient than a pure Stellarator system. This is not something I can imagine/visualize, and that's why I asked for some detailed clarification.
Robthebob wrote:I think we can probably go back to the drawing board to make things be even better... just a thought.
I think W7-X will clear MANYmany of the doubts still pending on defining if the best road to a commercial machine will be based on a Tokamak or on a Stellarator Design.
Than of course the real issue will be what politics will decide.....
Robthebob wrote:Hybrid machines research are still going strong at Auburn as far as I know. What I was trying to convey is the features of Stellarators and Tokamaks are not mutually exclusive, and it's not conjecture, it's been done, it's still going.
All the info I have is that they are just modelling MHD disruption patterns. Even with a google search I could not find much more than that and nothing of relevant in the last years. If you have anything interesting feel free to post, I am always looking for new stuff to read while I wait sun rise.