Is the Dynomak concept physically sound? I recently stumpled upon this article:


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*Inside the Dynomak: A Fusion Technology Cheaper Than Coal
Is the Dynomak concept physically sound? What kind of challenges could it run into? Can it make fusion energy really cheaper than coal?
 A: After reading this paper, my executive summary would be that this design is even more unproven than tokamaks. Indeed, tokamaks have at least demonstrated that they can confine plasma enough to achieve fusion, the issue being whether a tokamak can produce more energy than it consumes. On the contrary, at the time that article was written, they only have a possible mechanism, imposed-dynamo current drive (IDCD), that they plan to use to control the currents in the plasma. But this had to be shown to work. This is crucial, note, because in such a spheromak, the confining magnetic field is generated by the currents in the plasma. Moreover, this is only the first step, as the article points out too: the fluctuations of the magnetic field induced by IDCD might eventually spoil the confinement of the plasma. That such fluctuations have that effect would be the traditional view actually but the article argues otherwise. Anyway, as the article acknowledged, this was still unproven as well. Thus pretty much the entire concept is experimentally unproven: right now, we are talking about simulations only. 
A note about cheaper than coal although this has nothing to do with physics: pretty much every source of energy is cheaper than coal these days! A pretty pointless quote for an otherwise reasonably good article… 
