Submitted by jarome on Fri, 04/18/2014 - 13:38

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As you can see from the above, the introduction of large currents, concommitant loop voltage, and runaways introduces the need for major expensive auxiliary systems to:

  • Initiate the currect (central solenoid)
  • Carefully measure the current profile on a few ms timescale
  • Control the current profile (by rf and microwaves, pellets to modify the density profile)
  • Drive the current in "steady state" (neutral beams, rf, microwaves)
  • Handle the power from any disruptions (armor)
  • Try and prevent disruptions (control parameters, use extra "disruption-prevention" coils)
  • Mitigate disruptions
  • Stop ELMs (a type of edge disruption)
  • Handle runaway electron dumps

None of these systems have anything to do with actually making fusion, and in a reactor, they cause a large amount of the plant's power output to be used to run these systems. Plasma current in a reactor is evil.

Stellarators with only small plasma currents caused by increasing plasma pressure, do not have or need the above systems to operate. That is why I say it is easier and cheaper to engineer a stellarator.

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