Investigation of beta-limit improvement of helical type plasmas in L=2 Heliotron/Torsatron devices by using higher harmonic modulation

Summary form only given, as follows. We have already shown that the application of the higher harmonic modulation principle to the winding law of the helical coil of the L=1 and L=2 Heliotron/Torsatron can reduce magnetic force on the helical coils. This finding is important from the viewpoint of the coil supporting technology of superconducting magnets. Also it was shown that proper values of the higher harmonic modulation constants can effectively produce the magnetic well in a vacuum field. The presence of the magnetic well generally means the possibility of high beta operation, where the beta is plasma pressure/magnetic pressure. We will present calculations for magnetohydrodynamic (MHD) equilibrium of plasmas with non-zero beta values and for the dependence of the beta-limit on the variation of the modulation constants. The latter is important from the economical standpoint of plasma confinement properties of the helical device. For these calculations a three-dimensional MHD spectral inverse equilibrium code VMEC was used.