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Author(s):
V.D. Pustovitov
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Title:
Control of Pfirsch-Schluter Current by External Poloidal Magnetic Field in Conventional Stellarators
Date of publication:
Dec. 1995
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Key words:
stellarator, Pfirsch-Schluter current, magnetic surfaces, vertical magnetic field, quadrupole field, magnetic axis shift, plasma equilibrium
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Abstract:
The problem is analyzed whether it is possible to create net-current-free equilibrium configurations without Pfirsch-Schluter current (j zeta = 0) in conventional stellarators with a planar circular axis. Recently such analysis was presented for the case, when only vertical magnetic field was a control parameter. Here external poloidal field is considered as arbitrary, which must be found from the condition j zeta=0. It is shown that such suppression of Pfirsch-Schluter current by means of external poloidal field is possible, theoretically, in shear-free systems and in stellarators with l geq 3 only. It can be said also by other words that in ordinary l=2 stellarators with a shear plasma equilibrium with j zeta = 0 is impossible at any choice of external poloidal field. In these systems, nevertheless, dipole component of Pfirsch-Schluter current can be suppressed or strongly reduced by joint effect of vertical and quadrupole fields. It is shown that in this case phase inversion of Pfirsch-Schluter current current could be obtained at realistic conditions. These results explain, in particular, experimental observations of configurations almost insensitive to plasma pressure in Heliotron E.
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