Assessment of Plasma Performance in a Magnetic Configuration with Reduced Poloidal Coils for a Helical DEMO Reactor FFHR-d1

Abstract

The performance of high-density plasmas heated by neutral beam (NB) injection in a vertically elongated configuration using four poloidal coils has been investigated in LHD and shown to be better than that in the normal configuration using six poloidal coils. Reduction of poloidal coils is favorable in designing an LHD-type helical reactor FFHR-d1, from both points of view of cost reduction and realization of large maintenance ports. In the experiment, no clear difference between the two configurations was recognized in the relation between the central density and the central pressure. Meanwhile, a factor C exp used in the direct profile extrapolation (DPE) method is smaller in the vertically elongated configuration, where C exp is proportional to the reactor size, R reactor , at a given reactor magnetic field, B reactor , i.e., R reactor ∝ C exp B reactor −4/3 . The difference in C exp between the two configurations is enhanced to > 10 % as the plasma beta increases. This might be due to the larger plasma volume and/or the mitigated Shafranov shift in the vertically elongated configuration.

Physics analyses on the core plasma properties in the helical fusion DEMO reactor FFHR-d1

“…One of the distinguished features of FFHR-d1 compared with the former FFHR design series is the robust similarity with LHD. The arrangement of superconducting magnet coils in FFHR-d1 is similar to that of LHD, except a pair of planar poloidal coils has been omitted to maximize the maintenance ports [14], as shown in figure 1. In FFHR-d1, a set of planar vertical field coils called 'IS' (inner shaping field) coils in LHD, shown in the lower half of figure 1, is omitted while 'IV' (inner vertical field) and 'OV' (outer vertical field) coils are retained.…”

Cartridge-Type Helical Blankets Aiming at Easy Construction and Maintenance for the FFHR-d1

“…The FFHR-d1 is basically a heliotron device similar to the LHD [3] and consists of two main helical coils and 4 planar poloidal field coils [4] of high-temperature superconducting (SC) magnet [5]. The device size is four times larger than the LHD.…”