Design of the ITER PF Coils

Abstract

ITER magnets are all designed using superconducting conductors with a high current carrying capability. The Poloidal Field (PF) coils are operated in pulsed mode with maximum operating currents of 48 kA for PF 1 and 6, 55 kA for PF 2,3, and 4 and 52 kA for PF 5. The PF system consists of 6 ring coils, PF1 through PF6, that serve to stabilize the position and control the shape of the plasma in the tokamak. The six PF coils are attached to the outside of the Toroidal Field (TF) coil cases through flexible plates or sliding supports allowing radial displacements. The PF coil positions and sizes have been optimized for the plasma requirements consistent with the constraints imposed by allowing access to the vacuum vessel and by considering pumping ducts to the in-vessel components.The PF coils will all be wound with Niobium-Titanium (NbTi) cable-in-conduit conductors (CICC), and range in diameter from 8 m to 24 m. The winding pack consists of stacked double pancakes, with joints only on the outer radius for access/repair and eddy current/AC loss reasons, while the helium inlets are located at the inner radius.Since the 2001 design option, the PF coil windings and their subcomponents have been redesigned to satisfy new operational requirements. The final detailed design has been established in 2009 and validated by the design review held the same year.In this paper, the up-to-date design of the PF coils and each sub-component such as winding pack, electrical insulation, joints and terminations, helium inlet, jumpers, and coils' supports are discussed together with their fabrication methods.

Fusion nuclear science facilities and pilot plants based on the spherical tokamak

“…Incorporating a ceramic radiation-resistant insulator may degrade this current density value somewhat, and research will be needed to verify that radiation will not induce arcing through the magnet cooling water [140]. Approximate winding-pack current density limits for low-temperature-superconductor (LTS) cablein-conduit conductor (CICC) [141] coils are 14 MA m −2 for ITER NbTi PF coils [142,143], 18 MA m −2 for 1000 A mm −2 critical current density Nb 3 Sn strand [144,145], and up to 25 MA m −2 for 2600 A mm −2 Nb 3 Sn strand [145] (when designed with a graded low-field/high-field winding pack) all at 4.2 K. Further, high-temperature-superconductor (HTS) cables such as the twisted stacked-tape cable conductor CICC show promise for providing 40 MA m −2 or higher winding-pack current density [146], and conductor on round core (CORC) cables have achieved up to 70 MA m −2 or higher winding-pack current density at fields up to 19 T in 'CORC-4' samples in [147]. For the design study described here, 40 MA m −2 was targeted as the nominal current density value for HTS and also used to conservatively establish the design space for a radiation-resistant Bitter-plate coils.…”

Quantitative correlation between the void morphology of niobium-tin wires and their irreversible critical current degradation upon mechanical loading

“…They enable nearly every superconducting device 4 , from magnetic resonance imaging (MRI) devices 5 , over fusion 6–8 and accelerator magnets 9 to nuclear magnetic resonance (NMR) systems 10 . In particular, Nb 3 Sn, a brittle inter-metallic compound of the A15 phase family 11 with an upper critical field of about 29 T 12 , is the conductor of choice for generating fields beyond 10 T 13 [chap.…”

Outgassing measurements for the turn insulation of CFETR poloidal field coils

“…The PF system is one of the important systems in CFETR, it consists of eight coils, namely PF1-PF6, DC1 and DC2, each coil consists of 6-9 double pancakes, and each double pancake is wound by "two-in-hand" configuration by NbTi cable-in-conduit conductors (CICC) [2,3]. The electrical insulation system of the coil is composed of multiple layers of polyimide film-glass as turn insulation and impregnated with epoxy resin, consolidated with VPI method [4][5][6]. The multilayer turn insulation is applied on the conductor during conductor turn winding.…”