Design of DEMO PF Coils Based on Cable-in-Conduit Conductor

Abstract

Based on the requirements defined by the EUROfusion 2015 DEMO baseline, the PF coils are designed. The conductors are forced flow, NbTi cable-in-conduit. The design addresses the dimensioning of the winding pack, the electromagnetic field calculation and mechanical load. The cross sections of the cable, i.e. superconductor, copper and helium are allocated to fulfil the design criteria for the temperature margin, quench/hot spot temperature and pressure drop in operation. The conductors have rectangular cross section and are layer wound, multiple-in-hand, to minimize the hydraulic length (1 single turn can be as long as 100 m). The orientation of the wide side parallel to the main field component minimizes the AC loss. The larger radius compared to ITER PF coils calls for larger electromagnetic load and hence much larger cross section for the structural support, which must be added on top of the conductor conduit to avoid unmanageable thick conduit walls. For PF1 and PF6 coils, a design option with Nb 3 Sn conductor may need to be considered due to the effective magnetic field in excess of 6.2 T.

Alternative PF Coil Winding Pack Design for the EU DEMO

“…All PF Coils are made with the Double Pancakes (DP), wound with 2-in-hand technique. The design of the conductor is well described in previous publications [3], [4]. The NbTibased rectangular Cable-In-Conduit Conductor (CICC) has a 316LN stainless steel jacket with stadium shaped inner cable space and carries current in the range from 50-60 kA [3].…”

“…The design of the conductor is well described in previous publications [3], [4]. The NbTibased rectangular Cable-In-Conduit Conductor (CICC) has a 316LN stainless steel jacket with stadium shaped inner cable space and carries current in the range from 50-60 kA [3]. It has no separated low impedance cooling channel for manufacturing M. Kumar, R. Guarino, K. Sedlak, X. Sarasola and P. Bruzzone are with École Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), CH-5232 Villigen PSI, Switzerland (e-mail: mithlesh.kumar@psi.ch).…”

“…Methodology for electromagnetic calculations and evaluation of parameters are already described in the previous publications [3], [4]. The whole 3-dimensional geometry of the magnet system is divided using elementary current-carrying bricks in the MC module of Cryosoft.…”

“…All six PF coils (PF1 to PF6) are designed as rectangular crosssection Winding Packs (WP). The design proposed by the Swiss Plasma Center (SPC) in 2018 satisfied the 19.6 MA plasma current scenario [3]. In 2019, a preliminary design was proposed for the newly available 17.86 MA plasma current scenario [4].…”