HELIAS module development for systems codes

Abstract

a b s t r a c tIn order to study and design next-step fusion devices such as DEMO, comprehensive systems codes are commonly employed. In this work HELIAS-specific models are proposed which are designed to be compatible with systems codes. The subsequently developed models include: a geometry model based on Fourier coefficients which can represent the complex 3-D plasma shape, a basic island divertor model which assumes diffusive cross-field transport and high radiation at the X-point, and a coil model which combines scaling aspects based on the HELIAS 5-B reactor design in combination with analytic inductance and field calculations. In addition, stellarator-specific plasma transport is discussed. A strategy is proposed which employs a predictive confinement time scaling derived from 1-D neoclassical and 3-D turbulence simulations.This paper reports on the progress of the development of the stellarator-specific models while an implementation and verification study within an existing systems code will be presented in a separate work.This approach is investigated to ultimately allow one to conduct stellarator system studies, develop design points of HELIAS burning plasma devices, and to facilitate a direct comparison between tokamak and stellarator DEMO and power plant designs.

Implementation and verification of a HELIAS module for the systems code PROCESS

“…The plasma geometry model [1] is based on Fourier coefficients which allows one to describe arbitrarily complex flux-surfaces. For the validation study the W7-X high-mirror configuration is chosen and the specific Fourier coefficients are obtained from the corresponding VMEC [7] equilibrium.…”

“…The model of the island divertor concept [1,8] consists of a geometrical description including cross-field diffusion and radiation around the X-point. For the verification with W7-X, experimental data are not yet available.…”

“…The model for the modular coils [1] is a combination of analytical calculations and scaling relations which are based on the detailed Helias 5-B coil design employing Nb 3 Sn as superconductor. To be able to compare the coil model with the existing W7-X coils a scaling for the critical current density of NbTi was implemented.…”

“…Based on this assessment, HELIAS-specific models have been developed in [1] designed for a systems code approach consisting of three major models. First, a geometry model to describe the plasma shape (flux surfaces) based on Fourier coefficients.…”

“…Moreover, a strategy for a predictive confinement time scaling has been discussed in [1] where it is shown that 3D turbulence, gyrokinetic geometries [3] with the aim of assessing the behaviour of e.g. ion-temperature-gradient instabilities.…”