Predictions of core plasma performance for the SPARC tokamak

Abstract

SPARC is designed to be a high-field, medium-size tokamak aimed at achieving net energy gain with ion cyclotron range-of-frequencies (ICRF) as its primary auxiliary heating mechanism. Empirical predictions with conservative physics indicate that SPARC baseline plasmas would reach $Q\approx 11$ , which is well above its mission objective of $Q>2$ . To build confidence that SPARC will be successful, physics-based integrated modelling has also been performed. The TRANSP code coupled with the theory-based trapped gyro-Landau fluid (TGLF) turbulence model and EPED predictions for pedestal stability find that $Q\approx 9$ is attainable in standard H-mode operation and confirms $Q > 2$ operation is feasible even with adverse assumptions. In this analysis, ion cyclotron waves are simulated with the full wave TORIC code and alpha heating is modelled with the Monte–Carlo fast ion NUBEAM module. Detailed analysis of expected turbulence regimes with linear and nonlinear CGYRO simulations is also presented, demonstrating that profile predictions with the TGLF reduced model are in reasonable agreement.

Divertor heat flux challenge and mitigation in SPARC

“…(2020), predict 29 MW of conducted power through the LCFS, whereas 1.5-D time-dependent core modelling simulations by Rodriguez-Fernandez et al . (2020), using different physics models and slightly different assumptions about impurities, yield P SOL = 19–21 MW, owing to reduced fusion power predictions and increased core radiation. Although the core impurity assumptions used are based on the existing tokamak database, they have wide uncertainties.…”

Projections of H-mode access and edge pedestal in the SPARC tokamak

“…The ICRF heating technique on SPARC will use 120 MHz RF minority heating on 3 He (Lin et al 2020), which is projected to heat ions efficiently. Integrated simulations of the DT H-mode predict the majority of the edge heat flux to be in the ion channel (Rodriguez-Fernandez et al 2020).…”

“…The SPARC tokamak (Creely et al 2020) is being designed to demonstrate significant fusion gain ( Q > 2) for the first time, using a modestly sized device with high magnetic field enabled by recent advances in high-temperature superconductor technology. The basic parameters needed to achieve the performance goals of SPARC can be estimated using zero-dimensional (0D) analysis based on empirical confinement scalings, with increasing confidence provided by full 1.5D transport simulations, grounded in validated physics models (Rodriguez-Fernandez et al 2020). Results of these efforts have a strong sensitivity to particular inputs.…”

“…Given these boundary conditions, the plasma H-factor is determined self-consistently by evaluation of turbulent and neoclassical fluxes in the core. Owing to the stiff nature of the core transport in high-performance plasma conditions, the H-factor is strongly dependent on the pedestal boundary condition (Rodriguez-Fernandez et al 2020). The link between pedestal quality and H-factor is well established in existing experiments, for example in Hughes et al (2011) and Leyland et al (2015).…”

“…The objective of this manuscript is to describe the methods used to make pedestal projections for SPARC, which can inform both the core performance projections and the divertor power handling requirements, as described in detail in separate papers (Kuang et al 2020; Rodriguez-Fernandez et al 2020). The methods described all have a basis in the extensive experience of the tokamak community.…”