Simulation as a tool to improve wave heating in fusion plasmas

Abstract

(Received ?; revised ?; accepted ?. -To be entered by editorial office)Firstly, a brief overview will be given on different models that are able to describe the behaviour of wave propagation as a function of specific frequency ranges. Each range corresponds to different heating systems, namely, 20-100 MHz for the Ion Cyclotron Resonant Heating (ICRH), 2-20 GHz for Lower Hybrid Heating or Current Drive (LHCD), and 100-250 GHz for Electron Cyclotron Resonant Heating (ERCH) or Current Drive (ECCD) systems. Every systems' specifications will be explained in detail, including the typical set of equations and the assumptions needed to describe the properties of these heating or current drive systems, as well as their specific domains of validity. In these descriptions, special attention will be paid to the boundary conditions. A review about specific physical problems associated with the wave heating systems will also be provided. Such review will detail the role of simulation in answering questions coming from experiments on magnetized plasma devices devoted to Fusion. A few examples which will be covered are the impact of edge turbulence on wave propagation and its consequences on the heating system performances, effects of the fast particles, ponderomotive effects, among others. A study that is more focused on Radio Frequency (RF) sheath effects will also be discussed. It shows that such simulations require very sophisticated tools to gain a partial understanding of the observations undertaken in dedicated experiments. To conclude this review, an overview will be given about the requirements and progress necessary to obtain relevant predictive simulation tools able to describe the wave heating systems used in fusion devices.

Benchmarking full-wave codes for studying the O-SX mode conversion in MAST Upgrade

“…As has been shown in previous works, this method is completely sufficient for a rather large set of problems [9,10]. More advanced methods exist for situations with extreme density gradients [11,12]. A Gaussian beam is injected into the grid as a soft source [6] with the electric field amplitude, as defined in Eq.…”

A tutorial on radio frequency sheath physics for magnetically confined fusion devices

“…The problem of global DC circuits may have to be assessed and treated in some fashion. Many of the individual pieces of these interactions are known or under development (Heuraux et al 2015;Bonoli et al 2020;Zhang et al 2021). It remains to assemble a practical high-fidelity integrated model.…”

“…The coupling of DC and RF currents and voltages was included in a simple geometry in the original SSWICH model (Colas et al 2012) which invoked a phenomenological cross-field conductivity constant; more recent discussions of this model are given in reviews of simulation tools and modelling (Heuraux et al 2015;Zhang et al 2021). Examples of other works considering asymmetric sheaths and DC current flow are described in D 'Ippolito et al (2002), Ngadjeu et al (2011), Jacquot et al (2014), Faudot (2015 and Perkins et al (2017).…”

Recent progress in modeling ICRF-edge plasma interactions with application to ASDEX Upgrade

“…Both RF and DC sheath BCs are therefore required to solve the coupled model. Equations (11) or (12) apply to the RF part while equation (13) applies to the DC part. The RF/DC splitting is evident in SSWICH but less apparent in rfSOL, where floating DC part is implicitly assumed (i.e.…”

“…Progresses in core ICRF modeling and cross benchmarking of RF codes are discussed in [9][10][11]. The development of RF sheath theories and modeling is reviewed in [12][13][14][15]. Some advances of integrated RF modeling are discussed in [16][17][18].…”