Heat loads to divertor nearby components from secondary radiation evolved during plasma instabilities

Abstract

A fundamental issue in tokamak operation related to power exhaust during plasma instabilities is the understanding of heat and particle transport from the core plasma into the scrape-off layer and to plasma-facing materials. During abnormal and disruptive operation in tokamaks, radiation transport processes play a critical role in divertor/edge-generated plasma dynamics and are very important in determining overall lifetimes of the divertor and nearby components. This is equivalent to or greater than the effect of the direct impact of escaped core plasma on the divertor plate. We have developed and implemented comprehensive enhanced physical and numerical models in the upgraded HEIGHTS package for simulating detailed photon and particle transport in the evolved edge plasma during various instabilities. The paper describes details of a newly developed 3D Monte Carlo radiation transport model, including optimization methods of generated plasma opacities in the full range of expected photon spectra. Response of the ITER divertor's nearby surfaces due to radiation from the divertor-developed plasma was simulated by using actual full 3D reactor design and magnetic configurations. We analyzed in detail the radiation emission spectra and compared the emission of both carbon and tungsten as divertor plate materials. The integrated 3D simulation predicted unexpectedly high damage risk to the open stainless steel legs of the dome structure in the current ITER design from the intense radiation during a disruption on the tungsten divertor plate.

Comprehensive 3-D simulation and performance of ITER plasma facing and nearby components during transient events—Serious design issues

“…The photon generated energy spectra included up to 20 000 energy groups for each hydrodynamic cell within the evolving plasma to ensure accurate photon transport and energy deposition on various surrounding and nearby components. 9 The escaped core plasma particles were determined the initial input energy source and boundary conditions for the MHD formation and evolution of the secondary divertor plasma. Initially, we assumed near vacuum conditions in the SOL for the secondary plasma: 10 Pa pressure and 500 K temperature, corresponding internal energy, and zero velocity.…”

“…We previously studied in detail the secondary plasma parameters, e.g., plasma temperatures and densities for both W and C as PFCs and the resulting surface damage for various disruption and ELM parameters. 9 The first step of our study was to calculate the time-temperature history for all surfaces regardless of identifying which specific heating source is the main contributing source, i.e., secondary plasma radiation or scattered/reflected incident core plasma particles. Additionally, the temporal maximum temperature history is recorded regardless of which specific location on the selected surface is reaching the maximum temperature calculated.…”

“…This problem is complicated to solve and requires integrated models where the secondary plasma dynamic plays the leading role. 9 In this work, we present new enhanced integrated models that accurately describe the plasma facing component response to a wide range of ELMs and disruption parameters in real 3D ITER-like geometry and operating conditions.…”

Physics of ultimate detachment of a tokamak divertor plasma

“…However, such violent events as large ELMs and disruptions can cause a strong ingress of impurity into the divertor plasma making the impurity radiation trapping significant (e.g. Sizyuk & Hassanein 2015).…”

Recycling of laser and plasma radiation energy for enhancement of extreme ultraviolet sources for nanolithography

“…More detailed description of plasma radiation transport can be found in our previous publication. 25 Following the splitting methods used in the HEIGHTS package, 20 the additional dissipative source-terms are calculated separately with the second (dissipative) stage of the solver used then as correctors of the main hydrodynamic module solution (Fig. 6).…”