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Thermal modeling of runaway electron induced damage in the SPARC tokamak

T. Rizzi, K. Paschalidis, S. Ratynskaia, P. Tolias, I. Ekmark, M. Hoppe, R. A. Tinguely, A. Feyrer, T. Looby

Abstract

The integrity of plasma-facing components (PFCs) in tokamaks is critically challenged by transient events such as runaway electron (RE) impacts. We report the first systematic analysis of the thermal damage to tungsten-based PFC tiles comprising the SPARC outboard off-midplane limiters that is induced by RE beams formed during vertical displacement events. Parametric scans in RE impacting characteristics as well as energy-pitch distribution functions from the Dream code are employed for calculations of the volumetric heat loads. A realistic panel design is adopted to enhance the fidelity of the thermal analysis. The PFC thermal responses are compared in terms of in-depth temperature profiles and damage characteristics, such as melt depth and vaporization losses.

Thermal modeling of runaway electron induced damage in the SPARC tokamak

Abstract

The integrity of plasma-facing components (PFCs) in tokamaks is critically challenged by transient events such as runaway electron (RE) impacts. We report the first systematic analysis of the thermal damage to tungsten-based PFC tiles comprising the SPARC outboard off-midplane limiters that is induced by RE beams formed during vertical displacement events. Parametric scans in RE impacting characteristics as well as energy-pitch distribution functions from the Dream code are employed for calculations of the volumetric heat loads. A realistic panel design is adopted to enhance the fidelity of the thermal analysis. The PFC thermal responses are compared in terms of in-depth temperature profiles and damage characteristics, such as melt depth and vaporization losses.
Paper Structure (22 sections, 6 equations, 9 figures, 2 tables)

This paper contains 22 sections, 6 equations, 9 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Problem postulation
  3. Geometry
  4. Material
  5. Impact scenarios
  6. Parametric scans.
  7. DREAM RE distributions.
  8. Monte Carlo simulations of the energy deposition
  9. Geant4 implementation of parametric scenarios
  10. Geant4 implementation of DREAM RE distribution functions
  11. MEMENTO simulations of the thermal response
  12. Results
  13. Simulations for simplified scenario
  14. Energy distribution on the panel.
  15. Energy density distribution on the panel.
  16. ...and 7 more sections

Figures (9)

  • Figure 1: Geometry of the panel. View from the side (a) and the top (b).
  • Figure 2: Runaway electron momentum space densities in energy-pitch angle space, $N(E,\theta)$: (a) calculated with the Hesslow fluid source term (Dream I), and (b) calculated with the Rosenbluth-Putvinski kinetic source term (Dream II).
  • Figure 3: Geant4 set-up for the full panel simulations accounting for the panel curvature, varying magnetic field inclination angle and finite pitch angle. The direction of the incident REs and the magnetic field are indicated in red and green, respectively. Strength of magnetic field is $|\textbf{B}| = 13.2$ T.
  • Figure 4: Geant4 set-up for the simplified geometry simulations with the division into sectors 1-4. The red arrows indicate the direction of the incident RE beam. For each sector, the average value of the magnetic field inclination angle $\alpha$ over the corresponding actual curved surface of the panel is provided.
  • Figure 5: Results of full panel simulation for energy deposition by an RE beam of 10 MeV & 5${^\circ}$ pitch. Cross section view for normalization of 100 kJ. The incoming REs are indicated by black arrows. Note that shadowing from neighboring tiles is not considered.
  • ...and 4 more figures