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Title: Vapor shielding models and the energy absorbed by divertor targets during transient events

Abstract

The erosion of divertor targets caused by high heat fluxes during transients is a serious threat to ITER operation, as it is going to be the main factor determining the divertor lifetime. Under the influence of extreme heat fluxes, the surface temperature of plasma facing components can reach some certain threshold, leading to an onset of intense material evaporation. The latter results in formation of cold dense vapor and secondary plasma cloud. This layer effectively absorbs the energy of the incident plasma flow, turning it into its own kinetic and internal energy and radiating it. This so called vapor shielding is a phenomenon that may help mitigating the erosion during transient events. In particular, the vapor shielding results in saturation of energy (per unit surface area) accumulated by the target during single pulse of heat load at some level E max. Matching this value is one of the possible tests to verify complicated numerical codes, developed to calculate the erosion rate during abnormal events in tokamaks. The study presents three very different models of vapor shielding, demonstrating that E max depends strongly on the heat pulse duration, thermodynamic properties, and evaporation energy of the irradiated target material. While its dependencemore » on the other shielding details such as radiation capabilities of material and dynamics of the vapor cloud is logarithmically weak. The reason for this is a strong (exponential) dependence of the target material evaporation rate, and therefore the “strength” of vapor shield on the target surface temperature. As a result, the influence of the vapor shielding phenomena details, such as radiation transport in the vapor cloud and evaporated material dynamics, on the E max is virtually completely masked by the strong dependence of the evaporation rate on the target surface temperature. However, the very same details define the amount of evaporated particles, needed to provide an effective shielding to the target, and, therefore, strongly influence resulting erosion rate. Finally and thus, E max cannot be used for validation of shielding models and codes, aimed at the target material erosion calculations.« less

Authors:
 [1]; ORCiD logo [2];  [1];  [2];  [2];  [3]
  1. Budker Inst. of Nuclear Physics, Novosibirsk (Russian Federation)
  2. National Research Nuclear Univ. MEPhI, Moscow (Russian Federation)
  3. National Research Nuclear Univ. MEPhI, Moscow (Russian Federation); Univ. of California, San Diego, CA (United States)
Publication Date:
Research Org.:
Univ. of California, San Diego, CA (United States); Budker Inst. of Nuclear Physics, Novosibirsk (Russian Federation); National Research Nuclear Univ. MEPhI, Moscow (Russian Federation)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24); Russian Foundation for Basic Research (RFBR); Russian Ministry of Education and Science
OSTI Identifier:
1469154
Alternate Identifier(s):
OSTI ID: 1236524
Grant/Contract Number:  
FG02-04ER54739; 15-32-20669; 14.Y26.31.0008
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 2; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; plasma flows; plasma confinement; plasma facing components; dimensional analysis; tokamaks; transition metals; chemical bonding; plasma dynamics; thermodynamic properties; thermodynamic states and processes

Citation Formats

Skovorodin, D. I., Pshenov, A. A., Arakcheev, A. S., Eksaeva, E. A., Marenkov, E. D., and Krasheninnikov, S. I. Vapor shielding models and the energy absorbed by divertor targets during transient events. United States: N. p., 2016. Web. doi:10.1063/1.4939537.
Skovorodin, D. I., Pshenov, A. A., Arakcheev, A. S., Eksaeva, E. A., Marenkov, E. D., & Krasheninnikov, S. I. Vapor shielding models and the energy absorbed by divertor targets during transient events. United States. doi:10.1063/1.4939537.
Skovorodin, D. I., Pshenov, A. A., Arakcheev, A. S., Eksaeva, E. A., Marenkov, E. D., and Krasheninnikov, S. I. Mon . "Vapor shielding models and the energy absorbed by divertor targets during transient events". United States. doi:10.1063/1.4939537. https://www.osti.gov/servlets/purl/1469154.
@article{osti_1469154,
title = {Vapor shielding models and the energy absorbed by divertor targets during transient events},
author = {Skovorodin, D. I. and Pshenov, A. A. and Arakcheev, A. S. and Eksaeva, E. A. and Marenkov, E. D. and Krasheninnikov, S. I.},
abstractNote = {The erosion of divertor targets caused by high heat fluxes during transients is a serious threat to ITER operation, as it is going to be the main factor determining the divertor lifetime. Under the influence of extreme heat fluxes, the surface temperature of plasma facing components can reach some certain threshold, leading to an onset of intense material evaporation. The latter results in formation of cold dense vapor and secondary plasma cloud. This layer effectively absorbs the energy of the incident plasma flow, turning it into its own kinetic and internal energy and radiating it. This so called vapor shielding is a phenomenon that may help mitigating the erosion during transient events. In particular, the vapor shielding results in saturation of energy (per unit surface area) accumulated by the target during single pulse of heat load at some level Emax. Matching this value is one of the possible tests to verify complicated numerical codes, developed to calculate the erosion rate during abnormal events in tokamaks. The study presents three very different models of vapor shielding, demonstrating that Emax depends strongly on the heat pulse duration, thermodynamic properties, and evaporation energy of the irradiated target material. While its dependence on the other shielding details such as radiation capabilities of material and dynamics of the vapor cloud is logarithmically weak. The reason for this is a strong (exponential) dependence of the target material evaporation rate, and therefore the “strength” of vapor shield on the target surface temperature. As a result, the influence of the vapor shielding phenomena details, such as radiation transport in the vapor cloud and evaporated material dynamics, on the Emax is virtually completely masked by the strong dependence of the evaporation rate on the target surface temperature. However, the very same details define the amount of evaporated particles, needed to provide an effective shielding to the target, and, therefore, strongly influence resulting erosion rate. Finally and thus, Emax cannot be used for validation of shielding models and codes, aimed at the target material erosion calculations.},
doi = {10.1063/1.4939537},
journal = {Physics of Plasmas},
number = 2,
volume = 23,
place = {United States},
year = {2016},
month = {2}
}

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Works referenced in this record:

Simulation of damage to tokamaks plasma facing components during intense abnormal power deposition
journal, April 2014


A model for the ablation rate of a solid hydrogen pellet in a plasma
journal, June 1977


The role of plasma–wall interactions in thermal instabilities at the tokamak edge
journal, November 2003

  • Tokar, M. Z.; Kelly, F. A.
  • Physics of Plasmas, Vol. 10, Issue 11
  • DOI: 10.1063/1.1613963

Tungsten melt layer motion and splashing on castellated tungsten surfaces at the tokamak TEXTOR
journal, August 2011


Steady-state radiative cooling rates for low-density, high-temperature plasmas
journal, November 1977


Experimental study of plasma energy transfer and material erosion under ELM-like heat loads
journal, June 2009


Tungsten damage and melt losses under plasma accelerator exposure with ITER ELM relevant conditions
journal, April 2014


Tungsten melt layer erosion due to J×B force under conditions relevant to ITER ELMs
journal, June 2007


Calculation and experimental test of the cooling factor of tungsten
journal, January 2010


Evaporation and vapor shielding of CFC targets exposed to plasma heat fluxes relevant to ITER ELMs
journal, April 2009


Experimental verification of FOREV-2D simulations for the plasma shield
journal, June 2009


Calculation of cracking under pulsed heat loads in tungsten manufactured according to ITER specifications
journal, December 2015


Divertor tungsten tile melting and its effect on core plasma performance
journal, October 2012


Damage to preheated tungsten targets after multiple plasma impacts simulating ITER ELMs
journal, April 2009


Experimental study of PFCs erosion under ITER-like transient loads at plasma gun facility QSPA
journal, June 2009


Simulation of tungsten plasma transport along magnetic field under ELM-like heat loads
journal, July 2013


Controlled tungsten melting and droplet ejection studies in ASDEX Upgrade
journal, December 2011


Application of powerful quasi-steady-state plasma accelerators for simulation of ITER transient heat loads on divertor surfaces
journal, March 2007

  • Tereshin, V. I.; Bandura, A. N.; Byrka, O. V.
  • Plasma Physics and Controlled Fusion, Vol. 49, Issue 5A
  • DOI: 10.1088/0741-3335/49/5A/S19

Hot electron target interaction experiments at the GOL-3 facility
journal, November 1997