Experimental estimation of tungsten impurity sputtering due to Type I ELMs in JET-ITER-like wall using pedestal electron cyclotron emission and target Langmuir probe measurements

C Guillemaut, A Jardin, J Horacek, I Borodkina, A Autricque, G Arnoux, J Boom, S Brezinsek, J W Coenen, E De La Luna, S Devaux, T Eich, D Harting, A Kirschner, B Lipschultz, G F Matthews, A Meigs, D Moulton, M O'Mullane, M Stamp

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Abstract

The ITER baseline scenario, with 500 MW of DT fusion power and Q = 10, will rely on a Type I ELMy H-mode and will be achieved with a tungsten (W) divertor. W atoms sputtered from divertor targets during mitigated ELMs are expected to be the dominant source in ITER. W impurity concentration in the plasma core can dramatically degrade its performance and lead to potentially damaging disruptions. Understanding the physics of the target W source due to sputtering during ELMs and inter-ELMs is important and can be helped by experimental measurements with improved precision. It has been established that the ELMy target ion impact energy has a simple linear dependence with the pedestal electron temperature measured by Electron Cyclotron Emission (ECE). It has also been shown that Langmuir Probes (LP) ion flux measurements are reliable during ELMs due to the surprisingly low electron temperature. Therefore, in this paper, LP and ECE measurements in JET-ITER-Like-Wall (ILW) unseeded Type I ELMy H-mode experiments have been used to estimate the W sputtering flux from divertor targets in ELM and inter-ELM conditions. Comparison with similar estimates using W I spectroscopy measurements shows a reasonable agreement for the ELM and inter-ELM W source. The main advantage of the method involving LP measurements is the very high time resolution of the diagnostic (∼10 μs) allowing very precise description of the W sputtering source during ELMs.

Original languageEnglish
Number of pages7
JournalPhysica Scripta
Volume2016
Issue numberT167
DOIs
Publication statusPublished - 8 Jan 2016
Event15th International Conference on Plasma-Facing Materials and Components for Fusion Applications, PFMC 2015 - Aix-en-Provence, France
Duration: 18 May 201522 May 2015

Keywords

  • edge localized mode
  • magnetic confinement fusion
  • tungsten sputtering

Cite this

Guillemaut, C., Jardin, A., Horacek, J., Borodkina, I., Autricque, A., Arnoux, G., Boom, J., Brezinsek, S., Coenen, J. W., De La Luna, E., Devaux, S., Eich, T., Harting, D., Kirschner, A., Lipschultz, B., Matthews, G. F., Meigs, A., Moulton, D., O'Mullane, M., & Stamp, M. (2016). Experimental estimation of tungsten impurity sputtering due to Type I ELMs in JET-ITER-like wall using pedestal electron cyclotron emission and target Langmuir probe measurements. Physica Scripta, 2016(T167). https://doi.org/10.1088/0031-8949/2015/T167/014005