Calculation of the Runaway Electrons Stopping Power in ITER

 

Yu. Igitkhanov, B. Bazelev and S. Murakami1 ,

 

Forschungszentrum Karlsruhe, IHM, Box 3640, 76021 Karlsruhe, Germany

1Kyoto University, Japan

 

e-mail of main author: yli@ipp.mpg.de or Juri.Igitkhanov@ihm.fzk.de

 

 

The stopping power was estimated in realistic ITER boundary plasma, where the inhomogeneous structure of the first wall segments and the shallow angle of incident were taken into account. The simulations are done for mono-energetic electrons of 10 and 50 MeV, energy densities of 50 MJm-2 and impact angles of 1o. After making several turns in the boundary plasma and slighting the wall, relativistic electron beam will eventually lose the energy in plasma and in the PSC structure. The calculations of the first wall damage in ITER by runaway electrons during disruptions are presented in this paper. The deposition profiles of runaway electrons into W and Be wall by the ENDIP Monte Carlo code were estimated by taking into account the relativistic electron energies and the effect of secondary electron production.. It is found that both Be and W melt to depths of ~1.2-2.5 mm for these conditions with the depth of the molten pool being lower for W. In the cases studied, the temperature of the cooling tubes remains under the melting temperature of their material (S.S. for Be and Cu for W). Key outstanding issues that need more refined modelling were described. The electromagnetic energy of RE beam will be dissipated due to inductivity to passive structure (wall, etc).

Suppression of runaway electrons by an external magnetic perturbation (low toroidal mode number n=1 and 2) has been demonstrated in TEXTOR, i.e., RE plateau is shortened, high energetic RE is absent, RE current is reduced. Required magnetic perturbation is estimated as dBr/B0.1% in the spatial region in which REs runaway electrons most likely to be generated (usually close to the pre-disruptive plasma centre). This value seems close to the previous JT-60U result using the DCW (disruption control winding). According to these experimental results, possibility appears in ITER to suppress REs by the ELM control coils to be installed inside the vessel. This possibility needs to be urgently confirmed by proper assessment of the required coil current and voltage for changing the mode to the relevant one (low m/n).

 

 

[1] Yu.L.Igitkhanov et., al.Fusion Science and Technology 50, 268-275, (2006)

[3] Yu. Igitkhanov, Contribution Plasma Phys. 28 1988 4/5 477