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EUROfusion

Abstract of RFDINITY Project

The radio-frequency (RF) plasma production technique in the ion cyclotron range of frequency (ICRF) is relied upon for producing and sustaining the ITER and W7-X 12 -3wall conditioning plasmas (ICWC) [1, 2, 3, 4, 5, 6] (Te = 3-5eV, ne < 10 cm ). ICRF plasma initiation has been studied intensively using single particle descriptions and basic analytic models [7]. For better understanding on the plasma production employing the vacuum RF field of ICRF antennas in presence of the toroidal magnetic field and its parametric dependencies, the Monte Carlo code RFdinity1D was developed in C++ using standard message-passing parallel programming for runtime optimization. The code studies the breakdown conditions and the electronic energy distribution evolution as function of e.g. (i) the RF vacuum field strength and distribution, (ii) the RF frequency, (iii) the neutral pressure (H2) and (iv) the dimensions of torus. While new results obtained in the HELIOS 3rd project cycle were in qualitative agreement to experimental breakdown times of the TEXTOR tokamak [8], necessary physics upgrades were identified for reproducing recent experimental data: e.g. the simulations on HELIOS revealed a critical importance of the Coulomb collisions in discharge production. Several upgrades could already be completed in the 3rd and 4th cycles. The 4th cycle was dedicated to simulations with the electric field produced by ITER antenna. The simulations confirmed possibility of ITER antenna to initiate a discharge. It was found that the discharge initiation is possible even at the low antenna power (P=1MW), which suggests an existence of a safe scenario for the plasma initiation in ITER. This year the model was transformed into PIC-MC model to describe another physics phenomena that were identified as critical for discharge thinitiation. The project for 5 the cycle on HELIOS will focus on (i) repeating the simulations with ITER antenna with Faraday screen, (ii) proposing of the safe scenarios for the discharge initiation in ITER, and (iii) further code improvements.

It is expected that the HLST support activity will maximize the benefit of using HELIOS with the possibility to run simulations with a high number of cores.

[1] A. Lyssoivan et al., J. Nucl. Mater. 337-339, 456 (2005).
[2] D. S. Lee et al., Trans. Fusion Sci. Technol. 94-97, 60 (2011).
[3] J. S. Hu et al., J. Nucl. Mater. 207-210, 376 (2008).
[4] D. Douai et al., 21st Int. Conf. on Plasma Surface Interactions, Japan, May 2014.
[5] T. Wauters et al., AIP Conf. Proc. 1580 (2014) 187.
[6] R. Brakel et al., J. Nucl. Mat. 290-293, 1160-1164 (2001).
[7] A. Lyssoivan et al., Plasma Phys. Control. Fusion 54, 074012 (2012).
[8] M. Tripský et al., 41st EPS Conf. Control Fusion and Plasma Physics, Berlin, Germany, 23- 27 June, (2014), to be published in AIP conference abstracts.