Search

Abstract: A systematic numerical study of the deposition of Be and C atoms on the ITER main chamber first mirrors and their erosion due to fast D(T) atoms has been carried out. The calculations are based on Monte-Carlo neutral transport modelling (with the EIRENE code) on a simulated steady-state plasma background. A generic reduced model of cylindrical and conical diagnostic ducts is considered. The results indicate that the sputtering of the mirrors can be made acceptably small if they are installed in sufficiently long ducts. At the same time the deposition of impurities can be a serious issue even for mirrors protected in long channels. However, the calculations of deposition are not very reliable at the current stage and a need to seriously improve them is indicated. [Copyright &y& Elsevier]

Abstract: Change of Hα intensity profiles depending on magnetic configurations is observed in the divertor plasma. It can be explained by the magnetic field line structures in the ergodic layer and the divertor legs. The behavior of neutral particles in the plasma periphery is investigated by a three-dimensional neutral particle transport simulation code which assumes that the distribution of the plasma flow onto the divertor plates corresponds to that of the strike points calculated by magnetic field line traces. Vertical Hα intensity profiles and polarization resolved Hα spectra are calculated by the simulation code including the effect of Doppler broadening, fine structure splitting and polarization of the Hα emission, which agree well with the measurements in various magnetic configurations. It shows spontaneous formation of high neutral density in inboard side of the torus, which is independent of the magnetic configurations in LHD. [Copyright &y& Elsevier]

Abstract: Predictive and interpretative edge plasma models often rely upon a kinetic neutral particle module. A virtually exact description of atomic, molecular and radiative reactions is provided via Monte Carlo synthesis of the relevant processes. For many integrated edge transport models, such as B2–EIRENE (‘SOLPS’), OEDGE, EDGE2D–EIRENE (all 2D) and EMC3–EIRENE (3D) the EIRENE Monte Carlo code provides this microscopic analysis for the macroscopic plasma flow fields. The current status of the neutral-particle and radiation transport model in the EIRENE Monte Carlo Code is presented. The directions of further developments of the databases are outlined. [Copyright &y& Elsevier]

Abstract: In Tore Supra long pulses, particle balance gives evidence that a constant fraction of the injected gas (typically 50%) is retained in the wall for the duration of the shot, showing no sign of wall saturation after more than 6min of discharge. During the discharge, the retention rate first decreases (phase 1), then remains constant throughout the pulse (phase 2). Phase 1 could be interpreted as implantation of particles combined with a constant codeposition rate, while phase 2 could correspond to codeposition alone, once the implanted surfaces are saturated with deuterium. This paper presents a possible contribution of charge exchange neutrals to the implantation process, based on modelling results with the Eirene neutral transport code. A complex pattern of particle implantation is evidenced, with saturation time constants ranging from less than one to several hundreds seconds, compatible with the experimental behaviour during phase 1. [Copyright &y& Elsevier]

Abstract: For some divertor aspects, such as detached plasmas or the private flux zone, it is not clear that the controlling physics has been fully identified. This is a particular concern when the details of the plasma are likely to be important in modeling the problem – for example, modeling co-deposition in detached inner divertors. An empirical method of ‘reconstructing’ the plasma based on direct experimental measurements may be useful in such situations. It is shown that a detached plasma in the outer divertor leg of DIII-D can be reconstructed reasonably well using spectroscopic and probe data as input to a simple onion-skin model and the Monte Carlo hydrogenic code, EIRENE. The calculated 2D distributions of n e and T e in the detached divertor were compared with direct measurements from the divertor Thomson scattering system, a diagnostic capability unique to DIII-D. [Copyright &y& Elsevier]

Abstract: The ITER divertor will be more collisional than divertors in existing tokamaks and the neutral modeling tools used for predictive ITER modeling need to be validated for similar divertor conditions in order to increase confidence in the results. The EIRENE neutral code has been applied to the Alcator C-Mod divertor, where collisional effects such as Lyman series photon trapping and neutral viscosity have been observed. The plasma solution used as input to EIRENE agrees well with the available diagnostic data for the divertor and was generated using an empirical Onion-Skin Method interpretive code that requires a large amount of experimental data as input. The calculated divertor pressure is 11±3 mTorr, a factor ∼2 lower than the measured value of 25±3 mTorr. The neutral solution is sensitive to photon trapping, viscosity, elastic collisions between plasma ions and molecules, and the amount of leakage through the outer divertor substructure. [Copyright &y& Elsevier]