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16 novembre 2015
Pure deuterium and nitrogen seeded H-mode plasma simulations for WEST

WEST H-mode-like configuration has been investigated using SOLEDGE2D-EIRENE simulation tool. Two cases at high plasma density have been studied : the first one in pure deuterium discharge and the second one with Nitrogen seeding. These simulations will provide guidance for the preparation of WEST operation.

 

In the perspective of operating WEST (W Environment Steady State) tokamak at Cadarache, a dedicated effort has been made to develop the transport code SOLEDGE2D-EIRENE. This code is used in a prospective way to investigate the operational domain of WEST, focusing on target heat loads and plasma conditions in the edge plasma. During the operation, the code will be used to analyze experiments, help interpreting edge plasma behavior (using synthetic diagnostics for instance), and link WEST results to ITER. Thanks to powerful numerical methods, SOLEDGE2D-EIRENE is able to provide a rather detailed description of the WEST divertor behavior, gaining insight into the interplay between plasma and neutrals as well as the role of various divertor components (baffle, antennas etc…).

 
Pure deuterium and nitrogen seeded H-mode plasma simulations for WEST

Plasma density in the edge and SOL region obtained from SOLEDGE-EIRENE simulation of WEST H-mode-like configuration, without impurity seeding. The input power is set to 8 MW and the separatrix density to 3.8·10 19 particles per cubic meter.

However, using edge transport codes in a predictive way is a challenge since turbulent transport is not modeled self-consistently. For this reason, in order to investigate WEST plasma properties it has been necessary to simulate H-mode plasma on ASDEX Upgrade which is a comparable medium size tokamak in Germany. The radial transport coefficients have been chosen taking into account parameters which have been adjusted so as to match experimental mid-plane profiles. After the validation of the code on an ASDEX H mode discharge, numerical simulations have been performed with SOLEDGE-EIRENE for a WEST H mode-like configuration, both for a pure deuterium discharge and for a case with Nitrogen seeding in the lower divertor private flux region. In the first case, a very high temperature on the targets has been observed and explained with respect to the density and temperature profiles. In the second case, activating a Nitrogen gas puffing in the private region, acceptable plasma temperatures on the targets have been recovered maintaining quite high heat fluxes on the targets.

 

A more complete analysis of simulation results obtained for a density scan is in progress. On the modelling side, further validations of SOLEDGE-EIRENE code on JET are planned, in particular for open divertor configurations and high power discharges. Associated with these numerical studies are also planned the improvement of the theoretical description of plasma-wall boundary conditions, taking into account for example the impact of secondary electron emission on the heat flux and temperature estimation.

 

 

 

 

 

 

Ion temperature in the edge and SOL region obtained from SOLEDGE-EIRENE simulation of WEST H-mode-like configuration, without impurity seeding. The divertor region has been magnified in order to show temperature on the strike points. The input power is set to 8 MW and the separatrix density to 3.8·1019 particles per cubic meter.

 

 
   

 

Nitrogen radiated power in the edge and SOL region obtained from SOLEDGE-EIRENE simulation of WEST H-mode-like configuration, with nitrogen seeding injected from the private flux region. The input power is set to 8 MW, the separatrix plasma density to 3.8·19 particles per cubic meter and the gas puffing rate to 3·1020 particles per second.

 

 

 

 

Ion temperature in the edge and SOL region obtained from SOLEDGE EIRENE simulation of WEST H-mode-like configuration, with nitrogen seeding injected from the private flux region. The divertor region has been magnified in order to show temperature on the strike points. The input power is set to 8 MW, the separatrix plasma density to 3.8 ·1019 particles per cubic meter and the gas puffing rate to 3·1020 particles per second.

 

 

 

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