A point plasma model for linear plasma devices based on SOLPS-ITER equations: application to helium plasma

Abstract

Linear plasma devices represent an essential tool for nuclear fusion research, whereby understanding crucial aspects related to plasma-wall interactions or edge plasma behaviour. Simplified models are of great importance to complement and integrate experimental and simulation results of complex systems such as plasmas in linear machines, because they are fast and simple to employ. In this work, we present a global volume-averaged (0D) model for plasma investigation in linear machines. The 0D model equations are based on the space integration of the state of the art edge plasma model implemented in the SOLPS-ITER code. Comparisons between helium plasmas described with 2D simulations performed with SOLPS-ITER and with the 0D model highlight that contributions often neglected in tokamak edge models, e.g. electron-neutral excitation, may be relevant when describing weakly ionized plasmas in linear devices. The model is used to perform sensitivity studies with respect to several parameters and to analyse the time evolution of the system, leading to the identification of two relevant time scales governing the system. Lastly, a comparison of 0D results with experimental data from the linear device GyM is performed, showing satisfactory agreement. Our methods and results provide crucial interpretative keys in the investigation of the physics of edge plasmas.

Linear plasma device GyM for plasma-material interaction studies

“…In support of the experimental program of GyM, modelling activities in the frame of a collaboration between NanoLab of Politecnico di Milano and ISTP-Milan, have been developed in the recent years [28,68,69]. First, the tokamak plasma edge SOLPS-ITER code [36] has been successfully applied to the argon plasma of GyM and benchmarked against the radial profiles of the electron density and temperature from Langmuir probe [28].…”

Global SOLPS-ITER and ERO2.0 coupling in a linear device for the study of plasma–wall interaction in helium plasma

“…SOLPS-ITER simulations of the GyM linear device were performed using the setup described in [21]. In particular, the electron cyclotron resonance heating exploited in GyM was simulated with a Gaussian power density profile peaked at the axial position of the resonance, as explained in detail in [20].…”

“…This machine operates at low magnetic field (B ≃ 0.1 T) and has plasma conditions similar to those of the scrape-off layer of toroidal devices. SOLPS-ITER has been recently used to simulate non-hydrogenic plasmas in GyM, like Ar [20] and He [21]. In both cases, the simulation results were benchmarked against experimental data, showing the capability of SOLPS-ITER of addressing the low temperature plasma conditions typical of linear devices.…”

“…In both cases, the simulation results were benchmarked against experimental data, showing the capability of SOLPS-ITER of addressing the low temperature plasma conditions typical of linear devices. In [21], moreover, SOLPS-ITER results were also successfully compared with a simplified 0D model developed by space averaging of plasma main parameters. Erosion studies in GyM with ERO2.0 focused on the microscale surface morphology evolution of materials under plasma exposure [22].…”

“…Specifically, we performed the first global coupling between SOLPS-ITER and ERO2.0 in the GyM linear device, considering He plasma and different wall materials, such as carbon (C), iron (Fe), copper (Cu) and tungsten (W). From the results obtained in [21], we first added few collisional processes in the EIRENE input file that were neglected in previous SOLPS simulations of He plasmas. Once selected the most complete atomic database for He simulations (see table 1), we simulated the GyM He plasma with SOLPS-ITER.…”