Gyrokinetic full-f particle-in-cell simulations on open field lines with PICLS

Abstract

While in recent years, gyrokinetic simulations have become the workhorse for theoretical turbulence and transport studies in the plasma core, their application to the edge and scrape-off layer (SOL) region presents significant challenges. In particular, steep density and temperature gradients as well as large fluctuation amplitudes call for a "full-f" treatment. To specifically study problems in the SOL region, the gyrokinetic particle-in-cell (PIC) code PICLS has been developed. The code is based on an electrostatic full-f model with linearised field equations and uses kinetic electrons. Here, the well-studied parallel transport problem during an edge-localized mode (ELM) in the SOL shall be investigated for one spatial dimension. The results are compared to previous gyrokinetic continuum and fully kinetic PIC simulations and show good agreement.

Kinetic modeling of neutral transport for a continuum gyrokinetic code

“…The recycling coefficient was α rec = 1.0 and the reflection coefficient was α b = 0. A hydrogen plasma is assumed, and input parameters are the following: B 0 = 0.5 T, n 0 = 5 × 10 18 m −3 , and 32). The simulation was run to t end = L z /c s0 , where c s0 = T e0 /m i .…”

“…Ionization and charge exchange interactions are included. The neutral grid resolution is (N x , N y , N z , N v x , N v y , N v z ) = (16,32,32,6,6,6), with the same configuration space extents as the gyrokinetic species and velocity space extents v x,y,z ∈ [−4v t,i0 , 4v t,i0 ] defined in terms of the ion thermal speed. Piecewise-linear basis functions are also used for the numerical solution of the neutral distribution function.…”

“…27,28 Gyrokinetic models, which have long been used to model core plasma turbulence, have been more recently adapted to the edge and SOL to capture important kinetic effects, such as parallel transport, trapped particles, nonlinear wave-particle interactions, etc., that drift-reduced fluid and gyrofluid codes may model less accurately. 25,[29][30][31][32][33][34] Including neutral interactions further improves the predictive capabilities of these models. Thus, in this work we present a continuum kinetic model of neutral transport coupled to a continuum gyrokinetic solver within the computational plasma physics framework Gkeyll, 35 which has previously been used to model plasma turbulence on open field lines.…”

Development and testing of an unstructured mesh method for whole plasma gyrokinetic simulations in realistic tokamak geometry

“…While the convergence of the simulation for the whole plasma volume is achieved, a benchmark with other codes with the treatment of the whole plasma geometry will be studied in the future. Missing physics in the TRIMEG code includes, but is not limited to, the fully nonlinear collision operator 33 ; a more realistic boundary condition such as a sheath boundary condition 34,35 ; the radial electric field consistent with neoclassical physics; and zonal flow physics. In addition, more comprehensive gyrokinetic/gyrofluid models for the edge also need to be considered 12,13 .…”

Turbulent field fluctuations in gyrokinetic and fluid plasmas

“…* mathewsa@mit.edu This is significant since validating the accuracy of reduced turbulence theories is amongst the greatest challenges to the advancement of plasma modelling. In the fusion community, both comprehensive full-f global gyrokinetic [6][7][8][9][10][11][12][13] and two-fluid [14][15][16][17][18] direct numerical simulations are under active development to improve predictive modelling capabilities and the design of future reactors, but no single code can currently capture all the dynamics present in the edge with sufficient numerical realism. It is therefore of paramount importance to recognize when certain numerical or analytical simplifications make no discernible difference, or when a given theoretical assumption is too risky-to clearly identify the limits of present simulations [4].…”