GTROTA: A code for the solution of the coupled nonlinear extended neoclassical rotation equations in tokamak plasmas using successive over-relaxation and simulated annealing

Abstract

GTROTA (Georgia Tech ROTAtion) is a code that solves the extended neoclassical rotation equations for tokamak plasmas, derived from the multifluid moment equations (including electromagnetic effects) in generalized toroidal magnetic flux surface geometry. It computes the toroidal and poloidal fluid rotation velocities and the in–out and up–down density asymmetries at each radial location. The solution of these equations is accomplished iteratively, using a physically motivated decomposition, successive over-relaxation and the concept of simulated annealing. Program summaryProgram title: GTROTAv1Catalogue identifier: AEPT_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEPT_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 12890No. of bytes in distributed program, including test data, etc.: 1099937Distribution format: tar.gzProgramming language: Matlab.Computer: Any workstation or PC where Matlab can be run.Operating system: Any with Matlab available. Tested on Windows 7.RAM: 1024 MB to run MatlabClassification: 19.11.Nature of problem:Tokamak plasma rotation velocities and the poloidal in–out and up–down asymmetries of plasma densities are calculated from the coupled set of nonlinear equations, which show a very instable iterative dynamics. To solve for the true solution for this nonlinearly coupled system that does not converge to a single solution, physics-based determination of the true solution becomes necessary and GTROTA provides the algorithm for users to find the true solution from the nonlinear topological maps.Solution method:The code decomposes the given system into three subsystems to stabilize the iterative dynamics and uses Successive Over-Relaxation and the concept of Simulated Annealing to determine the true solution.Restrictions:The code is designed for strong rotation analysis. An updated code for slow rotation and plasma edge analysis is to be developed in the future.Unusual features:For a new rotation calculation, the code requires several test runs to determine the iterations step for the true solution.Additional comments:Due to the extreme nonlinearity of the extended rotation calculation model, the signs of the inputs must be adjusted correctly to yield correct solutions. Refer to the User’s Manual for this discussion.Running time:8 s (except test runs that depend on the complexity of the nonlinear dynamics).