Stellarator Optimization - in progress
An energy optimizing method for stellarators is developed and numerically implemented in the code SORSSA. SORSSA is developed for optimizing stellarators with fixed coil design. The figure of merit is the total stored energy in the plasma volume. In the used model, the energy depends on the effective ripple εeff, which is a measure for the neoclassical transport. To optimize the configurations, the currents of the magnetic field coils are varied such that the energy in the plasma is maximized. In addition to the coil currents, it is possible to vary, the coil positions and the angles between the coils. Thus, it is possible to use the code for the design of simple stellarators. The magnetic field is computed directly from the coil currents with help of a Biot-Savart code. Because magnetic field lines are independent of each other in vacuum magnetic fields, the computation of the field lines has been parallelized which significantly increases the speed of the computations. For the optimization process, the Simulated Annealing algorithm is used.
Currently some upgrades/tasks are ongoing/planned:
- automatic magnetic axis finder - in progress
- computation of α-particle confinement properties - not started
- optimization of H-1 configurations exhibiting stellarator symmetry - in progress
- optimization of H-1 configurations without stellarator symmetry - not started
SORSSA has been successfully applied to the following fusion experiments:
TJ-II (CIEMAT, Spain), U-2M (Kharkov, Ukraine), CNT (Columbia University, New York, USA).
Keywords: stochastic optimization, neoclassical transport, parallel processing (MPI)