Abstract. This work demonstrates that simulations of advanced burning plasma operation scenarios can be successfully parallelized in time using the parareal algorithm. CORSICAan advanced operation scenario code for tokamak plasmas is used as a test case. This is a unique application since the parareal algorithm has so far been applied to relatively much simpler systems except for the case of turbulence. In the present application, a computational gain of an order of magnitude has been achieved which is extremely promising. A successful implementation of the Parareal algorithm to codes like CORSICA ushers in the possibility of time efficient simulations of ITER plasmas.
IntroductionWith the construction of the ITER project well under way, understanding and predicting burning plasma scenarios have gained tremendous importance. These studies are used for designing of components for the world's largest tokamak and contribute towards its successful operation. Plasma scenario studies are carried out by codes such as CORSICA [1,2]. CORSICA employs a free or fixed boundary 2D equilibrium package that is coupled with various transport and source models. The advanced capabilities of these simulations allow studies with realistic physics and engineering constraints. CORSICA has also been used to predict and analyse plasma operations in the existing tokamak DIII-D[3] which served as a means of validation and verification.It must be borne in mind that simulations of plasma operation scenarios require extremely long wallclock time. Space parallelization is a common approach to achieve computational speedup although this technique experiences saturation while reduction in computation time is still desired. The option of time parallelization introduces a new opportunity, although this approach has not been explored much in the past for these kinds of simulations. The parareal algorithm [4] lays out a scheme for the application of temporal parallelization to simulations. The algorithm has attracted significant attention in recent times and has undergone modifications to maximize computational speed-up and efficiency [5,6,7,8].Except for turbulence [5,9] which is a complex system with high dimensional chaos, the parareal algorithm has so far been applied to relatively simple problems [10,11,12,13,14]. This work demonstrates that the parareal algorithm may be successfully applied to CORSICA to attain computational speed-up for plasma scenario simulations. The coupling of the equilibrium solver with the transport and source modules makes this a unique application compared to previous attempts. These simulations are characterized by quasi steady states interrupted by