Abstract of COCHLEA-19 Project

In fusion experiments gyrotrons are the main source of RF radiation, needed for the ECRH (plasma heating, instabilities treatment and current drive). Modern gyrotrons are electrically and physically large devices and their study becomes a very demanding job. There have been developed several semi–analytical methods and the corresponding numerical codes to treat such structures; however, the required computational resources are extremely large. A code based on the Finite Difference in Time Domain (FDTD) method has been initiated in the previous years, which can study any cylindrical–like waveguide structure in the time domain. This code supports different sources (modal and current distributions) as well as various materials (PEC and dielectric). The main output of the code includes the field components in time and space, whereas specific post–processing procedures have been also developed to calculate the energy and the power characteristics of such structures. The numerical code also incorporates the beam–wave interaction module. The latter is based on the Particle–In–Cell (PIC) technique, where the electron beam is modelled as a large number of distinct particles. These particles interact self–consistently with the electromagnetic fields. Up to now, the necessary physical model was developed and partially implemented in the numerical code. The calculation of the fields has already been parallelized using OpenMP, while other parts and the post–processing procedures need further parallelization and optimization. Note that the FDTD scheme is based on the Yee1 algorithm (an extensively parallelized algorithm), therefore its parallelization using domain decomposition method will significantly improve the performance of the code. The aim of this project is to continue the parallelization and optimization of the code using a hybrid OpenMP–MPI scheme, the parallelization of the PIC module and the development of the necessary parallel output using the parallel netCDF library. Our team has responded to the 3rd production cycle call for the usage of CINECA's Marconi–Fusion HPC (A3 partition). This proposal will be the continuation of the COCHLEA–HLST project under the WP17 HLST framework (June 2017 – January 2018). It should be mentioned that the mathematical formulation and the corresponding numerical code development is included in the EUROfusion WPHCD activities.