Four-Dimensional Finite-Orbit-Width Fokker-Planck Code with Sources

Theory-based kinetic (Fokker-Planck) codes that calculate distribution functions of charged particles in fusion plasmas, including an accurate collision model and heating sources, are essential computational tools for the theoretical interpretation of existing fusion energy plasma experiments, and for projections to new experiments. The kinetic code CQL3D developed by CompX is used by many national laboratories, universities and private companies in the US, and also by many research centers outside of US. The code is favored by experimentalists because of (1) its large set of synthetic diagnostics tools, (2) its speed, (3) simplicity of use starting from a set of run templates, and (4) ready support from CompX. It is also coupled to other codes and is part of SciDAC Integrated Plasma Simulator project. The code & apos;s speed is achieved by averaging the kinetic equations over all periodic coordinates, under the assumption of low collisionality. On the other hand, the averaging over periodic closed orbits is not valid in conditions of high collisionality or open flux surfaces, that typically happen near the plasma center and plasma edge. We propose to remove the above collisionality and edge-physics limitations by constructing a new, four-dimensional code that will incorporate best features of the existing CQL3D bounce-averaged code, and will be valid for any collisionality regime, and for the whole plasma. This goal is achieved by creating an interface between different modules of the two types of kinetic codes: the modules that describe collisions, plasma heating and synthetic diagnostics from the bounce-averaged code, and modules that perform integration of kinetic equations in four dimensions (two spatial plus two velocity dimensions) that will be imported from the well-known TEMPEST gyro-kinetic code. In Phase I, will explore different options for unification of the two types of codes. A key feature of the CompX code suite is that they are released as open-source software. This enables code investigation and modification by the user, promotes confidence in the code, and ensures that researchers will in any eventuality be able to continue using codes in which they have invested their time. CompX, which is very familiar with all aspects of its complicated codes, markets services for the codes: code applications, code support, and additional development of the code suite for the specific needs of customers. The new code will extend the CompX & apos;s present code suite, which will widen the range of opportunities for code application and development contracts to CompX, and will also directly serve the interests of the USDOE. Based upon past performance, the enhanced simulation capabilities developed under this initiative can produce follow on contacts with DOE, and subcontracts with DOE funded and private enterprise fusion energy facilities. The experimentalists, not only in US but internationally, will obtain the code sufficiently robust and low enough in computer requirements to be accessible to comprehensive coupled simulations. Similar to CQL3D, the new code will be an efficient tool for facilitating comparison of simulation results with experimental data, since it will inherit the widely-used CQL3D synthetic diagnostics modules.