Real-time beam tracing for control of the deposition location of electron cyclotron waves

Plasma control techniques that use electron cyclotron (EC) resonance heating and current drive such as control of neoclassical tearing modes require accurate control of the deposition location of EC beams. ASDEX Upgrade has successfully implemented a real-time version of the beam-tracing code TORBEAM into its real-time diagnostic system to act as a globally available module that calculates current deposition location and its sensitivity from other real-time diagnostic measurements for all its moveable EC wave launchers. Based on a highly (100×) accelerated version of TORBEAM, the software implementation as a diagnostic process uses parallelization and achieves cycle times of 15-20 ms for determining the radial deposition location of 12 beams in the plasma. This cycle time includes data input-output overhead arising from the use of available real-time signals. The system is by design portable to other machines such as ITER.