Overview of latest runaway electron experiments and analysis at COMPASS

In the last runaway electron campaigns that were performed in 2020, broad range of experi- mental results were obtained in several areas of runaway electron physics. Special diagnostic tools and methods were applied including HXR spectrometry, limiter calorimetry, estimates of energy based on runaway electron equilibrium, synchrotron radiation diagnostics (REIS2), matrix SXR detectors and passive and active high frequency antennas. The measurements of RE beam average energy based on the relativistic pressure and equilibrium properties seem to present a fast and efficient method that can be compared well with the methods based on the hard X-ray bremsstralung and synchrotron radiation diagnostics. The comparison of RE beams generated by injections of different gas species and amounts shows that the least dangerous terminations of the RE beam can be achieved via Ne injection or impurity injection followed by a D2 secondary injection. The D2 secondary injection beneficial effects tend to be consistent with DIII-D and JET results. The RMP experiments have also provided many interesting results including significant reduction of HXRs and impact energy of the RE beam with application of RMPs during the RE beam generation. Measurements with high frequency antennas, which will be briefly introduced, also showed presence of wide range of high frequency kinetic instabilities including the whistler-like and various chirping phenomena. Last but not least the room temperature solid state pellet injector has been implemented and used for RE beam generation as well as for enhancing the RE dissipation.