We derive a formula for the effective critical electric field for runaway generation and decay that accounts for the presence of partially ionized impurities in combination with synchrotron and bremsstrahlung radiation losses. We show that the effective critical field is drastically larger than the classical Connor-Hastie field, and even exceeds the value obtained by replacing the free electron density by the total electron density (including both free and bound electrons). Using a kinetic equation solver with an inductive electric field, we show that the runaway current decay after an impurity injection is expected to be linear in time and proportional to the effective critical electric field in highly inductive tokamak devices. This is relevant for the efficacy of mitigation strategies for runaway electrons since it reduces the required amount of injected impurities to achieve a certain current decay rate.
Runaway electron avalanche and macroscopic beam formation: simulations of the DTT full power scenario
Politecnico di Torino（都灵理工大学）；DTT S.C.a.r.l.；Max Planck Institute for Plasma Physics（马克斯·普朗克等离子体物理研究所）；CEA, IRFM（法国原子能和替代能源委员会，聚变研究部）；Indian Institute of Technology Guwahati（印度理工学院古瓦哈提分校）；ITER Organization（国际热核聚变实验堆组织）；Consorzio RFX（RFX联合体）；CNR-ISTP（国家研究委员会-等离子体科学和技术研究所）；ENEA（意大利国家新能源与可再生能源机构）；Università della Tuscia（图斯卡大学）
