Anomalous-energy runaway electrons(RAEs),whose energy exceeds the maximum potential difference across the discharge gap,are widely observed in various plasma phenomena.This study investigates the origination of anomal...Anomalous-energy runaway electrons(RAEs),whose energy exceeds the maximum potential difference across the discharge gap,are widely observed in various plasma phenomena.This study investigates the origination of anomalous-energy RAEs in fast ionisation waves(FIWs)formed during pulsed gas breakdown.Synchronised observation of RAEs and their induced bremsstrahlung X-ray at different locations of the FIW is performed,which is combined with measurement of spatial-temporal evolution of FIW potential.It is revealed that anomalous-energy RAEs,preceding regular RAEs,have an ultrashort beam with a picosecond pulse width,and RAEs tend to maintain their energy during FIW propagation before being deposited into the anode.Particle-in-cell Monte Carlo collision(PIC-MCC)simulation illustrates that the‘pace-matching’between initial electron acceleration through cathode potential drop and potential lift-up during FIW inception opens a narrow window for forming anomalous-energy RAEs.展开更多
基金supported by the National Natural Science Foundation of China(Grants 52350072,52437007,52277167)the Beijing Nova Program(Grant 20240484512)the Beijing Natural Science Foundation(Grant 1242030).
文摘Anomalous-energy runaway electrons(RAEs),whose energy exceeds the maximum potential difference across the discharge gap,are widely observed in various plasma phenomena.This study investigates the origination of anomalous-energy RAEs in fast ionisation waves(FIWs)formed during pulsed gas breakdown.Synchronised observation of RAEs and their induced bremsstrahlung X-ray at different locations of the FIW is performed,which is combined with measurement of spatial-temporal evolution of FIW potential.It is revealed that anomalous-energy RAEs,preceding regular RAEs,have an ultrashort beam with a picosecond pulse width,and RAEs tend to maintain their energy during FIW propagation before being deposited into the anode.Particle-in-cell Monte Carlo collision(PIC-MCC)simulation illustrates that the‘pace-matching’between initial electron acceleration through cathode potential drop and potential lift-up during FIW inception opens a narrow window for forming anomalous-energy RAEs.
