Resonant interaction of runaway electrons with magnetic field ripple in tokamak plasmas

The toroidal magnetic field of tokamaks is generated by a finite number of coils, which slightly modulates the magnetic field and runaway electrons experience this modulation. The resonant interaction between runaway electrons and the magnetic field ripple has been observed in the HT-7 tokamak. The maximum energy of runaways in the edge region could be blocked by the resonance of gyromotion with the nth harmonic of the magnetic field ripple. This resonant interaction is favorable for the control of runaway energy.