Low-frequency magnetic fluctuation measurement during magnetic reconnection in counter-helicity plasma merging experiment

Magnetic fluctuations with frequency lower than the local ion cyclotron frequency was observed associated with magnetic reconnection event in TS-3 plasma merging device. Counter helicity merging of spheromaks provides significant ion heating by magnetic reconnection to form high-β field-reversed configuration plasma. The magnitude of the fluctuation observed during and after the counter helicity merging has stronger dependency on ion mass than reconnection speed, indicating that fast ion outflow from X-point would bring about excitation of large amplitude low frequency magnetic fluctuations which may be responsible for direct ion heating.