Frequency Dependence of Parameters of an Inductive RF Discharge Placed in a Weak Magnetic Field

The properties of an inductive RF discharge placed in a longitudinal external magnetic field with an induction of less than 70 G at frequencies of 2, 4, and 13.56 MHz are studied. The dependences of the region of existence of the discharge, the efficiency of the RF power input and the structure of the RF magnetic field on the external magnetic field induction are studied experimentally. The experimental results are compared with calculations based on a previously developed electromagnetic discharge model. It is shown that the local maximum of the plasma density observed at weak magnetic fields is associated with the resonant excitation of waves in the plasma source. The excited wave is close to a transverse helicon at a frequency of 2 MHz, and its properties approach the Trivelpiece–Gould wave at a frequency of 13.56 MHz,.