Experimental investigation of a localized electron temperature elevation near electron cyclotron resonance

摘要

The authors examined detailed properties of a plasma/wave interaction in an inhomogeneous magnetic field. An electron cyclotron resonant cavity produces a plasma column that is tuned so that an electron cyclotron wave launched from a helical antenna couples to the plasma. The wave then interacts with the langmuir probe to produce a localized electron temperature elevation. The authors have studied the dependence of the elevation on launched wave frequency, plasma density, neutral pressure, and plasma source tuning. Langmuir probes with different impedances were used to illustrate the dependence of the temperature elevation on probe impedance. It was found that the temperature elevation process is maximum when the probe is near but substantially shifted from the cold electron cyclotron resonance position in an inhomogeneous plasma. Collisionless wave absorption near resonance, magnetic field, and plasma source tuning play important roles in determining the temperature elevation phenomenon. Two-probe correlation measurements were carried out to determine the radial and axial extent of the elevation and will be used to construct a model of the mechanism responsible.