It has been claimed that in the presence of an oblique magnetic field, the sheath exhibits a double structure consisting of an electrostatic sheath the order of a Debye length and a magnetic sheath the order of the ion gyroradius evaluated at the ion sound speed. Measurements of sheath potential, occurring in front of negatively or positively biased plate, have been performed in the presence of an external DC magnetic field with orientations nearly parallel or perpendicular to the plate in an electrodeless RF induction plasma in a multidipole device. This source operates at frequencies ranging from approximately 1 MHz to approximately 20 MHz, depending on the tuned resonance frequency, and at a neutral gas pressure <5*10/sup -5/ torr. It has been operated with DC magnetic fields up to approximately 100 G, and a strong electron cyclotron resonance effect has been observed. Plasmas produced at low neutral pressure (>1*10/sup -3/ torr) have good spatial uniformity independently of magnetic field direction.
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