Experimental investigation of the magnetic presheath in a magnetized argon plasma

Summary form only given, as follows. The sheath of a plasma in contact with an absorbing target in an oblique magnetic field exhibits a double structure: the electric Debye sheath which has a thickness of several Debye lengths, and the magnetic presheath which has a width which is governed by the ion Larmor radius, and hence scales with the magnetic field as c/sub a//w/sub ci/.c/sub s/ is the sound speed while w/sub ci/ is the ion cyclotron frequency. The impact angle of the ions onto the target is dependent on the potential structure of the presheath. As a first step, we have investigated this presheath region by measuring the spatial distribution of the density, the electron temperature and the potential of the plasma as a function of distance from the surface for different angles between the target and the magnetic field. We use an ECR argon plasma flowing along a relatively uniform magnetic field to impact an inclinable aluminum target. The measurements have been made with an emissive probe and a Langmuir collecting probe.