Angular Resolved Energy and Particle Flux Measurements in a Magnetized Plasma

A flat probe allowing simultaneous energy flux and current density measurements as functions of an applied voltage was rotated in a homogeneous plasma. The probe dimensions ( a ) were larger or comparable to the ion gyro radius ( r i ). Current density ( j i ), floating potential ( U f ), energy flux density ( q ), ion energy reflection coefficient R E and the sheath energy transmission coefficient γ were determined as functions of the angle α between the probe surface normal and the magnetic field. For normal incidence conditions ( α = 0) all measured quantities do agree well with the theoretical predictions. With | α | approaching 90°, finite gyro‐radii effects of the ions become important. To lowest order the angular variations can be understood by assuming Γ e,i ∝ cos α + 2 r e,i / a for the ion particle flux density. Most remarkably, a pronounced reduction of the floating potential and the ion impact energy was found experimentally at shallow angles. In contrast, relatively small angular dependencies were found for γ and R E . (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)