Determining the electron distribution function from RF measurements using an impedance probe

Summary form only given. Using a network analyzer which returns Re(Z_ac) and Im(Z_ac) for a spherical probe in a plasma, we have demonstrated the existence of collisionless resistance in the sheath, shown that this leads to a method of finding the electron sheath density profile, and proposed a method of measuring electron temperature using the rf results. The magnitude of the applied signal from the network analyzer is much smaller in magnitude than typical applied dc potentials and it is therefore transparent to the existing plasma/probe interface. Recently, from determination of plasma potential, we are able to construct the electron distribution function, f(E), from the rf measurements. This method requires only a first derivative of the inverse Re(Z_ac) with respect to bias. We will present the method and results for f(E) for three spherical probes of varying sizes.