Phase resolved measurement of anisotropic electron velocity distribution functions in a radio-frequency discharge

Oscillating radio-frequency (RF) electric fields penetrating into a plasma lead to a corresponding oscillation of the electron velocity distribution function. Here we report on the first time measurement of this oscillation by Thomson scattering in a low-pressure inductively coupled plasma. The local current density is inferred by combining the oscillation amplitude with the plasma density, also resulting from Thomson scattering. The results are compared with a novel emission spectroscopic technique, RF modulation spectroscopy, which also provides direct determination of the electron oscillation velocity.