Argon ion velocity distributions in a helicon discharge measured by laser induced fluorescence

Abstract

A Helicon discharge in argon at low gas pressure of 0.1 Pa is generated with a flat coil antenna operated with 13.56 MHz. The power coupled into the discharge is around 1 kW which leads to an electron density of 1012 cm-3. The velocity and temperature of the argon ions is measured by laser induced fluorescence (LIF) spatially resolved in radial and axial direction. Ambipolar diffusion accelerates the ions out of the heating region of the discharge with velocities up to 800 m/s. Due to homogenisation of the kinetic energy, the ion temperature increases from 0.15 eV in the centre to 0.4 eV at the edge of the plasma volume. © 2010 IOP Publishing Ltd.