TRANSITION FROM FREE TO AMBIPOLAR DIFFUSION IN AN ELECTRODELESS DISCHARGE.

An approximate relationship for the effective diffusion coefficient in the transition region between free and ambipolar diffusion due to Allis and Rose is incorporated into the previously derived characteristic equation for a steady state, inductive radiofrequency discharge. The resultant relationship is evaluated for hydrogen. It furnishes equilibrium values for the induced electric field at the tube wall and substantiates a previous assumption that ambipolar diffusion is established when the skin depth becomes of the order of the tube radius. A plot of electron density against the applied magnetic field reveals that the transition zone is unstable. Author