»N TEMPWÄTURE ^NSITIVE EFFECT ||vj TRANSIENT LAhJGMUiR PRQBE RESPONSE

A theory Is presented for a method, recently proposed by Hester and Sonln, of determining the Ion temperature In a plasma by measuring the transient current response of a highly negative, cylindrical Langmuir probe under conditions where collection Is collision-free and the ratio of probe radius to Debye length Is small. The Ion component of the current does not approach Its final, steady-state value monotonlcally, but exhibits a strong. Ion temperature dependent overshoot In the first few Ion-plasma periods following the biasing of the probe. Analytical formulae are derived for a Maxwelllan plasma, and convenient graphical results are presented. The possible masking of the overshoot by a transient displacement current Is discussed and found to be often negligible. For other conditions an alternative measuring method is suggested in which the contribution of the displacement current cancels out.