APPLICATION OF A QUADRUPLE PROBE TECHNIQUE TO MPD THRUSTER PLUME MEASUREMENTS

A new quadruple Langmuir probe diagnostic technique is applied to the plume of a pulsed magnetoplasmadynamic (MPD) thruster with argon prope llant. The probe permits simultaneous measurement of electron temperat ure T(e), density n(e), and ion now velocity u in the exhaust stream. For distances of 3-25 cm from the thruster face, T(e) is 8-1.5 eV, n(e ) is 4.8-1.2 x 10(19) m-3, and u is 0.7-1.8 x 10(4) m/s. The measureme nts suggest that the plume is well-collimated, and that the ion temper ature is significantly higher than the electron temperature, consisten t with an ion-conduction model of the thruster.