A contamination-free Langmuir probe of novel design is described. Surf
ace contaminants, which lead to erroneous evaluation of plasma paramet
ers by distortion of the probe's current-voltage characteristic, are r
emoved by the indirect heating of the probe tip with separate heating
elements running parallel to the probe wire in multibore alumina tubin
g. This configuration minimizes magnetic field perturbations, while ma
intaining the compact profile and construction ease of an unheated pro
be. The design and operating characteristics of such a probe are repor
ted. Temperatures at the probe tip, as measured by a subminiature ther
mocouple, can exceed 500-degrees-C. Experiments determining the effect
of probe temperature, T(probe), on the characteristic have been perfo
rmed in a Q-machine plasma (T(i) almost-equal-to T(e) almost-equal-to
0.2 eV). We find that for T(probe) < 250-degrees-C, the measured elect
ron temperature is up to several times too large, indicating the prese
nce of a eontamination layer. This contamination layer is removed for
T(probe) greater-than-or-equal-to 300-degrees-C, and accurate electron
temperatures are recovered.