Electrostatic probe measurements of low-density medium-pressure magneto-plasmas

The influence of secondary electron emission from a probe surface on the probe diagnostics are studied in a medium-pressure low-density plasma with a weak magnetic field. Both electron and ion saturation currents are used to obtain N e , and the results are compared with microwave measurements. The increase of I i due to electron emission occurs; this prevents the accurate determination of N e in the same manner as that reported in a plasma without a magnetic field. Even though the uncertainty in determining N e due to the effect of emission decreases with increasing B, I is is not always suitable for N e determination. On the other hand, N e determined from I es corrected for magnetic field effects agrees with microwave measurements within 50%.