Comparison of Langmuir Probe and Laser Thomson Scattering Methods in the Electron Temperature Measurement in Divertor Simulator MAP‐II

Abstract In order to investigate details of anomaly in the Langmuir probe current (I)‐voltage (V) characteristics, electron temperatures and densities are measured by both Langmuir probe and laser Thomson scattering methods. The electron densities measured with both methods show good agreement in hydrogen‐molecular assisted recombination (H2‐MAR) plasmas. On the other hand, the electron temperatures measured with Langmuir probe are overestimated compared with that obtained from the Thomson scattering spectrum in the H2‐MAR plasmas. Histogram of electron current deviated from its average shows that fluctuation appeared in the electron current becomes large and the histogram distorted in temperature‐overestimated condition, especially when the probe voltage is negatively biased. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)