Measurement of emission current and temperature profile of emissive probe materials using CO 2 LASER

Abstract

Emissive probes have been used for the direct measurement of plasma potential in many plasma devices. Different approaches have been introduced to measure the plasma potential using emissive probes. But the biggest disadvantage of the emissive probe is short life span due to its self-arrangement and different plasma environment. Few initiations have been made to measure plasma potential by using LASER heated emissive probe. In case of LASER heated emissive probe, mostly graphite and LaB 6 are being used as probe tip to emit electrons by heating with LASER light. However, very little studies have been done to understand the mechanism of heating process of the LaB 6 and graphite materials. The complete heating dynamics of these materials, heated by a CW CO 2 LASER with a maximum 55 W power have been studied in this work. In-situ temperature of the probe tip has been measured by using an IR camera. Complete theoretical and simulated model have been developed to understand the experimentally measured data. Further, the experimental results are compared with ANSYS simulations. The emission current from the probe with respect to the bias voltage applied to the probe has also been measured.