Measurement of emission current and temperature profile of emissive probe materials using CO2 LASER

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 LaB6 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 LaB6 and graphite materials. The complete heating dynamics of these materials, heated by a CW CO2 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.

► The heating dynamics of Graphite and LaB6 materials, heated by a CW CO2 LASER have been studied. ► Emissivity of LaB6 has been found to be 0.98. The convective and the radiative losses have also been considered in this calculation processes. ► From 3D transient analysis of the model in ANSYS, temperature variations in the front side of LaB6 material after 120 s shows the difference from the centre to the edge is almost 2380 °C.