Temporal Profiling of Electron Temperatures Using the H_α–H_β Line Emission and Triple Langmuir Probe Array in the Pre-Ionization Discharge of the MT-I Spherical Tokamak

Photodiodes masked with narrow-band filters have been used to obtain the temporal profiles of H_α and H_β line emissions in the pre-ionization phase of hydrogen discharge in the MT-I Spherical Tokamak. The line ratio method relating the emission intensities of the above mentioned lines, having different excitation thresholds, provides the temporal profile of electron temperature. A triple Langmuir probe array having three individual sets of triple probes, arranged linearly, has also been used to measure the temporal profile of electron temperature at three different radial positions simultaneously. Additionally, a spectrometer HR4000+ is used to get the line-integrated emission intensity of H-Balmer lines. The objective of this experiment is to demonstrate the successful development of the optical and electric probe as a diagnostic tool for tokamak discharge.