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

Abstract

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.

Keywords:

• Electron cyclotron resonance heating assisted pre-ionization
• temporal profile of electron temperature
• line ratio method
• triple Langmuir probe array

Acknowledgments

This work was supported by the Planning Commission of Pakistan and the International Atomic Energy Agency through the Coordinated Research Project “Utilization of the Network of Small and Medium Size Magnetic Confinement Fusion Devices for Fusion Research (F13019),” under grant F12019-22771. The authors are grateful to Mr. Liaqat Ali DG-TNO for his everlasting support.