Abstract
Triple-probe has been developed and operated successfully to characterize ECRH-assisted argon as well as hydrogen microwave plasmas in GLAST Spherical Tokamak. This technique enables to determine transient plasma parameters such as floating potential, electron temperature and electron number density in rapidly time-varying plasmas. An effective electron heating mechanism is applied to produce microwave plasma by injecting radiofrequency (RF) radiation at a frequency of 2.45 GHz in the presence of resonant toroidal magnetic field. Plasma parameters and corresponding fluctuations are measured as a function of time in different gas fill pressures for various applied magnetic fields. The results demonstrate the dependence of plasma parameters such as V f , T e , n e and their fluctuations on gas fill pressure during the pre-ionization phase of the GLAST operation. Plasma behavior is observed to be closely depending on the coupling of RF power during microwave discharge. Additionally, the hydrogen plasma shows pronounced fluctuations in comparison with argon plasma with some decrease in electron temperature and densities.
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Acknowledgments
The authors are extremely grateful to NILOP for their generous support in developing the triple-probe system. The authors are also thankful to Mr. Sarwar (P.T), Mr. Naseem Ishaq, Mr. Mubashair Imran and GLAST team for their technical support in manufacturing the probe assemblage and electrical circuitry so nicely. Partial support from IAEA CRP Contract No. 16997 is highly acknowledged.
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Qayyum, A., Ahmad, S., Khan, R. et al. Triple-probe Diagnostic Measurements in Plasma of GLAST Spherical Tokamak. J Fusion Energ 35, 205–213 (2016). https://doi.org/10.1007/s10894-015-0010-9
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DOI: https://doi.org/10.1007/s10894-015-0010-9