Speaker
Description
R. Manchanda1, M. B. Chowdhuri1, Nandini Yadava2, J. Ghosh1, 3, S. Banerjee1, Nilam Nimavat, K. Tahiliani, M. V. Gopalakrishna, U. C. Nagora1, P. K. Atrey1, J. Raval1, Y. S. Joisa1,
K. A. Jadeja1, R. L. Tanna1, and Aditya team
1Institute for Plasma Research, Bhat, Gandhinagar 382 428, India
2Gujarat University, Navrangpura, Ahmedabad 380 009, India
3Homi Bhabha National Institute, Mumbai, 400094, India
E-mail : rmanchanda@ipr.res.in
Abstract
Impurity behaviour has been studied for the high density Aditya tokamak plasmas. These discharges were operated with higher toroidal magnetic fields and thereby it sustained higher plasma current. Higher densities were achieved with the help of multiple gas puffs. High energy confinement times, sometimes higher than the values predicated by Neo-Alcator scaling for Ohmically heated tokamak plasma were achieved for these discharges [1]. In Aditya tokamak, visible and VUV spectroscopy have been extensively used to study the impurity behaviour. The neutral hydrogen and impurity emissions were routinely monitored by optical fiber, interference filter and PMT based system in the visible range. The spectral line emissions from higher ionized charge state of impurities, such as C4+, and O5+, were recorded by a VUV survey spectrometer operated in the 10 - 180 nm. This wavelength range covers the important lines of partially ionized low and medium Z impurities, as for example iron and also emissions from higher excited states of highly ionized low Z impurities, like carbon and oxygen. It has been found that H, OII, and CIII emissions normalized with density (ne), and visible continuum normalized with ne2 show a gradual decrease with increase in density indicating lower impurity concentration in the high density discharges. This is also corroborated by the observed reduction in radiation power losses with increase in ne. These results clearly suggest the achievement of improved confinement for Aditya plasma and are correlated with obtained higher energy confinement times in those discharges. In this presentation, details studies on impurity behaviour for its role into the improved plasma properties in these high densities plasma discharges will be discussed.
[1] R. L. Tanna, J. Ghosh et al, Nucl. Fusion 57 (2017) 102008
| Country or International Organization | India |
|---|---|
| Paper Number | EX/P4-6 |
