Modeling of the Hα Emission from ADITYA Tokamak Plasmas

Ritu Dey,Parveen K Atrey,Malay B Chowdhuri,Ranjana Manchanda,Rakesh L Tanna,Y Shankara Joisa,Umeshkumar C Nagora,Joydeep Ghosh,Nandini Yadava,Jayesh V Raval

doi:10.3390/atoms7040095

Ritu Dey, Parveen K Atrey + Show 8 more

Open Access

https://doi.org/10.3390/atoms7040095

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Abstract

The spatial profile of Hα spectrum is regularly measured using a high-resolution multi-track spectrometer in ADITYA tokamak to study the neutral particle behavior. The Monte Carlo neutral particle transport code DEGAS2 is used to model the experimental Hα spectral emissions. Through the modeling of the spectral line profile of Hα, it is found that the neutral hydrogen, which is produced from molecular hydrogen and molecular hydrogen ion dissociation processes contributes 56% to the total Hα emission, and the atoms which are produced from charge-exchange process have 30% contribution. Furthermore, the experimentally measured spatial profile of chord integrated brightness was modeled for the two plasma discharges having relatively high and low density to understand the neutral particle penetration. The presence of neutrals inside the core region of the ADITYA tokamak is mainly due to the charge-exchange process. Furthermore, it is observed that neutral particle penetration is lower in higher density discharge.

Highlights

The neutrals are introduced into the tokamak plasma in many ways such as direct recycling from the material surface, gas puffs, supersonic molecular beam injection (SMBI), and pellet injection
It is found that the increase in neutral density in the scrape-off layer region increases the plasma density, which in turn increases the opacity to the neutrals and so reduces neutral particle penetration [5]
The experimental spectrum of a typical discharge of ADITYA tokamak is modeled using DEGAS2 code to find out the contribution from molecular dissociation, charge- exchange, and reflection processes [8,12]

Summary

Introduction

The neutrals are introduced into the tokamak plasma in many ways such as direct recycling from the material surface, gas puffs, supersonic molecular beam injection (SMBI), and pellet injection. The neutral particle transport code DEGAS2, which is already applied to understand the neutral particle behavior for typical ADITYA discharges [12,13], is used to model experimental. Hα emission to understand the role of charge-exchange process to the presence of neutral particles in the central region of the ADITYA tokamak This is done by modeling the experimental Hα spectrum to find out the temperature of the warm components (coming from molecular hydrogen, molecular hydrogen ion dissociation, and Franck–Condon dissociation processes) and hot components (coming from the charge-exchange process) [9] of the neutral to understand their penetration in the plasma as the penetration length of the product atom depends on its velocity.

ADITYA Tokamak and Its Diagnostics

DEGAS2 Code and Its Input Parameters

Results and Discussions

Conclusions