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Title: Investigation of neutral particle dynamics in Aditya tokamak plasma with DEGAS2 code

Abstract

Neutral particle behavior in Aditya tokamak, which has a circular poloidal ring limiter at one particular toroidal location, has been investigated using DEGAS2 code. The code is based on the calculation using Monte Carlo algorithms and is mainly used in tokamaks with divertor configuration. This code has been successfully implemented in Aditya tokamak with limiter configuration. The penetration of neutral hydrogen atom is studied with various atomic and molecular contributions and it is found that the maximum contribution comes from the dissociation processes. For the same, H α spectrum is also simulated which was matched with the experimental one. The dominant contribution around 64% comes from molecular dissociation processes and neutral particle is generated by those processes have energy of ~ 2.0 eV. Furthermore, the variation of neutral hydrogen density and H α emissivity profile are analysed for various edge temperature profiles and found that there is not much changes in H α emission at the plasma edge with the variation of edge temperature (7 to 40 eV).

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [2]
  1. Inst. for Plasma Research, Gandhinagar, Gujarat (India)
  2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1373089
Grant/Contract Number:
AC02-09CH11466
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 8; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; neutral particle; atomic and molecular processes; Aditya; DEGAS2;

Citation Formats

Dey, Ritu, Ghosh, Joydeep, Chowdhuri, M. B., Manchanda, R., Banerjee, S., Ramaiya, N., Sharma, Deepti, Srinivasan, R., and Stotler, D. P. Investigation of neutral particle dynamics in Aditya tokamak plasma with DEGAS2 code. United States: N. p., 2017. Web. doi:10.1088/1741-4326/aa739c.
Dey, Ritu, Ghosh, Joydeep, Chowdhuri, M. B., Manchanda, R., Banerjee, S., Ramaiya, N., Sharma, Deepti, Srinivasan, R., & Stotler, D. P. Investigation of neutral particle dynamics in Aditya tokamak plasma with DEGAS2 code. United States. doi:10.1088/1741-4326/aa739c.
Dey, Ritu, Ghosh, Joydeep, Chowdhuri, M. B., Manchanda, R., Banerjee, S., Ramaiya, N., Sharma, Deepti, Srinivasan, R., and Stotler, D. P. 2017. "Investigation of neutral particle dynamics in Aditya tokamak plasma with DEGAS2 code". United States. doi:10.1088/1741-4326/aa739c.
@article{osti_1373089,
title = {Investigation of neutral particle dynamics in Aditya tokamak plasma with DEGAS2 code},
author = {Dey, Ritu and Ghosh, Joydeep and Chowdhuri, M. B. and Manchanda, R. and Banerjee, S. and Ramaiya, N. and Sharma, Deepti and Srinivasan, R. and Stotler, D. P.},
abstractNote = {Neutral particle behavior in Aditya tokamak, which has a circular poloidal ring limiter at one particular toroidal location, has been investigated using DEGAS2 code. The code is based on the calculation using Monte Carlo algorithms and is mainly used in tokamaks with divertor configuration. This code has been successfully implemented in Aditya tokamak with limiter configuration. The penetration of neutral hydrogen atom is studied with various atomic and molecular contributions and it is found that the maximum contribution comes from the dissociation processes. For the same, Hα spectrum is also simulated which was matched with the experimental one. The dominant contribution around 64% comes from molecular dissociation processes and neutral particle is generated by those processes have energy of ~ 2.0 eV. Furthermore, the variation of neutral hydrogen density and Hα emissivity profile are analysed for various edge temperature profiles and found that there is not much changes in Hα emission at the plasma edge with the variation of edge temperature (7 to 40 eV).},
doi = {10.1088/1741-4326/aa739c},
journal = {Nuclear Fusion},
number = 8,
volume = 57,
place = {United States},
year = 2017,
month = 6
}

Journal Article:
Free Publicly Available Full Text
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  • Core-ion temperature measurements have been carried out by the energy analysis of passive charge exchange (CX) neutrals escaping out of the ADITYA tokamak plasma (minor radius, a= 25 cm and major radius, R= 75 cm) using a 45 Degree-Sign parallel plate electrostatic energy analyzer. The neutral particle analyzer (NPA) uses a gas cell configuration for re-ionizing the CX-neutrals and channel electron multipliers (CEMs) as detectors. Energy calibration of the NPA has been carried out using ion-source and {Delta}E/E of high-energy channel has been found to be {approx}10%. Low signal to noise ratio (SNR) due to VUV reflections on the CEMsmore » was identified during the operation of the NPA with ADITYA plasma discharges. This problem was rectified by upgrading the system by incorporating the additional components and arrangements to suppress VUV radiations and improve its VUV rejection capabilities. The noise rejection capability of the NPA was experimentally confirmed using a standard UV-source and also during the plasma discharges to get an adequate SNR (>30) at the energy channels. Core-ion temperature T{sub i}(0) during flattop of the plasma current has been measured to be up to 150 eV during ohmically heated plasma discharges which is nearly 40% of the average core-electron temperature (typically T{sub e}(0) {approx} 400 eV). The present paper describes the principle of tokamak ion temperature measurement, NPA's design, development, and calibration along with the modifications carried out for minimizing the interference of plasma radiations in the CX-spectrum. Performance of the NPA during plasma discharges and experimental results on the measurement of ion-temperature have also been reported here.« less
  • The dust particles are unavoidably present in all fusion devises. Dust particles can provide important source of impurities in tokamak plasma. D-T fuel accumulation in dusty particles in future thermonuclear devises can present a potentially serious safety problem. We investigated dust particle transport dynamics in tokamaks using newly developed 3D code DUSTT and present the results obtained for ITER tokamak.
  • The wall conditioning of the ADITYA tokamak is usually done, by first producing an electron cyclotron resonance (ECR) plasma inside the vessel and then superimposing a pulsed ohmic discharge on the ECR background. Sometimes, helium gas is used as a working gas. In this article, the spectral line emissions of neutral helium for the two different plasmas -namely, the ECR and the pulsed discharge cleaning (PDC) plasmas - have been analyzed using a collisional-radiative (CR)-model code to estimate the electron density and temperature. We are able to match the experimentally obtained relative intensity ratios with those predicted by the modelmore » under the assumption of ionizing plasma condition if the possible effects of the metastable states are not ignored. This has been done by using the populations of two metastable levels (2 {sup 1}S and 2 {sup 3}S) as independent parameters in addition to the ground states of neutrals and ions in the CR model under a quasisteady-state approximation. It is further seen that, it is the metastables and not the recombination (including dielectronic) processes that lead to a better fit with experimental observations. The column density of neutrals inferred from this analysis implies that the emission from the PDC discharge emanates from a large region of the vessel, while in the ECR discharge, the plasma responsible for the emission is restricted to a narrow region. This is also borne out by experimental observation.« less
  • Vortex-like coherent structures are observed in the edge plasma of ohmically heated ADITYA tokamak [ Phys. Rev. Lett. {bold 69}, 1375 (1992)]. The structures are observed on statistical basis when the floating potential fluctuations are analyzed using conditional averaging technique. The structures, which have dipole nature, experience stretching until their radial isolation across the limiter is destroyed. The potential fluctuation also shows non-Gaussian statistics indicating intermittency in broadband turbulence of the edge plasma. {copyright} {ital 1997 American Institute of Physics.}
  • The magnetized Mach probe is used to make measurement of plasma flows in the scrape-off layer of the Aditya tokamak [R. Jha et al., Plasma Phys. Controlled Fusion 51, 095010 (2009)]. This probe is further used to measure dependencies of Mach number on local plasma densities and radial distances of the probe in the scrape-off layer. The measured Mach number has contributions from E Multiplication-Sign B drift, Pfrisch-Schlueter, and transport driven flows. We have determined that the toroidal flow is towards the ion side of the limiter and the poloidal flow direction is towards the contact of the last closedmore » flux surface with the limiter.« less