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M B Chowdhuri, R Manchanda,
J Ghosh,
S B Bhatt,
Ajai Kumar,
B K Das,
K A Jadeja,
P A Raijada,
Manoj Kumar,
S Banerjee, [......],
R Bhattacharyay,
R L Tanna,
Y Shankara,
P K Atrey,
C V S Rao,
D Chenna,
P K Chattopadhyay,
R Jha,
Y C Saxena,
Aditya Team
[show abstract]
[hide abstract]
ABSTRACT: Lithiumization of the vacuum vessel wall of the Aditya tokamak using a lithium rod exposed to glow discharge cleaning plasma has been done to understand its effect on plasma performance. After the Li-coating, an increment of ∼100 eV in plasma electron temperature has been observed in most of the discharges compared to discharges without Li coating, and the shot reproducibility is considerably improved. Detailed studies of impurity behaviour and hydrogen recycling are made in the Li coated discharges by observing spectral lines of hydrogen, carbon, and oxygen in the visible region using optical fiber, an interference filter, and PMT based systems. A large reduction in O I signal (up to ∼ 40% to 50%) and a 20% to 30% decrease of Hα signal indicate significant reduction of wall recycling. Furthermore, VUV emissions from O V and Fe XV monitored by a grazing incidence monochromator also show the reduction. Lower Fe XV emission indicates the declined impurity penetration to the core plasma in the Li coated discharges. Significant increase of the particle and energy confinement times and the reduction of Z eff of the plasma certainly indicate the improved plasma parameters in the Aditya tokamak after lithium wall conditioning.
Plasma Science and Technology 02/2013; 15(2):123-128. · 0.41 Impact Factor
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M.B. Chowdhuri,
J. Ghosh,
S. Banerjee,
Ritu Dey, R. Manchanda,
Vinay Kumar,
P. Vasu,
K.M. Patel,
P.K. Atrey,
Y. Shankara Joisa,
C.V.S. Rao,
R.L. Tanna,
D. Raju,
P.K. Chattopadhyay,
R. Jha,
C.N. Gupta,
S.B. Bhatt,
Y.C. Saxena,
Aditya Team
[show abstract]
[hide abstract]
ABSTRACT: Intense visible lines from Be-like oxygen impurity are routinely observed in the Aditya tokamak. The spatial
profile of brightness of a Be-like oxygen spectral line (2p3p 3D3–2p3d 3F4) at 650.024 nm is used to investigate
oxygen impurity transport in typical discharges of the Aditya tokamak. A 1.0m multi-track spectrometer (Czerny–
Turner) capable of simultaneous measurements from eight lines of sight is used to obtain the radial profile of
brightness of O4+ spectral emission. The emissivity profile of O4+ spectral emission is obtained from the spatial
profile of brightness using an Abel-like matrix inversion. The oxygen transport coefficients are determined by
reproducing the experimentally measured emissivity profiles of O4+, using a one-dimensional empirical impurity
transport code, STRAHL. Much higher values of the diffusion coefficient compared with the neo-classical values are
observed in both the high magnetic field edge region (Dmax
inboard
∼ 30m2 s−1) and the low magnetic field edge region
(Dmax
outboard
∼ 45m2 s−1) of typical Aditya ohmic plasmas, which seems to be due to fluctuation-induced transport.
The diffusion coefficient at the limiter radius in the low-field (outboard) region is typically ∼ twice as high as that
at the limiter radius in the high-field (inboard) region.
Nuclear Fusion 02/2013; 53:023006. · 4.09 Impact Factor
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M.B. Chowdhuri a,
J. Ghosh,
S. Banerjee,
Ritu Dey, R. Manchanda,
Vinay Kumar,
P. Vasu,
K.M. Patel,
P.K. Atrey,
Y. Shankara Joisa,
C.V.S. Rao,
R.L. Tanna,
D. Raju,
P.K. Chattopadhyay,
R. Jha,
C.N. Gupta,
S.B. Bhatt,
Y.C. Saxena and the Aditya Team
[show abstract]
[hide abstract]
ABSTRACT: Intense visible lines from Be-like oxygen impurity are routinely observed in Aditya tokamak. Spatial profile of brightness of Be-like oxygen spectral line (2p3p 3D3-2p3d 3F4) at 650.024 nm is utilized to investigate oxygen impurity transport in typical discharges of Aditya tokamak. A 1.0 m multi-track spectrometer (Czerny-Turner) capable of simultaneous measurements from eight lines of sights is used to obtain radial profile of brightness of O4+ spectral emission. The emissivity profile of O4+ spectral emission is obtained from the spatial profile of brightness using an Abel-like matrix inversion. The oxygen transport coefficients are determined by reproducing the experimentally measured emissivity profiles of O4+, using a one-dimensional empirical impurity transport code, STRAHL. Much higher values of diffusion coefficient compared to the neo-classical values are observed in both the high magnetic field edge region ( Dmaxinboard ~ 30m2/s) and the low magnetic field edge region (Dmaxoutboard ~45 m2/s ) of typical Aditya Ohmic plasmas, which seems to be due to the fluctuation induce transport. The diffusion coefficient at the limiter radius in the low field (outboard) region is typically ~ 2 times higher than that at the limiter radius in the high field (inboard) region.
Nuclear Fusion 02/2013; 63:023006. · 4.09 Impact Factor
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Kishore Mishra,
S V Kulkarni,
D Rathi,
Atul D Varia,
H M Jadav,
K M Parmar,
B R Kadia,
R Joshi,
Y S S Srinivas,
Raj Singh, [......],
J Ghosh,
P K Atrey,
S B Bhatt,
C N Gupta,
P K Chattopadhyaya,
A K Chattopadhyaya,
R Srinivasan,
Dhiraj Bora,
P K Kaw,
Aditya Team
[show abstract]
[hide abstract]
ABSTRACT: Second harmonic heating experiments using fast waves are carried out on the Aditya tokamak in the ion cyclotron resonance frequency (ICRF) range with the help of a 200 kW, 20–40 MHz RF heating system, which is developed indigenously. Significant direct electron heating is observed in a hydrogen plasma. The rise in electron temperature is prompt with the application of RF power and the increment in electron temperature increases linearly with RF power. A corresponding increase in plasma beta and hence an increase in stored diamagnetic energy are also observed in the presence of RF power. The low-Z impurity radiation and electron density do not increase significantly with RF power. The direct electron heating by fast wave in Aditya is also predicted by the ion cyclotron resonance heating code TORIC.
Plasma Physics and Controlled Fusion 08/2011; 53(9):095011. · 2.42 Impact Factor
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Kishore Mishra,
S V Kulkarni,
D Rathi,
Atul D Varia,
H M Jadav,
K M Parmar,
B. R Kadia,
R Joshi,
Y S S Srinivas,
Raj Singh, [......],
A Gayatri,
R A Yogi,
Y S Joisa,
C V S Rao,
Sameer Kumar,
R Jha, R Manchanda,
J Ghosh,
P K Atrey,
S B Bhatt
Plasma Phys. Control. Fusion. 01/2011; 53:095011.
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Bhooshan Paradkar,
J. Ghosh,
P. K. Chattopadhyay,
R. L. Tanna,
D. Raju,
S. B. Bhatt,
C. V. S. Rao,
Sankar Joisa,
Santanu Banerjee, R. Manchanda,
C. N. Gupta,
Y. C. Saxena
[show abstract]
[hide abstract]
ABSTRACT: Negative spikes followed by positive ones in the loop voltage signal during the discharge are observed in the Aditya Tokamak [
S. B. Bhatt et al., Indian J. Pure Appl. Phys. 27, 710 (1989)
]. These spikes are always accompanied by hard x-ray bursts caused by sudden loss of runaway electrons. The observed growth of m = 3 mode seemed responsible for the losses of localized beams of runaway electrons (Eγ ∼ 1–5 MeV) from the plasma region around q = 3 magnetic surface. The movement of these runaway electrons during their extraction from inside the plasma induces both positive and negative electric fields at those locations. In this paper, a one-dimensional toroidal electric field diffusion model is used to estimate the induced electric field at the plasma boundary, which matches quite well with the observed spikes in loop voltage in both magnitude as well as its temporal evolution.
Physics of Plasmas 09/2010; 17(9):092504-092504-6. · 2.15 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The feasibility of inferring the plasma parameters of a Penning discharge in helium, from the experimentally observed intensities of a number of spectral lines in the visible wavelength region, is explored. The collisional-radiative model of ADAS (atomic data analysis structure) code and database has been used for this analysis. The electron density, electron temperature, ground-state atom and ion densities and also the 2 3S metastable state density are the parameters thus estimated. The results are encouraging. The derived plasma parameters are then used to obtain the intensities of a few lines in the vacuum ultraviolet (VUV) region. This has been compared with the observed VUV spectral lines, recorded simultaneously with the visible lines, using a VUV spectrometer for which intensity calibration was not available, to arrive at calibration factors. It is expected that this approach might provide an alternative to the 'branching ratio' method for calibration in the VUV region once the analysis is improved and the possible re-absorption of certain lines is accounted for.
Journal of Physics B Atomic Molecular and Optical Physics 07/2010; 43(14):144012. · 1.88 Impact Factor
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R. Manchanda,
J. Ghosh,
P. K. Chattopadhyay,
M. B. Chowdhuri,
Santanu Banerjee,
N. Ramasubramanian,
Ketan. M. Patel,
Vinay kumar,
P. Vasu,
R. L. Tanna,
S. B. Bhatt,
D. Raju,
R. Jha,
P. K. Atrey,
S. Joisa,
C. V. S. Rao,
Y. C. Saxena,
Aditya Team
Phys. Plasmas. 01/2010; 17:072515.
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Santanu Banerjee,
J. Ghosh, R. Manchanda,
R. Dey,
N. Ramasubramanian,
M.B. Chowdhuri,
Ketan M. Patel,
Vinay Kumar,
P. Vasu,
P. K. Chattopadhyay,
P.K. Atrey,
Aditya Team
J. Plasma Fusion Res. SERIES. 01/2010; 9:29-32.
-
Bhooshan Paradkar,
J. Ghosh,
P. K. Chattopadhyay,
R. L. Tanna,
D. Raju,
S. B. Bhatt,
C. V. S. Rao,
Sankar Joisa,
Santanu Banerjee, R. Manchanda,
Y. C. Saxena,
Aditya Team
Phys. Plasmas. 01/2010; 17:092504.
-
J. Phys. B: At. Mol. Opt. Phys. 01/2010; 43:144012.
-
R. Manchanda,
J. Ghosh,
P. K. Chattopadhyay,
M. B. Chowdhuri,
Santanu Banerjee,
N. Ramasubramanian,
Ketan. M. Patel,
Vinay kumar,
P. Vasu,
R. L. Tanna,
S. B. Bhatt,
D. Raju,
R. Jha,
P. K. Atrey,
S. Joisa,
C. V. S. Rao,
Y. C. Saxena,
Aditya Team
[show abstract]
[hide abstract]
ABSTRACT: In Aditya tokamak �S. B. Bhatt et al. Indian J. Pure Appl. Phys. 27, 710 �1989��, an increase in the
H� alpha and C2+ intensity fluctuations from the edge region is observed with an increase in the
magnetohydrodynamic �MHD� activity. Very small fluctuation amplitudes of H� alpha and C2+ intensity
are observed in discharges where there is no MHD activity compared to the discharges with MHD
activity. These fluctuations in the H� and C2+, measured by optical filter—photomultiplier tube
combination—are modulated by Mirnov oscillations having a dominant peak with a common
frequency �7–10 kHz. Further investigation reveals the presence of strong coherent fluctuations in
density and floating potential at same frequency as well. These observations indicate the existence
of a nonelectrostatic instability, which may be based on the coupled mode of the drift mode and the
Alfven mode. The coherent density fluctuations give rise to the experimentally observed coherent
H� alpha and C2+ intensity fluctuations.
Physics of Plasmas 01/2010; 17:072515. · 2.15 Impact Factor
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Bhooshan Paradkar,
J. Ghosh,
P. K. Chattopadhyay,
R. L. Tanna,
D. Raju,
S. B. Bhatt,
C. V. S. Rao,
Sankar Joisa,
Santanu Banerjee, R. Manchanda,
Y. C. Saxena,
Aditya Team
[show abstract]
[hide abstract]
ABSTRACT: Negative spikes followed by positive ones in the loop voltage signal during the discharge are
observed in the Aditya Tokamak �S. B. Bhatt et al., Indian J. Pure Appl. Phys. 27, 710 �1989��.
These spikes are always accompanied by hard x-ray bursts caused by sudden loss of runaway
electrons. The observed growth of m=3 mode seemed responsible for the losses of localized beams
of runaway electrons �E~��1–5 MeV� from the plasma region around q=3 magnetic surface. The
movement of these runaway electrons during their extraction from inside the plasma induces both
positive and negative electric fields at those locations. In this paper, a one-dimensional toroidal
electric field diffusion model is used to estimate the induced electric field at the plasma boundary,
which matches quite well with the observed spikes in loop voltage in both magnitude as well as its
temporal evolution.
Physics of Plasmas 01/2010; 17:092504. · 2.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The feasibility of inferring the plasma parameters of a Penning discharge in helium, from the
experimentally observed intensities of a number of spectral lines in the visible wavelength
region, is explored. The collisional-radiative model of ADAS (atomic data analysis structure)
code and database has been used for this analysis. The electron density, electron temperature,
ground-state atom and ion densities and also the 2 3S metastable state density are the
parameters thus estimated. The results are encouraging. The derived plasma parameters are
then used to obtain the intensities of a few lines in the vacuum ultraviolet (VUV) region. This
has been compared with the observed VUV spectral lines, recorded simultaneously with the
visible lines, using a VUV spectrometer for which intensity calibration was not available, to
arrive at calibration factors. It is expected that this approach might provide an alternative to the
‘branching ratio’ method for calibration in the VUV region once the analysis is improved and
the possible re-absorption of certain lines is accounted for.
Journal of Physics B Atomic Molecular and Optical Physics 01/2010; 43:144012. · 1.88 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A diagnostic system based on a multi-fiber input high resolution spectrograph has been set up
on the Aditya tokamak (Bhatt et al 1989 Ind. J. Pure Appl. Phys. 27 710) for utilizing the
passive light emission to measure different kinds of plasma flow and to identify the location of
emissions of hydrogen and impurities along with their temperatures. Eight simultaneous
vertically collimated lines-of-sight from a top port view a poloidal cross-section of the plasma.
This arrangement simplifies the analysis of spectra in terms of making the Zeeman splitting
easier to account for, since each chord passes through a region of nearly constant toroidal
magnetic field (BT). This paper describes the complete set-up, the wavelength and intensity
calibrations performed and the initial results including the impurity emissivity profiles and
simultaneous flow measurements in the inboard and outboard regions of the Aditya tokamak.
Measurement Science and Technology 01/2008; 19:045603. · 1.49 Impact Factor
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Meas. Sci. Technol. 01/2008; 19:045603.
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[show abstract]
[hide abstract]
ABSTRACT: 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 model 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 and 2 ) 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.
Journal of Applied Physics 01/2005; 97(4):043301-043301-7. · 2.17 Impact Factor
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M. B. Chowdhuri,
D. Raju, R. Manchanda,
Vinay Kumar,
Shankar Joisa,
P. K. Atrey,
C. V. S. Rao,
R. Jha,
R. Singh,
P. Vasu,
the Aditya Collaboration
[show abstract]
[hide abstract]
ABSTRACT: Understanding of the transport in a Tokamak plasma is an important issue. Various mechanisms have been reported in the literature to relate the core phenomenon to edge phenomenon. Sawtooth and Mirnov oscillations caused by MHD instabilities are generally observed in Tokamak discharges. Observation of these effects in the visible radiation from outer edge may offer a possible means to understand the transport.Oscillations in the visible radiation from outer region of the plasma have been observed during recent Aditya discharges. Percentage modulation of these oscillations vary with the Lines of Sight (LOS) of the chords and surfaces on which they terminate. This has been found in both the low frequency (~1 kHz) oscillations that seem to correlate with sawteething in SXR signals and the higher frequency (~10 kHz) oscillations that correlate well with Mirnov signals indicative of m/n=2/1 mode rotation. This suggests that the extent to which the MHD instabilities in the central region of the plasma column are reflected in the edge radiation depends on the interaction of the plasma with the surface at the extremity of the LOS. The release of particle/ energy accompanying the MHD instabilities leads to a large influx of particles from such surfaces. Cross-bispectral analysis suggests that a mode (having frequency of ~20 kHz) is also generated due to the interaction of m/n=1/1 (~10 kHz, seen in SXR) and m/n=2/1 (~10 kHz, seen in Mirnov, Visible & Microwave Interferometer signals). By possible selection rules, this mode seems to be a m/n=3/2 mode. This mode is seen in Mirnov, Visible & Interferometer signals. Behaviour of these oscillations on various LOS and their relation to SXR&Mirnov signals can lead to an understanding of the transport phenomenon. These observations and our interpretations will be presented.
12/2004;
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I Bandyopadhyay,
S M Ahmed,
P K Atrey,
S B Bhatt,
R Bhattacharya,
M B Chaudhury,
S P Deshpande,
C N Gupta,
R Jha,
Y Shankar Joisa,
Vinay Kumar, R Manchanda,
D Raju,
C V S Rao,
P Vasu,
the ADITYA Team
[show abstract]
[hide abstract]
ABSTRACT: Several Ohmic discharges of the ADITYA tokamak are simulated using the Tokamak Simulation Code (TSC), similar to that done earlier for the TFTR tokamak. Unlike TFTR, the dominant radiation process in ADITYA is through impurity line radiation. TSC can follow the experimental plasma current and position to very good accuracy. The thermal transport model of TSC including impurity line radiation gives a good match of the simulated results with experimental data for the Ohmic flux consumption, electron temperature and Zeff. Even the simulated magnetic probe signals are in reasonably good agreement with the experimental values.
Plasma Physics and Controlled Fusion 07/2004; 46(9):1443. · 2.42 Impact Factor
