967 research outputs found
Study of laser produced plasma of limiter of the aditya tokomak for detection of molecular bands
No full textThe tokamak wall protection is one of the prime concerns, and for this purpose, limiters are used. Graphite is commonly used as a limiter material and first wall material for complete coverage of the internal vacuum vessel surfaces of the tokamak. From the past few years, we are working to identify and quantify the impurities deposited on the different part of Aditya Tokamak in collaboration with the Scientists at Institute of Plasma Research, Ahmedabad, India using Laser Induced Breakdown Spectroscopy (LIBS) [1-3]. Laser induced breakdown spectroscopy (LIBS) spectra of limiter of Aditya Tokamak have been recorded in the spectral range of 200-900 nm in open atmosphere. Along with atomic and ionic spectral lines of the constituent elements of the limiter (1-3), LIBS spectra also give the molecular bands. When a high power laser beam is focused on the sample, laser induced plasma is produced on its surface. In early stage of the plasma Back ground continuum is dominated due to free-free or free-bound emission. Just after few nanoseconds the light from the plasma is dominated by ionic emission. Atomic emission spectra is dominated from the laser induced plasma during the first few microsecond after an ablation pulse where as molecular spectra is generated later when the plasma further cools down. For this purpose the LIBS spectra has been recorded with varying gate delay and gate width. The spectra of the limiter show the presence of molecular bands of CN and C2. To get better signal to background ratios of the molecular bands, different experimental parameters like gate delay, gate width, collection angle and collection point (spatial analysis off the plasama) of the plasma have been optimized. Thus the present paper deals with the variation of spectral intensity of the molecular bands with different experimental parameters.
Keywords: Limiter, Molecular bands, C2, CN.
References:
1.Proof-of-concept experiment for On-line LIBS Analysis of Impurity Layer Deposited on ptical Window and Other Plasma Facing Components of Aditya Tokamak G. S. Maurya, R. Kumar, A. Kumar and A. K. Rai, Review of Scientific Instruments (In Press)
2.Analysis of deposited impurity material on the surface of optical window of the Tokamak using LIBS, (2014) G. S. Maurya, A. Jyotsana, R. Kumar, A. Kumar and A. K. Rai, Physica Scripta 89, 075601
3.Spatial analysis of impurities on the surface of flange and optical window of the Tokamak using Laser Induced Breakdown Spectroscopy, G. S. Maurya, A. Jyotsana, A. Kumar and A. K. Rai,(2014), Optics and Lasers in Engineering, 56, 13–1
Bollywood cinema: A critical genealogy
No full text"Bollywood" has finally made it to the Oxford English Dictionary. The 2005 edition defines it as: "a name for the Indian popular film industry, based in Bombay. Origin 1970s. Blend of Bombay and Hollywood." The incorporation of the word in the OED acknowledges the strength of a film industry which, with the coming of sound in 1931, has produced some 9,000 films. (This must not be confused with the output of Indian cinema generally, which would be four times more). What is less evident from the OED definition is the way in which the word has acquired its current meaning and has displaced its earlier descriptors (Bombay Cinema, Indian Popular Cinema, Hindi Cinema), functioning, perhaps even horrifyingly, as an "empty signifier" (Prasad) that may be variously used for a reading of popular Indian cinema. The triumph of the term (over the others) is nothing less than spectacular and indicates, furthermore, the growing global sweep of this cinema not just as cinema qua cinema but as cinema qua social effects and national cultural coding. Although Indian film producers in particular, and pockets of Indian spectators generally, continue to feel uneasy with it (the vernacular press came around to using "Bollywood" only reluctantly), its ascendancy has been such that Bombay Dreams (the Andrew Lloyd Weber musical) and the homegrown Merchants of Bollywood both become signifiers of a cultural logic which transcends cinema and is a global marker of Indian modernity. As the Melbourne (March 2006) closing ceremony of the Commonwealth Games showed, Bollywood will be the cultural practice through which Indian national culture will be projected when the games are held in Delhi in 2010. International games (the Olympics, World Cup Soccer, Asian Games, Commonwealth Games, and so on) are often expressions of a nation's own emerging modernity. For India that modernity, in the realm of culture, is increasingly being interpellated by Bollywood
Study of laser produced plasma of limiter of the aditya tokomak for detection of molecular bands
No full textThe tokamak wall protection is one of the prime concerns, and for this purpose, limiters are used. Graphite is commonly used as a limiter material and first wall material for complete coverage of the internal vacuum vessel surfaces of the tokamak. From the past few years, we are working to identify and quantify the impurities deposited on the different part of Aditya Tokamak in collaboration with the Scientists at Institute of Plasma Research, Ahmedabad, India using Laser Induced Breakdown Spectroscopy (LIBS) [1-3]. Laser induced breakdown spectroscopy (LIBS) spectra of limiter of Aditya Tokamak have been recorded in the spectral range of 200-900 nm in open atmosphere. Along with atomic and ionic spectral lines of the constituent elements of the limiter (1-3), LIBS spectra also give the molecular bands. When a high power laser beam is focused on the sample, laser induced plasma is produced on its surface. In early stage of the plasma Back ground continuum is dominated due to free-free or free-bound emission. Just after few nanoseconds the light from the plasma is dominated by ionic emission. Atomic emission spectra is dominated from the laser induced plasma during the first few microsecond after an ablation pulse where as molecular spectra is generated later when the plasma further cools down. For this purpose the LIBS spectra has been recorded with varying gate delay and gate width. The spectra of the limiter show the presence of molecular bands of CN and C2. To get better signal to background ratios of the molecular bands, different experimental parameters like gate delay, gate width, collection angle and collection point (spatial analysis off the plasama) of the plasma have been optimized. Thus the present paper deals with the variation of spectral intensity of the molecular bands with different experimental parameters.
Keywords: Limiter, Molecular bands, C2, CN.
References:
1.Proof-of-concept experiment for On-line LIBS Analysis of Impurity Layer Deposited on ptical Window and Other Plasma Facing Components of Aditya Tokamak G. S. Maurya, R. Kumar, A. Kumar and A. K. Rai, Review of Scientific Instruments (In Press)
2.Analysis of deposited impurity material on the surface of optical window of the Tokamak using LIBS, (2014) G. S. Maurya, A. Jyotsana, R. Kumar, A. Kumar and A. K. Rai, Physica Scripta 89, 075601
3.Spatial analysis of impurities on the surface of flange and optical window of the Tokamak using Laser Induced Breakdown Spectroscopy, G. S. Maurya, A. Jyotsana, A. Kumar and A. K. Rai,(2014), Optics and Lasers in Engineering, 56, 13–18Made available in DSpace on 2017-01-26T21:40:14Z (GMT). No. of bitstreams: 4
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Previous issue date: 2016-06-2
The Political thinking of B R Ambedkar : an analytical study
No full textThesis: Ph.D., Vidyasagar University, Midnapore, Department of Political Science with Rural Administration,2013The Political thinking of B R Ambedkar : an analytical studyDepartment of Political Science with Rural Administration, Vidyasagar University, Midnapore, West Bengal, Indi
Asynchronous distributed coordinated hybrid precoding in multi-cell mmWave wireless networks
No full textAsynchronous distributed hybrid beamformers (ADBF) are conceived for minimizing the total transmit power subject to signal-to-interference-plus-noise ratio (SINR) constraints at the users. Our design requires only limited information exchange between the base stations (BSs) of the mmWave multi-cell coordinated (MCC) networks considered. To begin with, a semidefinite relaxation (SDR)-based fullydigital (FD) beamformer is designed for a centralized MCC system. Subsequently, a Bayesian learning (BL) technique is harnessed for decomposing the FD beamformer into its analog and baseband components and construct a hybrid transmit precoder (TPC). However, the centralized TPC design requires global channel state information (CSI), hence it results in a high signaling overhead. An alternating direction based method of multipliers (ADMM) technique is developed for a synchronous distributed beamformer (SDBF) design, which relies only on limited information exchange among the BSs, thus reducing the signaling overheads required by the centralized TPC design procedure. However, the SDBF design is challenging, since it requires the updates from the BSs to be strictly synchronized. As a remedy, an ADBF framework is developed that mitigates the inter-cell interference (ICI) and also control the asynchrony in the system. Furthermore, the above ADBF framework is also extended to the robust ADBF (R-ADBF) algorithm that incorporates the CSI uncertainty into the design procedure for minimizing the the worst-case transmit power. Our simulation results illustrate both the enhanced performance and the improved convergence properties of the ADMM-based ADBF and R-ADBF schemes
Overview of physics results from the ADITYA-U tokamak and future experiments
No full textThe ADITYA upgrade (ADITYA-U), a medium-sized conventional tokamak facility in India, has been consistently producing experiments findings by using circular and shaped-plasmas. Recognizing the plasma parameters aligning closely with the design parameters of circular limited plasmas, ADITYA-U shifted its focus toward exploring the operational regime for experimentation on saw-tooth and MHD phenomena. Moreover, ADITYA-U has made consistent advancements toward conducting preliminary plasma shaping experiments through the activation of top and bottom divertor coils utilizing hydrogen as well as deuterium fuels. Confinement is improved by a factor of ∼1.5 in plasmas when compared to H _2 plasmas of ADITYA-U. Further, ADITYA-U operations emphasize preventing disruptions and runaway electrons (REs) to ensure safe operations for future fusion devices. Significant suppression of REs has been achieved in ADITYA-U with the application of pulsed localized vertical magnetic field (LVF) perturbation, thereby establishing the technique’s independence from the tokamak device. The successful RE mitigation requires a critical threshold of LVF pulse magnitude, which is approximately 1% of the toroidal magnetic field, and a minimum duration of ∼5 ms. Apart from this, several novel findings have been achieved in the ADITYA-U experiments, including the modification of sawtooth duration through gas-puff, the emergence of MHD-induced geodesic acoustic mode-like oscillations, the propagation of fast heat pulses induced by MHD activity, the control of RE dynamics through Gas-puffs, the propagation of pinch-driven cold-pulses, the transport and core accumulations of argon impurities, the mass dependency of plasma toroidal rotation and the detection of ‘RICE’ scaling, as well as the characterization of edge plasma using wall conditioning methods, such as glow discharge cleaning using a combination of Ar -H _2 mixture, localized wall cleaning by electron cyclotron resonant plasma, and the development of machine learning-based disruption predictions, will be discussed in this paper
Real-time feedback control system for ADITYA-U horizontal plasma position stabilisation
No full textThe ADITYA-U tokamak (R-0 = 0.75 m, a = 0.25 m) is designed to shape plasma column in both single and double null diverter configurations. It is quite well known that sustaining a shaped plasma in tokamak requires very good plasma column position control, both horizontal and vertical. An FPGA-based proportional-integral-derivative (PID) control system has been designed and operated to achieve horizontal plasma position control in ADITYA-U tokamak. The complete system has been rigorously tested with sample signals before implementing to the ADITYA-U plasma discharges. The control system is integrated and time-synchronized with the plasma discharge operation of ADITYA -U. Furthermore, the system has been trained to take appropriate actions during the disruption or plasma failure in the tokamak operation. Detailed experimental results have been obtained by the operation of the digital PID controller. The complete design, installation, operation, tuning of the system along with all the relevant testing and operating experience of the digital PID controller for real-time horizontal plasma position control is presented in the paper.SP
Measurement of spatial and temporal behavior of H-alpha emission from Aditya tokamak using a diagnostic based on a photomultiplier tube array
No full textA photo multiplier tube (PMT) array based spectroscopic diagnostic with fast time response of 10 mu s and spatial resolution similar to 3 cm has been developed and installed on Aditya tokamak to study the spatial and temporal behavior of H-alpha emissions from typical discharges. Collimated light has been collected from the plasma along 16 lines of sight passing through entire plasma poloidal cross section of Aditya and detected by two 8 channels PMT arrays after selecting H-alpha emission using interference filter. The studies are carried out during plasma formation phase of Aditya by changing vertical field and its delay with respect to loop voltage. It is observed that plasma initiated in the high field side in typical discharges of Aditya. The plasma formation position is matched with null field location estimated through simulation. (C) 2014 AIP Publishing LLC
Non-inductive current drive at zero loop voltage using LHCD PAM launcher on ADITYA-U
No full textFor the first time, the ADITYA-U tokamak has sustained a plasma current of ∼40 kA purely through lower hybrid waves (LHWs) using a passive-active multijunction (PAM) launcher, without any loop voltage. While inductive discharges are limited to ∼150 ms by the available loop voltage, injection of LHWs at 80 ms extended the plasma pulse to 320 ms at a peak parallel refractive index of −2.5. Efficient coupling was achieved, with the reflection coefficient remaining below 5%, in agreement with ALOHA predictions, and a figure of merit of ∼0.2 × 10 ^19 A m ^−2 W ^–1 was obtained during the non-inductive phase. Suprathermal electron generation, evidenced by bremsstrahlung emission and hard x-ray energy spectrum (20–200 keV) measured with a CdTe detector, confirmed effective power transfer from LHWs. These first LHCD results with a PAM launcher on ADITYA-U demonstrate reliable wave–plasma coupling, extended discharge duration, and non-inductive current drive capability
Probing the Heliosphere Using <i>in Situ</i> Payloads On-Board Aditya-L1
No full textAditya-L1, the first ever Indian scientific space mis-
sion dedicated to probe the Sun, our nearest star, is
slated for launch by the Indian Space Research Organi-
sation (ISRO) most likely in 2020, the year coinciding
with the expected start of the rising phase of solar cy-
cle 25. Of the seven science payloads on-board Aditya-
L1, three are in situ instruments, namely the Aditya
Solar wind Particle EXperiment, the Plasma Analyser
Package for Aditya and a magnetometer package.
These three payloads will sample heliospheric data
from the L1 Lagrangian point of the Sun–Earth sys-
tem, at a distance of ~1% of the distance to the Sun,
along the Sun–Earth line. This is therefore a unique
opportunity for the solar physics community to gain a
better understanding of the inner heliosphere and
predict space weather more accuratel
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