Daniel Raju is involved in tokamak research since 1995. He has started his career in the Institute for Plasma Research (India) as a Scientist and taken up tasks of designing and developing magnetic diagnostics system for ADITYA tokamak and Super-conducting Steady-state tokamak (SST-1). He has been involved in various spectral data analysis, modeling and computational activities related to plasma experiments. He was deputed to CRPP, Laussane (Switzerland) for about six months for a collaboration work on plasma modeling using DINA code. He has also worked on plasma operation and control at General Atomics, San Diego (USA) during Jun 2008 - Feb 2009. He has also worked on Plasma control and related areas on tokamak WEST in CEA during his deputation(2015-16). He is currently heading the SST-1 tokamak operation. Address: Institute for Plasma Research Near Indira Bridge, Bhat Gandhinagar, Gujarat-382428 (India)
Abstract Several Ohmic discharges of the ADITYA tokamak are simulated using the Tokamak Simulatio... more 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.
Abstract. Plasma production and confinement using a simple toroidal magnetic field in the experim... more Abstract. Plasma production and confinement using a simple toroidal magnetic field in the experiment described here results in a spread of residual fast electrons in bulk plasma. Often a prior knowledge of this spread is essential before making interpretations about bulk plasma measurements using various diagnostics, for example, Langmuir probes. Retarding field energy analyzer is used to obtain radial spread of relative population of these fast electrons with different energies.
The flow and fluctuation measurements in a simple magnetized current less toroidal plasma have be... more The flow and fluctuation measurements in a simple magnetized current less toroidal plasma have been conducted. The measured plasma parameter profiles are observed to be accompanied by large fluctuations. The existence of large fluctuations and filling of plasma in the entire radial domain are observed to be closely related to each other. The E× B drift velocities calculated from the gradient of measured mean plasma potential profile have shown significant deviation from the net flow velocity measurements.
For sustenance of the long duration discharges in the Steady State Tokamak (SST-1), it would be n... more For sustenance of the long duration discharges in the Steady State Tokamak (SST-1), it would be necessary to accurately measure and control the plasma shape, radial and vertical positions. While the plasma shape and position would be controlled by a set of superconducting coils placed outside the vessel and copper feedback control coils placed inside the vessel, their diagnostics would be carried out by an array of magnetic probes placed inside the vessel, just outside the first wall.
Description/Abstract: A summary of results from measurements and analysis of edge turbulence in A... more Description/Abstract: A summary of results from measurements and analysis of edge turbulence in ADITYA tokamak is presented. The floating potential is found to be positive in the scrape-off layer as well as in the edge plasma with a minimum near the shear layer. The electrostatic Reynolds stress, estimated by a conditional averaging technique, is found to be highest near the shear layer. Measurements with gas-puff show strong suppression of edge fluctuations with concomitant reduction in Reynolds stress.
Abstract We study the effect of a background of microturbulence generated by unstable short scale... more Abstract We study the effect of a background of microturbulence generated by unstable short scale length electron temperature gradient (ETG) modes on the excitation and nonlinear evolution of neoclassical tearing modes (NTMs) in a tokamak. A self-consistent model calculation is carried out in which low frequency stresses generated by the ETG modes act on the NTM and which in turn acts back on the ETG evolution by modulating the turbulence profile.
The steady state superconducting tokamak (SST-1) central control system is a distributed heteroge... more The steady state superconducting tokamak (SST-1) central control system is a distributed heterogeneous process communication system built on socket programming. It consists of machine, experiment and discharge control plus timing and a database. The software controls and monitors SST-1 subsystems: water-cooling, power supplies, cryogenics and vacuum over a local area network (LAN).
Abstract. We have performed uniform triaxial deformation of single crystal copper at high strain ... more Abstract. We have performed uniform triaxial deformation of single crystal copper at high strain rate using molecular dynamics code LAMMPS. The best-fit void nucleation and growth parameters are obtained using a macroscopic nucleation and growth (NAG) model. The detailed analysis of the data shows that voids nucleate at specific locations in the domain, and subsequently grow and coalesce.
Abstract Generation of fluctuations and poloidal flow is investigated in a simple toroidal plasma... more Abstract Generation of fluctuations and poloidal flow is investigated in a simple toroidal plasma, at a given magnetic field strength for varying ion masses. Under similar discharge conditions, the fluctuation induced poloidal flux is found to decrease with increasing ion mass. Consequently, the absolute net poloidal flow velocity is found to scale down systematically with increase in the ion mass.
Summary This study discusses the utility of joint interpretation of gravity and magnetic fields t... more Summary This study discusses the utility of joint interpretation of gravity and magnetic fields to delineate the basement features hidden beneath the volcanic layer in the Krishna-Godavari (KG) basin located on the east coast of India. Detailed gravity and magnetic (GM) measurements over a part of the KG basin depicts anomaly trends which coincides with the major tectonic trends of the region. Gravity and magnetic anomaly maps primarily reflects the effect of basement relief depicting horsts and depressions.
Abstract. ADITYA (R0= 75 cm, a= 25 cm), an ohmically heated circular limiter tokamak is regularly... more Abstract. ADITYA (R0= 75 cm, a= 25 cm), an ohmically heated circular limiter tokamak is regularly being operated to carry out several experiments related to controlled thermonuclear fusion research. In recent operational campaign, various experiments have been carried out to enhance the discharge performance as well as improve the plasma parameters. A comparative plasma discharges study with SiC and Graphite limiter was carried out to increase the plasma heating and reduce runaways.
Abstract Predictive simulations investigating steady-state advanced reversed shear configurations... more Abstract Predictive simulations investigating steady-state advanced reversed shear configurations for steady state tokamak (SST-1) in LHCD+ ECRH/CD operations are carried out using the TSC+ LSC+ TORAY-GA code package. We also explore in detail current profile control scenarios using ECCD at various frequency ranges.
Abstract Singular value decomposition (SVD) of the fast imaging data of plumes in the laser-blow-... more Abstract Singular value decomposition (SVD) of the fast imaging data of plumes in the laser-blow-off experiment at various background gas pressures is analyzed. It has been observed that structures in the plasma plume are developed not only at the edge but also inside the plume. The principal components based on eigenvectors clearly show the dynamics of plume and its structures both in the longitudinal and lateral directions.
Abstract Creeping wave modes on smooth structures are of importance in the control of scattering ... more Abstract Creeping wave modes on smooth structures are of importance in the control of scattering properties, such as radar cross section of such structures. We have shown a novel procedure to examine the excitation of creeping wave modes by plane wave illumination of a perfectly electrically conducting (PEC) cylinder.
In a simple toroidal plasma, self consistent poloidal flow generation at different toroidal field... more In a simple toroidal plasma, self consistent poloidal flow generation at different toroidal fields is observed. On changing the magnitude of toroidal field, transition occurs in the nature of fluctuation from highly coherent modes at low magnetic field to a turbulent broadband spectrum at high field accompanied by significant improvement in the confinement. Interestingly, though the coherence is reduced with the increasing field, the fluctuation driven poloidal flux remains comparable.
Abstract Several Ohmic discharges of the ADITYA tokamak are simulated using the Tokamak Simulatio... more 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.
Abstract. Plasma production and confinement using a simple toroidal magnetic field in the experim... more Abstract. Plasma production and confinement using a simple toroidal magnetic field in the experiment described here results in a spread of residual fast electrons in bulk plasma. Often a prior knowledge of this spread is essential before making interpretations about bulk plasma measurements using various diagnostics, for example, Langmuir probes. Retarding field energy analyzer is used to obtain radial spread of relative population of these fast electrons with different energies.
The flow and fluctuation measurements in a simple magnetized current less toroidal plasma have be... more The flow and fluctuation measurements in a simple magnetized current less toroidal plasma have been conducted. The measured plasma parameter profiles are observed to be accompanied by large fluctuations. The existence of large fluctuations and filling of plasma in the entire radial domain are observed to be closely related to each other. The E× B drift velocities calculated from the gradient of measured mean plasma potential profile have shown significant deviation from the net flow velocity measurements.
For sustenance of the long duration discharges in the Steady State Tokamak (SST-1), it would be n... more For sustenance of the long duration discharges in the Steady State Tokamak (SST-1), it would be necessary to accurately measure and control the plasma shape, radial and vertical positions. While the plasma shape and position would be controlled by a set of superconducting coils placed outside the vessel and copper feedback control coils placed inside the vessel, their diagnostics would be carried out by an array of magnetic probes placed inside the vessel, just outside the first wall.
Description/Abstract: A summary of results from measurements and analysis of edge turbulence in A... more Description/Abstract: A summary of results from measurements and analysis of edge turbulence in ADITYA tokamak is presented. The floating potential is found to be positive in the scrape-off layer as well as in the edge plasma with a minimum near the shear layer. The electrostatic Reynolds stress, estimated by a conditional averaging technique, is found to be highest near the shear layer. Measurements with gas-puff show strong suppression of edge fluctuations with concomitant reduction in Reynolds stress.
Abstract We study the effect of a background of microturbulence generated by unstable short scale... more Abstract We study the effect of a background of microturbulence generated by unstable short scale length electron temperature gradient (ETG) modes on the excitation and nonlinear evolution of neoclassical tearing modes (NTMs) in a tokamak. A self-consistent model calculation is carried out in which low frequency stresses generated by the ETG modes act on the NTM and which in turn acts back on the ETG evolution by modulating the turbulence profile.
The steady state superconducting tokamak (SST-1) central control system is a distributed heteroge... more The steady state superconducting tokamak (SST-1) central control system is a distributed heterogeneous process communication system built on socket programming. It consists of machine, experiment and discharge control plus timing and a database. The software controls and monitors SST-1 subsystems: water-cooling, power supplies, cryogenics and vacuum over a local area network (LAN).
Abstract. We have performed uniform triaxial deformation of single crystal copper at high strain ... more Abstract. We have performed uniform triaxial deformation of single crystal copper at high strain rate using molecular dynamics code LAMMPS. The best-fit void nucleation and growth parameters are obtained using a macroscopic nucleation and growth (NAG) model. The detailed analysis of the data shows that voids nucleate at specific locations in the domain, and subsequently grow and coalesce.
Abstract Generation of fluctuations and poloidal flow is investigated in a simple toroidal plasma... more Abstract Generation of fluctuations and poloidal flow is investigated in a simple toroidal plasma, at a given magnetic field strength for varying ion masses. Under similar discharge conditions, the fluctuation induced poloidal flux is found to decrease with increasing ion mass. Consequently, the absolute net poloidal flow velocity is found to scale down systematically with increase in the ion mass.
Summary This study discusses the utility of joint interpretation of gravity and magnetic fields t... more Summary This study discusses the utility of joint interpretation of gravity and magnetic fields to delineate the basement features hidden beneath the volcanic layer in the Krishna-Godavari (KG) basin located on the east coast of India. Detailed gravity and magnetic (GM) measurements over a part of the KG basin depicts anomaly trends which coincides with the major tectonic trends of the region. Gravity and magnetic anomaly maps primarily reflects the effect of basement relief depicting horsts and depressions.
Abstract. ADITYA (R0= 75 cm, a= 25 cm), an ohmically heated circular limiter tokamak is regularly... more Abstract. ADITYA (R0= 75 cm, a= 25 cm), an ohmically heated circular limiter tokamak is regularly being operated to carry out several experiments related to controlled thermonuclear fusion research. In recent operational campaign, various experiments have been carried out to enhance the discharge performance as well as improve the plasma parameters. A comparative plasma discharges study with SiC and Graphite limiter was carried out to increase the plasma heating and reduce runaways.
Abstract Predictive simulations investigating steady-state advanced reversed shear configurations... more Abstract Predictive simulations investigating steady-state advanced reversed shear configurations for steady state tokamak (SST-1) in LHCD+ ECRH/CD operations are carried out using the TSC+ LSC+ TORAY-GA code package. We also explore in detail current profile control scenarios using ECCD at various frequency ranges.
Abstract Singular value decomposition (SVD) of the fast imaging data of plumes in the laser-blow-... more Abstract Singular value decomposition (SVD) of the fast imaging data of plumes in the laser-blow-off experiment at various background gas pressures is analyzed. It has been observed that structures in the plasma plume are developed not only at the edge but also inside the plume. The principal components based on eigenvectors clearly show the dynamics of plume and its structures both in the longitudinal and lateral directions.
Abstract Creeping wave modes on smooth structures are of importance in the control of scattering ... more Abstract Creeping wave modes on smooth structures are of importance in the control of scattering properties, such as radar cross section of such structures. We have shown a novel procedure to examine the excitation of creeping wave modes by plane wave illumination of a perfectly electrically conducting (PEC) cylinder.
In a simple toroidal plasma, self consistent poloidal flow generation at different toroidal field... more In a simple toroidal plasma, self consistent poloidal flow generation at different toroidal fields is observed. On changing the magnitude of toroidal field, transition occurs in the nature of fluctuation from highly coherent modes at low magnetic field to a turbulent broadband spectrum at high field accompanied by significant improvement in the confinement. Interestingly, though the coherence is reduced with the increasing field, the fluctuation driven poloidal flux remains comparable.
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Papers by Raju Daniel