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Author

V. Narayanan

Bio: V. Narayanan is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Laser & Plasma. The author has an hindex of 14, co-authored 34 publications receiving 615 citations. Previous affiliations of V. Narayanan include Indian Institute of Technology Kanpur & University of Milan.
Topics: Laser, Plasma, Photon, Fock space, Quantum state


Papers
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Journal ArticleDOI
TL;DR: The results are not only fundamentally interesting but should also arouse interest on the role of magnetic turbulence induced resistivity in the context of fast ignition of laser fusion, and the possibility of experimentally simulating such structures with respect to the sun and other stellar environments.
Abstract: Turbulence in fluids is a ubiquitous, fascinating, and complex natural phenomenon that is not yet fully understood. Unraveling turbulence in high density, high temperature plasmas is an even bigger challenge because of the importance of electromagnetic forces and the typically violent environments. Fascinating and novel behavior of hot dense matter has so far been only indirectly inferred because of the enormous difficulties of making observations on such matter. Here, we present direct evidence of turbulence in giant magnetic fields created in an overdense, hot plasma by relativistic intensity (1018W/cm2) femtosecond laser pulses. We have obtained magneto-optic polarigrams at femtosecond time intervals, simultaneously with micrometer spatial resolution. The spatial profiles of the magnetic field show randomness and their k spectra exhibit a power law along with certain well defined peaks at scales shorter than skin depth. Detailed two-dimensional particle-in-cell simulations delineate the underlying interaction between forward currents of relativistic energy “hot” electrons created by the laser pulse and “cold” return currents of thermal electrons induced in the target. Our results are not only fundamentally interesting but should also arouse interest on the role of magnetic turbulence induced resistivity in the context of fast ignition of laser fusion, and the possibility of experimentally simulating such structures with respect to the sun and other stellar environments.

114 citations

Journal ArticleDOI
TL;DR: In this paper, a megaelectronvolt beam of atoms is generated by ionizing argon clusters, and then neutralizing the ions using Rydberg atoms, which demonstrates a high neutral yield and could find an important application as a sensitive probe of matter.
Abstract: A megaelectronvolt beam of atoms is now generated by ionizing argon clusters, and then neutralizing the ions using Rydberg atoms. The compact system demonstrates a high neutral yield, and could find an important application as a sensitive probe of matter.

78 citations

Journal ArticleDOI
TL;DR: In this article, the authors reported a 43-fold enhancement in hard x-ray emission from copper nanorod arrays when excited by 30-fs, 800-nm laser pulses with an intensity of ${10}^{16}$ W/cm${}^{2}$.
Abstract: We report a 43-fold enhancement in the hard x-ray emission (in the 150--300 keV range) from copper nanorod arrays (compared to a polished Cu surface) when excited by 30-fs, 800-nm laser pulses with an intensity of ${10}^{16}$ W/cm${}^{2}$. The temperature of the hot electrons that emit the x rays is 11 times higher. Significantly, the x-ray yield enhancement is found to depend on both the aspect ratio as well as the cluster size of the nanorods. We show that the higher yield arises from enhanced laser absorption owing to the extremely high local electric fields around the nanorod tips. Particle-in-cell plasma simulations reproduce these observations and provide pointers to further optimization of the x-ray emission.

63 citations

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TL;DR: In this paper, the laser ablation of Si in vacuum, and in the presence of helium ambient at 1 and 10 Torr, respectively, is reported, where optical emission spectroscopy and images of the plume are used to study the spatial and temporal variation of the silicon plasma.

46 citations

Journal ArticleDOI
TL;DR: It is demonstrated that aligned carbon-nanotube arrays are efficient transporters of laser-generated mega-ampere electron currents over distances as large as a millimeter.
Abstract: We demonstrate that aligned carbon-nanotube arrays are efficient transporters of laser-generated megaampere electron currents over distances as large as a millimeter. A direct polarimetric measurement of the temporal and the spatial evolution of the megagauss magnetic fields (as high as 120 MG) at the target rear at an intensity of (10(18)-10(19)) W/cm(2) was corroborated by the rear-side hot electron spectra. Simulations show that such high magnetic flux densities can only be generated by a very well collimated fast electron bunch.

45 citations


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TL;DR: The first direct detection of gravitational waves and the first observation of a binary black hole merger were reported in this paper, with a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ.
Abstract: On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160) Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

4,375 citations

01 Jul 2013
TL;DR: In this article, the authors inject squeezed states to improve the performance of one of the detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) beyond the quantum noise limit, most notably in the frequency region down to 150 Hz.
Abstract: Nearly a century after Einstein first predicted the existence of gravitational waves, a global network of Earth-based gravitational wave observatories1, 2, 3, 4 is seeking to directly detect this faint radiation using precision laser interferometry. Photon shot noise, due to the quantum nature of light, imposes a fundamental limit on the attometre-level sensitivity of the kilometre-scale Michelson interferometers deployed for this task. Here, we inject squeezed states to improve the performance of one of the detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) beyond the quantum noise limit, most notably in the frequency region down to 150 Hz, critically important for several astrophysical sources, with no deterioration of performance observed at any frequency. With the injection of squeezed states, this LIGO detector demonstrated the best broadband sensitivity to gravitational waves ever achieved, with important implications for observing the gravitational-wave Universe with unprecedented sensitivity.

589 citations

Journal ArticleDOI
TL;DR: Filamentation due to the growth of a Weibel-type instability was observed in the interaction of a pair of counterstreaming, ablatively driven plasma flows, in a supersonic, collisionless regime relevant to astrophysical collisionless shocks.
Abstract: Filamentation due to the growth of a Weibel-type instability was observed in the interaction of a pair of counterstreaming, ablatively driven plasma flows, in a supersonic, collisionless regime relevant to astrophysical collisionless shocks. The flows were created by irradiating a pair of opposing plastic (CH) foils with 1.8 kJ, 2-ns laser pulses on the OMEGA EP Laser System. Ultrafast laser-driven proton radiography was used to image the Weibel-generated electromagnetic fields. The experimental observations are in good agreement with the analytical theory of the Weibel instability and with particle-in-cell simulations.

189 citations

Journal ArticleDOI
TL;DR: When electrons are accelerated to near light-speeds through an overdense plasma by an intense laser beam, the usually opaque plasma becomes optically transparent as discussed by the authors, and high-speed laser experiments provide unprecedented insight into the dynamics of this process.
Abstract: When electrons are accelerated to near light-speeds through an overdense plasma by an intense laser beam, the usually opaque plasma becomes optically transparent. High-speed laser experiments provide unprecedented insight into the dynamics of this process.

184 citations