Doppler Spectrometry for Ultrafast Temporal Mapping of Density Dynamics in Laser-Induced Plasmas

Mondal, Sudipta; Lad, Amit D.; Ahmed, Saima; Narayanan, V.; Pasley, J.; Rajeev, P. P.; Robinson, A. P. L.; Kumar, G. Ravindra

doi:10.1103/physrevlett.105.105002

Cited by 38 publications

(41 citation statements)

References 21 publications

(23 reference statements)

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“…We extracted 5% of the main beam and converted that to the second harmonic (2ω) (400 nm) and used as a probe, so that it can penetrate up to four times the critical density that corresponds to 800 nm (36). Another advantage of using 2ω probe is the suppression of pump noise (36). The probe was time delayed by a high precision translation stage.…”

Section: Methodsmentioning

confidence: 99%

“…The output Stokes' vector of one slab is fed into the next slab as the input and the evolution equation of the Stokes' vector is solved numerically in each slab to finally yield the ellipticity (and hence the magnetic field) of the laser pulse emerging from the plasma box. An exponential plasma density profile was used for the numerical integration with a plasma expansion velocity of 5 × 10 6 cm∕ sec derived from Doppler shift measurement of the reflected probe from plasma (36). The above procedure was implemented for each CCD pixel to get a 2D spatial mapping of the magnetic field at the critical surface of the 400-nm probe beam.…”

Section: Methodsmentioning

confidence: 99%

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Direct observation of turbulent magnetic fields in hot, dense laser produced plasmas

Mondal

Narayanan²,

Ding³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

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150

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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 (10 18 W∕cm 2 ) 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.intense laser matter interaction | high energy density | astrophysical simulations | filamentary structures T he largest terrestrially available magnetic fields are generated when an intense laser pulse (intensity above 10 18 W∕cm 2 ) irradiates a solid target (1-3). The high energy density produced by laser irradiation generates relativistic electron jets, through the process of wave breaking. These relativistic electron jets carry the laser energy deep into the target ionizing and heating the colder portions behind the laser generated plasma and exciting return shielding currents. In the laboratory, such heating is extremely important for fast ignition of highly compressed targets in laser fusion (4, 5), simulation of intra planetary matter existing at ultrahigh pressure (6), ultrafast X-ray pulses (7), as well as proton and ion acceleration up to the MeV-GeV levels (3). It also serves as an excellent tool for modeling astrophysical systems (8-10). The transport of relativistic electrons through hot dense matter is very complex and is barely understood (11,12). Simulations have shown that relativistic electron transport in plasma media is fraught with severe plasma instabilities particularly the Weibel instability (13), which leads to spatial separation of forward and backward currents and eventually to the emergence of turbulent structures (14) and rapid energy dissipation. A major physical parameter that mirrors this complex physics is the giant magnetic field-as high as hundreds of megagauss-generated in this interaction. In earlier st...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Direct observation of turbulent magnetic fields in hot, dense laser produced plasmas

Mondal

Narayanan²,

Ding³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

150

View full text Add to dashboard Cite

show abstract

“…On the other hand, creation of high energy density plasmas in the laboratory is possible by virtue of intense laser-solid interactions 1,3 which can lead to the realization of dynamic compression of the material achieving much higher pressures than those in diamond anvil cells 2 . The technique of chirped pulse amplification 4 produces intense ultrashort laser pulses on a table top and has spurred controllable exploration of 'extreme conditions' of matter [5][6][7][8][9][10][11][12][13][14][15][16][17] . The temporal dynamics of ultrashort laser-plasma interactions have just begun to be explored in overdense and near solid density plasma [10][11][12] .…”

Section: Introductionmentioning

confidence: 99%

Controlling femtosecond-laser-driven shock-waves in hot, dense plasma

et al. 2017

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Ultrafast pump-probe reflectometry and Doppler spectrometry of a supercritical density plasma layer excited by 10 17 − 10 18 W/cm 2 intensity, 30 fs, 800 nm laser pulses reveal the interplay of laser intensity contrast and inward shock wave strength. The inward shock wave velocity increases with an increase in laser intensity contrast. This trend is supported by simulations as well as by a separate independent experiment employing an external prepulse to control the inward motion of the shock wave. This kind of cost-effective control of shock wave strength using femtosecond pulses could open up new applications in medicine, science, and engineering.

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“…Therefore, a ten fold increase in spot size will bring in a 100 fold decrease in both focused laser intensity and electron temperature. The cold electron temperature of the plasma (at w ≈ 12 µm) in our experiments is about 300 eV 27 and so, in the defocused condition, the pre-plasma temperature is expected to be about a few eV or less. Beyond the optimal defocusing the pre-pulse level goes below the pre-plasma formation threshold.…”

Section: Resultsmentioning

confidence: 73%

Mass selection in laser-plasma ion accelerator on nanostructured surfaces

et al. 2017

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Recent advances in high-intensity laser-produced plasmas have demonstrated their potential as compact charge particle accelerators. Unlike conventional accelerators, transient quasi-static charge separation acceleration fields in laser produced plasmas are highly localized and orders of magnitude larger. Manipulating these ion accelerators, to covert the fast ions to neutral atoms with little change in momentum, transform these to a bright source of MeV atoms. The emittance of the neutral atom beam would be similar to that expected for an ion beam. Since intense laser-produced plasmas have been demonstrated to produce high-brightness-low-emittance beams, it is possible to envisage generation of high-flux, low-emittance, high energy neutral atom beams in length scale of less than a milimeter. Here, we show a scheme where more than 80% of the fast ions are reduced to energetic neutral atoms and demonstrate the feasibility of a high energy neutral atom accelerator that could significantly impact applications in neutral atom lithography and diagnostics.

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Doppler Spectrometry for Ultrafast Temporal Mapping of Density Dynamics in Laser-Induced Plasmas

Cited by 38 publications

References 21 publications

Direct observation of turbulent magnetic fields in hot, dense laser produced plasmas

Direct observation of turbulent magnetic fields in hot, dense laser produced plasmas

Controlling femtosecond-laser-driven shock-waves in hot, dense plasma

Mass selection in laser-plasma ion accelerator on nanostructured surfaces

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