Faraday-Rotation Measurements of Megagauss Magnetic Fields in Laser-Produced Plasmas

Stamper, J. A.; Ripin, B. H.

doi:10.1103/physrevlett.34.138

Cited by 301 publications

(80 citation statements)

References 7 publications

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“…Faraday rotation method (Stamper and Ripin 1975) measured the magnetic field in laser-produced plasmas, which can be up to a megaGauss. At that time, the structure of magnetic field was not very clear until the proton radiography technique became available.…”

Section: Outflows Observed During Laser-driven Reconnectionmentioning

confidence: 99%

Review on Current Sheets in CME Development: Theories and Observations

et al. 2015

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We introduce how the catastrophe model for solar eruptions predicted the formation and development of the long current sheet (CS) and how the observations were used to recognize the CS at the place where the CS is presumably located. Then, we discuss the direct measurement of the CS region thickness by studying the brightness distribution of the CS region at different wavelengths. The thickness ranges from 10 4 km to about 10 5 km at heights between 0.27 and 1.16 R from the solar surface. But the traditional theory indicates that the CS is as thin as the proton Larmor radius, which is of order tens of meters in the corona. We look into the huge difference in the thickness between observations and theoretical expectations. The possible impacts that affect measurements and results are studied, and physical causes leading to a thick CS region in which reconnection can still occur at a reasonably fast rate are analyzed. Studies in both theories and observations suggest that the difference between the true value and the apparent value of the CS thickness is not significant as long as the CS could be recognised in observations. We review observations that show complex structures and flows inside the CS region and present recent numerical modelling results on some aspects of these structures. Both observations and numerical experiments indicate that the downward reconnection outflows are usually slower than the upward ones in the same eruptive event. Numerical simulations show that the complex structure inside CS and its temporal behavior as a result of turbulence and the Petschek-type slow-mode shock could probably account for the thick CS and fast reconnection. But whether the CS itself is that thick still remains unknown since, for the time being, we cannot measure the electric current directly in that region. We also review the most recent laboratory experiments of reconnection driven by energetic laser beams, and discuss some important topics for future works.

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Section: Outflows Observed During Laser-driven Reconnectionmentioning

confidence: 99%

Review on Current Sheets in CME Development: Theories and Observations

et al. 2015

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“…The plasma wave has been observed so far in single-shot, yet time-integrating schemes 19,20 . Thus, the measurements were incapable of providing insight into the relevant plasma wave dynamics and of timing the accelerated electron bunch with respect to the plasma wave.In this work we present snapshots of the magnetic field generated by the accelerated electron bunch and-simultaneously-of the plasma wave by the combination of two techniques: time-resolved polarimetry 21,22 and plasma shadowgraphy 23 . The novelty in our experimental investigation is the few-cycle duration of our laser pulses, which is even shorter than half of the plasma period.…”

mentioning

confidence: 99%

“…In this work we present snapshots of the magnetic field generated by the accelerated electron bunch and-simultaneously-of the plasma wave by the combination of two techniques: time-resolved polarimetry 21,22 and plasma shadowgraphy 23 . The novelty in our experimental investigation is the few-cycle duration of our laser pulses, which is even shorter than half of the plasma period.…”

mentioning

confidence: 99%

Real-time observation of laser-driven electron acceleration

et al. 2011

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Electron acceleration by laser-driven plasma waves 1,2 is capable of producing ultra-relativistic, quasi-monoenergetic electron bunches 3-5 with orders of magnitude higher accelerating gradients and much shorter electron pulses than state-of-the-art radio-frequency accelerators. Recent developments have shown peak energies reaching into the GeV range 6 and improved stability and control over the energy spectrum and charge 7 . Future applications, such as the development of laboratory X-ray sources with unprecedented peak brilliance 8,9 or ultrafast time-resolved measurements 10 critically rely on a temporal characterization of the acceleration process and the electron bunch. Here, we report the first real-time observation of the accelerated electron pulse and the accelerating plasma wave. Our time-resolved study allows a single-shot measurement of the 5.8 +1.9 −2.1 fs electron bunch duration full-width at half-maximum (2.5 +0.8 −0.9 fs root mean square) as well as the plasma wave with a density-dependent period of 12-22 fs and reveals the evolution of the bunch, its position in the surrounding plasma wave and the wake dynamics. The results afford promise for brilliant, sub-ångström-wavelength ultrafast electron and photon sources for diffraction imaging with atomic resolution in space and time 11 .The recent development in laser wakefield acceleration (LWFA) is made feasible by transverse breaking of the plasma wave 12 , which results in self-injection and trapping of electrons in the accelerating structure 2,13,14 . Whereas beam parameters such as the energy spectrum, accelerated charge, beam divergence and pointing are now being measured routinely with methods adopted from conventional accelerator technology, the duration of electron bunches arising from LWFA has so far defied accurate determination. Bunch duration measurements up to now have relied on techniques using THz radiation emitted by the electrons, yielding upper limits for the electron pulse length corresponding to the temporal resolution of ≥30 fs (refs 15-18). The plasma wave has been observed so far in single-shot, yet time-integrating schemes 19,20 . Thus, the measurements were incapable of providing insight into the relevant plasma wave dynamics and of timing the accelerated electron bunch with respect to the plasma wave.In this work we present snapshots of the magnetic field generated by the accelerated electron bunch and-simultaneously-of the plasma wave by the combination of two techniques: time-resolved polarimetry 21,22 and plasma shadowgraphy 23 . The novelty in our experimental investigation is the few-cycle duration of our laser pulses, which is even shorter than half of the plasma period. This, in combination with a high spatial resolution, allows

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“…A tempemof Te = 5 kev can be approximated with a flux limiter of f = 0.01 or equivalently reducing Spitzer conductivity by a factor of 10. While this finding is not presently understood, it does indicate that it is necessary to include heat transport limiting effects into the modeling, e.g., magnetic fields (21,22) or non local transport (23). In this paper we will present some simulations which include the toroidal magnetic field while neglecting the axial component.…”

Section: -mentioning

confidence: 99%

Thomson scattering from inertial confinement fusion plasmas

Glenzer¹,

Back²,

Suter³

et al. 1997

The 13th International Conference on Laser Interactions and Related Plasma Phenomena

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Abstract.Thomson scattering has been developed at the Nova laser facility as a direct and accurate diagnostic to characterize inertial confinement fusion plasmas. Flat diska coated with thin multilayers of gold and beryllium we= imdated with one laser beam to produce a two ion species plasma with a controlled amount of both speeies. Thomson scattering speetra from these plasmas showed two ion acoustic waves belonging to gold and beryllium. The phase velocities of the ion acoustic waves are shown to be a sensitive function of the relative concentrations of the two ion species and are in good agreement with theoretical calculations. These open geometry experiments further show that an accurate measurement of the ion temperature can be derived from the relative damping of the two ion acoustic waves. Subsequent Thomson scattering measurements from methane-filled, ignition-relevant hohlraums apply the theory for two ion species plasmas to obtain the electron and ion temperatures with high accuracy. The experimental data provide a benchmark for twodimensional hydrodynamic simulations using LASNEX,which is presently in use to predict the performance of fhture megajoule Ihser-driven hohlraums of the National Ignition Facility (NIF). The data are consistent with modeling using significantly inhibited heat transport at the peak of the drive. Applied to NIF targets, this flux limitation has little effect on x-ray production. The spatial distribution of x-rays is slightly mcdlied but optimal symmetry can be re-established by small changes in power balance or pointing. Furthermore, we find that stagnating plasma regions on the hohlraum axis are well &scribed by the calculations. This result implies that stagnation in gas-filled hohlraums occurs too late to dmtly affect the capsule implosion in ignition experiments.

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Faraday-Rotation Measurements of Megagauss Magnetic Fields in Laser-Produced Plasmas

Cited by 301 publications

References 7 publications

Review on Current Sheets in CME Development: Theories and Observations

Review on Current Sheets in CME Development: Theories and Observations

Real-time observation of laser-driven electron acceleration

Thomson scattering from inertial confinement fusion plasmas

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