Megagauss Magnetic Fields Research Articles

Megagauss magnetic field generation and related topics Report on the 5th International Conference held at Novosibirsk, USSR, 3-7 July 1989

The Fifth International Conference on Megagauss Magnetic Field Generation and Related Topics was hosted by the Lavrentyev Institute of Hydrodynamics, Siberian Division of the USSR Academy of Sciences, which has performed this service for the world scientific community for the second time; Megagauss III was held in Novosibirsk in 1983. The International Advisory Committee of Megagauss V was chaired by Academician E.P. Velikhov, with Professor V.M. Titov, Director of the Lavrentyev Institute of Hydrodynamics, serving as Vice-Chairman and Dr. G.A. Shvetsov as Scientific Secretary. The conference again provided a forum for discussion of the physics, technology and the application of high magnetic fields and of related pulsed electrical power systems involving multimegaampere currents. The conference was preceded by the International Workshop on Opening Switch Physics and Techniques, chaired by Academician G.A. Mesyats. The participants visited several institutes in Leningrad, Moscow, Tomsk and Novosibirsk before and after the workshop and the conference.

Structure and dynamics of a plasma piston in rail-gun accelerators for solid objects

of megagauss magnetic fields," Zh. Prikl. Mekh. Tekh. Fiz., No. 3 (1987). 55. K. Nagayama and T. Mashimo, "Explosive-driven magnetic flux cumulation by the propagation of shock compressed conductive region in highly porous metal powders," J. Appl. Phys., 61, No. i0 (1987). 56. A. D. Sakharov, R. Z. Lyudaev, E. I. Smirnov, et al., "Magnetic cumulation," Dokl. Akad. Nauk SSSR, 165, No. 1 (1965). 57. C.M. Fowler, R. S. Caird, and W. B. Carn, "Production of very high magnetic fields by explosion," J. Appl. Phys., 31, No. 3 (1960). 58. A. I. Pavlovskii, N. P. Kolokol'chikov, M. I. Dolotenko, et al., "Cascade magnetic cumulation generator of superstrong magnetic fields," in: Superstrong Magnetic Fields: Proc3rd Int. Conf. on the Generation of Megagauss Magnetic Fields, Nauka, Moscow (1984)o 59. A. I. Pavlovskii, A. I. Bykov, M. I. Dolotenko, et al., "Limiting value of reproducible magnetic field in cascade generator MC-I," in: Megagauss Technology and Pulsed Power Applications: Proc. 4th Int. Conf. on Megagauss Magnetic Field Generation, New York (1987).

Phase-amplitude imaging: The fully automated analysis of megagauss magnetic field measurements in laser-produced plasmas

This paper describes the application of phase-amplitude imaging to the measurement of self-generated magnetic fields in laser-produced plasmas. The magnitude of the magnetic field is determined by polarimetry and the plasma density profile by interferometry. Both pieces of information are recorded on a single interferogram in a form that can be analyzed automatically using computer-based image processing. We describe a method for successfully determining the magnetic field profile in plasmas generated by 70-ps Nd laser pulses at high intensity on planar targets when plasma motion or turbulence introduces an additional difficulty by reducing the visibility of the fringes.

Nonlinear Effects of a Gaussian Laser Beam on Megagauss Magnetic Field Generation in Laser Produced Plasma

AbstractThe generation of megagauss magnetic field due to the time dependent part of the ponderomotive force of a self‐focused Gaussian laser beam indicent on a plasma has been studied. Defocusing of the laser beam becomes possible due to diffraction divergence in the case of a weakly nonlinear medium. The influence of defocusing of a laser beam on magnetic field generation has also been investigated. It is found that the magnitude of the magnetic field due to self focusing of the beam is enhanced and is comparable with the observed values, while there is a reduction in the magnitude of the magnetic field when the beam defocuses due to diffraction divergence in the presence of weak nonlinearity.

Megagauss Magnetic Field Generation and Related Topics (Report on the Fourth International Conference, Santa Fe, NM, 14–17 July 1986)

In 1986, after three years of additional research progress, the international community devoted to the generation and application of ultrahigh magnetic fields and currents, it reconvened at Santa Fe, New Mexico. The Conference had been announced at the previous meeting (Megagauss III) held at Novosibirsk, USSR, in 1983 under the auspices of the Lavrentyev Institute of Hydrodynamics and the Siberian Branch of the Soviet Academy of Sciences. The present meeting (Megagauss IIII) was hosted by Los Alamos National Laboratory (LANL) with active assistance by scientists from Lawrence Livermore National Laboratory (LLNL), the Air Force Weapons Laboratory (AFWL) and Sandia National Laboratories, Albuquerque, NM (SNLA). Over 220 scientists and engineers from eight countries (including, for the first time, the People's Republic of China) participated in the technical sessions of the Conference, which included more than one hundred papers, and in the subsequent tours of local laboratories (LANL, SNLA, AFWL).

Summary of the Fourth International Conference on Megagauss Magnetic Field Generation and Related Topics (Megagauss IV), Santa Fe, New Mexico, July 14–17, 1986

"Summary of the Fourth International Conference on Megagauss Magnetic Field Generation and Related Topics (Megagauss IV), Santa Fe, New Mexico, July 14–17, 1986." Fusion Technology, 11(2), pp. 456–457

Megagauss Magnetic Field Generation in Laser Produced Plasmas due to Self‐Focussing of the Laser Beam

AbstractThe magnetic field generated in a plasma due to the irradiation of a Gaussian laser beam is estimated, taking into consideration the self‐focusing effect of the laser. It is found that a self focusing of the beam propagating in a plasma increases the magnitude of the magnetic field and it is comparable with the measured values.

Comment on "Free-electron laser and laser electron acceleration based on the megagauss magnetic fields in laser-produced plasmas."

Comment on "Free-electron laser and laser electron acceleration based on the megagauss magnetic fields in laser-produced plasmas."

Free-electron laser and laser electron acceleration based on the megagauss magnetic fields in laser-produced plasmas.

It is suggested that the megagauss magnetic fields generated in laser-produced plasmas be applied for (a) the construction of a wiggler for an x-ray free-electron laser and (b) charged-particle acceleration to high energies using the inverse free-electron laser and the autoresonance laser acceleration schemes. Coherent amplification of 10-\AA{} radiation with a 150-MeV electron beam seems feasible and gigaelectronvolt electron beams may induce a $\ensuremath{\gamma}$-ray laser. An acceleration gradient of about [100 MV/cm] ${[\frac{z}{(10cm)}]}^{\frac{\ensuremath{-}1}{3}}$ can be achieved at a distance $z$ along a 1-MG axial magnetic field in the autoresonance laser acceleration scheme, using a Nd:glass laser of ${10}^{18}$ W/${\mathrm{cm}}^{2}$.

Megagauss magnetic fields — generation and application to magnetism

A review is presented on the recently constructed facilities for generating ultra-high magnetic fields in the megagauss range. These facilities include electromagnetic flux compression, direct discharge to a single turn coil and conventional non-destructive pulse magnets. Applications of the high fields to studies of magnetism are discussed.

Two Dimensional Megagauss Magnetic Field Variation Along Axial and Radial Direction of Laser Axis for a Plasma Produced due to Laser Irradiation on the Surface of a Wire Target

AbstractThe variation of megagauss magnetic field in two dimensions for a cylindrical target plasma produced by lasers irradiation on the surface of a cylindrical wire has been solved analytically making use of Hankel and Fourier transforms. The results have been compared with the experiments of RAVEN et al. (1978).

Nonlocal energy deposition in high-intensity laser-plasma interactions.

Electrons heated by the absorption of laser energy on planar targets generate megagauss magnetic field which, together with the coproduced electric fields, transport the electrons away from the laser spot. We present a computational model showing that these superthermal electrons deposit their energy into plasma thermal energy in an expanding annular region in the target plane centered at the spot. The model provides a quantitative explanation for some complex and heretofore poorly understood lateral transport phenomenology.

Megagauss Magnetic Field Generation and Related Topics (Report on the 3rd International Conference, Novosibirsk, 1983)

There is a community of scientists and engineers devoted to developing the physics and technology of very high magnetic field systems. This community recently convened in Novosibirsk (Akademgorodok), USSR, at the Third International Conference on Megagauss Magnetic Field Generation and Related Topics (Megagauss III), 13–17 June 1983. The direct coupling of the Conference activities to controlled nuclear fusion interests occurred in three areas: liner compression of plasma, imploding liners as high-power sources for ICF, and a visit at the Institute of Nuclear Physics (INP). It is believed, however, that the other topics of the Conference should also be of general interest to many of the readers of “Nuclear Fusion”.

Faraday rotation and magnetization observed for EuS and EuSe in megagauss fields

Faraday rotation was observed for EuS and EuSe under megagauss magnetic fields. From the temperature dependence of the Verdet constant and the non-linear field dependence of the Faraday rotation, it turned out that the Faraday rotations in those substances are almost proportional to the magnetization.

Is the Sun an oblique magnetic rotator?

The recent observation1 of rotational splitting of the non-radial p modes of l = 1 and l = 2 (with it n∼20) of the 5-min global oscillation of the Sun was interpreted in terms of rotational splitting associated with a rapid rotation of the solar interior. The precise value deduced for the angular velocity Ω of the interior depends on the assumed variation of Ω with depth and on the weighting function. Thus with a weighting function2 of the form &Ω=∫Ω(r)/V(r) dr ∫dr/V(r) (1) where V(r) is the local velocity of sound at radius r, one obtains values of Ωcore/Ωsurface ranging from 2 to 9 as the radius at which Ω, assumed to be constant for smaller r, ranges from 0.6 to 0.15 of the solar radius. Such a weighting function proportional to the time the wave spends at any particular radius seems very plausible for the effect of any parameter, be it angular velocity or magnetic field, on the propagation of nearly plane waves as they bounce between the centre and the surface. Here I attempt to correlate the size of the observed rotational splitting with the enigmatic 12.2-day variation in the measurement of solar oblateness discovered by Dicke3 previously4 and to interpret the observed near equality of the amplitudes of the m- components of the l = 1 and l = 2 rotationally split modes. This leads to the first empirical evidence that an asymmetric magnetic rotator with megagauss magnetic fields exists in the interior of the Sun. It also suggests that the magnetic energy of young stars is a sizeable fraction of their gravitational energy.

Megagauss magnetic fields on laser irradiated spherical targets

Strong thermo-electric magnetic fields have been obserbed on non-uniformly illuminated microballoon targets at irradiances of 10 13 to 10 14 W cm -2 using a 1.2 ns Nd glass laser heating pulse and a 50 ps Raman shifted second harmonic probe pulse. For uniformly irradiated spherical targets no large scale magnetic fields above 100 kG were observed.

Megagauss Physics and Technology

'The 2nd international conference on megagauss magnetic field generation and related topics, held in Washington, DC, 29 May–1 June 1979', describes the contents of this book more aptly than its somewhat misleading title. This conference report is almost exclusively concerned with the awesome technology required to generate magnetic fields greater than 100 T, with great emphasis on flux compression and implosion driven systems.

Calculation of the compression of a DT mixture by an electrically exploded cylindrical shell

A possible path to the solution of the problem of controlled thermonuclear fusion consists of heating up a target containing a DT mixture by compressing it with a dense shell accelerated to velocities 3~ 107 cm/sec [1 ]. One of the methods for achieving such compression is the use of megagauss magnetic fields [2]. This method is attractive due to the possibility of obtaining a comparatively high (~ 1%) transfer coefficient of the initially stored energy to the shell. An accumulation of kinetic energy occurs both due to the pressure of the magnetic field and due to the dispersion of material from the shell surface. Both acceleration mechanisms operate when the shell is subject to an electrical explosion (EE) by a strong current pulse. A calculation of the electrical explosion of a thin cylindrical shell upon the discharge of a megajoule capacitor bank into it is performed in [3]. Compression rates up to 3 X 10 T cm/sec are obtained in the calculation; however, the comparatively low rates of current growth provided by a capacitor bank have led to the necessity of choosing a very small initial relative shell thickness %10 -s . The heating of the gas filling the shell and the conditions for the occurrence of thermonuclear reactions were not considered in this research.

Decay instability of laser radiation in a magnetoplasma

The self-generated mega-Gauss magnetic fields in laser pellet fusion plasmas open some potential channels of parametric decay of laser radiation. In the vicinity of the cutoff, the pump decays efficiently into (i) lower hybrid and upper hybrid modes, (ii) ion acoustic and upper hybrid modes, (iii) fast ion wave and plasma wave, and (iv) Bernstein mode and plasma wave. At higher pump powers, nonlinear Landau damping and cyclotron damping by electrons possess large growth rates. These instabilities are also relevant to tokamak-type plasmas where nonlinear effects are important in the vicinity of the upper hybrid resonance.

Qualitative Aspects of Underdense Magnetic Fields in Laser-Fusion Plasmas

Computer simulations present evidence that the localized anisotropic heating from resonant absorption drives a Weibel-like instability that generates megagauss magnetic fields for typical laser-fusion parameters. The magnetic fields can inhibit heat transport and partially isotropize the hot electrons.