Megagauss magnetic fields

Herlach, F.

doi:10.1088/0034-4885/31/1/307

Cited by 56 publications

(27 citation statements)

References 40 publications

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“…[5]) and the external fields that can be generated by coils. Magnetic-flux compression [6] is a viable path to generating tens of MG magnetic fields with adequate size compression of a metal liner driven by high explosives [7,8] or by pulsed power. The latter approach has been pursued by the Z-pinch [9] communities.…”

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confidence: 99%

Laser-Driven Magnetic-Flux Compression in High-Energy-Density Plasmas

et al. 2009

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The demonstration of magnetic field compression to many tens of megagauss in cylindrical implosions of inertial confinement fusion targets is reported for the first time. The OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] was used to implode cylindrical CH targets filled with deuterium gas and seeded with a strong external field (>50 kG) from a specially developed magnetic pulse generator. This seed field was trapped (frozen) in the shock-heated gas fill and compressed by the imploding shell at a high implosion velocity, minimizing the effect of resistive flux diffusion. The magnetic fields in the compressed core were probed via proton deflectrometry using the fusion products from an imploding D 3 He target. Line-averaged magnetic fields between 30 and 40 MG were observed. In the magnetic fusion energy (MFE) concept, a strong magnetic field confines the plasma and reduces the electron thermal conduction to the vessel wall [1]. The magnetic pressure of typical $0:1-MG fields is higher than the total energy density of the plasma (with ¼ 2 0 p=B 2 < 1). MFE plasmas are fully magnetized and characterized by a Hall parameter ! ce > 1 since the modest gyrofrequency ! ce is matched by long collision times . In contrast, typical inertial confinement fusion (ICF) plasmas have collision frequencies higher by 10 to 12 orders of magnitude because of their extreme density. In such systems, thermal conduction losses are a major factor in the energy balance of an implosion. While it can be more difficult, magnetizing the hot spot in ICF implosions can lead to improved gains and to a reduction of the energy required for ignition. A similar approach is used in the magnetized target fusion concept [2], where the fusion burn requires relatively low-implosion velocities, provided there is an adequate magnetic thermal insulation. In ICF implosions, lower implosion velocities lead to higher gains [3]. However, tens of MG are needed to achieve ! ce $ 1 in the hot spot of a typical, direct drive DT ignition target [4] with hot-spot density of $30 g=cc and a temperature of $7 keV. Such a field is higher than both the self-generated magnetic fields (see Ref. [5]) and the external fields that can be generated by coils. Magnetic-flux compression [6] is a viable path to generating tens of MG magnetic fields with adequate size compression of a metal liner driven by high explosives [7,8] or by pulsed power. The latter approach has been pursued by the Z-pinch [9] communities. The results from the first experiments on a new approach that provides very effective flux compression are reported here. The field is compressed by the ablative pressure exerted on an imploding ICF capsule by the driving laser [10]. This approach was proposed in the 1980s [11] as a way to achieve record compressed fields with possible applications for fusion [12] but no laser experiments were performed. There are numerous advantages to this approach as the implosion velocity is high (a few 10 7 cm=s) and the hot plasma is an effective conductor that tra...

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confidence: 99%

Laser-Driven Magnetic-Flux Compression in High-Energy-Density Plasmas

et al. 2009

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“…Magnetic field is a useful tool to investigate the nature of matter by directly acting on spin, orbital and phases of electrons. Ultrahigh magnetic fields reaching 100-1000 T (=1-10 Megagauss) have very large Zeeman energy that well exceeds that of the room temperature 1 . Such high magnetic field is used not only for better characterization of matter in resonance methods but also used for bringing about emergent quantum phase of matter that is stable even at room temperature.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, magnetic fields reaching or approaching 100 T with millisecond pulse duration have been generated in nondestructive manner in several facilities in the world, being used for solid state researches. On the other hand, megagauss fields with much shorter pulse duration (a few micron seconds) have been generated in destructive manner using flux compression methods and fast discharge of capacitor bank for decades [1]- [3]. Measurements of condensed matter properties in such destructively generated megagauss fields severely suffer from 1 the limited time and space of the generated magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

Magnetostriction studies up to megagauss fields using fiber Bragg grating technique

Ikeda

Matsuda

Nakamura

et al. 2018

2018 16th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS)

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We here report magnetostriction measurements under pulsed megagauss fields using a high-speed 100 MHz strain monitoring system devised using fiber Bragg grating (FBG) technique with optical filter method. The optical filter method is a detection scheme of the strain of FBG, where the changing Bragg wavelength of the FBG reflection is converted to the intensity of reflected light to enable the 100 MHz measurement. In order to show the usefulness and reliability of the method, we report the measurements for solid oxygen, spin-controlled crystal, and volborthite, a deformed Kagomé quantum spin lattice, using static magnetic fields up to 7 T and non-destructive millisecond pulse magnets up to 50 T. Then, we show the application of the method for the magnetostriction measurements of CaV4O9, a two-dimensional antiferromagnet with spin-halves, and LaCoO3, an anomalous spin-crossover oxide, in the megagauss fields.

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“…The theory of nonlinear magnetic diffusion into a metal is presented in a book by Knoepfel and other books and surveys [2,3] and a broad range of related phenomena, such as metal vaporization and plasma formation was considered in the classical papers of Lyudaev [4]. The diffusion of megagauss fields into a metal plays an important role for both the generation of these fields and for their numerous applications, such as the acceleration of liners by a magnetic field, and has been studied beginning in the very early classical papers devoted to high magnetic fields.…”

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Diffusion of a megagauss field into a metal

Garanin

Ivanova

Karmishin

et al. 2005

J Appl Mech Tech Phys

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The plane one-dimensional problem of the diffusion of a megagauss field into a metal wall is solved taking into account heat conduction and radiation transfer. At the interface, the magnetic field is assumed to be constant, and in this sense, the problem is close to the self-similar diffusion problem with parameters dependent on the self-similar variable x/ √ t. It is shown that if heat conduction and radiation transfer are taken into account, in megagauss fields (in the examined formulation for fields B > 1.6 MGs) there is no loss of conductivity of the material evaporated by the magnetic field because of the formation of a plasma layer at the interface with a temperature in the electronvolt range. However, the role of the plasma layer in the structure of the skin layer remains insignificant up to fields B ≈ 10 MGs.

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Megagauss magnetic fields

Cited by 56 publications

References 40 publications

Laser-Driven Magnetic-Flux Compression in High-Energy-Density Plasmas

Laser-Driven Magnetic-Flux Compression in High-Energy-Density Plasmas

Magnetostriction studies up to megagauss fields using fiber Bragg grating technique

Diffusion of a megagauss field into a metal

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