Megagauss Magnetic Field Profiles in Laser-Produced Plasmas

Raven, A. M.; Willi, O.; Rumsby, P.T.

doi:10.1103/physrevlett.41.554

Cited by 160 publications

(63 citation statements)

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“…Fi, 52.25.Xz, The existence of large self-generated magnetic fields in laser-produced plasmas (∼100T) has long been known [2,3]. These fields can significantly affect the distribution of thermal energy in plasma targets by suppressing the cross-field thermal conductivity [4].…”

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confidence: 99%

Field Compressing Magnetothermal Instability in Laser Plasmas

2010

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The mechanism for a new instability in magnetized plasmas is presented and a dispersion relation derived. Unstable behaviour is shown to result purely from transport processes -feedback between the Nernst effect and the Righi-Leduc heat-flow phenomena in particular -neither hydrodynamic motion nor density gradients are required. Calculations based on a recent nanosecond laser gas-jet experiment [1] predict growth of magnetic field and temperature perturbations with typical wavelengths of order 50µm and characteristic growth times of ∼0.1ns. The instability yields propagating magneto-thermal waves whose direction depends on the magnitude of the Hall Parameter.PACS numbers: 52.25. Fi, 52.25.Xz, The existence of large self-generated magnetic fields in laser-produced plasmas (∼100T) has long been known [2,3]. These fields can significantly affect the distribution of thermal energy in plasma targets by suppressing the cross-field thermal conductivity [4]. In recent years several experiments have been designed to assess their impact on inertial confinement fusion (ICF) schemes [5] and to study more general magnetic phenomena in laser plasmas, such as magnetic reconnection [6] and instability [7]. In addition, there has been increased discussion of the possible uses for applied magnetic fields in the suppression of non-local transport [1], control of plasma density channels [8], wakefield acceleration [9] and magnetized target fusion (MTF) schemes [10].In this letter we report a new instability shown computationally to impact on magnetized plasmas, though it may also take effect in the presence of self-generated fields. The instability compresses the magnetic field and distorts thermal energy profiles by concentrating the heat-flow (see figure 1), and may be important when a high degree of symmetry or control of heat transport is needed, or where uniform fields are applied for a specific purpose, such as those cases mentioned above [1,[8][9][10].Feedback is driven solely by classical (Braginskii) transport processes [4]: specifically the interaction of the Nernst effect, which describes advection of magnetic field with heat-flow down temperature gradients q ⊥ and with velocity v N ≈ 2q ⊥ /5P e , where P e is the isotropic pressure [11]; and the Righi-Leduc heat-flow, the cross-field thermal-flux 'bent' by magnetic fields acting on negatively charged heat-carrying electrons. Consequently we require only the presence of temperature gradients ∇T e perpendicular to an existing magnetic field for instability. Gradients in electron number density n e are not needed (i.e. ∇n e = 0, precluding ∇T e × ∇n e field generation), nor hydrodynamic motion or anisotropic pressure. Thus, what we see is distinct from instabilities existing in the literature: such as those of Tidman-Shanny [12][13][14], for which ∇T e × ∇n e is necessarily non-zero; Weibel [15], where magnetic fields are not essential; Haines [16,17], which does not require either Righi-Leduc heat-flow or the Nernst effect; and Davies [18], where unstable filamentation ar...

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confidence: 99%

Field Compressing Magnetothermal Instability in Laser Plasmas

2010

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“…Previous work has focused largely on regimes in which fields are generated by shortpulse, high-intensity lasers [5,[11][12][13][14], and field measurements were based on Faraday rotation [11,13] and probes [4], or high-order laser harmonics [14]. It has also been proposed that proton radiography could provide a different method for measuring these fields through the deflections they induce in proton trajectories; recent work by Mackinnon et al [15] demonstrated that highresolution images containing deflection information could be obtained, although no direct connections were made between images and fields.…”

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MeasuringEandBFields in Laser-Produced Plasmas with Monoenergetic Proton Radiography

et al. 2006

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“…Due to normal incidence of the probe beams, the relation between and remains un-altered all along the z axis as there are no plasma refraction effects deviating the beams. Substituting for the value of in equation (1), one gets equation (2).…”

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confidence: 99%

“…(2 ). Care has to be taken in choosing the sign of K 1 and K 2 appropriately in the above expression so as to make E 1 and E 2 positive.…”

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Determination of self generated magnetic field and the plasma density using Cotton Mouton polarimetry with two color probes

Joshi

2013

EPJ Web of Conferences

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Abstract. Self generated magnetic fields (SGMF) in laser produced plasmas are conventionally determined by measuring the Faraday rotation angle of a linearly polarized laser probe beam passing through the plasma along with the interferogram for obtaining plasma density. In this paper, we propose a new method to obtain the plasma density and the SGMF distribution from two simultaneous measurements of Cotton Mouton polarimetry of two linearly polarized probe beams of different colors that pass through plasma in a direction normal to the planar target. It is shown that this technique allows us to determine the distribution of SGMF and the plasma density without doing interferometry of laser produced plasmas.

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Megagauss Magnetic Field Profiles in Laser-Produced Plasmas

Cited by 160 publications

References 12 publications

Field Compressing Magnetothermal Instability in Laser Plasmas

Field Compressing Magnetothermal Instability in Laser Plasmas

MeasuringEandBFields in Laser-Produced Plasmas with Monoenergetic Proton Radiography

Determination of self generated magnetic field and the plasma density using Cotton Mouton polarimetry with two color probes

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