Extended-magnetohydrodynamics in under-dense plasmas

Walsh, C. A.; Chittenden, J. P.; Hill, D.; Ridgers, C. P.

doi:10.1063/1.5124144

Cited by 47 publications

(56 citation statements)

References 31 publications

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“…The simulations were run without the convection of magnetic field by heat flow (the Nernst effect). In general 71 – 73 , thermally-driven magnetic field transport occurs both perpendicular to the magnetic field at the Nernst velocity and perpendicular to both the magnetic field and the temperature gradient at the Nernst-cross-field velocity where are the components of the thermoelectric tensor 74 , 75 . Nernst advection dominates over the cross-field advection at low magnetization, while the opposite is true for .…”

Section: Methodsmentioning

confidence: 99%

Enhanced X-ray emission arising from laser-plasma confinement by a strong transverse magnetic field

Filippov

Makarov

Burdonov

et al. 2021

Sci Rep

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We analyze, using experiments and 3D MHD numerical simulations, the dynamic and radiative properties of a plasma ablated by a laser (1 ns, 10$$^{12}$$ 12 –10$$^{13}$$ 13 W/cm$$^2$$ 2 ) from a solid target as it expands into a homogeneous, strong magnetic field (up to 30 T) that is transverse to its main expansion axis. We find that as early as 2 ns after the start of the expansion, the plasma becomes constrained by the magnetic field. As the magnetic field strength is increased, more plasma is confined close to the target and is heated by magnetic compression. We also observe that after $$\sim 8$$ ∼ 8 ns, the plasma is being overall shaped in a slab, with the plasma being compressed perpendicularly to the magnetic field, and being extended along the magnetic field direction. This dense slab rapidly expands into vacuum; however, it contains only $$\sim 2\%$$ ∼ 2 % of the total plasma. As a result of the higher density and increased heating of the plasma confined against the laser-irradiated solid target, there is a net enhancement of the total X-ray emissivity induced by the magnetization.

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Section: Methodsmentioning

confidence: 99%

Enhanced X-ray emission arising from laser-plasma confinement by a strong transverse magnetic field

Filippov

Makarov

Burdonov

et al. 2021

Sci Rep

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show abstract

“…The significant kinetic effects on the Biermann battery provide motivation to validate our modelling with experiment. We have proposed a simple experiment where a ns pulse length laser of intensity ∼10 14 W cm −2 heats an underdense gas (electron density ∼10 19 cm −3 ) similar to previous experiments [ 2 , 31 ] (and suggested experiments [ 32 ]). Synthetic proton radiography shows that such an experiment can demonstrate the inaccuracy of MHD modelling of the Biermann battery when a thermal flux limiter is used, although the direct effect of the distortion of the electron distribution function is smaller and so harder to observe, requiring a proton radiography set-up at the limit of size that could be fielded experimentally for sufficient magnification (though measurement of the indirect effect would not require such a high magnification).…”

Section: Discussionmentioning

confidence: 62%

The inadequacy of a magnetohydrodynamic approach to the Biermann battery

Ridgers

Arran

Bissell

et al. 2020

Phil. Trans. R. Soc. A.

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Magnetic fields can be generated in plasmas by the Biermann battery when the electric field produced by the electron pressure gradient has a curl. The commonly employed magnetohydrodynamic (MHD) model of the Biermann battery breaks down when the electron distribution function is distorted away from Maxwellian. Using both MHD and kinetic simulations of a laser-plasma interaction relevant to inertial confinement fusion we have shown that this distortion can reduce the Biermann-producing electric field by around 50%. More importantly, the use of a flux limiter in an MHD treatment to deal with the effect of the non-Maxwellian electron distribution on electron thermal transport leads to a completely unphysical prediction of the Biermann-producing electric field and so results in erroneous predictions for the generated magnetic field. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 2)’.

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“…The final form of the induction equation is therefore composed only of an advection term, a diffusion term, the resistivity gradient term and two source terms that are still active even when B = 0 [9], right left right left right left right left right left right left3pt0.278em 2em 0.278em 2em 0.278em 2em 0.278em 2em 0.278em 2em 0.278em∂B∂t=∇×(bolduboldB×B)+η0normal∇2B−∇η0×(∇×B)−∇ne×∇Tenee+β0normal′(Z~)e∇Z~×∇Te. The first term causes advection of the magnetic field at velocity u B , although it has no effect when the advection is along the field line. The field advection velocity is given by uB=boldu−false(1+δ⊥false)Jnee+δ∧boldJ×<...>…”

Section: Discussionmentioning

confidence: 99%

Magnetic field generation from composition gradients in inertial confinement fusion fuel

Sadler

Flippo

2020

Phil. Trans. R. Soc. A.

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Experimental asymmetries in fusion implosions can lead to magnetic field generation in the hot plasma core. For typical parameters, previous studies found that the magnetization Hall parameter, given by the product of the electron gyro-frequency and Coulomb collision time, can exceed one. This will affect the hydrodynamics through inhibition and deflection of the electron heat flux. The magnetic field source is the collisionless Biermann term, which arises from the Debye shielding potential in electron pressure gradients. We show that there is an additional source term due to the Z dependence of the Coulomb collision operator. If there are ion composition gradients, such as jets of carbon ablator mix entering the hot-spot, this source term can rapidly exceed the Biermann fields. In addition, the Biermann fields are enhanced due to the increased temperature gradients from carbon radiative cooling. With even stronger self-generated fields, heat loss to the carbon regions will be reduced, potentially reducing the negative effect of carbon mix. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 1)’.

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Extended-magnetohydrodynamics in under-dense plasmas

Cited by 47 publications

References 31 publications

Enhanced X-ray emission arising from laser-plasma confinement by a strong transverse magnetic field

Enhanced X-ray emission arising from laser-plasma confinement by a strong transverse magnetic field

The inadequacy of a magnetohydrodynamic approach to the Biermann battery

Magnetic field generation from composition gradients in inertial confinement fusion fuel

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