Behaviour of Laser-Produced Plasma in a Uniform Magnetic Field–Plasma Instabilities

Abstract

A nearly-cylindrical column of laser-produced plasma has been generated successfully in a uniform magnetic field. The radius of the column initially increases and then decreases (bouncing motion). In the vicinity of the outer surface of this plasma column, where there is a steep density gradient with scale length shorter than the local ion Larmor radius, an azimuthal modulation appears in the plasma luminosity. This is indicative of flute-like instability with the azimuthal wave number k ⊥∼4×103 B 0.8 (in MKSA units). The dispersion equation based upon the linearized Vlasov equation with the local approsimation is derived and the occurrence of the lower-hybrid-drift instability is predicted. Fairly good agreement is found between theory and experiment.

Large-Larmor-radius interchange instability

“…The instability wavelengths also do not appear to be a strong function of the magnetic field strength in contrast to Ref. 7. The flute amplitude grows rapidly after onset with a linear growth rate of about 10 8 s _1 as seen in Fig.…”

“…6 A previous laser-plasma experiment in a regime of moderate-sized ion Larmor radius also measured instability growth. 7 In this paper, we observe a robust interchangelike instability in the limit of very large ion Larmor radius. The instability exhibits a rapid linear phase with subsequent nonlinear free-streaming flutes and examples of density clumping, flute-tip bifurcation, and interesting late-time spirallike structures.…”

Confinement and re-expansion of laser induced plasma in transverse magnetic field: Dynamical behaviour and geometrical aspect of expanding plume

“…The plasma plume experiences the decelerating force and it expands until the displaced magnetic field reaches the maximum i.e. displaced magnetic energy balances the kinetic energy of the plasma plume [8,14].…”

“…[13]. Also several pioneer works related to the basic understanding of plasma plume-magnetic field interactions have been done with regard to the formation of diamagnetic cavity and flute like structures [14][15][16], plasma oscillations [17], edge instability and dramatic structuring [18,19], sub-Alfvenic plasma expansion [20] and laser plasma expansion in magnetized background [21].…”

“…Therefore, two different approaches have been made to explain the dynamics of laser produced plasma across the transverse magnetic field. In the first approach expansion of the plasma plume is treated as expansion in the diamagnetic limit where the applied electric field is displaced by the induced field due to diamagnetic current in plasma and the plasma plume experiences the decelerating force [2,8,14]. In the second approach, it is considered that external magnetic field is diffused in the plasma plume and produces polarized electric filed (due to the deflection of electrons and ions in opposite direction) perpendicular to both the expansion direction and the magnetic field [8,22,23].…”