Structure of an Exploding Laser-Produced Plasma

Abstract

We describe the first-ever volumetric, time-resolved measurements performed with a moving probe within an expanding dense plasma, embedded in a background magnetized plasma. High-resolution probe measurements of the magnetic field and floating potential in multiple 2D cut planes combined with a 1 Hz laser system reveal complex three-dimensional current systems within the expanding plasma. Static (ωreal=0) flutelike density striations are observed at the leading edge of the plasma, which are correlated to variations in the current layer at the edge of the expanding plasma.

Fast gated imaging of the collisionless interaction of a laser-produced and magnetized ambient plasma

“…In the xy plane, these instabilities are visible as fingers or flutes pointing radially outward. The flutes grow exponentially with a growth rate of 6 × 10 6 s −1 (measured frame-by-frame in the xy plane), consistant with the large Larmor radius limit of the Rayleigh-Taylor instability [18,8]. The flutes reach their maximum extent by 500 ns, then are visible for a further several hundred nanoseconds before they dissipate by 800 ns.…”

“…Fast-gated fluorescence imaging is a non-invasive diagnostic technique that captures a 2D image of plasma self-emission over a short (< 10 ns) exposure period [7,8]. Since self-emission intensity is dependent on the plasma density, these images provide some information about the density distribution.…”

Dynamics of exploding plasmas in a large magnetized plasma

“…Numerous experiments of this type have been performed previously at the LAPD, using smaller lasers with energies around 1 J but higher shot-rates. [16][17][18][19][20] Those experiments have investigated the plasma diamagnetism in the presence of the ambient plasma, 9 discovered that shear-Alfv en waves 16 and whistlers 19 are emitted from the laser-plasma plume, and have produced colliding laser-plasmas with relevance to magnetic reconnection. 18 The experiments described here employ a laser-pulse that contains two-orders of magnitude higher energy at intensities three orders of magnitude higher, and extend earlier work to the super-Alfv enic regime with significantly stronger coupling between the laser and the ambient plasma.…”

An exact solution of the moving boundary problem for the relativistic plasma expansion in a dipole magnetic field

“…For instance, an important example is the expansion of a plasma cloud with a sharp boundary across an ambient magnetic field. Such kind of processes are particularly of interest for many space and laboratory investigations (see [5][6][7][8][9] and references therein). This is a topic of intense interest across a wide variety of disciplines within plasma physics, with applications to laser generated plasmas [9], solar [10] a e-mail: hrachya@irphe.am and magnetospheric [11,12] physics, astrophysics [13], and pellet injection for tokamak refueling [14].…”