Kinetics of the Collisionless Expansion of Spherical Nanoplasmas

Abstract

The collisionless expansion of spherical plasmas composed of cold ions and hot electrons is analyzed using a novel kinetic model, with special emphasis on the influence of the electron dynamics.Simple, general laws are found, relating the relevant expansion features to the initial conditions of the plasma, determined from a single dimensionless parameter. A transition is identified in the behavior of the ion energy spectrum, which is monotonic only for high electron temperatures, otherwise exhibiting a local peak far from the cutoff energy.

Modeling laser wakefield accelerator experiments with ultrafast particle-in-cell simulations in boosted frames

“…OSIRIS is a fully relativistic, electromagnetic, and massively parallel PIC code that has been extensively used in LWFA simulations, 6,15,16,21,22 but also in astrophysical scenarios, [23][24][25] nanoplasma dynamics, 26 and fast ignition. 27,28 The framework includes an advanced visualization infrastructure for fast data display, analysis, and postprocessing.…”

Ergodic model for the expansion of spherical nanoplasmas

“…[18], the SPE approach provides excellent results for the expansion of a spherical plasma in a wide range of the parameter T 0 . There is a number of reasons to explain its success, even though it is not easy to quantify their relative importance.…”

“…Figure 1 shows the evolution of the electronic charge contained within the ion sphere, for the representative low-temperature ( T 0 = 7.2×10 −3 ) and high-temperature ( T 0 = 7.2×10 −2 ) cases of Ref. [18], as obtained with the pure VP model (ν = 0) and with the collisional model, Eq. (9), (using ν = ω pe ).…”

“…(11)- (14), as follows [18]. A Lagrangian approach can be used both for the ions (which move in radial direction, starting from the initial position r 0 , with zero velocity) and for the electrons (whose energy ǫ evolves in time starting from the initial value ǫ 0 ), by determining the ions trajectories r i (r 0 , t), the electron energies ǫ (ǫ 0 , t), the ion density n i (r, t), the electron density n e (r, t), the electron energy distributions ρ e (ǫ, t), and the potential Φ (r, t) according to the set of equations…”

“…Recently, the Authors presented a kinetic analysis of the collisionless expansion of spherical plasmas driven by hot electrons, based on a peculiar ergodic model, which accounts for the radial motion of the ions and for the three-dimensional motion of nonrelativistic electrons [18]. In the present paper, the model is derived in detail, and its validity is tested against reference solutions of the full VP equations (here obtained using ad-hoc numerical techniques).…”