arXiv subjects

Gonzalo Avaria

Publications and source records attributed to Gonzalo Avaria.

3 recordsLinked to original sources

arXiv2025

Influence of Conical Wire Array Geometry on Flow and Temperature Profiles Measured via Thomson Scattering and Optical Techniques

Conical wire arrays with different opening angles are used as load of a 400kA, 1kA/ns generator. The differences in opening angle allow the study of the influence of the array geometry on the jet properties. The characterization of the jets is performed using a combination of advanced diagnostic techniques, including moiré schlieren deflectometry, visible self-emission spectroscopy, and optical Thomson scattering. The results reveal that, under the experimental conditions, the plasma jets exhibit electron temperatures ranging from $8$ to $17$ eV, increasing along the axial direction. In contrast, the ion temperature decreases from approximately $35$ eV near the base of the jet to about $20$ eV at higher axial positions. The electron density profile peaks at $\sim 4 \times 10^{18}$ cm$^{-3}$ in the central lower region of the jet and decreases with height exponentially with a characteristic lenght $L_n = $2.86 mm. This behavior is reproducible and independent of the conical array geometry. However, the cone opening angle significantly affect the jet propagation velocity, with larger opening angles producing higher axial velocities ($V_{ϕ=40^\circ} \approx 125\pm3$ km/s, $V_{ϕ=20^\circ} \approx 98\pm5$ km/s), demonstrating that the cone geometry provides effective control over the jet propagation velocity.

physics.plasm-ph↗

arXiv2023

Kappa distribution from particle correlations in non-equilibrium, steady-state plasmas

Kappa-distributed velocities in plasmas are common in a wide variety of settings, from low-density to high-density plasmas. To date, they have been found mainly in space plasmas, but are recently being considered also in the modelling of laboratory plasmas. Despite being routinely employed, the origin of the kappa distribution remains, to this day, unclear. For instance, deviations from the Maxwell-Boltzmann distribution are sometimes regarded as a signature of the non-additivity of the thermodynamic entropy, although there are alternative frameworks such as superstatistics where such an assumption is not needed. In this work we recover the kappa distribution for particle velocities from the formalism of non-equilibrium steady-states, assuming only a single requirement on the dependence between the kinetic energy of a test particle and that of its immediate environment. Our results go beyond the standard derivation based on superstatistics, as we do not require any assumption about the existence of temperature or its statistical distribution, instead obtaining them from the requirement on kinetic energies. All of this suggests that this family of distributions may be more common than usually assumed, widening its domain of application in particular to the description of plasmas from fusion experiments. Furthermore, we show that a description of kappa-distributed plasma is simpler in terms of features of the superstatistical inverse temperature distribution rather than the traditional parameters $κ$ and the thermal velocity $v_{\text{th}}$.

cond-mat.stat-mech↗

arXiv2019

Single-particle velocity distributions of collisionless, steady-state plasmas must follow Superstatistics

The correct modelling of velocity distribution functions for particles in steady-state plasmas is a central element in the study of nuclear fusion and also in the description of space plasmas. In this work, a statistical mechanical formalism for the description of collisionless plasmas in a steady state is presented, based solely on the application of the rules of probability and not relying on the concept of entropy. Beck and Cohen's superstatistical framework is recovered as a limiting case, and a "microscopic" definition of inverse temperature $β$ is given. Non-extensivity is not invoked a priori but enters the picture only through the analysis of correlations between parts of the system.

cond-mat.stat-mech↗