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

TL;DR

This study investigates how the geometry of conical wire arrays influences plasma jet properties using advanced optical diagnostics, revealing that cone angle significantly affects jet velocity but not temperature or density profiles.

Contribution

It provides new insights into how conical wire array geometry controls plasma jet velocity, with detailed measurements of temperature and density profiles using Thomson scattering and optical techniques.

Findings

Jet electron temperatures range from 8 to 17 eV, increasing along the jet.

Ion temperature decreases from 35 eV to 20 eV along the jet.

Larger cone angles produce higher axial jet velocities.

Abstract

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 moir\'e 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_{\phi=40^\circ} \approx 125\pm3$ km/s, $V_{\phi=20^\circ} \approx 98\pm5$ km/s), demonstrating that the cone geometry provides effective control over the jet propagation velocity.