Model of Thomson scattering from z-pinch plasma: Application in experimental design for Plasma Focus

Abstract

The present work develops a model of Thomson scattering (TS) for z-pinch plasmas. Sustained on the phenomenology observed in dynamical-pinch discharges of interest in fusion studies, the plasma dynamics is modeled by axisymmetric bi-Maxwellian velocity distribution with axial and radial drift velocities. Expressions for TS form factor and screening integrals are deduced, and TS spectra are reconstructed. A characteristic temperature of the spectrum is identified, which is determined by a weighted-sum of the axial and radial temperatures, whose coefficients are given by the square of the respective axial and radial components of k→ over the square of the magnitude of k→. It is shown that it is not possible to determine the velocity distribution function of the plasma from just one direction of measurement. Additionally, an experimental setup, which requires two complementary observation directions for a complete determination of the proposed distribution function, is analyzed and its capacity to measure thermal anisotropy and drift velocities is studied for plasma conditions expected in the pinch phase of a plasma focus discharge.

Keywords

• Non-Maxwellian
• Bi-Maxwellian
• Anisotropy
• Drift velocity
• Velocity distribution
• Optical diagnostic