Free space Thomson scattering to study high energy density shocks

Area of Science:

• Plasma Physics
• Pulsed Power Science
• Diagnostic Techniques

Background:

• Traditional Thomson scattering diagnostics use fiber optics, limiting spatial resolution.
• Pulsed power plasmas require advanced diagnostics for accurate characterization.
• Free space coupling offers potential for improved spatial imaging of plasmas.

Purpose of the Study:

• To develop and demonstrate a free space collective Thomson scattering system for pulsed power plasmas.
• To enable spatially continuous imaging of plasma characteristics.
• To measure plasma flow velocity and investigate plasma phenomena like bow shocks.

Main Methods:

• Developed a free space collective Thomson scattering diagnostic system.
• Coupled scattered light from plasma to spectrometer via free space, not fibers.
• Performed initial experiments on inverse wire array plasmas generated by a 200 kA pulse power generator.
• Utilized low frequency ion acoustic wave features in Thomson scattering spectra to determine plasma flow velocity.

Main Results:

• Achieved spatially continuous plasma imaging.
• Successfully measured plasma flow velocities ranging from 20 to 40 km/s.
• Demonstrated velocity measurement accuracy of 4.7 km/s at 600 μm resolution and 8.9 km/s at 150 μm resolution.
• Observed a bow shock in plasma flow, correlating with increased scattering intensity and decreased velocity.

Conclusions:

• The free space Thomson scattering system is a viable diagnostic for pulsed power plasmas.
• The diagnostic provides high spatial resolution and accurate velocity measurements.
• The system successfully identified complex plasma structures, such as bow shocks, offering new insights into plasma dynamics.