Thomson scattering measurements in a laser heated THETA-pinch

Measurements of the interaction of CO2 laser radiation with a theta pinch plasma have been made using laser scattering as a diagnostic technique. Laser scattering is particularly suited for these types of measurements because the small observation volume with respect to the size of the plasma reduces problems of plasma temperature and density gradients. In addition the technique does not require the existence of local thermodynamic equilibrium for validity. Laser scattering theory is presented including a discussion of magnetic, collisional, quantum mechanical and relativistic effects. Design and construction of the scattering experiment are described along with measurements of the ruby and CO2 lasers. The plasma was heated axially with a TEA CO2 pin laser. A density minimum in the core of the plasma which was observed by image converter photographs resulted in light piping of the CO2 laser beam. The scattering measurements have shown the time evolution of the laser heated plasma during and after heating by the ''spike'' of the CO2 laser. The observation of a rapid temperature rise from 20,0000K to 39,0000K followed by an increase in plasma density from 1.5 x 1016 to 2.5 x 1016 electrons/ cm3 is shown to correlate with predictions of a theoretical plasma heating model. The energies involved in the change of plasma conditions agree well with the theoretical absorption associated with the inverse bremsstrahlung mechanism