Observation of LPI Thresholds for the Nike Laser*

The Nike laser is being used to study thresholds for laser plasma instabilities (LPI) at intensities (10$^{15}$-10$^{16}$ W/cm$^{2})$ relevant to advanced implosion designs for direct drive inertial confinement fusion. The combination of short wavelength (248 nm), large bandwidth (1-2 THz), and beam smoothing by induced spatial incoherence available with this krypton-fluoride laser make these experiments unique among current facilities. This talk will present an overview of results with an emphasis on the two-plasmon decay instability (2$\omega _{p})$. Measurements of x-rays and emission near $^{1}$/$_{2} \quad \omega _{o}$ and $^{3}$/$_{2}$ $\omega _{o}$ harmonics of the laser wavelength have been collected over a wide range of intensities for both solid and foam targets. Data indicate collective multiple-angle driven excitation compatible with previous observations using solid planar targets.