Rear Surface Light Emission Measurements from Laser-produced Shock Waves in Clear and Al-coated Polystyrene Targets

The Nike KrF laser, with its very uniform focal distributions, has been used at intensities near 1014 W/cm2 to launch shock waves in polystyrene targets. The rear surface visible light emission differed between clear CH targets and targets with a thin (125 nm) Al coating on the rear side. The uncoated CH targets showed a relatively slowly rising emission followed by a sudden fall when the shock emerges, while the Al-coated targets showed a rapid rise in emission when the shock emerges followed by a slower fall -allowing an unambiguous determination of the time the shock arrived at the rear surface. A half-aluminized target allowed us to observe this difference in a single shot. The brightness temperature of both the aluminized targets and the non-aluminized targets were slightly below but close to rear surface temperature predictions of a hydrodynamic code. A discussion of preheat effects is given. PACS: 52.50.Lp; 62.50+p; 52.50Jm; 52.70.Kz