Ramp-Wave Compression Experiment with Direct Laser Illumination on ShenGuang-III Prototype Laser Facility

Ramp-wave compression experiment to balance the high compression pressure generation in aluminum and x-ray blanking effect in transparent window is demonstrated with an imaging velocity interferometer system for any reflector (VISAR) on ShenGuang-III prototype laser facility. The highest pressure is about 500 GPa after using the multilayer target design Al/Au/Al/LiF and $\sim$ 10¹³ W/cm² laser pulse illuminated on the planar Al target, which generates the spatial uniformity to $<1\%$ over 500 μm on the ablation layer. A 2-μm-thick Au layer is used to prevent the x-ray from preheating the planar ablation Al layer and window material LiF. The imaging VISAR system can be used to record the abrupt loss of the probe beam ( $\lambda =532$ nm) caused by absorption and reflection of 20-μm, 30-μm and 40-μm-thick Al, i.e., the blanking effect. Although there are slight shocks in the target, the peak pressure 500 GPa, which is the highest data up to now, is obtained with ramp-wave compression. (paper)