Observation of ultra-high energy density state with x-ray free electron laser SACLA

Abstract Typical inertial confinement fusion (ICF) plasmas have ultra-high energy density state (UHEDs) with an energy density exceeding 1×108 Jcm−3, which corresponds to a pressure of beyond 1 Gbar. In previous investigation, it is suggested that such an UHEDs condition could be generated with a tabletop ultrahigh intensity laser, by irradiating onto a nanowire array. In this research, we have developed to observe the laser energy absorption and transport mechanism in nanowire array samples with x-ray free electron laser facility SACLA. We obtained time-resolved snapshots of x-ray shadowgraph image with very high temporal resolution. From the measured images, however, the UHEDs might be generated only on very thin portion of the target surface because the mean density of the nanowire array was large. On the other hand, we observed significant rear surface expansion in late timing, suggesting that large laser energy deposition was achieved for the nanowire array samples.