Implosion Experiments using Glass Ablators for Direct-Drive Inertial Confinement Fusion

Direct-drive implosions with 20-μm-thick glass shells were conducted on the Omega Laser Facility to test the performance of high-Z glass ablators for direct-drive, inertial confinement fusion. The x-ray signal caused by hot electrons generated by two-plasmon-decay instability was reduced by more than ~40× and hot-electron temperature by ~2× in the glass compared to plastic ablators at ignition-relevant drive intensities of ~1×10¹⁵ W/cm², suggesting reduced target preheat. The measured absorption and compression were close to $1D$ predictions. The measured soft x-ray production in the spectral range of ~2 to 4 keV was ~2× to 3× lower than $1D$ predictions, indicating that the shell preheat caused by soft x-rays is less than predicted. A direct-drive-ignition design based on glass ablators is introduced.