Optimized x-ray emission from 10ns long germanium x-ray sources at the National Ignition Facility.

Abstract

This study investigates methods to optimize quasi-monochromatic, ∼10ns long x-ray sources (XRS) for time-resolved x-ray diffraction measurements of phase transitions during dynamic laser compression measurements at the National Ignition Facility (NIF). To support this, we produce continuous and pulsed XRS by irradiating a Ge foil with NIF lasers to achieve an intensity of 2 × 1015 W/cm2, optimizing the laser-to-x-ray conversion efficiency. Our x-ray source is dominated by Ge He-α line emission. We discuss methods to optimize the source to maintain a uniform XRS for ∼10ns, mitigating cold plasma and higher energy x-ray emission lines.