High-energy x-ray source generation by short-pulse high-intensity lasers

Abstract

ABSTRACT We are studying the feasibility of utilizing K D x-ray sources in the range of 20 to 100 keV as a backlighters for imagingvarious stages of implosions and high aerial density pl anar samples driven by the NIF laser facility. The hard x-ray K Dsources are created by relativistic electron plasm a interactions in the targ et material after a radiation by short pulse highintensity lasers. In order to understand KD source characteristics such as production efficiency and brightness as a function of laser parameters, we have performed ex periments using the 10 J, 100 fs JanUSP laser. We utilized single-photon counting spectroscopy and x-ray imaging diagnostics to characterize the KD source. We find that the KDconversion efficiency from the laser energy at 22 keV is ~3 x 10 -4 .Keywords: Short pulse laser, K D source, backlighter INTRODUCTION X-ray radiography using back lighter sources has been an important tool for diagnosing and imaging various stages oflaser induced implosion. Until now, implosion experiments at Omega utilize <9 keV backlighter x-rays emitted bythermal plasmas generated from a target material. However, the larger and denser NIF targets will need an x-ray probewith energies of 20 to 100 keV to study their hydrodynam ics, atomic structure, equations -of-state, and other properties.An efficient high-energy x-ray radiograp hy source can be created using an ultra-high-intensity laser, which produceshigh-energy non-thermal x-rays from interactions bet ween relativistic electrons and cold target atoms. These electronsproduce K D fluorescence emission in any mid-t o-high Z solid, and these 20-100 keV x-rays can be used as semi-monoenergetic backlight sources for rad iography. The construc tion of a multi-kJ, 1-10 ps Petawatt laser at the NIF is plannedfor generating adequate 20-100 keV x-rays for high-energy x -ray radiography applications.However, we do not currently have a va lidated model that predicts x-ray source parameters for experimental conditionsof interest. Previous experiments