Absolute X-Ray Yields From Laser-Irradiated, Ge-Doped Aerogel Targets

Bright, multi-keV x-ray sources are essential for radiography of inertial-confinement fusion (ICF) experiments. In this context, there are two parameters of importance: the energy of the emitted photons, which determines how penetrating the x-rays are for radiographic purposes, and the brightness of the source, which determines the ability of a radiograph to resolve small features. As ICF experiments continue to get larger, such as those that will be carried out at the National Ignition Facility at Lawrence Livermore National Laboratory, or at the French Commissariat a l'Energie Atomique's (CEA) Laser MegaJoule, and compression in fuel capsules gets higher, sources for x-ray backlighting will have to have harder-photon spectra. For a given laser energy available to drive the multi-keV x-ray-backlight source, the only way for the source to get brighter is for it to convert the laser to x-rays more efficiently. We have been developing and characterizing laser-driven, underdense x-ray sources that are highly efficient in recent years [2-5]. CEA researchers have also recently had great success efficiently making multi-keV x-rays from pre-pulsed foils [6]