High-energy Kα radiography using high-intensity, short-pulse lasers

TLDR

High‑energy Kα x‑ray sources from 100‑TW to petawatt lasers are being developed to enable radiography of high‑Z, dense materials in high‑energy‑density experiments, and future work also requires suitable imaging detectors and diagnostics. The study aims to develop and implement workable radiography solutions using high‑energy Kα x‑ray sources from high‑intensity lasers to probe high‑Z and dense materials in high‑energy‑density experiments. The authors measured the characteristics of 22–40 keV Kα sources and tested small‑volume 2‑D point sources (cones, wires, embedded wires), measuring photon yields and comparing them with hybrid‑PIC simulations. Measurements revealed that the Kα source size exceeds 60 μm, making it unsuitable for most radiography, that yield is independent of target thickness due to refluxing, that smaller radiating volumes produce brighter radiation, and that one‑dimensional radiography with small‑edge‑on foils resolved 10 μm features with high contrast, while preliminary detector studies were also presented.

Abstract

The characteristics of 22–40keV Kα x-ray sources are measured. These high-energy sources are produced by 100TW and petawatt high-intensity lasers and will be used to develop and implement workable radiography solutions to probe high-Z and dense materials for the high-energy density experiments. The measurements show that the Kα source size from a simple foil target is larger than 60μm, too large for most radiography applications. The total Kα yield is independent of target thicknesses, verifying that refluxing plays a major role in photon generation. Smaller radiating volumes emit brighter Kα radiation. One-dimensional radiography experiments using small-edge-on foils resolved 10μm features with high contrast. Experiments were performed to test a variety of small volume two-dimensional point sources such as cones, wires, and embedded wires, measured photon yields, and compared the measurements with predictions from hybrid-particle-in-cell simulations. In addition to high-energy, high-resolution backlighters, future experiments will also need imaging detectors and diagnostic tools that are workable in the high-energy range. An initial look at some of these detector issues is also presented.