Photonuclear Physics when a Multiterawatt Laser Pulse Interacts with Solid Targets

TLDR

A 10^19 W cm⁻² laser pulse striking solid targets generates tens‑of‑MeV electrons. In tantalum, these electrons produce a highly directional gamma‑ray beam that drives photonuclear reactions. The VULCAN laser produced (γ,n) isotopes such as 11C, 38K, 62/64Cu, 63Zn, 106Ag, 140Pr, 180Ta, demonstrated laser‑induced fission of 238U, and enabled shot‑by‑shot temperature diagnostics via 11C/62Cu beta+ activity ratios.

Abstract

When a laser pulse of intensity 10(19) W cm(-2) interacts with solid targets, electrons of energies of some tens of MeV are produced. In a tantalum target, the electrons generate an intense highly directional gamma-ray beam that can be used to carry out photonuclear reactions. The isotopes 11C, 38K, (62,64)Cu, 63Zn, 106Ag, 140Pr, and 180Ta have been produced by (gamma,n) reactions using the VULCAN laser beam. In addition, laser-induced nuclear fission in 238U has been demonstrated, a process which was theoretically predicted at such laser intensities more than ten years ago. The ratio of the 11C and the 62Cu beta(+) activities yields shot-by-shot temperatures of the suprathermal electrons at laser intensities of approximately 10(19) W cm(-2).