Using Nano-Structured Targets and Ultra-Intense Lasers for Nuclear Science and Source Development

Project Overview

Intense laser-pulse irradiation of targets constructed from nanostructured materials have been studied theoretically and empirically to understand the interactions of the laser with the unstructured materials and to understand and optimize their performance for fast neutron production and light-ion nuclear reactions in a high-energy-density plasma—both important needs of the Lab's nuclear-weapons-science mission-focus area. Initial studies have found that neutron production in nanofoams has been observed and indicates that either the volume of interaction between the hot electron flux and the nanofoam ligaments is quite small, O(1) µm3, or that pre-pulse induced density waves are altering the nanofoam structures adversely, prior to the hot-electron flux. In the case of nanowire targets, the initial studies were carried out using the NIF ARC laser, where the diagnostic signature studied was proton production, which is a suitable surrogate and allows better diagnostic coverage. These studies showed that the nanowires significantly increased electron production and high-energy proton production over traditional flat foil targets and most distinctively, at oblique angles of incidence of the irradiating laser.

Mission Impact

We are developing a platform to generate nuclear data in extremely hot, near-solid-density, plasma conditions, as well as intense, fast, neutrons sources. Both these efforts are aimed to provide support for the Lab's mission-focus areas, as well as basic science applications. By providing the next generation of ultra-short-pulse neutron sources suitable for radiography and nondestructive testing, this work is uniquely suited to the laboratory mission of nuclear-weapons stockpile stewardship. The results and scientific advances are exceptionally aligned with the HEDS core competencies. Neutron sources that are generated independently, with zero impact to optical damage of the main NIF laser system and that are time-independent of the NIF laser drive, represent a tool with capabilities difficult to overstate. This work supports our effort to develop these neutron sources on the NIF/ARC, under the discovery-science experiments allocation that our group has already been awarded.

Publications, Presentations, and Patents

Kemp, A. J., et al.. 2021. "Absorption of Relativistic Multi-Picosecond Laser Pulses in Wire Arrays." Phys. Plasmas, 28, 103102 (2021); doi: 10.1063/5.0061670.

Kemp, A. "Relativistic Multi-Picosecond Laser Pulses in Wire Arrays." Presentation, Meeting of American Physical Society, Division of Plasma Physics, Pittsburgh, PA. November 2021. LLNL-PRES-828425.

Cochran, G. "Neutron and Hot Electron Production in Nanofoam Targets Using Ultra-Intense Short Pulse Lasers." Abstract, Meeting of American Physical Society, Division of Plasma Physics, Pittsburgh, PA. November 2021.

Cochran, G. 2021. "Update on Nano-Structured Target Experiments." LASERNET Users Meeting. Virtual. August 2021.

Grim, G. "Generating Light Ion Nuclear Reactions Using Nano-Foam Structures Irradiated with Intense Short Pulse Lasers." 3rd Annual International Conference on Nuclear Photonics. Virtual. June 2021.

Cochran, G. "Hot Electron Flux Studies in Nanofoam Targets Using Ultra-Intense Short Pulse Lasers." 3rd Annual International Conference on Nuclear Photonics. Virtual. June 2021.

Grim, G. "Update on LLNL's Investment in Nuclear Science Using LaserNet Capabilities." Presentation to K. Akli, DOE Office of Fusion Energy Sciences, GPM, August 2021.