Visualization of ultrafast melting initiated from radiation-driven defects in solids

Abstract

Materials exposed to extreme radiation environments such as fusion reactors or deep spaces accumulate substantial defect populations that alter their properties and subsequently the melting behavior. The quantitative characterization requires visualization with femtosecond temporal resolution on the atomic-scale length through measurements of the pair correlation function. Here, we demonstrate experimentally that electron diffraction at relativistic energies opens a new approach for studies of melting kinetics. Our measurements in radiation-damaged tungsten show that the tungsten target subjected to 10 displacements per atom of damage undergoes a melting transition below the melting temperature. Two-temperature molecular dynamics simulations reveal the crucial role of defect clusters, particularly nanovoids, in driving the ultrafast melting process observed on the time scale of less than 10 ps. These results provide new atomic-level insights into the ultrafast melting processes of materials in extreme environments.

Ultrafast Imaging of Molecular Dynamics Using Ultrafast Low-Frequency Lasers, X-ray Free Electron Lasers, and Electron Pulses

“…Nonthermal melting for aluminum and bismuth as well as the formation of warm dense matter in gold are explored with keV-UED patterns by analyzing intensities and the pair correlation function (PCF). Another visualization for melting via UED happens on 30 nm-thick polycrystalline tungsten films with highly populated defects caused by an extreme radiation environment which also confirms the molecular dynamic simulation for ultrafast melting . Ultrafast electronic and lattice dynamics in materials undergoing charge density wave (CDW) phase transition, which are ideal model systems for the study of highly cooperative phenomena caused by interactions among electrons, phonons, and spins on the nanoscale, are also observed by UED.…”

Sub-micron thick liquid sheets produced by isotropically etched glass nozzles

“…In HED science, targets have typically been solid state with very carefully prepared surfaces. 6 These targets are heated and compressed by optical absorption of high-intensity laser pulses. Surface roughness plays a role in absorption and surfaces that are optically smooth or better are desired.…”

Inclusion of Energy Loss in Models of Laser-Irradiated Gold Films via Classical Molecular Dynamics

“…These transient states occur during the formation of all high energy density plasmas, also known as warm dense matter (WDM), with particular relevance to laser micromachining [4][5][6][7] and inertial confinement fusion experiments [8]. In the laboratory, these transient states serve as a testbed where quantum mechanical theories of electron-ion interactions, nuclei dynamics, and phase transitions can be validated [9][10][11][12].…”