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Trident Home: Techniques |
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Laser Driven Dynamic Loading of Condensed Matter & Related DiagnosticsDynamic materials experiments over a wide range of strain rates are essential to studying constitutive relations (e.g., plasticity), damage (e.g., spall), equations of state, phase transitions and kinetics, and novel materials. The Trident laser facility supplies unique, efficient and versatile loading techniques and a suite of temporally and spatially resolved diagnostics. Laser-launched flyer plate, confined ablation and free ablation can induce supported shock, Taylor-wave, isentropic or off-Hugoniot loading with a strain rate of 104-108 s-1 and a peak stress of 1-500 GPa. Routine diagnostics at Trident include point and line-imaging velocimeters (VISAR) for particle velocity history measurement, and transient imaging displacement interferometer (TIDI) for 2D out-of-plane displacement field measurement. These diagnostics record data with high speed photomultiplier tubes, and streak and frame cameras. The velocity-per-fringe of these VISARs ranges from 80 m s-1 to 5 km s-1. The spatial resolution of the line-imaging VISAR is about 25 microns. The Greenfield TIDI has a 6 micron spatial resolution and 10 nm displacement resolution, and an inter-frame separation of 6 ns – 50 ns or higher.
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(a) Particle velocity history of Cu(100) impacted by a Cu(100) flyer plate from VISAR measurements, showing well defined elastic precursor, supported shock, quasielastic release, and spall pullback. (b) An example of TIDI measurements: 2D out-of-plane displacement field of shocked multicrystalline Cu which correlates well with grain boundaries. (c) A cross-section of 3D X-ray tomography of shock-spalled Be. (d) A novel carbon cage structure formed via laser-shock loading of graphite. |
Other diagnostics include transient X-ray diffraction (TXD) for temporally resolved diffraction measurements, multi-color pyrometry for temperature measurement, and ellipsometry for optical properties measurement. All these diagnostics allow for investigating dynamic material response at multiple spatial and temporal scales. Since these laser-based loading techniques involve small or negligible momentum transfer and collateral damage to the target, shock recovery is readily achievable even for such brittle materials as Be, and post-mortem metallurgical examinations can be performed with advanced in-house analytical techniques, or at synchrotron and neutron sources.
Contacts Shengnian Luo |
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