HPCAT: Looking Forward

1. Time-dependent transformations & off-Hugoniot processes The scientific understanding of the dynamics of chemical and structural transitions can be dramatically advanced through the development of time-resolved x-ray diagnostics integrated with a variety of impulsive drives (pressure, temperature, photons, field) or pump-probe measurements. These advances will broadly address dynamic processes including reaction chemistry, phase changes, material performance, technological material synthesis, and basic science. HPCAT: Looking Forward geoscience Time-resolved chemical/structural changes Material synthesis Catalysis mechano-, photo- pressure-, thermal- Material performance

2. Time-dependent transformations & off-Hugoniot processes Strain rate HPCAT: Looking Forward 102 105 109 1/s Quasistatic, MTS, piezodevice Kolsky bar Gas gun, explosives Laser s-ms 100 ms 100 ns-msfs-ns HPCAT HPCAT HPCAT as a complementary venue for time-resolved measurements to DCS and LCLS; opening to any new ideas.

3. Coherent x-ray diffraction imaging, W. Yang et al. A case: Void growth Molecular dynamics, Luo et al. • CDI: individual voids • SAXS and WAXS to cover sufficient q range: statistics of voids. Helium chamber SAX + WAX (medium E) WAX + SAX (high E) Sector 1

4. Priority Research Directions and scientific challenges • PRD: Pulsed P/T/photon/EM field induced structural/chemical changes and dynamics • Non-equilibrium transformations and “equilibrium” phase boundary, e.g., superheating/supercooling, over-/under-pressurization. • A wide variety of materials, hard/soft materials including proteins, and processes. • Nano-, microscale microstructure interactions and evolution • Scientific challenges: • Atomic rearrangement: lattice structure and interface (scattering/imaging), including nanomaterials. • Valance (XEAFS); spin (e.g., domain walls); photon, electron, spin, phonon interactions; chemistry (spectroscopy). • Complementary physical properties: mechanical, electrical, magnetic, transport… • Dynamics/kinetics for thermo-mechano-chemical pathways: phonons, phase changes, chemical reactions, plasticity (loading, and detection). HPCAT: Looking Forward

5. Experimental Capabilities • Diagnostics techniques: spatially/temporally resolved scattering/diffraction, imaging, spectroscopy measurement, others. • CDI; XANES tomography (composition and microstructure). • X-ray sources • Spatially coherent + monochromatic; high flux; focused and unfocused beams. • Time structure: 100 ps (time resolution limit); repetition rate (4 APS modes). • Pulsed loading: P/T/photons/electromagnetic field • Synchronization of loading, X-ray pulses and detectors. • IR, UV lasers; fs laser. • Detectors • High speed: gating (single pulse), and framing (exposure time 100s ns to ms) • Large area for diffraction. • Direct and indirect x-ray detection; indirect, scintillators. • Software • Timing, loading, and detector controls. • Big data processing: storage, transfer, and processing, including physics and data mining. • Offline capabilities. HPCAT: Looking Forward

6. Technical challenges • X-ray sources • Tunable, high flux, monochromatic light (radiation damage). • Shorter pulses would be better (1 ps vs. 100 ps). • Detectors • High speed: gating (single pulse), and framing (exposure time 100s ns to ms) • Large area for diffraction. • Direct and indirect x-ray detection; indirect, fast and efficient scintillators; point spread function. • Loading: exact loading/unloading conditions, e.g., stress/T field? • Synchronization of loading, X-ray pulses and detectors; sensor/detector damage. • Software • Timing, loading, and detector controls. • Big data processing: storage, transfer, and processing, including physics and data mining. • A learning curve: acquisition of knowledge and experience. HPCAT: Looking Forward

7. Contributors • W. Evans and S. Luo (chairs) • M. Armstrong (panelist) • J.-Y. Chen (panelist) • E. Chronister (panelist) • D. Hooks (panelist) • N. Velisavljevich (panelist) • W. Yang (panelist) • G. Boman • Y. Gupta • S. Gramsch • D. Funk • T. Sekine • Many others HPCAT: Looking Forward

8. Nanoscale interactions • Use low angle scattering/imaging to characterize the evolution of nanoscale material distributions in time and space upon rapid heating or compression • Nanoscale mixing kinetics/chemistry • Quench/passivate nanoparticles for recovery at room pressure • Characterize defect migration under dynamic conditions HPCAT: Looking Forward Scientific challenges Technical challenges • How can nucleation at the nanoscale be controlled by pressure? • How do surface chemistry and grain boundary interactions depend on pressure? • Difficult to observe nanoscale material dynamics under a wide variety of initial conditions • Requires precise control and characterization of the thermodynamic state

10. Non-equilibrium transformations • Characterize the formation of materials in non-equilibrium situations • Coherent chemistry • Very rapid quench • Anisotropic chemistry • Non-thermal kinetic energy distribution HPCAT: Looking Forward Scientific challenges Technical challenges • Is it possible to find higher yield/cheaper synthesis methods using non-equilibrium phenomena? • Is it possible to recover previously unknown metastable materials? • Where to start? Potential synthesis methods are difficult to evaluate to estimate chances of success. Need to formulate some general principles

11. Time-resolved structural changes associated with µm-scale chemical/physical changes • chemical and structural changes in photo-mechanical microcrystals, • kinetics of: a) polymorphic crystalline phase changes, b) photo-mechanical changes, and c) mechano-chemistry, d) protein folding kinetics, • initiation by microsecond (or submicrosecond) dynamic pressure. HPCAT: Looking Forward Scientific challenges Technical challenges Time and Spatial constraints: • ms or sub-ms time resolution • 10mm scale samples • ms or sub-ms dynamic pressure Structural changes in: • macromolecules • crystal structure • crystalline disorder

12. Phase/Chemical Transition Dynamics Time-resolved diffraction and imaging studies Super-compressed liquid HPCAT: Looking Forward Solid time-> Scientific challenges Technical challenges • Develop an understanding of the dynamics of phase transitions: • Microscopic (nucleation) • Macroscopic (growth) • Influence of compression rate • Microstructure evolution • adequate flux • High-speed, high-efficiency, high-resolution detectors • process/analyze large data sets • drives (dDAC, laser, explosive, strain,…) with micro-positioning • X-ray beam with variable focus (sub-micron to mm’s) • Tunable energy to match experiment • Large adaptable experimental bay

13. Time-dependent evolution of microstructure • Time resolved structural evolution • Variables: pressure, temperature, strain, particle size, phase … • Diagnostic Methods: • Time resolved optical properties, x-ray diffraction, imaging, spectroscopy, • transport property HPCAT: Looking Forward Scientific challenges Technical challenges • Atomic rearrangement • Charge transfer • Spin transition • Kinetics • Pressure/temperature vs. Time • order/disorder • Recrystallization • Chemical reaction/dissociation • Fast and high sensitive detector • High probing flux, but radiation damage • Pump-probe • Stability and repeatability • Transport property in line with shock, pump probe • Fast acquisition vs. S/N ratio