About

June Wicks is an Assistant Professor in the Department of Earth & Planetary Sciences at Johns Hopkins University. Her research interests include planetary interiors and evolution, building equation of state and phase diagram models of matter at extreme conditions, and the kinetics of phase transitions at extreme conditions. She holds a PhD from Caltech in Earth & Planetary Sciences. June also has a joint appointment in the Department of Mechanical Engineering at Johns Hopkins University.

Research topics

• Geology
• Physics
• Seismology
• Paleontology
• Materials science
• Geodesy
• Metallurgy
• Thermodynamics
• Oceanography
• Geophysics
• Composite material
• Quantum mechanics

Selected publications

• Application of ultrafast x-ray lasers in studying the material structure under shock compression

  Journal of Applied Physics · 2025-02-21

  articleOpen accessSenior author

  For more than a century, x rays have been an essential tool in physics, chemistry, biology, materials science, and other subjects, considerably expanding our understanding of the fundamental structure of materials. X rays and electrons are among the most useful tools in the scientific toolbox for understanding the properties and functions of materials and molecules because of their capacity to penetrate matter and differentiate the structural changes at the atomic level. This information has a wide range of applications, including the development of innovative materials for electronics and clean energy technologies, as well as more effective pharmaceuticals with fewer side effects. A major new field in x-ray science has been opened by recent developments in ultrafast x-ray sources operating in the femtosecond (fs) to atto-second regimes. These advancements make possible element-specific probing of dynamics of charge particles and electronic configurations of electronic motions at fundamental timescales, sensitive probing of structural dynamics in materials at the atomic and electronic level at fundamental timescales, and efficient new methods for examining the coupling between atomic and electronic structural dynamics to investigate the material properties and functions. The most significant advancement has been the latest discovery of x-ray free-electron lasers (XFELs), of which there are now many new facilities either operational or under development worldwide. In addition, the development of high-order harmonic extreme ultraviolet sources based on lasers that operate in the atto-second regime as well as the tabletop and synchrotron-based laser-plasma x-ray sources that operate in the fs regime complement the achievements of XFEL. The current article provides a comprehensive discussion and future perspectives on the application of ultrafast XFELs to study the structure of matter under shock compression.

  PublisherDOI

• Low viscosity of solid MgO at high pressures and strain rates measured using the laser-driven Richtmyer-Meshkov instability

  Physical review. B./Physical review. B · 2025-04-23 · 2 citations

  articleOpen accessSenior author

  Solids are often assumed to behave as viscous fluids under high-strain rates. This behavior has been studied experimentally in metals but largely unexplored in brittle ceramic materials. In this study, we present a technique for measuring the viscosity of MgO using time-resolved velocimetry to track the growth rate of a perturbation caused by the Richtmyer-Meshkov instability at the OMEGA EP laser facility. To interpret the results, we use an in-house Eulerian hydrocode to simulate our experiments and model the plastic deformation of solid MgO as a viscous fluid. Results indicate that MgO has a surprisingly low upper bound to its effective viscosity of $\ensuremath{\sim}{10}^{2}\phantom{\rule{0.16em}{0ex}}\mathrm{Pa}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$ at $175\ifmmode\pm\else\textpm\fi{}15\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}, \ensuremath{\sim}3500\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, and ${10}^{6}\ensuremath{-}{10}^{7}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ strain rate.

  PublisherOA PDFDOI

• Laser pulse-length dependent ablation and shock generation in silicon at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>5</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>14</mml:mn></mml:msup></mml:mrow></mml:math> W/<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi mathvariant="normal">cm</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math> intensities

  Physical Review Research · 2024-07-11 · 1 citations

  articleOpen access

  The effect of laser pulse duration on energy coupling into a planar silicon target is investigated in experiments at the OMEGA-EP facility by varying the laser pulse length <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>τ</a:mi></a:math>—spanning 3 orders of magnitude from 100 ps to 10 ns—while maintaining a constant peak laser intensity, <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:msub><b:mi>I</b:mi><b:mn>0</b:mn></b:msub><b:mo>=</b:mo><b:mn>5</b:mn><b:mo>×</b:mo><b:msup><b:mn>10</b:mn><b:mn>14</b:mn></b:msup></b:mrow></b:math> W/<c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:msup><c:mi mathvariant="normal">cm</c:mi><c:mn>2</c:mn></c:msup></c:math>. In theoretical models, the ablation pressure primarily scales for a given material with laser intensity and wavelength, which are all fixed variables here, allowing us to explore the specific role of laser pulse duration. Two-dimensional radiation-hydrodynamics simulations benchmarked with optical probing of the expanding plasma show that the pulse duration is critical for the ablation pressure to reach a steady state. Moreover, the pulse duration impacts shock decay and multiple wave effects, which strongly dictate the evolving shock profile that propagates within the laser-shocked target as ultimately measured by rear-surface diagnostics. The shock velocities inferred from the theoretical model, after considering shock decay, impedance matching, and shock Hugoniot, are found to be in good agreement with velocimetry measurements. However, discrepancies are observed with simulations for the shorter (0.1 ns) and longer (10 ns) pulse durations, which are respectively attributed to unaccounted contributions of kinetic absorption mechanisms and instabilities in simulations. Published by the American Physical Society 2024

  PublisherOA PDFDOI

• Shock equation of state experiments in MgO up to 1.5 TPa and the effects of optical depth on temperature determination

  Journal of Applied Physics · 2024-09-13 · 5 citations

  articleOpen accessSenior author

  Laser-driven shock compression enables an experimental study of phase transitions at unprecedented pressures and temperatures. One example is the shock Hugoniot of magnesium oxide (MgO), which crosses the B1–B2-liquid triple point at 400–600 GPa, 10 000–13 000 K (0.86–1.12 eV). MgO is a major component within the mantles of terrestrial planets and has long been a focus of high-pressure research. Here, we combine time-resolved velocimetry and pyrometry measurements with a decaying shock platform to obtain pressure–temperature data on MgO from 300 to 1500 GPa and 9000 to 50 000 K. Pressure–temperature–density Hugoniot data are reported at 1500 GPa. These data represent the near-instantaneous response of an MgO [100] single crystal to shock compression. We report on a prominent temperature anomaly between 400 and 460 GPa, in general agreement with previous shock studies, and draw comparison with equation-of-state models. We provide a detailed analysis of the decaying shock compression platform, including a treatment of a pressure-dependent optical depth near the shock front. We show that if the optical depth of the shocked material is larger than 1 μm, treating the shock front as an optically thick gray body will lead to a noticeable overestimation of the shock temperature.

  PublisherDOI

• B1-B2 transition in shock-compressed MgO

  Science Advances · 2024-06-07 · 22 citations

  articleOpen access1st authorCorresponding

  Magnesium oxide (MgO) is a major component of the Earth’s mantle and is expected to play a similar role in the mantles of large rocky exoplanets. At extreme pressures, MgO transitions from the NaCl B 1 crystal structure to a CsCl B 2 structure, which may have implications for exoplanetary deep mantle dynamics. In this study, we constrain the phase diagram of MgO with laser-compression along the shock Hugoniot, with simultaneous measurements of crystal structure, density, pressure, and temperature. We identify the B 1 to B 2 phase transition between 397 and 425 gigapascal (around 9700 kelvin), in agreement with recent theory that accounts for phonon anharmonicity. From 425 to 493 gigapascal, we observe a mixed-phase region of B1 and B2 coexistence. The transformation follows the Watanabe-Tokonami-Morimoto mechanism. Our data are consistent with B 2-liquid coexistence above 500 gigapascal and complete melting at 634 gigapascal. This study bridges the gap between previous theoretical and experimental studies, providing insights into the timescale of this phase transition.

  PublisherOA PDFDOI

• Structural study of hcp and liquid iron under shock compression up to 275 GPa

  Physical review. B./Physical review. B · 2023-11-13 · 18 citations

  articleOpen access

  We combine nanosecond laser shock compression with in situ picosecond x-ray diffraction to provide structural data on iron up to 275 GPa. We constrain the extent of hcp-liquid coexistence, the onset of total melt, and the structure within the liquid phase. Our results indicate that iron, under shock compression, melts completely by 258(8) GPa. A coordination number analysis indicates that iron is a simple liquid at these pressure-temperature conditions. We also perform texture analysis between the ambient body-centered-cubic (bcc) $\ensuremath{\alpha}$, and the hexagonal-closed-packed (hcp) high-pressure $\ensuremath{\epsilon}\ensuremath{-}\mathrm{phase}$. We rule out the Rong-Dunlop orientation relationship (OR) between the $\ensuremath{\alpha}$ and $\ensuremath{\epsilon}\ensuremath{-}\mathrm{phase}\mathrm{s}$. However, we cannot distinguish between three other closely related ORs: Burger's, Mao-Bassett-Takahashi, and Potter's OR. The solid-liquid coexistence region is constrained from a melt onset pressure of 225(3) GPa from previously published sound speed measurements and full melt [246.5(1.8)--258(8) GPa] from x-ray diffraction measurements, with an associated maximum latent heat of melting of 623 J/g. This value is lower than recently reported theoretical estimates and suggests that the contribution to the earth's geodynamo energy budget from heat release due to freezing of the inner core is smaller than previously thought. Melt pressures for these nanosecond shock experiments are consistent with gas gun shock experiments that last for microseconds, indicating that the melt transition occurs rapidly.

  PublisherOA PDFDOI

• A structural study of hcp and liquid iron under shock compression up to 275 GPa

  arXiv (Cornell University) · 2023-04-17 · 2 citations

  preprintOpen access

  We combine nanosecond laser shock compression with \emph{in-situ} picosecond X-ray diffraction to provide structural data on iron up to 275 GPa. We constrain the extent of hcp-liquid coexistence, the onset of total melt, and the structure within the liquid phase. Our results indicate that iron, under shock compression, melts completely by 258(8) GPa. A coordination number analysis indicates that iron is a simple liquid at these pressure-temperature conditions. We also perform texture analysis between the ambient body-centered-cubic (bcc) $α$, and the hexagonal-closed-packed (hcp) high-pressure $ε-$phase. We rule out the Rong-Dunlop orientation relationship (OR) between the $α$ and $ε-$phases. However, we cannot distinguish between three other closely related ORs: Burger's, Mao-Bassett-Takahashi, and Potter's OR. The solid-liquid coexistence region is constrained from a melt onset pressure of 225(3) GPa from previously published sound speed measurements and full melt (246.5(1.8)-258(8) GPa) from X-ray diffraction measurements, with an associated maximum latent heat of melting of 623 J/g. This value is lower than recently reported theoretical estimates and suggests that the contribution to the earth's geodynamo energy budget from heat release due to freezing of the inner core is smaller than previously thought. Melt pressures for these nanosecond shock experiments are consistent with gas gun shock experiments that last for microseconds, indicating that the melt transition occurs rapidly.

  PublisherOA PDFDOI

• Ramp Compression of Germanium Dioxide to Extreme Conditions: Phase Transitions in an <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>SiO</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> Analog

  Physical Review X · 2023-09-08 · 2 citations

  articleOpen access

  Observation of the crystal structure of GeO${}_{2}$ at pressures of hundreds of gigapascals offers insights into the high-pressure behavior of SiO${}_{2}$, which is expected to exist in the deep interior of large rocky exoplanets.

  PublisherOA PDFDOI

• Development of slurry targets for high repetition-rate x-ray free electron laser experiments

  Journal of Applied Physics · 2022-06-27 · 4 citations

  articleOpen accessSenior author

  Combining an x-ray free electron laser with a high-power laser driver enables the study of equations-of-state, high strain-rate deformation processes, structural phase transitions, and transformation pathways as a function of pressure to hundreds of GPa along different thermodynamic compression paths. Future high repetition-rate laser operation will enable data to be accumulated at &amp;gt;1 Hz, which poses a number of experimental challenges, including the need to rapidly replenish the target. Here, we present a combined shock compression and an x-ray diffraction study on epoxy (50% vol.)-crystalline grains (50% vol.) slurry targets, which can be fashioned into extruded ribbons for high repetition-rate operation. For shock-loaded NaCl-slurry samples, we observe pressure, density, and temperature states within the embedded NaCl grains consistent with observations from shock-compressed single-crystal NaCl.

  PublisherOA PDFDOI

• In situ X-ray diffraction of Al₂O₃ during laser compression and release

  2022-07-11

  preprintSenior author
  PublisherDOI

Frequent coauthors

• J. H. Eggert

  Lawrence Livermore National Laboratory

  35 shared

• R. F. Smith

  Lawrence Livermore National Laboratory

  32 shared

• T. S. Duffy

  Princeton University

  30 shared

• F. Coppari

  Lawrence Livermore National Laboratory

  23 shared

• W. Sturhahn

  21 shared

• D. E. Fratanduono

  Lawrence Livermore National Laboratory

  20 shared

• Hae Ja Lee

  SLAC National Accelerator Laboratory

  20 shared

• A. E. Gleason

  Menlo School

  17 shared

Education

• PhD, Div. of Geological and Planetary Sciences

  California Institute of Technology

  2013