Bob Nagler

All Publications

• Superheating gold beyond the predicted entropy catastrophe threshold. Nature White, T. G., Griffin, T. D., Haden, D., Lee, H. J., Galtier, E., Cunningham, E., Khaghani, D., Descamps, A., Wollenweber, L., Armentrout, B., Convery, C., Appel, K., Fletcher, L. B., Goede, S., Hastings, J. B., Iratcabal, J., McBride, E. E., Molina, J., Monaco, G., Morrison, L., Stramel, H., Yunus, S., Zastrau, U., Glenzer, S. H., Gregori, G., Gericke, D. O., Nagler, B. 2025; 643 (8073): 950-954

  Abstract

  In their landmark study1, Fecht and Johnson unveiled a phenomenon that they termed the 'entropy catastrophe', a critical point where the entropy of superheated crystals equates to that of their liquid counterparts. This point marks the uppermost stability boundary for solids at temperatures typically around three times their melting point. Despite the theoretical prediction of this ultimate stability threshold, its practical exploration has been prevented by numerous intermediate destabilizing events, colloquially known as a hierarchy of catastrophes2-5, which occur at far lower temperatures. Here we experimentally test this limit under ultrafast heating conditions, directly tracking the lattice temperature by using high-resolution inelastic X-ray scattering. Our gold samples are heated to temperatures over 14 times their melting point while retaining their crystalline structure, far surpassing the predicted threshold and suggesting a substantially higher or potentially no limit for superheating. We point to the inability of our samples to expand on these very short timescales as an important difference from previous estimates. These observations provide insights into the dynamics of melting under extreme conditions.

  View details for DOI 10.1038/s41586-025-09253-y

  View details for PubMedID 40702260

  View details for PubMedCentralID PMC12286838

• Direct imaging of ultrafast lattice dynamics. Science advances Brown, S. B., Gleason, A. E., Galtier, E., Higginbotham, A., Arnold, B., Fry, A., Granados, E., Hashim, A., Schroer, C. G., Schropp, A., Seiboth, F., Tavella, F., Xing, Z., Mao, W., Lee, H. J., Nagler, B. 2019; 5 (3): eaau8044

  Abstract

  Under rapid high-temperature, high-pressure loading, lattices exhibit complex elastic-inelastic responses. The dynamics of these responses are challenging to measure experimentally because of high sample density and extremely small relevant spatial and temporal scales. Here, we use an x-ray free-electron laser providing simultaneous in situ direct imaging and x-ray diffraction to spatially resolve lattice dynamics of silicon under high-strain rate conditions. We present the first imaging of a new intermediate elastic feature modulating compression along the axis of applied stress, and we identify the structure, compression, and density behind each observed wave. The ultrafast probe x-rays enabled time-resolved characterization of the intermediate elastic feature, which is leveraged to constrain kinetic inhibition of the phase transformation between 2 and 4 ns. These results not only address long-standing questions about the response of silicon under extreme environments but also demonstrate the potential for ultrafast direct measurements to illuminate new lattice dynamics.

  View details for PubMedID 30873430

• In situ X-ray diffraction measurement of shock-wave-driven twinning and lattice dynamics. Nature Wehrenberg, C. E., McGonegle, D., Bolme, C., Higginbotham, A., Lazicki, A., Lee, H. J., Nagler, B., Park, H. S., Remington, B. A., Rudd, R. E., Sliwa, M., Suggit, M., Swift, D., Tavella, F., Zepeda-Ruiz, L., Wark, J. S. 2017; 550 (7677): 496-499

  Abstract

  Pressure-driven shock waves in solid materials can cause extreme damage and deformation. Understanding this deformation and the associated defects that are created in the material is crucial in the study of a wide range of phenomena, including planetary formation and asteroid impact sites, the formation of interstellar dust clouds, ballistic penetrators, spacecraft shielding and ductility in high-performance ceramics. At the lattice level, the basic mechanisms of plastic deformation are twinning (whereby crystallites with a mirror-image lattice form) and slip (whereby lattice dislocations are generated and move), but determining which of these mechanisms is active during deformation is challenging. Experiments that characterized lattice defects have typically examined the microstructure of samples after deformation, and so are complicated by post-shock annealing and reverberations. In addition, measurements have been limited to relatively modest pressures (less than 100 gigapascals). In situ X-ray diffraction experiments can provide insights into the dynamic behaviour of materials, but have only recently been applied to plasticity during shock compression and have yet to provide detailed insight into competing deformation mechanisms. Here we present X-ray diffraction experiments with femtosecond resolution that capture in situ, lattice-level information on the microstructural processes that drive shock-wave-driven deformation. To demonstrate this method we shock-compress the body-centred-cubic material tantalum-an important material for high-energy-density physics owing to its high shock impedance and high X-ray opacity. Tantalum is also a material for which previous shock compression simulations and experiments have provided conflicting information about the dominant deformation mechanism. Our experiments reveal twinning and related lattice rotation occurring on the timescale of tens of picoseconds. In addition, despite the common association between twinning and strong shocks, we find a transition from twinning to dislocation-slip-dominated plasticity at high pressure (more than 150 gigapascals), a regime that recovery experiments cannot accurately access. The techniques demonstrated here will be useful for studying shock waves and other high-strain-rate phenomena, as well as a broad range of processes induced by plasticity.

  View details for DOI 10.1038/nature24061

  View details for PubMedID 29072261

• The Matter in Extreme Conditions instrument at the Linac Coherent Light Source JOURNAL OF SYNCHROTRON RADIATION Nagler, B., Arnold, B., Bouchard, G., Boyce, R. F., Boyce, R. M., Callen, A., Campell, M., Curiel, R., Galtier, E., Garofoli, J., Granados, E., Hastings, J., Hays, G., Heimann, P., Lee, R. W., Milathianaki, D., Plummer, L., Schropp, A., Wallace, A., Welch, M., White, W., Xing, Z., Yin, J., Young, J., Zastrau, U., Lee, H. J. 2015; 22: 520-525

  Abstract

  The LCLS beam provides revolutionary capabilities for studying the transient behavior of matter in extreme conditions. The particular strength of the Matter in Extreme Conditions instrument is that it combines the unique LCLS beam with high-power optical laser beams, and a suite of dedicated diagnostics tailored for this field of science. In this paper an overview of the beamline, the capabilities of the instrumentation, and selected highlights of experiments and commissioning results are presented.

  View details for DOI 10.1107/S1600577515004865

  View details for Web of Science ID 000353920300010

  View details for PubMedID 25931063

  View details for PubMedCentralID PMC4416670

• Creation and diagnosis of a solid-density plasma with an X-ray free-electron laser NATURE Vinko, S. M., Ciricosta, O., Cho, B. I., Engelhorn, K., Chung, H., Brown, C. R., Burian, T., Chalupsky, J., Falcone, R. W., Graves, C., Hajkova, V., Higginbotham, A., Juha, L., Krzywinski, J., Lee, H. J., Messerschmidt, M., Murphy, C. D., Ping, Y., Scherz, A., Schlotter, W., Toleikis, S., Turner, J. J., Vysin, L., Wang, T., Wu, B., Zastrau, U., Zhu, D., Lee, R. W., Heimann, P. A., Nagler, B., Wark, J. S. 2012; 482 (7383): 59-U75

  Abstract

  Matter with a high energy density (>10(5) joules per cm(3)) is prevalent throughout the Universe, being present in all types of stars and towards the centre of the giant planets; it is also relevant for inertial confinement fusion. Its thermodynamic and transport properties are challenging to measure, requiring the creation of sufficiently long-lived samples at homogeneous temperatures and densities. With the advent of the Linac Coherent Light Source (LCLS) X-ray laser, high-intensity radiation (>10(17) watts per cm(2), previously the domain of optical lasers) can be produced at X-ray wavelengths. The interaction of single atoms with such intense X-rays has recently been investigated. An understanding of the contrasting case of intense X-ray interaction with dense systems is important from a fundamental viewpoint and for applications. Here we report the experimental creation of a solid-density plasma at temperatures in excess of 10(6) kelvin on inertial-confinement timescales using an X-ray free-electron laser. We discuss the pertinent physics of the intense X-ray-matter interactions, and illustrate the importance of electron-ion collisions. Detailed simulations of the interaction process conducted with a radiative-collisional code show good qualitative agreement with the experimental results. We obtain insights into the evolution of the charge state distribution of the system, the electron density and temperature, and the timescales of collisional processes. Our results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological systems, material science investigations, and the study of matter in extreme conditions.

  View details for DOI 10.1038/nature10746

  View details for Web of Science ID 000299726000034

  View details for PubMedID 22278059

• Turning solid aluminium transparent by intense soft X-ray photoionization NATURE PHYSICS Nagler, B., Zastrau, U., Faeustlin, R. R., Vinko, S. M., Whitcher, T., Nelson, A. J., Sobierajski, R., Krzywinski, J., Chalupsky, J., Abreu, E., Bajt, S., Bornath, T., Burian, T., Chapman, H., Cihelka, J., Doeppner, T., Duesterer, S., Dzelzainis, T., Fajardo, M., Foerster, E., Fortmann, C., Galtier, E., Glenzer, S. H., Goede, S., Gregori, G., Hajkova, V., Heimann, P., Juha, L., Jurek, M., Khattak, F. Y., Khorsand, A. R., Klinger, D., Kozlova, M., Laarmann, T., Lee, H. J., Lee, R. W., Meiwes-Broer, K., Mercere, P., Murphy, W. J., Przystawik, A., Redmer, R., Reinholz, H., Riley, D., Roepke, G., Rosmej, F., Saksl, K., Schott, R., Thiele, R., Tiggesbaeumker, J., Toleikis, S., Tschentscher, T., Uschmann, I., Vollmer, H. J., Wark, J. S. 2009; 5 (9): 693-696

  View details for DOI 10.1038/NPHYS1341

  View details for Web of Science ID 000270095600024

• GeV electron beams from a centimetre-scale accelerator NATURE PHYSICS Leemans, W. P., Nagler, B., Gonsalves, A. J., Toth, C., Nakamura, K., Geddes, C. R., Esarey, E., Schroeder, C. B., Hooker, S. M. 2006; 2 (10): 696-699

  View details for DOI 10.1038/nphys418

  View details for Web of Science ID 000241493100020