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  • richardmitnick 11:48 am on April 17, 2018 Permalink | Reply
    Tags: , , , Marriage of a 20keV superconducting XFEL with a 100PW laser, , , XFELs   

    From SPIE: “Marriage of a 20keV superconducting XFEL with a 100PW laser” 

    SPIE

    SPIE

    16 April 2018
    Toshiki Tajima, University of California, Irvine
    Ruxin Li, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences

    A new regime of science at exawatts and zeptoseconds.

    The Chinese national science and technology major infrastructure, Shanghai Coherent Light Facility (SCLF), organized an international review meeting for the Station of Extreme Light (SEL) in Shanghai on July 10, 2017.

    The Shanghai Institute of Applied Physics is building a Soft X-ray Free Electron Laser that is set to open to users in 2019. Credit Michael Banks

    The reviewing committee members included experts in strong-field laser physics, high-energy-density physics, and theoretical physics from Germany, USA, UK, France, Japan, Canada; and China chaired by R. Sauerbrey and N .Wang. The working group, led by Ruxin Li of the Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences (CAS), has made a series of breakthroughs on high energy, high power, and high-repetition laser system development.

    Reflecting on this, the Review Committee Report1 stated: “The architecture of the laser system of the Optical Parametric Chirped Pulse Amplification (OPCPA) and its interaction with the XFEL are well thought out. The proposed 1023 W/cm2 peak laser power is feasible. The working group has made a series of breakthroughs on high-power laser technologies in the past decades. Their constant effort has resulted in valuable experience, outstanding engineering skills, and international recognition for the group. Their strong track record has laid a strong foundation, which will provide the basis for successful construction of the 100 PW laser system.”

    Based on this, the Committee applauded the work, stating: “The Station of Extreme Light at Shanghai Coherent Light Facility is dedicated to cutting-edge research in strong field science and applications. This includes, for example, astrophysics, nuclear physics, cosmology, and matter under extreme conditions. The combination of the hard XFEL and the world-leading 100PW laser in SEL will initiate exploration of effects such as vacuum birefringence, one of the most prominent strong-field QED effects, acceleration mechanisms leading to ultra-high energy cosmic rays, simulation of black hole physics, and generation of new forms of matter.”

    The developments proposed are based on solid research carried out at SIOM (and other scientific organizations). In particular, the research and development of the OPCPA laser amplifier at the highest power level at SIOM. Shown in Figure 1 is SIOM’s 10PW laser CPA device and the 10PW laser system. The 10PW laser system, Shanghai Superintense-Ultrafast Lasers Facility (SULF), is based on CPA technology and the diameter of the Ti-Sapphire used in the main amplifier is 235mm, which is the largest crystal for the laser manufactured by the scientists at SIOM.

    Based on these developments, SIOM has launched a 100PW laser system, Station for Extreme Light (SEL). This system has two significant salient features. First, the level of its power will be an order of magnitude beyond the planned highest-powered laser, Extreme Light Infrastructure (ELI). Secondly, its design is a combination of the 100PW laser as part of the system in the SCLF’s XFEL. This project received strong endorsement from the International Review Meeting that convened at SCLF of SIOM on July 10, 2017, and was approved by the Government of China. The overall funding level is approximately USD$1.3 Billion.

    Figure 1 10PW laser system in Shanghai pumped by CPA.

    II. Extreme field regime
    The parameters of SEL are well beyond what has so far been available. Table 1 shows typical principal physical parameters. The coherent x-ray energy from the SCLF ranges between 3 to 15 keV (hard x-rays) produced from the superconducting x-ray free electron laser (XFEL). The photon number per pulse of this XFEL is 1012. Its pulse focusability is 200nm with the energy resolution of 0.6eV. The x-ray’s intensity at focus is as high as 1021W/cm2.

    The parameters of the 100PW laser for optical photons are as follows: Its peak power is 100PW, while its focal intensity is as high as 1023W/cm2. (If we can managed to focus better than this, it could go toward 1025W/cm2). While this is a single shot performance, it could deliver the repetition rate of 1Hz of optical laser if the power is at 0.1 to 1PW.

    These parameters by themselves are exciting. However, their coexistence and marriage as a combined unit shows a remarkable capability for future scienctific exploration. The combination of a synchrotron light source and an intense laser was first suggested and conducted in 1990s. Toshiki Tajima suggested that Professor Mamoru Fujiwara at Osaka University make use of the high-energy (8GeV) electrons of the SPRing-8 combined with an intense laser to make extremely high-energy gamma photons, which he did in his lab.2 Since then, the combination of these accelerator-based synchrotron light sources (or even more advanced XFEL with intense lasers) have come a long way. The present SCLF’s marriage of these two will uncover a new regime of science and greatly impact various technologies and applications, such as nuclear photonics and nonlinear interferometry.

    4
    Table 1 shows the schematic layout of the SEL. The interaction of XFEL and the plasma chamber takes place in the experimental area. Figure 3 indicates the 100PW laser based on the OPCPA technology.

    4
    Figure 2: Schematic layout figure of SEL that couples the 100PW laser with the XFEL.

    5
    Figure 3: Details of the amplification stages of the 100PW laser based on OPCPA.

    The scheme of this marriage is seen in the concept of the SEL at which the coherent high-energy x-rays photons are shone in the configuration shown in Figure 2. This way we will be able to observe the interaction of the high-energy x-ray photons and most intense lasers and their developed matter interaction. This will greatly increase the experimental probe of intense laser-matter interaction. The XFEL beam will provide ultra-short MHz x-ray beam with energy range of 3-5keV and significantly large photon number of 1012. Specific x-ray energy of 12.914keV will be used for QED experiments with very low energy spread of 0.6eV. The x-ray beam will collide head-on with the 100PW laser pulse in the experimental chamber. The 100PW laser system contains four beams and each beam reaches the peak power of 25 PW.

    Figure 2 shows that the main laser system will occupy two floors and its power supply and control system are set at different floors. After the four-beam combination, the laser pulse will be sent to the experimental area on the bottom floor. There is a large-size vacuum chamber, where the 100PW laser pulse will be focused to 5μm and collide with the x-ray beam.

    Details of the 100PW laser system are shown in Figure 3. At the core is the OPCPA system. The 100PW laser pulse starts at high temporal laser source, where its temporal synchronization signal comes from the XFEL beam. This source will generate high-quality seed pulses, which will go into the PW level repetition-rate OPCPA front-end. The laser energy will reach 25J and its spectrum width will support 15fs at PW level OPCPA front-end.

    The main amplifier is based on OPCPA technology and it provides 99% energy gain of the whole laser system, which requires sufficient pump energy from a Nd Glass pump laser. The final optics assembly will compress the high-energy of 2500J 4ns laser pulse to 15fs. After the compression, the laser pulse will be sent into the experimental chamber with the peak intensity 1023 W/cm2. As shown in Figure 1, we developed and tested the performance of a high-intensity laser with CPA up to 10PW level.

    III. High Field Science
    The proposed SEL aims to achieve the ultimate in high field science [3],[4],[5]. Here, we describe a simple way to reach that goal.

    The radiation dominance regime (1023 W/cm2) as described in Ref. 2 may be accessible and experimentally explored for the first time in sufficient details with the help of the coherent X-ray probe. As discussed in Sec. 1, if one can focus a bit narrowly, we may be able to enter the so-called QED Quantum regime (~1024 W/cm2)[4],[5].

    The particle acceleration by laser will enter a new regime. The wakefield generation [6] becomes so nonlinear that it enters what is sometimes called the bow-wake regime [7]. This may be relevant to the astrophysical extreme high-energy cosmic ray genesis by AGN (active galactic nuclei) jets [8]. In this regime, the physics of wakefield acceleration and that of the radiation pressure acceleration begin to merge (1023W/cm2)[9],[10]. Thus, the laser pulse should be able to pick up ions as well as electrons to become accelerated. Soon or later, the energy of ions begins to exceed that of electrons and their acceleration should become as coherent as the electron acceleration in this regime. Such acceleration will allow ion accelerators to be smaller. (A broader scope at this regime and slightly higher intensity regime than just mentioned has been reviewed [9].)

    However, it could go much further than that, since the invention of a new compression technique called “thin film compression11.” With this technique, a laser may be compressed to even higher power and intensity such as EW and further by relativistic compression into the shortest possible pulses ever in zs12. We will thus see the continuous manifestation of the Intensity-Pulse Duration Theorem into the extension of EW and zs [13]. It will not only explore strong field QED physics [14],[15], but we will also see the emergence of new phenomena at play in a wider variety of fundamental physics, including: (1) possible search of the proposed “fifth force” [16],[17]; (2) dark matter search by four wave mixing [18]; (3) x-ray wakefield in solid state matter [19] and related x-ray and optical solid state plasmonics [20]; (4) possible testing of the energy dependence of gamma photon propagation speed in a vacuum to test the foundational assumption of the Theory of Special Theory of Relativity [21]; and (5) zeptosecond streaking of the QED process [22].

    Chen et al.[23] suggested the exploration of general relativity using the equivalence principle of acceleration-gravity to test the Hawking-Unruh process.

    IV. Gamma-ray diagnosis and the marriage of XFEL and HFS
    In the issues of high field science, we often enter into the physical processes in higher energies and shorter timescales, which may not be easily resolvable in optical diagnosis. Here, the powerful XFEL’s resolution in time and space come in [24]. X-rays can be also signatures in high intensity experiments such as laser-driven acceleration experiments [25]. A typical display of such interplay may be seen in the diagnostics of the physical processes in the problem of x-ray wakefield acceleration in solid-state matter. In this case, nanoscopic materials with a nanohole structure [20] need to be observed and controlled. The surface of the nanotubes may be exhibiting surface plasmons and polaritons in nanometer size and zs temporal dynamics, best diagnosed by the XFEL. This is but an example of the marriage of a 20keV superconducting XFEL and a 100PW laser. In addition this technology will enhance studies in photon-induced nuclear physics [26] and the treatment of nuclear materials [27] (including nuclear waste), nuclear pharmacology, nuclear biochemistry, and medicine [28],[29].

    Another example is to use gamma photons to mediate the vacuum nonlinearity caused by intense laser pulse to exploit zeptosecond streaking via the gamma photon mediation [22]. In this scheme the presence of intense laser pulse and x-ray photon play a crucial role. If this example elucidates a beginning of exploration of zeptosecond photometric and zeptosecond optics, it would be an achievement comparable of the opening of the femtosecond optics flowing by attosecond optics [30].

    One more example of exploring the proposition was recently made for the Fifth Force [17]. In the Hungarian nuclear experiment, a mysterious photon at the energy of 17MeV was observed. The paper [5] suggested this emission of gamma photon may be due to the unknown force (the Fifth Force). It may be helpful if we can inject a large amount of monoenergetic photons at this energy to see if the reversal of this process of photon emission (i.e. injection of photon) can explore this process more quantitatively. We can check of the fifth force (17MeV gamma)16,17,31 with the process and an outcome of the following, utilizing the energy specific laser induced gamma photon interaction: e + 17MeV gamma → e + X.

    Finally, there is a recent suggestion by Day and Fairbairn [32] that XFEL laser pulses at 3.5keV may be used to investigate the astrophysically observed x-ray excess by fluorescent dark matter. Such an avenue may open up with this device. Such an effort along with the astrophysical observations may become an important interdisciplinary development.

    In order to maximize the success of these implications, we recommend the formation of a broad international collaboration with the organizations and institutions that are engaging in related fields. Learning from these labs in their technologies, practice, and collaborative engagements should reduce risks and duplications and enhance learning and the scope of experience. Collaborations with a variety technology sectors are important both for the execution of experiments and their applications.

    The authors are grateful for close discussions with all the committee members (Naiyan Wang, Roland Sauerbrey, Pisin Chen, See Leang Chin, Thomas Edward Cowan, Thomas Heinzl, Yongfeng Lu, Gerard Mourou, Edmond Turcu, Hitoki Yoneda, Lu Yu) of SEL. The discussions with Profs. T. Tait, K. Abazajian, T. Ebisuzaki, and K. Homma were also very useful. Prof. X. M. Zhang helped with our manuscript.

    References:
    1. Report of the International Review Meeting for Station of Extreme Light (2017).

    2. G. A. Mourou, T. Tajima and S. V. Bulanov, Optics in the relativistic regime, Rev. Mod. Phys. 78, p. 309, 2006.

    3. T. Tajima, K. Mima and H. Baldis, Eds., High-Field Science, Kluwer Academic/Plenum Publishers, New York, NY, 2000.

    4. T. Tajima and G. Mourou, Zettawatt-exawatt lasers and their applications in ultrastrong-field physics, Phys. Rev. ST AB 5, p. 031301, 2002.

    5. G. Mourou and T. Tajima, Summary of the IZEST science and aspiration, Eur. Phys. J. ST 223, pp. 979-984, 2014.

    6. T. Tajima and J. M. Dawson, Laser electron accelerator, Phys. Rev. Lett. 43, p. 267, 1979.

    7. C. K. Lau, P. C. Yeh, O. Luk, J. McClenaghan, T. Ebisuzaki and T. Tajima, Ponderomotive acceleration by relativistic waves, Phys. Rev. ST AB 18, p. 024401, 2015; T. Tajima, Laser acceleration in novel media, Eur. Phys. J. ST 223, pp. 1037-1044, 2014.

    8. T. Ebisuzaki and T. Tajima, Astrophysical ZeV acceleration in the relativistic jet from an accreting supermassive blackhole, Astropart. Phys. 56, pp. 9-15, 2014.

    9. T. Tajima, B. C. Barish, C. P. Barty, S. Bulanov, P. Chen, J. Feldhaus, et al., Science of extreme light infrastructure, AIP Conf. Proc. 1228, pp. 11-35, 2010.

    10. T. Esirkepov, M. Borghesi, S. V. Bulanov, G. Mourou and T. Tajima, Highly efficient relativistic-ion generation in the laser-piston regime, Phys. Rev. Lett. 92, p. 175003, 2004.

    11. G. Mourou, S. Mironov, E. Khazanov and A. Sergeev, Single cycle thin film compressor opening the door to Zeptosecond-Exawatt physics, Eur. Phys. J. ST 223, pp. 1181-1188, 2014.

    12. N. Naumova, J. Nees, I. Sokolov, and G. Mourou, Relativistic generation of isolated attosecond pulses in a λ3 focal volume, Phys. Rev. Lett. 92, p. 063902, 2004.

    13. G. Mourou and T. Tajima, More intense, shorter pulses, Science 331, pp. 41-42, 2011.

    14. M. Marklund and P. K. Shukla, Nonlinear collective effects in photon-photon and photon-plasma interactions, Rev. Mod. Phys. 78, p. 591, 2006.

    15. A. Di Piazza, C. Müller, K. Z. Hatsagortsyan and C. H. Keitel, Extremely high-intensity laser interactions with fundamental quantum systems, Rev. Mod. Phys. 84, p. 1177, 2012.

    16. A. J. Krasznahorkay, M. Csatlós, L. Csige, Z. Gácsi, J. Gulyás, M. Hunyadi, et al., Observation of anomalous internal pair creation in Be 8: a possible indication of a light, neutral boson, Phys. Rev. Lett. 116, p. 042501, 2016.

    17. J. L. Feng, B. Fornal, I. Galon, S. Gardner, J. Smolinsky, T. M. Tait and P. Tanedo, Protophobic fifth-force interpretation of the observed anomaly in Be-8 nuclear transitions, Phys. Rev. Lett. 117, p. 071803, 2016.

    18. K. Homma, D. Habs and T. Tajima, Probing the semi-macroscopic vacuum by higher-harmonic generation under focused intense laser fields, Appl. Phys. B 106, pp. 229-240, 2012.

    19. T. Tajima, Laser acceleration in novel media, Eur. Phys. J. ST 223, pp. 1037-1044, 2014.

    20. X. Zhang, T. Tajima, D. Farinella, Y. Shin, G. Mourou, J. Wheeler and B. Shen, Particle-in-cell simulation of x-ray wakefield acceleration and betatron radiation in nanotubes, Phys. Rev. AB 19, p. 101004, 2016.

    21. T. Tajima, M. Kando and M. Teshima, Feeling the texture of vacuum: laser acceleration toward PeV, Progr. Theor. Phys. 125, pp. 617-631, 2011.

    22. T. Tajima, G. Mourou and K. Nakajima, Laser acceleration, Riv. Nuovo Cim. 40, p. 1, 2017.

    23. P. Chen and G. Mourou, Accelerating plasma mirrors to investigate the black hole information loss paradox, Phys. Rev. Lett. 118, p. 045001, 2017.

    24. C. Pellegrini, A. Marinelli and S. Reiche, The physics of x-ray free-electron lasers, Rev. Mod. Phys. 88, p. 015006, 2016.

    25. S. Corde, K. T. Phuoc, G. Lambert, R. Fitour, V. Malka, A. Rousse and E. Lefebvre, Femtosecond x rays from laser-plasma accelerators, Rev. Mod. Phys. 85, p. 1, 2013.

    26. S. V. Bulanov, T. Z. Esirkepov, M. Kando, H. Kiriyama and K. Kondo, Relativistically strong electromagnetic radiation in a plasma, J. Exp. Theor. Phys. 122, pp. 426-433, 2016.

    27. S. Gales, IZEST meeting presentation, ELI-EP, French Embassy in Tokyo, 2013. https://gargantua.polytechnique.fr/siatel-web/linkto/mICYYYSI7yY6. Accessed 10 November 2017.

    28. D. Habs and U. Köster, Production of medical radioisotopes with high specific activity in photonuclear reactions with γ-beams of high intensity and large brilliance, Appl. Phys. B 103, pp. 501-519, 2011; Ö. Özdemir, Eds., Current Cancer Treatment – Novel Beyond Conventional Approaches, INTECH Open Access Publisher, 2011.

    29. A. Bracco and G. Köerner, Eds., Nuclear Physics for Medicine, Nuclear Physics European Collaboration Committee, 2014.

    30. F. Krausz and M. Ivanov, Attosecond physics, Rev. Mod. Phys. 81, p. 163, 2009.

    31. T. Tajima, T. Tait, and J. Feng, private comment, 2017.

    32. F. Day and M. Fairbairn, submitted to J. High Energy Phys., 2017.

    See the full article here.

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  • richardmitnick 3:49 pm on February 1, 2018 Permalink | Reply
    Tags: , , , , CompactLight, European Commission’s Horizon 2020 programme, , XFELs   

    From CERN Courier: “EU project lights up X-band technology” 


    CERN Courier

    Nov 10, 2017

    1
    A CLIC X-band prototype structure built by PSI using Swiss FEL technology. (Image credit: M Volpi)

    Advanced linear-accelerator (linac) technology developed at CERN and elsewhere will be used to develop a new generation of compact X-ray free-electron lasers (XFELs), thanks to a €3 million project funded by the European Commission’s Horizon 2020 programme. Beginning in January 2018, “CompactLight” aims to design the first hard XFEL based on 12 GHz X-band technology, which originated from research for a high-energy linear collider. A consortium of 21 leading European institutions, including Elettra, CERN, PSI, KIT and INFN, in addition to seven universities and two industry partners (Kyma and VDL), are partnering to achieve this ambitious goal within the three-year duration of the recently awarded grant.

    X-band technology, which provides accelerating-gradients of 100 MV/m and above in a highly compact device, is now a reality. This is the result of many years of intense R&D carried out at SLAC (US) and KEK (Japan), for the former NLC and JLC projects, and at CERN in the context of the Compact Linear Collider (CLIC). This pioneering technology also withstood validation at the Elettra and PSI laboratories.

    XFELs, the latest generation of light sources based on linacs, are particularly suitable applications for high-gradient X-band technology. Following decades of growth in the use of synchrotron X-ray facilities to study materials across a wide spectrum of sciences, technologies and applications, XFELs (as opposed to circular light sources) are capable of delivering high-intensity photon beams of unprecedented brilliance and quality. This provides novel ways to probe matter and allows researchers to make “movies” of ultrafast biological processes. Currently, three XFELs are up and running in Europe – FERMI@Elettra in Italy and FLASH and FLASH II in Germany, which operate in the soft X-ray range – while two are under commissioning: SwissFEL at PSI and the European XFEL in Germany (CERN Courier July/August 2017 p18), which operates in the hard X-ray region. Yet, the demand for such high-quality X-rays is large, as the field still has great and largely unexplored potential for science and innovation – potential that can be unlocked if the linacs that drive the X-ray generation can be made smaller and cheaper.

    This is where CompactLight steps in. While most of the existing XFELs worldwide use conventional 3 GHz S-band technology (e.g. LCLS in the US and PAL in South Korea) or superconducting 1.3 GHz structures (e.g. European XFEL and LCLS-II), others use newer designs based on 6 GHz C-band technology (e.g. SCALA in Japan), which increases the accelerating gradient while reducing the linac’s length and cost. CompactLight gathers leading experts to design a hard-X-ray facility beyond today’s state of the art, using the latest concepts for bright electron-photo injectors, very-high-gradient X-band structures operating at frequencies of 12 GHz, and innovative compact short-period undulators (long devices that produce an alternating magnetic field along which relativistic electrons are deflected to produce synchrotron X-rays). Compared with existing XFELs, the proposed facility will benefit from a lower electron-beam energy (due to the enhanced undulator performance), be significantly more compact (as a consequence both of the lower energy and of the high-gradient X-band structures), have lower electrical power demand and a smaller footprint.

    Success for CompactLight will have a much wider impact: not just affirming X-band technology as a new standard for accelerator-based facilities, but advancing undulators to the next generation of compact photon sources. This will facilitate the widespread distribution of a new generation of compact X-band-based accelerators and light sources, with a large range of applications including medical use, and enable the development of compact cost-effective X-ray facilities at national or even university level across and beyond Europe.

    See the full article here .

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  • richardmitnick 3:35 pm on December 28, 2017 Permalink | Reply
    Tags: Femtosecond X-ray lasers, Inelastic X-ray scattering, , , , , , , XFELs   

    From Optics & Photonics: “X-Ray Studies Probe Water’s Elusive Properties” 

    Optics & Photonics

    28 December 2017
    Stewart Wills

    1
    Unlike most substances, liquid water is denser than its solid phase, ice. [Image: Stockholm University]

    In two different X-ray investigations, researchers have dug into some of the exotic properties of that most familiar of substances—water.

    In one study, researchers from Sweden, Japan and South Korea used a femtosecond X-ray laser to investigate the behavior of evaporatively supercooled liquid water, and to confirm the long-suspected view that water at low temperatures can exist in two different liquid phases (Science). In the other, a U.S.-Japanese team used high-resolution inelastic X-ray scattering to probe the dynamics of water molecules and how the liquid’s hydrogen bonds contribute to its unusual characteristics (Science Advances).

    Burst pipes and floating cubes

    Anyone who has confronted a burst water pipe on a frozen winter morning has firsthand knowledge of one of H20’s unusual characteristics. Whereas most substances increase in density as they go from a liquid to a solid state, water reaches its maximum density at 4°C, above its nominal freezing point of 0°C. That’s also the reason that the ice cubes float at the top of your water glass rather than sinking to the bottom.

    Grappling with this anomalous behavior, a research team at Boston University suggested around 25 years ago, based on computer simulations, that in a metastable, supercooled state, water might actually coexist in two liquid phases—a low-density liquid and a high-density liquid. Those two phases, the researchers proposed, merged into a single phase at a critical point in water phase diagram at around –44°C (analogous to the better-known critical point at a higher temperature between water’s liquid and gas phases).

    3
    Experiments using femtosecond X-ray free-electron lasers illuminated fluctuations between two different phases of liquid water—a high-density liquid (red) and a low-density liquid (blue)—as a function of temperature in the supercooled regime. [Image: Stockholm University]

    Actually getting liquid water to that frigid point has, however, seemed a bit of a pipe dream. While very pure liquid water can be rapidly supercooled to temperatures moderately below 0°C relatively easily, the proposed critical point lies far below that temperature range, in what researchers have dubbed a “no-man’s land” in which ice crystalizes much faster than the timescale of conventional lab measurements.

    Leveraging ultrafast lasers

    To move past that barrier, a research team led by Anders Nilsson of Stockholm University, Sweden, turned to the rapid timescales enabled by femtosecond X-ray free-electron lasers (XFELs). At XFEL facilities in Korea and Japan [un-named], the team sent a stream of tiny water droplets (approximately 14 microns in diameter) into a vacuum chamber, and fired the XFEL at the droplets at varying distances from the water-dispensing nozzle to obtain ultrafast X-ray scattering data.

    The tiny size of the droplets meant that as they traveled through the vacuum they rapidly evaporatively cooled—with the amount of cooling related to the time they spent in vacuum under a well-established formula. Thus, by taking X-ray measurements at varying distances from the nozzle, the researchers could examine the structural behavior of the liquid water at multiple temperatures in the deep-supercooling regime, near the hypothesized critical point. “We were able to X-ray unimaginably fast before the ice froze,” Nilsson said in a press release, “and could observe how it fluctuated” between the two hypothesized metastable phases of liquid water.

    The experiments allowed the team to flesh out the phase diagram of liquid water in a supercooled region previously thought to be inaccessible to experiment. And the researchers believe that the use of femtosecond XFELs to probe thermodynamic functions and structural changes at extreme states “can be generalized to many supercooled liquids.”

    Illuminating water’s dynamics

    4
    A team led by scientists at the U.S. Oak Ridge National Laboratory used inelastic X-ray scattering to visualize and quantify the movement of water molecules in space and time. [Image: Jason Richards/Oak Ridge National Laboratory, US Dept. of Energy]

    A second set of experiments, from researchers at the U.S. Oak Ridge National Laboratory, the University of Tennessee, and the SPring-8 synchrotron laboratory in Japan, looked at water’s dynamics at room temperature, using inelastic X-ray scattering (IXS).

    SPring-8 synchrotron, located in Hyōgo Prefecture, Japan

    The researchers illuminated these dynamics through a series of experiments in which they trained radiation from the SPring-8 facility’s high-resolution IXS beamline, BL35XU, onto a 2-mm-thick sample of liquid water. Through multiple scattering measurements across a range of momentum and energy-transfer values, the team was able to build a detailed picture of the so-called Van Hove function, which describes the probability of interactions between a molecule and its nearest neighbors as a function of distance and time.

    The team found that water’s hydrogen bonds behave in a highly correlated fashion with respect to one another, which gives liquid water its high stability and explains its viscosity characteristics. And, in a press release, the researchers further speculated that the techniques used here could be extended to studying the dynamics and viscosity of a variety of other liquids. Some of those studies, they suggested, could prove useful in “the development of new types of semiconductor devices with liquid electrolyte insulating layers, better batteries and improved lubricants.”

    Here, the research team was interested in sussing out how water molecules interact in real time, and how the strongly directional hydrogen bonds of water molecules work together to determine properties such the liquid’s viscosity.

    See the full article here .

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