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| Open AccessDroplets move over viscoelastic substrates by surfing a ridge
The wetting on soft surfaces is less understood than that on rigid ones because it is challenging to quantify substrate deformation. Here, the authors monitor the deformation over a large range of droplet velocities, and propose a dynamical model that captures contact line motion and depinning.
- S. Karpitschka
- , S. Das
- & J. H. Snoeijer
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| Open AccessInvestigating Alfvénic wave propagation in coronal open-field regions
Alfvénic waves are oscillations that occur in a plasma threaded by a magnetic field and their propagation, reflection and dissipation is believed to be partly responsible for the solar wind. Here, the authors observe the counter-propagating Alfvénic waves that most models require for solar-wind acceleration.
- R. J. Morton
- , S. Tomczyk
- & R. Pinto
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| Open AccessQuantitative X-ray phase-contrast microtomography from a compact laser-driven betatron source
With excellent resolving power and tissue contrast, X-ray phase-contrast imaging holds great promise but the source requirements have limited its use. Here, Wenz et al. show a phase-contrast microtomogram of a biological sample using X-ray radiation driven by a high-power laser.
- J. Wenz
- , S. Schleede
- & S. Karsch
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Strongly correlated two-dimensional plasma explored from entropy measurements
Electrons trapped to a two-dimensional plane can exhibit many exotic properties. Here, the authors use a technique that measures entropy per electron to explore the evolution of such a system from the Fermi liquid regime to a previously unexplored regime of a strongly correlated charged plasma.
- A. Y. Kuntsevich
- , Y. V. Tupikov
- & I. S. Burmistrov
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| Open AccessThe solvation of electrons by an atmospheric-pressure plasma
Free, or solvated, electrons in a solution are known to form at the interface between a liquid and a gas. Here, the authors use absorption spectroscopy in a total internal reflection geometry to probe solvated electrons generated at a plasma in contact with the surface of an aqueous solution
- Paul Rumbach
- , David M. Bartels
- & David B. Go
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| Open AccessEmergent vortices in populations of colloidal rollers
Confined populations of interacting motile particles often display collective motion in the form of large-scale vortices, such as fish groups and bacteria colonies. Bricard et al.study a model system with self-propelled colloidal rollers and identify the constituents responsible for emergent vortices.
- Antoine Bricard
- , Jean-Baptiste Caussin
- & Denis Bartolo
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A novel coarsening mechanism of droplets in immiscible fluid mixtures
Droplet coarsening during phase separation is widely thought to be a random process, relying on Brownian diffusion and coagulation. Here, Shimizu and Tanaka show that the process is hydrodynamically driven, where the droplet motion is directional due to an interfacial tension gradient in droplets.
- Ryotaro Shimizu
- & Hajime Tanaka
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| Open AccessInfluence of slip on the Plateau–Rayleigh instability on a fibre
A thin liquid coating on a fibre can break up into droplets due to the Plateau–Rayleigh instability, as for instance on a spider web. Here, Haefner et al. show that the growth rate of the droplet undulations strongly depends on the fibre–liquid boundary condition and slip accelerates the instability.
- Sabrina Haefner
- , Michael Benzaquen
- & Kari Dalnoki-Veress
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| Open AccessNoncontact friction via capillary shear interaction at nanoscale
The contribution from water bridges at nanoscale between rough surfaces is important for macroscopic friction under ambient conditions. Here, Lee et al. show that water nanobridge produce noncontact friction originated from the pinning–depinning dynamics of the contact line at the interface.
- Manhee Lee
- , Bongsu Kim
- & Wonho Jhe
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Article
| Open AccessThe evolution of spatial ordering of oil drops fast spreading on a water surface
The spreading of liquids on water can lead to complex drop assemblies, but none of them so far exhibits coordinated dynamics. Here, Yamamoto et al. observe a dance of insoluble oil drops on a water surface evolving from linear to hexagonal arrays, due to dewetting transition and evaporation of oil.
- Daigo Yamamoto
- , Chika Nakajima
- & Kenichi Yoshikawa
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Coherent control of plasma dynamics
Intense laser pulses can induce the propagation of coherent waves through a plasma, which are useful for accelerating electrons. Here, the authors use a genetic algorithm and a deformable mirror to optimize the wavefront and improve electron beam intensity and divergence.
- Z.-H. He
- , B. Hou
- & A.G.R. Thomas
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Article
| Open AccessWave energy budget analysis in the Earth’s radiation belts uncovers a missing energy
Whistler-mode waves regulate trapped electrons in the magnetosphere, but an accurate determination of their energy budget has remained elusive. This study presents a full analysis of their magnetic and electric field contributions and finds that a large amount of energy is stored in oblique waves.
- A.V. Artemyev
- , O.V. Agapitov
- & F.S. Mozer
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| Open AccessWitnessing magnetic twist with high-resolution observation from the 1.6-m New Solar Telescope
Understanding the behaviour of magnetic flux ropes in the Sun is crucial for explaining solar phenomena such as flares and space weather. Exploiting the high resolution available in the 1.6 m New Solar Telescope, Wang et al.capture the evolution of a flaring twisted flux rope in the low solar corona.
- Haimin Wang
- , Wenda Cao
- & Haisheng Ji
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Achieving a long-lived high-beta plasma state by energetic beam injection
A stable plasma state with a high ratio of plasma to magnetic pressures is likely to be a key requirement for any future magnetic fusion reactor. Here, the authors create such a plasma using a field reversed configuration and active plasma boundary control and demonstrate its stability.
- H. Y. Guo
- , M. W. Binderbauer
- & E. Trask
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| Open AccessGeneration of neutral and high-density electron–positron pair plasmas in the laboratory
Electron–positron pair plasma—a state of matter with a complete symmetry between negatively and positively charged particles—are found in many astrophysical object. Here, the authors use high-power laser to create an ion-free electron–positron plasma in the laboratory.
- G. Sarri
- , K. Poder
- & M. Zepf
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| Open AccessObservation of finite-wavelength screening in high-energy-density matter
Charge screening dominates the behaviour of high-energy plasmas, which exist in stars and possibly in future fusion technology. Here, the authors describe a theoretical framework for charge screening that goes beyond the conventional model and demonstrate its importance in analysing experimental data.
- D. A. Chapman
- , J. Vorberger
- & D. O. Gericke
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| Open AccessDemonstration of relativistic electron beam focusing by a laser-plasma lens
Laser-driven plasmas can accelerate electrons in set-ups far smaller than conventional particle accelerators, but beam divergence is a problem. Here, the authors demonstrate a laser-plasma lens that can focus the beam thanks to field gradients five order of magnitude larger than using traditional optics.
- C. Thaury
- , E. Guillaume
- & V. Malka
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Red blood cell as an adaptive optofluidic microlens
The shape of red blood cells is highly sensitive to surrounding liquid environment. Here, Miccio et al. make red blood cells into optofluidic lenses with fully controllable focal length at the microscale, which can be used for imaging and optical magnification in addition to blood diseases detection.
- L. Miccio
- , P. Memmolo
- & P. Ferraro
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Investigation of femtosecond collisional ionization rates in a solid-density aluminium plasma
The electrons in a plasma can further ionize the ions when the two collide. Vinko et al. now study this ultrafast process in an unconventional plasma with a density similar to that of a solid, and show that the rate is several times higher than that predicted by standard theoretical models.
- S. M. Vinko
- , O. Ciricosta
- & J. S. Wark
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A laboratory study of asymmetric magnetic reconnection in strongly driven plasmas
Magnetic reconnection occurs close to the surface of the sun, in the Earth’s magnetosphere and in astronomical plasmas. Here, the authors investigate magnetic reconnection in a laboratory-based experiments with an asymmetric configuration similar to those found in real astrophysical situations.
- M.J. Rosenberg
- , C.K. Li
- & R.D. Petrasso
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Vortex flows impart chirality-specific lift forces
The separation of enantiomers by flows holds promise in food and pharmaceutical industries, but the feasibility remains uncertain. Here, Hermans et al.separate macroscopic particles of opposite chirality at a liquid interface using shear flows, which provides insights into the mechanism at nanoscale.
- Thomas M. Hermans
- , Kyle J. M. Bishop
- & Bartosz A. Grzybowski
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| Open AccessFlow damping due to stochastization of the magnetic field
Understanding the transport of ions, electrons and heat in magnetized plasmas is important to the development of fusion power as well as our understanding of the behaviour of astrophysical objects. Ida et al.find that stochastization of magnetic field lines in a plasma damps plasma flow more strongly than expected.
- K. Ida
- , M. Yoshinuma
- & A. Komori
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Time-resolved compression of a capsule with a cone to high density for fast-ignition laser fusion
One of the challenges in fast-ignition fusion is to laser-compress an asymmetric cone-in-shell target to a density at which it can be ignited by a second laser. Theobald et al. report the achievement of areal densities in excess of 300 mg cm−2, to a point at which ignition might soon be possible.
- W. Theobald
- , A. A. Solodov
- & M. S. Wei
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Loss-proof self-accelerating beams and their use in non-paraxial manipulation of particles’ trajectories
Self-accelerating beams are attractive for light-matter interaction applications but their propagation has been limited by absorption. Here, Schley et al.demonstrate self-healing in shape-maintaining, accelerating beams where the central peak intensity is preserved despite losses and apply these beams to particle manipulation.
- Ran Schley
- , Ido Kaminer
- & Mordechai Segev
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Modelling the influence of photospheric turbulence on solar flare statistics
Solar flares follow complex statistical patterns, making it hard to understand and model their underlying physical processes. Here, the authors present a model based on reconnection of magnetic flux tubes twisted by turbulent photospheric flow that reproduces flare statistics and energy–time correlations.
- M. Mendoza
- , A. Kaydul
- & H. J. Herrmann
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High-quality electron beams from a helical inverse free-electron laser accelerator
Electrons moving in strongly curved paths emit radiation that is used in free-electron laser designs. Here, the authors demonstrate the inverse force principle, where a laser light field is used in a compact experimental design to accelerate electrons to produce high-quality electron beams.
- J. Duris
- , P. Musumeci
- & V. Yakimenko
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Conversion of magnetic energy in the magnetic reconnection layer of a laboratory plasma
Magnetic reconnection is believed to play a key role in the acceleration and heating of particles in astrophysical plasmas but the details are unclear. Yamada et al. study reconnection in a laboratory plasma, enabling them to determine the exact mechanisms of energy flow from magnetic field to particles.
- Masaaki Yamada
- , Jongsoo Yoo
- & Clayton E. Myers
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An ultracompact X-ray source based on a laser-plasma undulator
Synchrotron radiation sources based on a combination of laser plasma accelerators and magnetic undulator have been limited in terms of brightness. Here, Andriyash et al.propose to use a sub-millimetre nano-wire array as a laser-plasma undulator that could produce bright, collimated and tunable X-ray pulses.
- I.A. Andriyash
- , R. Lehe
- & V. Malka
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| Open AccessPetawatt laser absorption bounded
Petawatt laser-matter interactions could open the way to fusion energy or compact particular accelerators, but predicting the amount of light absorbed in these interactions is challenging. New analysis by Levy et al.reveals the theoretical upper and lower limits of this absorption.
- Matthew C. Levy
- , Scott C. Wilks
- & Matthew G. Baring
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| Open AccessLaser light triggers increased Raman amplification in the regime of nonlinear Landau damping
Stimulated Raman scattering is one of the methods being explored to generate ultrahigh intensity short laser pulses. Depierreux et al. explore a new regime, also relevant to inertial confinement thermonuclear fusion, in which nonlinear kinetic response of a hot plasma enhances Raman amplification.
- S. Depierreux
- , V. Yahia
- & C. Labaune
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Plasma irregularities in the D-region ionosphere in association with sprite streamer initiation
Sprites are spectacular optical emissions in the mesosphere with an enigmatic filamentary nature. Qin et al.present high-speed video and modelling data revealing sub-millisecond dynamics to reconstruct the structures on a km-scale, showing that pre-existing plasma irregularities are responsible for their initiation.
- Jianqi Qin
- , Victor P. Pasko
- & Hans C. Stenbaek-Nielsen
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Density functional theory calculations of continuum lowering in strongly coupled plasmas
The plasma environment induces an ionization potential depression on its ions, yet a clear description of this effect remains elusive. Towards this aim, Vinko et al.offer a method to study the structure and position of the continuum of highly ionized dense plasmas that accurately reproduces recent experiments.
- S. M. Vinko
- , O. Ciricosta
- & J. S. Wark
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Observations of an extreme storm in interplanetary space caused by successive coronal mass ejections
Coronal mass ejections are large expulsions of plasma from the solar corona into space, and are drivers of major space weather effects. Here, the authors report observations of two successive ejections, whose interaction led to extremely enhanced magnetic fields and high solar wind speeds near 1 AU.
- Ying D. Liu
- , Janet G. Luhmann
- & Antoinette B. Galvin
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| Open AccessOptical properties of relativistic plasma mirrors
Next generation high power lasers will produce fields so intense they can only be controlled with components made of plasmas. Vincenti et al.explore the properties of one such component—the relativistic plasma mirror—and construct an analytical framework to improve their use in focusing intense laser fields.
- H. Vincenti
- , S. Monchocé
- & F. Quéré
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Discovery of the action of a geophysical synchrotron in the Earth’s Van Allen radiation belts
The processes influencing the Van Allen belt – a layer of charged particles inside the Earth’s magnetosphere – are poorly understood. Using CRRES and NASA’s Van Allen Probes data, Mann et al.suggest that ultra-low frequency waves may play a larger role in accelerating particles than previously thought.
- Ian R. Mann
- , E. A. Lee
- & F. Honary
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Fusion reactions initiated by laser-accelerated particle beams in a laser-produced plasma
The nuclear fusion of hydrogen and boron nuclei has potential advantages over the fusion of deuterium and tritium for energy production as it produces no neutrons. Labaune et al. report progress towards achieving this by colliding a laser-driven particle beam into a laser-generated plasma.
- C. Labaune
- , C. Baccou
- & J. Rafelski
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Virtual hyperbolic metamaterials for manipulating radar signals in air
Controlling the propagation of microwaves in air is hard because of their divergence and the lack of suitable optics. Kudyshev et al. show how this can be overcome using plasma channels to create virtual hyperbolic metamaterials to collimate and guide radar beams.
- Zhaxylyk A. Kudyshev
- , Martin C. Richardson
- & Natalia M. Litchinitser
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| Open AccessOptical control of hard X-ray polarization by electron injection in a laser wakefield accelerator
Radiation sources driven by laser-plasma accelerators have the potential to produce shorter bursts of radiation at lower cost than those based on conventional accelerators. Schnell et al.demonstrate the ability to control the polarization of the bursts of hard X-rays produced by such a source.
- Michael Schnell
- , Alexander Sävert
- & Christian Spielmann
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| Open AccessQuasi-monoenergetic laser-plasma acceleration of electrons to 2 GeV
Laser-plasma accelerators can produce high-energy electron bunches over just a few centimetres of distance, offering possible table-top accelerator capabilities. Wang et al.break the current 1 GeV barrier by applying a petawatt laser to accelerate electrons nearly monoenergetically up to 2 GeV.
- Xiaoming Wang
- , Rafal Zgadzaj
- & M. C. Downer
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Article
| Open AccessObservation and theory of X-ray mirages
X-ray lasers are of interest to study various properties of materials down to the atomic scale. The discovery by Magnitskiy et al. of a mirage interference effect in X-ray plasma lasers could lead to new possibilities to control the output of such lasers.
- Sergey Magnitskiy
- , Nikolay Nagorskiy
- & Yoshiaki Kato
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Observation of longitudinal and transverse self-injections in laser-plasma accelerators
Laser-plasma accelerators can produce giga electronvolt energy electrons over centimetre scales, but their properties depend on the initial injection into the accelerator. Corde et al.study self-injection of electrons into the plasma wake and identify both transverse and longitudinal injection mechanisms.
- S. Corde
- , C. Thaury
- & V. Malka
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Observations of ubiquitous compressive waves in the Sun’s chromosphere
A full understanding of the heating and dynamics of the Sun's atmosphere remains elusive, but magnetohydrodynamic waves are believed to be crucial. Using observations from the ROSA imager, this study finds compressive waves in the solar chromosphere, which may provide the energy needed for coronal heating.
- Richard J. Morton
- , Gary Verth
- & Robertus Erdélyi
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Single-shot ultrafast tomographic imaging by spectral multiplexing
Computed tomography relies on scanning to measure an object from many angles, which fails for shot-to-shot changes and ultrafast phenomena. Matliset al. demonstrate an approach based on spectral multiplexing for single-shot tomographic imaging and use it to measure femtosecond plasma filaments.
- N.H. Matlis
- , A. Axley
- & W.P. Leemans
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| Open AccessDirect observation of prompt pre-thermal laser ion sheath acceleration
High-intensity laser-plasma ion generation is promising as a compact proton source for applications like ion beam therapy. Using a femtosecond table-top laser system, Zeilet al. show that protons efficiently gain energy in the pre-thermal intra-pulse phase of the generation process.
- K. Zeil
- , J. Metzkes
- & U. Schramm
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Control of magnetohydrodynamic stability by phase space engineering of energetic ions in tokamak plasmas
Tokamak plasmas suffer from magnetohydrodynamic instabilities, driven by gradients in current density or pressure, but techniques to control them are power-hungry and reduce reactor efficiency. Here, an efficient method to control such instabilities using asymmetric ion populations is demonstrated at JET.
- J.P. Graves
- , I.T. Chapman
- & M. Jucker
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| Open AccessEvidence of superdense aluminium synthesized by ultrafast microexplosion
At extreme temperature and pressure, materials can form new dense phases with unusual physical properties. Here, laser-induced microexplosions are used to produce a superdense, stable, body-centred-cubic form of aluminium, which was previously predicted to exist at pressures above 380GPa.
- Arturas Vailionis
- , Eugene G. Gamaly
- & Saulius Juodkazis
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| Open AccessSize limits the formation of liquid jets during bubble bursting
A bubble at an air–liquid interface can form a liquid jet upon bursting, spraying aerosol droplets into the air. Leeet al. show that jetting is analogous to pinching-off in liquid coalescence, which may be useful in applications that prevent jet formation and in the improved incorporation of aerosols in climate models.
- Ji San Lee
- , Byung Mook Weon
- & Wah-Keat Lee
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| Open AccessFractal fronts of diffusion in microgravity
Theory and simulations predict scale-invariant concentration fluctuations during diffusion in liquids, but on Earth, large-scale fluctuations are damped by gravity. Microgravity experiments by Vailatiet al. reveal the scale-invariant nature of diffusion, associated with fractal fronts and long-ranged correlations.
- Alberto Vailati
- , Roberto Cerbino
- & Marzio Giglio
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Current drive at plasma densities required for thermonuclear reactors
Future tokamak nuclear fusion reactors depend on efficient current drive methods, but it is hard to penetrate the high-density plasma in these devices. In this paper the authors show that radio frequency waves coupled to lower hybrid plasma waves, when the peripheral temperature of the plasma is high, can penetrate the plasma core.
- R. Cesario
- , L. Amicucci
- & F. Zonca