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In the article, olivine-structured pure LiNiPO4 and yttrium-doped LiNiPO4 powder were prepared by sol-gel method using citric acid as chelating agent. The effect of 1.0 mol% Y doping on the structure and electrochemical properties of LiNiPO4 materials using powder X-ray diffraction pattern, scanning electron microscope, cyclic voltammetry, and electrochemical impedance spectroscopy was investigated. It was found that 1.0 mol% Y doping could induce an increase in lattice parameters and a decrease in particle sizes, which could enlarge lithium-ion diffusion channel, increase carriers concentration, and shorten diffusion lengths, thus decreasing polarization and improving lithium-ion diffusion and conductivity. All those could result in enhanced redox peak current density, decreased charge-transfer resistance, and potential separation between oxidation peak and reduction peak. Y doping could also decrease the highest occupied molecular orbital (HOMO) of NiO6 octahedron caused by Jahn-Teller effect, which caused the raises of redox potential.

In this paper, titanium oxide (TiO2) films were prepared by cathodic electrodeposition using titanium oxysulfate (TiOSO4), potassium nitrate (KNO3), citric acid, and hydrogen peroxide (H2O2) as reactants. The article investigated the effect of citric acid and deposition temperature on the structure and electrochemical properties of TiO2 films. The results indicated that hydrous TiO2 thin films were prepared at 60°C when no citric acid was added, while thin films containing hydrous TiO2 and anatase phase were fabricated at 60–75°C when citric acid was added. It was found that adding citric acid and raising the reaction temperature (60–75°C) were beneficial to reduce crack width until cracks disappeared. Adding citric acid facilitated phase transition from hydrous TiO2 to anatase. Continuous and uniform TiO2 thin film was prepared at 75°C, which was found to have ideal capacitive behavior with a rectangular cyclic voltammogram and high photocurrent performance with photocurrent 2.89 μA, which is several times higher than that of cracked samples.

Fusion reactions in a plasma environment are fundamental issues with general interest in high energy density sciences. The reaction rate in an astro-system, which may differ from cold matter, is an important subject in the ambiguous problems of elemental abundance. In addition, the stopping of charged particle in plasma has a considerable impact on the design of nuclear fusion reactors as it is related to the α-particle heating process and ion-driven fast ignition, but still needs better understanding. In this research, an experiment on laser-driven D–D fusion reactions (D + D → 3He + n) has been carried out to investigate the effects of ion stopping power in plasma on fusion reactivities. The neutron yields, plasma density, and deuteron energy loss in the plasma have been measured simultaneously, and the plasma temperature has been analyzed from simulations. It is experimentally demonstrated that the fusion reaction yield is closely correlated with ion beam transportation in the plasma. As a cold target heated to plasma, the reaction probabilities from a deuteron beam and deuterated target interactions can be enhanced or suppressed, which is ascribed to the deuteron stopping power variation in the plasma. The results show the importance of considering the temperature adjusted ion stopping power to correctly model the fusion reaction yields. This work has an impact on understanding the fusion reactions in plasma environment, which is also likely to help achieve higher neutron yields.

In this article, SnO2/carbon composites were prepared by hydrothermal electrochemical method. Stannous chloride dihydrate (SnCl2·H2O) and glucose were used as Sn sources and carbon sources, respectively. Effects of the molar ratio of glucose/SnCl2 on structure, morphology, and properties of the composites were investigated by X-ray diffraction (XRD), Raman, FTIR, SEM, and cyclic voltammetry. Results indicated that SnO2 had the tetragonal rutile structure and carbon was diamond like carbon (DLC) structure. It was observed that the morphology and electrochemical properties of samples were affected by the molar ratio of glucose/SnCl2. Increasing the molar ratio of glucose/SnCl2 induced grain shape change from cube to spherical, decrease in grain size and increase of cyclic reversibility. When the molar ratio of glucose/SnCl2 was 100%, 100 nm spherical SnO2/carbon composites could be prepared by hydrothermal electrochemical method, which had a pair of redox peaks, and the peak positions were − 0.32/− 0.14 V and − 0.18/0.10 V at 5 mV/s in 1 M LiOH solution. At various scanning rates, there was little variation in the oxidation/reduction peak positions. It was considered to be a promising material for fast and reversible Li-ion alloying and de-alloying.

We have investigated hydrogen plasma induced by intense extreme ultraviolet (EUV) radiation by measuring the plasma parameters and population density of radicals, which is expected to clean the tin contamination on the optics in EUV sources, using a time-resolved optical emission spectroscopy. The obtained electron density was n e = (2 ± 0.4) × 1013 cm−3, and the electron temperature was T e = 1 ± 0.2 eV. The electron density was five orders of magnitude higher than that of previous study. The radical population density determined by the experiment was consistent with that calculated with a collisional radiative model, showing excitation and recombination are dominant production processes.

An ever-increasing number of strong-field applications, such as ultrafast coherent control over matter and light, require driver light pulses that are both high power and spectrally tunable. The realization of such a source in the terahertz (THz) band has long been a formidable challenge. Here, we demonstrate, via experiment and theory, efficient production of terawatt (TW)-level THz pulses from high-intensity picosecond laser irradiation on a metal foil. It is shown that the THz spectrum can be manipulated effectively by tuning the laser pulse duration or target size. A general analytical framework for THz generation is developed, involving both the high-current electron emission and a time-varying electron sheath at the target rear, and the spectral tunability is found to stem from the change of the dominant THz generation mechanism. In addition to being an ultrabright source (brightness temperature of about 10^{21} K) for extreme THz science, the THz radiation presented here also enables a unique in situ laser-plasma diagnostic. Employing the THz radiation to quantify the escaping electrons and the transient sheath shows good agreement with experimental measurements.

In this paper, LiNiPO4 powders were prepared by sol gel method using citric acid as chelating agent. The article investigated the effect of annealing temperature and citric acid: Li molar ratio (cit/Li) on the structure and electrochemical properties of LiNiPO4 material. The results indicated that pure Pnma LiNiPO4 phase was synthesized at 700 and 800 °C. It was found that the increase of annealing temperature and cit/Li induced rod-to-sphere transition. The particles sizes increased with increasing annealing temperature, while the particles sizes were increasing firstly and then decreasing with increasing the ratio of cit/Li. Decreasing particles sizes had an advantage of both decreasing the charge transfer resistance (Rct) and improving the reversible capacity of pure olivine LiNiPO4 samples. Spherical particles (100–200 nm) prepared at 700 °C with cit/Li molar ratio of 2:1 were found to have low resistance, high electrochemical reversibility, cycle stability.

When comets interacting with solar wind, straight and narrow plasma tails will be often formed. The most remarkable phenomenon of the plasma tails is the disconnection event, in which a plasma tail is uprooted from the comet’s head and moves away from the comet. In this paper, the interaction process between a comet and solar wind is simulated by using a laser-driven plasma cloud to hit a cylinder obstacle. A disconnected plasma tail is observed behind the obstacle by optical shadowgraphy and interferometry. Our particle-in-cell simulations show that the difference in thermal velocity between ions and electrons induces an electrostatic field behind the obstacle. This field can lead to the convergence of ions to the central region, resulting in a disconnected plasma tail. This electrostatic-field-induced model may be a possible explanation for the disconnection events of cometary tails.

Microalgae are renewable feedstock for sustainable biofuel production, cell factory for valuable chemicals and promising in alleviation of greenhouse gas CO2. However, the carbon assimilation capacity is still the bottleneck for higher productivity. Molecular characterization of CO2 sequestration and assimilation in microalgae has advanced in the past few years and are reviewed here. In some cyanobacteria, genes for 2-oxoglytarate dehydrogenase was replaced by four alternative mechanisms to fulfill TCA cycle. In green algae Coccomyxa subellipsoidea C-169, alternative carbon assimilation pathway was upregulated under high CO2 conditions. These advances thus provide new insights and new targets for accelerating CO2 sequestration rate and enhancing bioproduct synthesis in microalgae. When integrated with conventional parameter optimization, molecular approach for microalgae modification targeting at different levels is promising in generating value-added chemicals from green algae and cyanobacteria efficiently in the near future.

Diamond-like carbon (DLC) thin films were prepared by hydrothermal electrochemical method in one-step process. The structural characterization of these films was carried out by scanning electron microscopy (SEM), Raman spectroscopy, and infrared reflectance spectroscopy (IR). It was found that there was an increased sp2 carbon content but decreased sp3 carbon and hydrogen contents with an increase in current density. The flexibility and internal stresses of the DLC films were affected by hydrogen, sp3 amorphous carbon and ordered crystalline sp2 carbon contents. The highly flexible DLC films with high sp3 carbon and hydrogen contents were prepared at a current density of 0.001 mA/cm2.

Aiming to evaluate the capability for CO

The bremsstrahlung x-ray emission profile from high intensity laser-solid interactions provides valuable insight to the internal fast electron transport. Using penumbral imaging, we characterise the spatial profile of this bremsstrahlung source as a function of laser intensity by incrementally increasing the laser focal spot size on target. The experimental data shows a dual-source structure; one from the central channel of electrons, the second a larger substrate source from the recirculating electron current. The results demonstrate than an order of magnitude improvement in the intensity contrast between the two x-ray sources is achieved with a large focal spot, indicating preferable conditions for applications in radiography. An analytical model is derived to describe the transport of suprathermal electron populations that contribute to substrate and central channel sources through a target. The model is in good agreement with the experimental results presented here and furthermore is applied to predict laser intensities for achieving optimum spatial contrast for a variety of target materials and thicknesses.

Significance Terahertz (THz) radiation, with frequencies spanning from 0.1 to 10 THz, has long been the most underdeveloped frequency band in electromagnetic waves, mainly due to the dearth of available high-power THz sources. Although the last decades have seen a surge of electronic and optical techniques for generating intense THz radiation, all THz sources reported until now have failed to produce above-millijoule (mJ) THz pulses. We present a THz source that enables a THz pulse energy up to tens of mJ, by using an intense laser pulse to irradiate a metal foil., Ultrahigh-power terahertz (THz) radiation sources are essential for many applications, for example, THz-wave-based compact accelerators and THz control over matter. However, to date none of the THz sources reported, whether based upon large-scale accelerators or high-power lasers, have produced THz pulses with energies above the millijoule (mJ) level. Here, we report a substantial increase in THz pulse energy, as high as tens of mJ, generated by a high-intensity, picosecond laser pulse irradiating a metal foil. A further up-scaling of THz energy by a factor of ∼4 is observed when introducing preplasmas at the target-rear side. Experimental measurements and theoretical models identify the dominant THz generation mechanism to be coherent transition radiation, induced by the laser-accelerated energetic electron bunch escaping the target. Observation of THz-field-induced carrier multiplication in high-resistivity silicon is presented as a proof-of-concept application demonstration. Such an extremely high THz energy not only triggers various nonlinear dynamics in matter, but also opens up the research era of relativistic THz optics.

A multi-channel Thomson parabola spectrometer was designed and employed to diagnose ion beams driven by intense laser pulses. Angular-resolved energy spectra for different ion species can be measured in a single shot. It contains parallel dipole magnets and wedged electrodes to fit ion dispersion of different charge-to-mass ratios. The diameter and separation of the entrance pinhole channels were designed properly to provide sufficient resolution and avoid overlapping of dispersed ion beams. To obtain a precise energy spectral resolving, three-dimensional distributions of the electric and magnetic fields were simulated. Experimental measurement of energy-dependent angular distributions of target normal sheath accelerated protons and deuterons was demonstrated. This novel compact design provides a comprehensive characterization for ion beams.

A Ti:sapphire femtosecond laser with a relativistic intensity is focused onto a four-loop solenoid target to produce an ultrafast pulsed magnetic field. The magnetic field is generated due to a cold electron bunch which flows toward the laser focal spot to neutralize the remaining positive charge from the escaping hot electrons. The temporal evolution of the magnetic fields is evaluated by an improved Faraday rotation measurement [Baojun Zhu et al., Applied Physics Letters 113.7(2018)]. Effects of pulse duration on laser-driven magnetic fields have been studied. A peak field strength is obtained when the laser pulse duration is extended to be 50 fs.

Recently generation of strong magnetic (B) fields has been demonstrated in capacitor coils heated by high power laser pulses [S. Fujioka et al., Sci. Rep. 3, 1170 (2013)]. This paper will present a direct measurement of B field generated with an open-ended coil target driven by a nanosecond laser pulse using ultrafast proton radiography. The radiographs are analyzed with particle-tracing simulations. The B field at the coil center is inferred to be ∼50 T at an irradiance of ∼5 × 1014 W·cm−2. The B field generation is attributed to the background cold electron flow pointing to the laser focal spot, where a target potential is induced due to the escape of energetic electrons. Keywords: Strong magnetic field, Laser-driven coil targets, Proton radiography, PACS codes: 52.70.Ds, 52.50.Jm, 52.38.Fz

We discuss the formation of a Kelvin–Helmholtz instability (KHI) produced by a laser-driven thin separate plastic (CH) foil plasma. The experimental design consists of magnetized plasma driven by intense laser irradiation and a small cylindrical permanent magnet. By comparing situations with and without an external magnetic field, we found that the KHI showed different rolling features which could be effectively suppressed by an external magnetic field. A quantitative analysis shows the consistency between the experiments and theory.

Laser wakefield accelerators have emerged as a promising candidate for compact synchrotron radiation and even x-ray free electron lasers. Today, to make the electrons emit electromagnetic radiation, the trajectories of laser wakefield accelerated electrons are deflected by transverse wakefield, counter-propagating laser field or external permanent magnet insertion device. Here, we propose a novel type of undulator that has a period of a few hundred microns and a magnetic field of tens of Tesla. The undulator consists of a bifilar capacitor-coil target that sustains a strong discharge current that generates a helical magnetic field around the coil axis when irradiated by a high-energy laser. Coupling this undulator with state-of-the-art laser wakefield accelerators can, simultaneously, produce ultra-bright quasi-monochromatic x-rays with tunable energy ranging 5-250 keV and optimize the free electron laser parameter and gain length compared with a permanent magnet-based undulator. This concept may pave a path toward ultra-compact synchrotron radiation and even x-ray free electron lasers.

We present laboratory measurement and theoretical analysis of silicon K-shell lines in plasmas produced by Shenguang II laser facility, and discuss the application of line ratios to diagnose the electron density and temperature of laser plasmas. Two types of shots were carried out to interpret silicon plasma spectra under two conditions, and the spectra from 6.6 Å to 6.85 Å were measured. The radiative-collisional code based on the flexible atomic code (RCF) is used to identify the lines, and it also well simulates the experimental spectra. Satellite lines, which are populated by dielectron capture and large radiative decay rate, influence the spectrum profile significantly. Because of the blending of lines, the traditional $G$ value and $R$ value are not applicable in diagnosing electron temperature and density of plasma. We take the contribution of satellite lines into the calculation of line ratios of He-$\unicode[STIX]{x1D6FC}$ lines, and discuss their relations with the electron temperature and density.

As a promising new way to generate a controllable strong magnetic field, laser-driven magnetic coils have attracted interest in many research fields. In 2013, a kilotesla level magnetic field was achieved at the Gekko XII laser facility with a capacitor–coil target. A similar approach has been adopted in a number of laboratories, with a variety of targets of different shapes. The peak strength of the magnetic field varies from a few tesla to kilotesla, with different spatio-temporal ranges. The differences are determined by the target geometry and the parameters of the incident laser. Here we present a review of the results of recent experimental studies of laser-driven magnetic field generation, as well as a discussion of the diagnostic techniques required for such rapidly changing magnetic fields. As an extension of the magnetic field generation, some applications are discussed.

Astrophysical collisionless shocks are amazing phenomena in space and astrophysical plasmas, where supersonic flows generate electromagnetic fields through instabilities and particles can be accelerated to high energy cosmic rays. Until now, understanding these micro-processes is still a challenge despite rich astrophysical observation data have been obtained. Laboratory astrophysics, a new route to study the astrophysics, allows us to investigate them at similar extreme physical conditions in laboratory. Here we will review the recent progress of the collisionless shock experiments performed at SG-II laser facility in China. The evolution of the electrostatic shocks and Weibel-type/filamentation instabilities are observed. Inspired by the configurations of the counter-streaming plasma flows, we also carry out a novel plasma collider to generate energetic neutrons relevant to the astrophysical nuclear reactions.

Nuclear fusion reactions are the most important processes in nature to power stars and produce new elements, and lie at the center of the understanding of nucleosynthesis in the universe. It is critically important to study the reactions in full plasma environments that are close to true astrophysical conditions. By using laser-driven counter-streaming collisionless plasmas, the fusion $d+d{\ensuremath{\rightarrow}}^{3}\mathrm{He}+n$ is studied in a Gamow-like window around 27 keV. The results give hints that astrophysical nuclear reaction yields can be modulated significantly by the self-generated electromagnetic fields and the collective motion of the plasma. This plasma-version minicollider may provide a novel tool for studies of astrophysics-interested nuclear reactions, as well as a useful tool to constrain the models of plasma colliding dynamic.

Black carbon-stabilized anatase particles were prepared by a simple one-step hydrothermal–electrochemical method using glucose and titanium citrate as the carbon and titanium source, respectively. Morphological, chemical, structural, and electrochemical characterizations of these powders were carried out by Raman spectroscopy, Fourier-transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy, and cyclic voltammetry. It was revealed that 200-nm carbon/anatase TiO2 was homogeneously dispersed, and the powders exhibited excellent cyclic performance at high current rates of 0.05 V/s. The powders are interesting potential materials that could be used as anodes for lithium-ion batteries.

Microalgae are renewable feedstock for sustainable biofuel production, cell factory for valuable chemicals and promising in alleviation of greenhouse gas CO

A pair of collisionless shocks that propagate in the opposite directions are firstly observed in the interactions of laser-produced counter-streaming flows. The flows are generated by irradiating a pair of opposing copper foils with eight laser beams at the Shenguang-II (SG-II) laser facility. The experimental results indicate that the excited shocks are collisionless and electrostatic, in good agreement with the theoretical model of electrostatic shock. The particle-in-cell (PIC) simulations verify that a strong electrostatic field growing from the interaction region contributes to the shocks formation. The evolution is driven by the thermal pressure gradient between the upstream and the downstream. Theoretical analysis indicates that the strength of the shocks is enhanced with the decreasing density ratio during both flows interpenetration. The positive feedback can offset the shock decay process. This is probable the main reason why the electrostatic shocks can keep stable for a longer time in our experiment.

Microwave radiation in several gigahertz frequency band is a common phenomenon in laser-plasma interactions. It can last hundreds of nanoseconds and cause huge electromagnetic pulse disturbances to electrical devices in experiments. It has been found that the microwave radiation might originate from the oscillation of charged chambers, the return current on target holders, the dipole radiation, the quadrupole radiation, and the electron bunch emitted from the plasma to the vacuum. The microwave radiation waveform, frequency spectrum, and intensity depend on many factors such as laser pulse, target, and chamber parameter. To distinguish the microwave radiation mechanisms, the influence of the experimental parameters on the radiation characteristics should be investigated systematically. In this paper we investigate the microwave radiation influenced by the laser intensity in nanosecond laser-plasma interactions. It is found that the microwave radiation intensity varies nonmonotonically with the laser intensity. For the lower laser intensity, the radiation intensity first increases and then decreases with laser intensity increasing, the radiation field continuously oscillates in tens of nanoseconds, and the radiation spectrum contains two components below and above 0.3 GHz, respectively. For the higher laser intensity, the radiation intensity increases with the laser intensity increasing, the radiation field has a unipolar radiation lasting tens of nanoseconds, and the radiation spectrum mainly includes the component below 0.3 GHz. The waveform and spectrum analysis show that these phenomena are due to the difference of the radiation mechanisms at different laser intensities. The frequency component below and above 0.3 GHz are induced by the electron bunch emitted from the plasma to the vacuum and the dipole radiation respectively. At low laser intensity, both the dipole radiation and the electron bunch emitted from the plasma contribute to the microwave radiation. At high laser intensity, the microwave radiation is mainly produced by the electron beam emitted from the plasma to the vacuum. This work is significant for understanding the microwave radiation mechanisms in nanosecond laser-plasma interactions, and implies the potential to provide a reference to the diagnosing of the escape electrons and the sheath field on the target surface by the microwave radiation in laser-plasma interaction.

A novel method of initiating nuclear fusion reactions in a full plasma environment was suggested, and a proof-of-concept experiment was carried out with the $$\hbox {D}+\hbox {D } \rightarrow \hbox { n}\,+\,^3$$ He reaction. In this new approach, two plasma jets generated by high-intensity lasers collide head-on-head. The center-of-mass energy of the nuclei increases accordingly, and therefore, reaction products can be significantly enhanced, especially in the sub-Coulomb barrier ranges. As a result of the fusion reaction, up to $$\sim 7.6\times 10^{5}$$ neutrons had been observed. This new type of “plasma collider” could provide an innovative tool to study nuclear reactions under astrophysical conditions.

Neutron energy is directly correlated with the energy of the incident ions in experiments involving laser-driven nuclear reactions. Using high-energy incident ions reduces the energy concentration of the generated neutrons. A novel “laser-collider” method was used at the Shenguang II laser facility to produce monoenergetic neutrons via 7Li (d, n) nuclear reactions. The specially designed K-shaped target significantly increased the numbers of incident d and Li ions at the keV level. Ultimately, 13.3 MeV neutrons were obtained. Considering the time resolution of the neutron detector, we demonstrated that the produced neutrons were monoenergetic. Interferometry and a Multi hydro-dynamics simulation confirmed the monoenergetic nature of these neutrons.

Coherent transition radiation in the terahertz (THz) region with energies of sub-mJ/pulse has been demonstrated by relativistic laser-driven electron beams crossing the solid-vacuum boundary. Targets including mass-limited foils and layered metal-plastic targets are used to verify the radiation mechanism and characterize the radiation properties. Observations of THz emissions as a function of target parameters agree well with the formation-zone and diffraction model of transition radiation. Particle-in-cell simulations also well reproduce the observed characteristics of THz emissions. The present THz transition radiation enables not only a potential tabletop brilliant THz source, but also a novel noninvasive diagnostic for fast electron generation and transport in laser-plasma interactions.

In this paper, the recent studies of laboratory astrophysics with strong magnetic fields in China have been reviewed. On the Shenguang-II laser facility of the National Laboratory on High-Power Lasers and Physics, a laser-driven strong magnetic field up to 200 T has been achieved. The experiment was performed to model the interaction of solar wind with dayside magnetosphere. Also the low beta plasma magnetic reconnection (MR) has been studied. Theoretically, the model has been developed to deal with the atomic structures and processes in strong magnetic field. Also the study of shock wave generation in the magnetized counter-streaming plasmas is introduced.

An ultrafast pulsed magnetic field from a two-loop solenoid is generated by a femtosecond (fs) laser. High temporal resolution is needed to measure the magnetic field. We describe an improved Faraday-rotation measurement to evaluate the evolution of the magnetic field with a resolution of ∼3.3 picoseconds (ps) in a single shot, with an uncompressed chirped pulse from a Ti:sapphire laser as the optical probe. A magnetic field of 0.52 T with a rise time of 20.8 ps has been measured with this chirped Faraday probe. In addition, we demonstrate the magnetic field strength driven by the femtosecond laser can be modified by adjusting the focal spot size.An ultrafast pulsed magnetic field from a two-loop solenoid is generated by a femtosecond (fs) laser. High temporal resolution is needed to measure the magnetic field. We describe an improved Faraday-rotation measurement to evaluate the evolution of the magnetic field with a resolution of ∼3.3 picoseconds (ps) in a single shot, with an uncompressed chirped pulse from a Ti:sapphire laser as the optical probe. A magnetic field of 0.52 T with a rise time of 20.8 ps has been measured with this chirped Faraday probe. In addition, we demonstrate the magnetic field strength driven by the femtosecond laser can be modified by adjusting the focal spot size.

Diagnosing fast electrons is important to understand the physics underpinning intense laser-produced plasmas. Here, we demonstrate experimentally that a Cherenkov radiation-based optical fibre can serve as a reliable diagnostic to characterize the fast electrons escaping from solid targets irradiated by ultra-intense laser pulses. Using optical fibre loops, the number and angular distributions of the escaping electrons are obtained. The data agrees well with measurements made using image plate stacks. The optical fibre can be operated at high-repetition rates and is insensitive to X-rays and ion beams, which makes it advantageous over other routinely-used fast electron diagnostics in some aspects.

A double-turn capacitor-coil is used to produce a magnetic field (38.5 T) and construct a topology of magnetic reconnection in a low-β (β < 1) plasma environment. The device is constructed with two metallic U-turn coils connecting two parallel metallic disks. High energy lasers are employed to ablate one disk spontaneously driving two currents in the two coils, which produces an interactive magnetic field topology. We demonstrated through experiments and numerical simulations that the reconnection process takes place between two non-uniform magnetic fields created by the coils, and that the plasma state and the associated magnetic topology in the process can be seen via the technology of the optical probe beam and the proton backlight.

The temporal evolution of electron density of air plasma filament induced by femtosecond laser pulse has been studied experimentally by a single shot electromagnetic induction method. Based on the detection of transient magnetic field around the electrified filament by an induction coil, the current in filament as well as electron density is estimated from the time dependent electromotive force signal. The experimental results indicate that our method significantly reduced the self-oscillation and interference signal, which are difficult to avoid in previous standard electrical diagnostic of filament, meanwhile the reliable temporal evolution of the electron density of filament is obtained.

Neutron yields have direct correlation with the energy of incident deuterons in experiments of laser deuterated target interaction [Roth et al., Phys. Rev. Lett. 110, 044802 (2013) and Higginson et al., Phys. Plasmas 18, 100703 (2011)], while deuterated plasma density is also an important parameter. Experiments at the Shenguang II laser facility have produced neutrons with energy of 2.45 MeV using d (d, n) He reaction. Deuterated foil target and K-shaped target were employed to study the influence of plasma density on neutron yields. Neutron yield generated by K-shaped target (nearly 10(6)) was two times higher than by foil target because the K-shaped target results in higher density plasma. Interferometry and multi hydro-dynamics simulation confirmed the importance of plasma density for enhancement of neutron yields.

A bow shock is formed in the interaction of a high-speed laser-driven plasma cloud with a cylinder obstacle. Its temporal and spatial structures are observed by shadowgraphy and interferometry. The width of the shock transition region is ~ 50 μm, comparable to the ion–ion collision mean free path, which indicates that collision is dominated in the shock probably. The Mach-number of the ablating plasma cloud is ~ 15 at first, and decreases with time resulting in a changing shock structure. A two-dimension hydrodynamics code, USim, is used to simulate the interaction process. The simulated shocks can well reproduce the observed.

We demonstrate a novel plasma device for magnetic reconnection, driven by Gekko XII lasers irradiating a double-turn Helmholtz capacitor-coil target. Optical probing revealed an accumulated plasma plume near the magnetic reconnection outflow. The background electron density and magnetic field were measured to be approximately 1018 cm−3 and 60 T by using Nomarski interferometry and the Faraday effect, respectively. In contrast with experiments on magnetic reconnection constructed by the Biermann battery effect, which produced high beta values, our beta value was much lower than one, which greatly extends the parameter regime of laser-driven magnetic reconnection and reveals its potential in astrophysical plasma applications.

A simple scheme to produce strong magnetic fields due to cold electron flow in an open-ended coil heated by high power laser pulses is proposed. It differs from previous generation of magnetic fields driven by fast electron current in a capacitor-coil target [S. Fujioka et al., Sci. Rep. 3, 1170 (2013)]. The fields in our experiments are measured by B-dot detectors and proton radiography, respectively. A 205 T strong magnetic field at the center of the coil target is generated in the free space at Iλ2 of 6.85 × 1014 W cm−2 μm2, where I is the laser intensity, and λ is the laser wavelength. The magnetic field strength is proportional to Iλ2. Compared with the capacitor-coil target, the generation mechanism of the magnetic field is straightforward and the coil is easy to be fabricated.