Ultrahigh Intensity Research Articles

Photon emission and radiation reaction effects in surface plasma waves in ultra-high intensities

Manipulating and harnessing plasmonic phenomena in the ultra-relativistic regime reveal promising prospects for the use of surface plasma waves (SPW) to create high-energy particle and radiation sources in the next generation of multi-petawatt lasers. Indeed, relativistic high-charge electron bunches can be produced by SPW excited by ultra-high intensity femtosecond lasers impinging on a periodically modulated solid-density target. In this regime, there is good evidence that SPW excitation survives and that the produced electron bunches experience strong acceleration, thus emitting large amounts of electromagnetic radiation. Therefore, extending the study to ultra-high laser intensities (I>1021 W/cm2), the use of a resonant grating for SPW generation represents an interesting alternative to light sources, as the energy lost by electrons due to radiation emission is transferred to high-energy γ photons. In addition, we show that using a laser with wavefront rotation coupled with a tailored blazed grating improves photon emission in the ultra-relativistic regime of interaction.

On the distribution function of electron spectra from hot laser plasmas

The emission of electrons from hot plasmas generated in the interaction of ultra-short (and ultra-high intensity) laser pulses with matter is often characterized by the so-called ‘hot electron temperature’. In this article it is shown that this number is not unambiguous. The reason is the following: to assign a temperature to an electron spectrum, it is necessary to describe the spectrum with a distribution function. However, different types of distribution functions are in use, e.g. the Boltzmann or Maxwell distribution, leading to different electron temperatures in spite of providing nearly the same form of the electron spectrum. For this reason, the main characteristics of all these distribution functions are presented in this article and compared. Depending on the distribution function used, the value of the hot electron temperature varies by up to 30% and in extreme cases by more than a factor of four. This fact should always be kept in mind when comparing values of hot electron temperatures. In addition, the reasons for using equilibrium distributions to describe the characteristics of laser-produced electrons—although probably no thermodynamic equilibrium is prevailing—are discussed.

Searching for axion resonances in vacuum birefringence with three-beam collisions

We consider birefringent (i.e., polarization changing) scattering of x-ray photons at the superposition of two optical laser beams of ultrahigh intensity and study the resonant contributions of axions or axionlike particles, which could also be short lived. Applying the specifications of the Helmholtz International Beamline for Extreme Fields (HIBEF), we find that this setup can be more sensitive than previous light-by-light scattering (birefringence) or light-shining-through-wall experiments in a certain domain of parameter space. By changing the pump and probe laser orientations and frequencies, one can even scan different axion masses, i.e., chart the axion propagator. Published by the American Physical Society 2024

Modeling of high-speed, methane–air, turbulent combustion, Part I: One-dimensional turbulence modeling with comparison to DNS

The ability of the one-dimensional turbulence (ODT) model to serve as a surrogate direct numerical simulation (DNS) is assessed for highly turbulent flames. The ODT model is applied to freely propagating premixed methane–air flames at Karlovitz numbers 10, 102, 103, and 104, and results are compared with DNS. The ODT model solves the conservation equations for momentum, energy, and species on a one-dimensional domain, which corresponds to a streamwise line of sight spanning the DNS domain. The effects of turbulent advection are modeled via a stochastic process, in which the Kolmogorov and reactive length and time scales are explicitly resolved. Molecular transport and chemical kinetics are concurrently advanced in time. Both the ODT and DNS simulations use a 21-species skeletal chemical model for methane combustion. The accuracy of the ODT model is assessed by comparing its predictions of several key characteristics of the flames for each Karlovitz number tested, including the turbulent flame speed and width and the joint probability density functions (jPDFs) of major and selected minor species as well as the heat release rate conditioned on temperature with the results of DNS under comparable conditions. The ODT model is shown to yield qualitative and quantitative agreement with the DNS data for most of the above flame characteristics. Discrepancies are observed primarily for the jPDFs of several minor species examined. Overall, the ODT approach is shown to be an effective surrogate of DNS, potentially useful for guiding chemical reaction model reduction and for assessing the sensitivities of the flame structure and the burning rate to chemistry under highly turbulent conditions.Novelty and Significance:The direct numerical simulations (DNS) of premixed turbulent methane–air flames presented in this work span a uniquely wide range of turbulent intensities, from relatively modest corresponding to Karlovitz number Ka=10 to ultra-high intensities at Ka=104. This represents virtually the entire range of turbulent intensities that could be encountered in any realistic situation. This is also the first time that such a wide range of conditions is probed for methane in high-fidelity, fully resolved simulations, which use a fully compressible set of flow equations. The one-dimensional turbulence (ODT) model utilizes the same forcing that is present in the DNS enabling a direct comparison between the ODT and DNS. The results show that ODT captures the key features of the DNS results. ODT is shown to be an effective surrogate for DNS and may be useful in guiding chemical reaction model reduction, where many simulations are required.

Quasi-instantaneous materials processing technology via high-intensity electrical nano pulsing

Despite many efforts, the outcomes obtained with field-assisted processing of materials still rely on long-term coupling with other electroless processes. This conceals the efficacy and the intrinsic contributions of electric current. A new device utilizing electrical nano pulsing (ENP) has been designed and constructed to bring quasi-instantaneous modifications to the micro- and nano-structure in materials. Featuring ultra-high intensity (~ 1011 A/m2) and ultra-short duration (< 1 μs), the ENP technology activates non-equilibrium structural evolutions at nanometer spatial scale and nanosecond temporal scale. Several examples are provided to demonstrate its utility far outpacing any conventional materials processing technology. The ENP technology gives a practical tool for exploring the intrinsic mechanism of electric-field effects and a pathway towards the rapid industrial manufacturing of materials with unique properties.

Hundreds-petawatt laser pulses shaping and heavy ion acceleration based on conical plasma channels

In this paper, the effects of conical plasma channels on the laser pulses shaping and the heavy ion acceleration under the extreme light field conditions of hundreds-petawatt are investigated using a particle simulation method. The law of influence of the conical plasma channel on the spatio-temporal waveform and intensity of the incident laser is analyzed, when the QED effect is taken into account. The reason for the shaping laser-enhanced heavy ion acceleration is given, and the role of the QED effect in the acceleration process is explained.&lt;br&gt;It is found that, due to the non-linear interference and focusing effects, the conical plasma channel can shape the spatio-temporal waveform of the laser pulse and enhance the laser intensity. A tightly focused (beam waist radius &lt; 1 μm) and ultra-high intensity (enhanced 6 times) shaping laser is obtained for a linearly polarized laser with an intensity of 5.46 × 10&lt;sup&gt;22&lt;/sup&gt; W/cm&lt;sup&gt;2&lt;/sup&gt; and a waist radius of 10 μm at an incident angle of &lt;i&gt;θ&lt;/i&gt; = 10°. In the simulation, the conical plasma channel is fully ionized high-Z gold plasma with the electron densities up to &lt;i&gt;n&lt;sub&gt;e&lt;/sub&gt;&lt;/i&gt;=2626.5&lt;i&gt;n&lt;sub&gt;c&lt;/sub&gt;&lt;/i&gt;. Therefore most of the laser energy in the channel is reflected by the channel wall, and the QED effect has less impact on laser focusing and shaping. Using this laser to accelerate an ultra-thin flat target placed at the end of the channel. It is found that, the radiation reaction force can effectively suppress the transverse expansion of the ultra-thin flat target caused by the electron heating and the transverse non-uniform of the laser intensity. The transparency time of the ultra-thin flat target is prolonged, which will allow the gold ions to be fully accelerated. Ultimately, gold ions with a cutoff energy of up to ~ 240 GeV can be obtained. The results are expected to provide theoretical references and technical support for the design of future hundreds-petawatt laser heavy ion acceleration experiments and their application research of high-quality ion source, such as nucleus-nucleus collisions.

Analysis of brines for the content of the main substance and impurities of magnesium and calcium salts by the sonoluminescence method

The use of the sonoluminescence method for the analysis of brines for the content of the main substance – sodium chloride and admixtures of magnesium and calcium salts – was studied. The use of sonoluminescence initiated by the ultra-high frequency ultrasound (10.0–25.0 MHz) to determine the content of the main substance – sodium chloride – in brines, as well as sonoluminescence initiated by the simultaneous action of ultra-high- (10.0–25.0 MHz) and low- (20–100 kHz) frequency ultrasound to determine the content of magnesium and calcium salts was experimentally investigated. When determining the content of sodium chloride in brines, the smallest relative standard deviation of the analysis results (Sr = 0.010–0.013) was when using the ultra-high-frequency ultrasound with a frequency of 22.0–23.0 MHz and intensity of 20.0 W/cm2. When determining the content of magnesium and calcium salts, for the initiation of sonoluminescence, it was optimal to use the simultaneous action of ultra-high frequency ultrasound (20.0–22.0 MHz) and intensity (20.0 W/cm2), and low-frequency ultrasound (19.0–22.0 kHz) and intensity 1.30–1.50 W/cm2, which made it possible to increase the sensitivity of determining magnesium and calcium in brines from 3.0–5.0 g/l when initializing sonoluminescence by the low-frequency ultrasound to 0.01 g/l when initializing sonoluminescence by the simultaneous action of ultra-high- and low-frequency ultrasound.&#x0D; Methods for determining the content of the main substance and impurities of magnesium and calcium salts in brines have been developed. The correctness of the methods was checked by analysing the same samples using alternative methods. When determining the content of the main substance, the following methods were used as alternative ones: gravimetry and the sonoluminescence method of low-frequency ultrasound, as well as with high-frequency ultrasound. When determining the content of magnesium and calcium salts, flame atomic absorption spectrometry and the sonoluminescence method of low-frequency ultrasound, as well as with the simultaneous action of high- and low-frequency ultrasound, were used as alternative methods.

The waist injuries and treatment methods of rowers

Rowing is one of the worlds competitive sports, and it is an extremely energy intensive aerobic sport. This sport requires very strict physical fitness for athletes. Therefore, rowers need to withstand extreme load training and ultra-high intensity endurance training, whether in daily training or in actual competitions. Rowers must possess good physical fitness and functional abilities, as well as flexibility and agility. However, the prolonged physical wear and tear experienced by rowing athletes during training and competition can easily lead to sports injuries. Due to the influence of many factors, emphasis has been placed on rowing physical fitness training. In the specific operation process, it is necessary to closely combine the characteristics of rowing and the actual physical condition of athletes and develop a scientific and reasonable plan for rowing and injury treatment. Therefore, this article first starts from the investigation of physical injuries and types of injuries among different athletes and finds that the proportion of waist injuries is the highest. At the same time, it elaborates on the basic reasons for waist injuries, and finally provides rehabilitation treatment plans, allowing rowing athletes to make more progress and development.

The femtosecond structure of extreme contrast, multi-terawatt second-harmonic laser pulses at 400 nm

Ultrahigh intensity contrast and short pulse laser–solid interactions offer an attractive platform for investigating high-energy-density matter, particularly in the context of structured and ultra-thin targets that form hot, dense plasma conditions. Harmonic generation can improve the contrast of laser pulses by several orders of magnitude. In this study, we present the characterization of extreme contrast, relativistic intensity second-harmonic pulses at 400 nm, using the self-diffraction frequency-resolved optical gating technique. The 400 nm pulses were generated at various input intensities using potassium dihydrogen phosphate and lithium triborate crystals. Our observations reveal the presence of spectral broadening, pulse compression, and complex structures at higher input intensities. We see that extreme contrast, few tens of femtosecond pulses can have multiple “prepulses” at the 100s femtosecond scale as large as ten percent of the peak value. These can preionize a solid significantly and may influence the interaction. Simulations based on nonlinear pulse propagation equations reinforce our findings.

A safety study on ultra‑high or moderate static magnetic fields combined with platycodin D against lung cancer.

Due to the serious side effects of chemotherapy drugs against lung cancer, and the antitumor properties and high safety of magnetic fields, the present study combined moderate or ultra-high intensity statics magnetic fields (SMFs) with platycodin D (PD) to explore the antitumor efficiency and biosafety. The antitumor effects of PD with or without moderate and ultra-high SMFs on A549 cells bearing mice were compared. Mouse body weight, food/water intake, hematology routine, blood biochemistry, tumor weight and tissues hematoxylin and eosin (H&E) staining were examined. Behavior was measured using the elevated plus maze, open field and vital signs tests. The combined targets of PD and SMFs were detected using RNA-sequencing (RNA-seq). The results showed that the antitumor effect of 22 Tesla (T) SMF group was 3.6-fold higher compared with that of the 2 mg/kg PD group (tumor growth inhibition=10.08%), while the antitumor effect of 150 mT SMF was only 1.56-fold higher compared with that of PD. Although PD reduced the food intake, there was no significant difference in body weight, water intake or food consumption among PD and SMF groups. Behavioral results indicated that PD ameliorated dysphoria in mice, but SMFs reduced this effect. However, no significant abnormalities were found in routine blood, blood biochemistry test, H&E staining or organ index, except renal index which was reduced by PD with or without SMFs. RNA-sequencing (RNA-seq) demonstrated that SMFs and PD synergistically targeted the expression of genes associated with tumor growth, inflammation and neurological disease. The present study showed the antitumor efficacy and biosafety of moderate or ultra-high SMF combined with PD, which exhibited only few side effects in the treatment of lung cancer, thus supporting further research for the clinical application of magnetic fields.

Spatio-temporal characterization of tightly focused femtosecond laser fields formed by paraboloidal mirrors with different F-numbers.

The focusing spatiotemporal property of a femtosecond laser pulse is presented under tight focusing conditions by using the frequency-resolved incident electric field and vector diffraction formulas with the wavefront correction term. In the ideal case, the focused laser intensity reaches its maximum at the F-number of ∼0.35 due to the strong diffraction effect under extremely tight focusing conditions. In spatio-temporal coupling distortion cases, their spatiotemporal Strehl ratios show a trend of improvement as the F-number decreases and this phenomenon is mainly concentrated along the y-direction. Based on the numerical calculation method used in this work, the precise information of tightly focused ultra-intense femtosecond laser fields can be obtained, which is crucial for assessing a focused intensity and describing the motion of charged particles under an extremely strong electric field. Moreover, the evolution law of focal fields with spatiotemporal distortions found in this paper can offer some theoretical guidance for realizing ultrahigh laser intensity in the near future.

Radiation-dominated injection of positrons generated by the nonlinear Breit–Wheeler process into a plasma channel

Plasma acceleration is considered a prospective technology for building a compact multi-TeV electron–positron collider in the future. The challenge of this endeavor is greater for positrons than for the electrons because usually the self-generated fields from laser–plasma interaction are not well-suited for positron focusing and on-axis guiding. In addition, an external positron source is required, while electrons are naturally available in the plasma. Here, we study electron–positron pair generation by an orthogonal collision of a multi-PW laser pulse and a GeV electron beam by the nonlinear Breit–Wheeler process. We studied conditions favorable for positron deflection in the direction of the laser pulse propagation, which favors injection into the plasma for further acceleration. We demonstrate using the OSIRIS particle-in-cell framework that the radiation reaction triggered by ultra-high laser intensity plays a crucial role in the positron injection. It provides a suppression of the initial transverse momentum gained by the positrons from the Breit-Wheeler process. For the parameters used in this work, the intensity of at least 2.2×1023 W/cm2 is needed in order to inject more than 1% of positrons created. Above this threshold, the percentage of injected positrons rapidly increases with intensity. Moreover, subsequent direct laser acceleration of positrons in a plasma channel, using the same laser pulse that created them, can ensure a boost of the final positron energy by a factor of two. The positron focusing and guiding on the axis is provided by significant electron beam loading that changes the internal structure of the channel fields.

Kinetic theory for spin-polarized relativistic plasmas

The investigation of spin and polarization effects in ultra-high intensity laser–plasma and laser–beam interactions has become an emergent topic in high-field science recently. In this paper, we derive a relativistic kinetic description of spin-polarized plasmas, where quantum-electrodynamics effects are taken into account via Boltzmann-type collision operators under the local constant field approximation. The emergence of anomalous precession is derived from one-loop self-energy contributions in a strong background field. We are interested, in particular, in the interplay between radiation reaction effects and the spin polarization of the radiating particles. For this, we derive equations for spin-polarized quantum radiation reaction from moments of the spin-polarized kinetic equations. By comparing with the classical theory, we identify and discuss the spin-dependent radiation reaction terms and radiative contributions to spin dynamics.

Study of antiprotons as drivers in inertial confinement fusion by fast ignition method

Inertial confinement fusion is a promising approach to achieve controlled nuclear fusion for clean and abundant energy production. One of the key challenges in Inertial confinement fusion is achieving efficient ignition of the fusion fuel. Fast ignition offers a potential solution to this challenge by using an ultra-high intensity laser or a charged particle beam to directly ignite a pre-compressed fusion fuel. In this manuscript, we propose an approach for fast ignition in ICF, utilizing an antiproton beam to drive ignition in a deuteron-tritium fuel with a uranium-238 seed. The use of antiproton beams in Inertial confinement fusion offers unique advantages, including their ability to deposit energy deeply into the fuel, leading to enhanced energy coupling and heating. The addition of uranium-238 as a seed material in the fuel can further improve ignition conditions by enhancing energy deposition and facilitating ignition reactions. We present detailed simulations and analyses to demonstrate the feasibility and potential benefits of this approach. We investigate the effects of antiproton beam parameters, such as energy, intensity, and pulse duration, on ignition conditions, as well as the impact of uranium-238 seed concentration and distribution in the fuel. Our results show that fast ignition driven by an antiproton beam in DT with uranium-238 seed has the potential to significantly improve ignition performance in Inertial confinement fusion, leading to enhanced energy output and higher gain. The use of antiproton beams allows for efficient energy deposition and heating of the fuel, while the inclusion of uranium-238 seed promotes ignition reactions and improves ignition conditions. This concept presents a promising pathway towards achieving practical and efficient ignition in Inertial confinement fusion, and could pave the way for next-generation fusion power plants.

Efficient ion acceleration driven by a Laguerre–Gaussian laser in near-critical-density plasma

Laser-driven ion accelerators have the advantages of compact size, high density, and short bunch duration over conventional accelerators. Nevertheless, it is still challenging to generate ion beams with quasi-monoenergetic peak and low divergence in experiments with the current ultrahigh intensity laser and thin target technologies. Here we propose a scheme that a Laguerre–Gaussian laser irradiates a near-critical-density (NCD) plasma to generate a quasi-monoenergetic and low-divergence proton beam. The Laguerre–Gaussian laser pulse in an NCD plasma excites a moving longitudinal electrostatic field with a large amplitude, and it maintains the inward bowl-shape for dozens of laser durations. This special distribution of the longitudinal electrostatic field can simultaneously accelerate and converge the protons. Our particle-in-cell (PIC) simulation shows that the efficient proton acceleration can be realized with the Laguerre–Gaussian laser intensity ranging from 3.9 × 1021 W⋅cm−2–1.6 × 1022 W⋅cm−2 available in the near future, e.g., a quasi-monoenergetic proton beam with peak energy ∼ 115 MeV and divergence angles less than 5° can be generated by a 5.3 × 1021 W⋅cm−2 pulse. This work could provide a reference for the high-quality ion beam generation with PWclass laser systems available recently.

Experimental and numerical investigation on ultra-high intensity premixed LPG- air combustion in a novel porous stack burner

Experimental and numerical investigation on ultra-high intensity premixed LPG- air combustion in a novel porous stack burner

Research on performance of ionization chamber used in medical laser proton accelerator based on Garfield++

Gas ionization chamber has the advantage of accurate and reliable measurement data, which is widely used in beam current monitoring of proton and heavy ion beam therapy systems. According to the characteristics of the proton beam signal of the laser accelerator, because of its ultra-high peak current intensity, the peak current intensity of the beam generated by the traditional accelerator is much higher than that of the traditional accelerator. The gas ionization chamber cannot measure the proton beam with this characteristic, and the incident laser proton beam is likely to cause signal saturation and distortion in the gas ionization chamber. Therefore, it is necessary to improve the physical design of the gas ionization chamber and the supporting electronic system to improve the detection technology of the gas ionization chamber dedicated to the ion beam generated by the laser acceleration. In this paper, the physical design of the gas ionization chamber is optimized to avoid signal saturation in the gas ionization chamber while measuring the laser proton beam signal. With the method of modeling and simulation analysis of the gas ionization chamber based on the Garfield++, the optimal value is given in three aspects: the type selection of the gas medium, the gas pressure setting and the setting of the voltage of the gas ionization chamber in order to optimize the measurement signal saturation phenomenon caused by the large transient beam current intensity, and bring theoretical basis and guiding significance to the actual experimental operation. The research concludes that when helium is selected as the gas medium of the gas ionization chamber, the signal saturation can be effectively reduced; when the integration time of the electronic system of the gas ionization chamber is 500 ns, and the current measurement range is ±16 μA in actual, the optimized gas pressure should be set lower than 540 Torr and the voltage value lower than 300 V to match the electronic measuring range of the gas ionization chamber while detecting the current signal; when the signal detected is the integrated charge, the voltage setting of the gas ionization chamber has nearly nothing to do with the signal collected, but to adjust the gas pressure in the gas ionization chamber to optimize the final data.

Design of Pauci-Adaptive, Spirally Tiled Mirrors for Large Size Optical Vortex Generation

We propose the optical design of an adaptive and flexible 4-quadrant, or N-facet, spirally tiled mirror setup, to generate an optical vortex on large diameter laser systems. From a far-field analysis, we derive the optimal angular parameters that generate the highest contents of the targeted Laguerre-Gaussian mode. The modal purities thus obtained are close to those obtained with standard segmented spiral phase plates or mirrors. The intensity behavior in the focal Rayleigh zone is regular, and the effect of a small laser astigmatism, known to break the circularity of the ring intensity profile at focus, can be corrected. This pauci-adaptive faceted mirror setup appears well suited for use on ultra-high intensity or high energy laser systems.

Heating in multi-layer targets at ultra-high intensity laser irradiation and the impact of density oscillation

We present a computational study of isochoric heating in multi-layered (ML) targets at ultra-high intensity laser irradiation (). Previous studies have shown enhanced ion heating at interfaces, but at the cost of large temperature gradients. Here, we study ML targets to spread this enhanced interface heating to the entirety of the target and find heating parameters at which the temperature distribution is more homogeneous than at a single interface while still exceeding the mean temperature of a non-layered target. Further, we identify a limiting process of pressure oscillations that causes the layers to alternate between expanding and being compressed and leads to lower ion temperatures. Based on that, we derive an analytical model estimating the oscillation period to find target conditions that optimize heating and temperature homogeneity. This model can also be used to infer the electron energy from the oscillation period which can be measured e.g. by XFEL probing.

Single-pulse characterization of the focal spot size of X-ray free-electron lasers using coherent diffraction imaging.

The characterization of X-ray focal spots is of great significance for the diagnosis and performance optimization of focusing systems. X-ray free-electron lasers (XFELs) are the latest generation of X-ray sources with ultrahigh brilliance, ultrashort pulse duration and nearly full transverse coherence. Because each XFEL pulse is unique and has an ultrahigh peak intensity, it is difficult to characterize its focal spot size individually with full power. Herein, a method for characterizing the spot size at the focus position is proposed based on coherent diffraction imaging. A numerical simulation was conducted to verify the feasibility of the proposed method. The focal spot size of the Coherent Scattering and Imaging endstation at the Shanghai Soft X-ray Free Electron Laser Facility was characterized using the method. The full width at half-maxima of the focal spot intensity and spot size in the horizontal and vertical directions were calculated to be 2.10 ± 0.24 µm and 2.00 ± 0.20 µm, respectively. An ablation imprint on the silicon frame was used to validate the results of the proposed method.