Propagation Of High Energy Particles Research Articles

Simultaneous macroscale and microscale wave–ion interaction in near-earth space plasmas

Identifying how energy transfer proceeds from macroscales down to microscales in collisionless plasmas is at the forefront of astrophysics and space physics. It provides information on the evolution of involved plasma systems and the generation of high-energy particles in the universe. Here we report two cross-scale energy-transfer events observed by NASA’s Magnetospheric Multiscale spacecraft in Earth’s magnetosphere. In these events, hot ions simultaneously undergo interactions with macroscale (~{10}^{5} km) ultra-low-frequency waves and microscale (sim {10}^{3} km) electromagnetic-ion-cyclotron (EMIC) waves. The cross-scale interactions cause energy to directly transfer from macroscales to microscales, and finally dissipate at microscales via EMIC-wave-induced ion energization. The direct measurements of the energy transfer rate in the second event confirm the efficiency of this cross-scale transfer process, whose timescale is estimated to be roughly ten EMIC-wave periods about (1 min). Therefore, these observations experimentally demonstrate that simultaneous macroscale and microscale wave-ion interactions provide an efficient mechanism for cross-scale energy transfer and plasma energization in astrophysical and space plasmas.

CRPropa 3.2 — an advanced framework for high-energy particle propagation in extragalactic and galactic spaces

The landscape of high- and ultra-high-energy astrophysics has changed in the last decade, largely due to the inflow of data collected by large-scale cosmic-ray, gamma-ray, and neutrino observatories. At the dawn of the multimessenger era, the interpretation of these observations within a consistent framework is important to elucidate the open questions in this field. CRPropa 3.2 is a Monte Carlo code for simulating the propagation of high-energy particles in the Universe.This version represents a major leap forward, significantly expanding the simulation framework and opening up the possibility for many more astrophysical applications. This includes, among others: efficient simulation of high-energy particles in diffusion-dominated domains, self-consistent and fast modelling of electromagnetic cascades with an extended set of channels for photon production, and studies of cosmic-ray diffusion tensors based on updated coherent and turbulent magnetic-field models. Furthermore, several technical updates and improvements are introduced with the new version, such as: enhanced interpolation, targeted emission of sources, and a new propagation algorithm (Boris push). The detailed description of all novel features is accompanied by a discussion and a selected number of example applications.

Deuterated polyethylene nanowire arrays for high-energy density physics

Abstract The interaction of intense, ultrashort laser pulses with ordered nanostructure arrays offers a path to the efficient creation of ultra-high-energy density (UHED) matter and the generation of high-energy particles with compact lasers. Irradiation of deuterated nanowires arrays results in a near-solid density environment with extremely high temperatures and large electromagnetic fields in which deuterons are accelerated to multi-megaelectronvolt energies, resulting in deuterium–deuterium (D–D) fusion. Here we focus on the method of fabrication and the characteristics of ordered arrays of deuterated polyethylene nanowires. The irradiation of these array targets with femtosecond pulses of relativistic intensity and joule-level energy creates a micro-scale fusion environment that produced $2\times {10}^6$ neutrons per joule, an increase of about 500 times with respect to flat solid CD2 targets irradiated with the same laser pulses. Irradiation with 8 J laser pulses was measured to generate up to 1.2 × 107 D–D fusion neutrons per shot.

Ultrahigh-order Maxwell solver with extreme scalability for electromagnetic PIC simulations of plasmas

The advent of massively parallel supercomputers, with their distributed-memory technology using many processing units, has favored the development of highly-scalable local low-order solvers at the expense of harder-to-scale global very high-order spectral methods. Indeed, FFT-based methods, which were very popular on shared memory computers, have been largely replaced by finite-difference (FD) methods for the solution of many problems, including plasmas simulations with electromagnetic Particle-In-Cell methods. For some problems, such as the modeling of so-called “plasma mirrors” for the generation of high-energy particles and ultra-short radiations, we have shown that the inaccuracies of standard FD-based PIC methods prevent the modeling on present supercomputers at sufficient accuracy. We demonstrate here that a new method, based on the use of local FFTs, enables ultrahigh-order accuracy with unprecedented scalability, and thus for the first time the accurate modeling of plasma mirrors in 3D.

The extragalactic background light revisited and the cosmic photon-photon opacity

In addition to its relevant astrophysical and cosmological significance, the Extragalactic Background Light (EBL) is a fundamental source of opacity for cosmic high energy photons, as well as a limitation for the propagation of high-energy particles in the Universe. We review our previously published determinations of the EBL photon density in the Universe and its evolution with cosmic time, in the light of recent surveys of IR sources at long wavelengths. We exploit deep survey observations by the Herschel Space Observatory and the Spitzer telescope, matched to optical and near-IR photometric and spectroscopic data, to re-estimate number counts and luminosity functions longwards of a few microns, and the contribution of resolved sources to the EBL. These new data indicate slightly lower photon densities in the mid- and far-infrared and sub-millimeter compared to previous determinations. This implies slightly lower cosmic opacity for photon-photon interactions. The new data do not modify previously published EBL modeling in the UV-optical and near-IR up to several microns, while reducing the photon density at longer wavelengths. This improved model of the EBL alleviates some tension that had emerged in the interpretation of the highest-energy TeV observations of local \textit{blazar}s, reducing the case for new physics beyond the standard model (like violations of the Lorenz Invariance, LIV, at the highest particle energies), or for exotic astrophysics, that had sometimes been called for to explain it. Applications of this improved EBL model on current data are considered, as well as perspectives for future instrumentation, the Cherenkov Telescope Array (CTA) in particular.

Electron trapping and acceleration by kinetic Alfvén waves in solar flares

Context. Theoretical models and spacecraft observations of solar flares highlight the role of wave-particle interaction for non-local electron acceleration. In one scenario, the acceleration of a large electron population up to high energies is due to the transport of electromagnetic energy from the loop-top region down to the footpoints, which is then followed by the energy being released in dense plasma in the lower atmosphere.Aims. We consider one particular mechanism of non-linear electron acceleration by kinetic Alfven waves. Here, waves are generated by plasma flows in the energy release region near the loop top. We estimate the efficiency of this mechanism and the energies of accelerated electrons.Methods. We use analytical estimates and test-particle modelling to investigate the effects of electron trapping and acceleration by kinetic Alfven waves in the inhomogeneous plasma of the solar corona.Results. We demonstrate that, for realistic wave amplitudes, electrons can be accelerated up to 10−1000 keV during their propagation along magnetic field lines. Here the electric field that is parallel to the direction of the background magnetic field is about 10 to 103 times the amplitude of the Dreicer electric field. The acceleration mechanism strongly depends on electron scattering which is due to collisions that only take place near the loop footpoints.Conclusions. The non-linear wave-particle interaction can play an important role in the generation of relativistic electrons within flare loops. Electron trapping and coherent acceleration by kinetic Alfven waves represent the energy cascade from large-scale plasma flows that originate at the loop-top region down to the electron scale. The non-diffusive character of the non-linear electron acceleration may be responsible for the fast generation of high-energy particles.

Dynamics of two microscale DPF devices

Dense plasma focus (DPF) devices are coaxial transient discharge devices capable of generating plasma densities greater than 1016 cm−3 with ion temperatures in excess of 1 keV by compression resulting from strong magnetic fields created by high pulsed current. They are predominately used for high energy particle generation, but they are also convenient for investigating pinch dynamics due to their relatively fast repetition rates. These devices have been extensively studied at length scales on the order of cm, and this work helps to bridge understanding of larger low pressure pinches and more recent moderate energy density sources with novel applications like portable sources for high energy particles. In this research, the dynamics of two significantly smaller DPF devices operating in 50–190 torr He at <5 J/pulse with anode radii of 550 μm and 100 μm have been investigated using a 50 ns gated ICCD to image discharges throughout their lifetimes. Typical discharge stages of breakdown, rundown, pinch and expansion are observed for the microscale DPF. Images during the breakdown process are compared with respect to their symmetry, the velocity of their features, and their relative pinch intensities. Applicable scaling parameters are also compared to those of other DPF devices. In addition, the applicability of Knudsen scaling to DPF operation is introduced. The images show that as the anode radius decreases, breakdown and rundown features tend towards symmetry at higher pressure and near the Paschen minimum.

High Energy Particle Generation in Cosmic Rays and Solar Particle Events

It is assumed that cosmic rays and other high-energy particles of extraterrestrial origin can be produced by first-order Fermi diffusive shock acceleration in plasma up to 5x1019 eV, the point where they interact with the cosmic microwave background (CMB). First-order Fermi shock acceleration is due to a supersonic shock with a Mach number dependent on the index (or logarithmic slope) of the shock-induced power-law spectrum. The local all-particle interstellar cosmic-ray spectrum can be obtained from the solution of a Fredholm integral equation in rigidity, yielding both the “knee” and the “ankle” of the primary spectrum. The effect of the maximum galactic acceleration mechanism at high energies near the ankle is to increase the relative number of heavy nuclei relative to protons. Multiple cutoffs of heavier nuclei due to interactions with the CMB have the opposite effect just below the Greisen-Zatsepin-Kuz’min (GZK) cutoff, resulting in fluxes enriched in protons. Earthward-directed supersonic coronal mass ejections are responsible for the great bulk of high-energy solarparticle events because of diffusive shock acceleration in the heliosphere. Keywords: Air shower data, cosmic rays, GZK cutoff, Monte Carlo solution to integral equations, plasma, Shock acceleration, solar modulation, the local interstellar spectrum.

Generation of high-energy particles, neutrino and fotons in magnetosphere of collapsing star

The generation of particles, photons and neutrinos in magnetosphere of collapsing star are considered. These processes are caused the self-interaction initial accelerating in magnetosphere protons and electrons. The second particles and photons will arise as a result of this self-interaction, which in turn will generate charged particles, photons and neutrino (cascade process). These processes are especially effective for the formation collapsing star magnetosphere from the secondary charged particles. In addition, the particles, photons and neutrinos will be generated in magnetosphere of collapsing star as result of these processes.

Medium-induced emissions of hard gluons

We present a derivation of the medium-induced gluon radiation spectrum beyond the current limitation of soft gluon emission. Making use of the path integral approach to describe the propagation of high-energy particles inside a medium, we study the limiting case of a hard gluon emission. Analytical and numerical results are presented and discussed within the multiple soft scattering approximation. An ansatz interpolating between soft and hard gluon emissions is provided. The Landau–Pomeranchuk–Migdal effect is observed in the expected kinematic region.

On specific features of chemical composition of solar energetic particles

The methodology of analysis and the results of determination of chemical composition of Solar Energetic Particles (SEP) events at energies ≥4 MeV per nucleon are presented. The systematic description of experimental data about chemical composition of SEP is necessary both for better understanding of the processes resulting in generation and propagation of high-energy particles, and for development of a quantitative calculation model of fluxes of SEP particles.

Generation of High-energy Particles and Radiation from Relativistic Plasma for Nuclear Research

Generation of High-energy Particles and Radiation from Relativistic Plasma for Nuclear Research

Effect of initial plasma density on laser induced ion acceleration

The effect of initial plasma density on the energetics of the laser accelerated ions is studied using one dimensional particle in cell simulations. It is observed that the initial plasma density plays an important role in the generation of high energy particles. In the case of a spatially constant initial density, there exists an optimum value for the maximum ion acceleration. Similarly for the case of a density ramp, an optimum value of ramp length exists for the maximum ion acceleration. At a laser intensity of 5×1020 W/cm2, a maximum energy of about 1 GeV is seen with an optimum initial density ramp.

Extragalactic optical-infrared background radiation, its time evolution and the cosmic photon-photon opacity

The background radiations in the optical and the infrared constitute a relevant cause of energy loss in the propagation of high energy particles through space. In particular, TeV observations with Cherenkov telescopes of extragalactic sources are influenced by the opacity effects due to the interaction of the very high-energy source photons with the background light. With the aim of assessing with the best possible detail these opacity terms, we have modelled the extragalactic optical and IR backgrounds using available information on cosmic sources in the universe from far-UV to sub-mm wavelengths over a wide range of cosmic epochs. We have exploited the relevant cosmological survey data - including number counts, redshift distributions, luminosity functions - from ground-based observatories in the optical, near-IR, and sub-mm, as well as multi-wavelength information coming from space telescopes, HST, ISO and Spitzer. Additional constraints have been used from direct measurements or upper limits on the extragalactic backgrounds by dedicated missions (COBE). All data were fitted and interpolated with a multi-wavelength backward evolutionary model, allowing us to estimate the background photon density and its redshift evolution. From the redshift-dependent background spectrum, the photon-photon opacities for sources of high-energy emission at any redshifts were then computed. The same results can also be used to compute the optical depths for any kind of processes in the intergalactic space involving interactions with background photons (like scattering of cosmic-ray particles). We have applied our photon-photon opacity estimates to the analysis of spectral data at TeV energies on a few BLAZARs of particular interest. [abridged]

Interaction between Alternating Magnetic Fields and a Relativistic Collisionless Shock

We investigate the interaction between alternating magnetic fields with cold current sheets and a relativistic collisionless shock wave. Many kinds of high-energy astrophysical objects may involve such alternating magnetic fields and a relativistic shock. They can be potent sources for the generation of high-energy particles. We found that a precursor wave, propagating upstream from the shock front, accelerates a dense current sheet plasma upstream. In the case that the width of the respective magnetic field reversal is larger than the downstream gyroradius, the current sheet generates a large-amplitude magnetosonic wave downstream by the collision with a shock front. The motional electric field accompanied by the magnetosonic wave can further accelerate the preaccelerated particles, forming a nonthermal energy spectrum. In addition, the current sheet structure is stable against not only the collision but also compression by other current sheets. In the thin current sheet case, which means the case that the width of the alternating magnetic field reversal is smaller than the downstream gyroradius, the magnetic field dissipates and the magnetosonic wave excitation is absent. This result is applied to pulsar wind nebulae. The result of the dissipation could solve the σ problem.

超短パルス超高強度レーザーと物質との相互作用

Recently, ultra-high intensity short pulse lasers have been developed quite successfully. They have been applied to the fields such as hard x-ray generation and high energy particle generation. The essence of such laser-produced plasmas is that the lasers can feed their ultra-high energy density into that of the electron motion in matter via the ponderomotive force. Then the electron energy is transferred into the atoms and ions which include excitation and ionization by the laser field and the electron collision. Ion acceleration occurs by the electrostatic potential formed by high energy electron bouncing in the finite size plasma. Subsequently, high flux x-ray with a few tens of MeV energy induces nuclear reactions, which open up the new fields of high energy plasma physics and applications. In this reviewed article, the basic ultra-short and high intensity laser-plasma interaction studies are introduced. These studies lead us to new attractive fields not only the practical applications but also the new aspects of the basic sciences such as control of a highly-nonlinear relativistic plasma.

Generation of magnetic field, vortices and relativistic particles by the nonpotential ponderomotive force

Effects of nonpotential ponderomotive force on kinetic phenomena in a plasma are presented. The particle distribution function is derived, which allows one to calculate the particle and heat fluxes. A novel relativistic hydrodynamic equation of motion, incorporating self-generated magnetic fields, is obtained, which admits no frozen-in condition. The generation of electron fluid vortices by a laser pulse in initially unmagnetized plasma is demonstrated. The merging, decay, and annihilation of vortices (filaments) are discussed. The launching of plasma jets by the vortex structures is disclosed. Self-consistent problem of magnetic, modulational, and filamentational instabilities is studied. The decay of photons into photons and the helicon waves are also discussed. The relevance of this work to recent PetaWatt experiments in connection with high-energy particle generation is pointed out. In addition, highly collimated, mass outflows (jets) are ubiquitous phenomena relevant to astrophysics.

Space–time fluctuations and ultra-high energy cosmic ray interactions

The intimate geometry of space–time is expected to suffer stochastic fluctuations as a result of quantum gravitational effects. These fluctuations may induce observable consequences on the propagation of high energy particles over large distances, so that the strength and the characteristics of these fluctuations may be constrained, mainly in the range of energies of interest for cosmic ray physics. While invoked as a possible explanation for the detection of the puzzling cosmic rays with energies in excess of the threshold for photopion production (the so-called super-Greisen–Zatsepin–Kuzmin particles), we demonstrate here that lower energy observations may provide strong constraints on the role of a fluctuating space–time structure.

Studies of intense laser-plasma interactions for the fast ignitor concept at ILE, Osaka University

We experimentally studied laser-hole boring with 100 ps/1 TW laser light and ultra-intense laser-plasma interactions using a 0.5 ps/100 TW laser system. Investigation into laser-hole boring was made by measurements of backscattered light spectra, x-ray image and electron density profiles in under- and overdense regions. For the first time x-ray laser light was used to directly observe the channel in the overdense plasma. We further examined short pulse laser interactions as well as the generation of high-energy particles with 100 TW laser light. Neutrons by D-D fusion reaction in the interaction plasma were measured to diagnose ion acceleration. High-energy electrons (MeV) were measured by a x-ray method.

Effect of hydrogen annealing on hot-carrier instability of X-Ray irradiated CMOS devices

In the very large scale integration (VLSI) technology, the need for high density and high performance integrated circuit (IC) chip demands advanced processing techniques that often result in the generation of high energy particles and photons. Frequently, the radiation damage are introduced by these energetic particles and photons during device processing. The radiation damage created by x-ray irradiation, which can often occur during metal sputtering process, has been shown to potentially enhance hot-carrier instability if the neutral traps which act as electron or hole traps in the silicon dioxide is not annealed out. In this paper, we investigate the effects of annealing using different hydrogen contents and temperatures on the device characteristics and hot carrier instability of 0.5 μm CMOS devices after 1500 mJ/cm2 synchrotron x-ray irradiation. Three different annealing conditions were employed; 400° C H2, 450° C H2, and 400° C H2 + N2. It is found that for all three different hydrogen anneals the normal characteristics of irradiated CMOS devices can be effectively recovered. The hot-carrier instability of bothp- andn-channel MOSFETs are significantly enhanced after x-ray irradiation due to the creation of neutral traps and positively charged oxide traps. After high H2 (100%) concentration anneals at 450° C, the hot-carrier instability in irradiatedn-channel devices is greatly reduced and comparable to the non-irradiated devices. Although the hot-carrier instability inp-channel devices is also significantly reduced after annealing, the threshold voltage shifts are still enhanced as compared to the devices without exposure to x-ray irradiation during maximum gate current stress. For those non-irradiated, but hydrogen-annealedp-channel devices, the hot-carrier instability was observed to be worse than the non-irradiated device without hydrogen annealing.