Intense Relativistic Beam Research Articles

Electromagnetic wave scattering in plasma beam-driven waveguides under strong magnetic fields

This study analyzes the scattering of electromagnetic waves in a cold and uniform plasma-filled waveguide driven by an intense relativistic plasma beam under a strong magnetic field. The strong interaction of plasma with electromagnetic waves enables its potential use in different types of waveguides. The Helmholtz equation governs the boundary value problem, which is solved by incorporating the mode matching technique. Invoking the boundary and matching conditions and the derived orthogonality and dispersion relations in this scheme gives an exact solution to the scattering problem. The numerical results shed light on the occurrence of reflection and transmission and flow of power. The power flux is plotted against angular frequency and various duct configurations. The solution is completely validated through the benefit of analytical and numerical results. The investigation of this structure reveals not only its mathematical, but also its physical features.

Upper hybrid wave excitation and particle acceleration by resonant beating of two hollow Gaussian laser beams in magnetized plasma

This paper investigates the excitation of the upper hybrid wave by resonant beating of two intense hollow Gaussian relativistic laser beams in a magnetized plasma. Hollow laser beams are taken in this study because they have the same power at different beam orders. The interaction of two intense hollow laser beams at the frequency difference ( Δ ω ≈ ω 1 − ω 2 ) and wavenumber ( Δ k = k 1 − k 2 ) excites the upper hybrid wave in the magnetized plasma. The excited upper hybrid wave accelerates the electrons to higher energies. The acceleration of electrons has also been studied. This study is carried out under a higher-order paraxial region, where the dielectric constant and the eikonal are expanded to the fourth power of the radial distance. Analytical expressions are obtained for the beam width parameter of the hollow Gaussian laser beams, the electric field of the upper hybrid wave, and the energy gain by the electrons. The effects of various laser and plasma parameters (such as beam order, plasma frequency, and electron cyclotron frequency) on the electric field of the upper hybrid wave and the energy gain of electrons have been explored. The results are compared with paraxial region and the Gaussian profile of laser beams. Numerical analysis has been performed for well-established laser and plasma parameters.

Relativistic self-focusing in the interaction of laser beam and plasma with periodical density ripple

AbstractIn the paper, relativistic self-focusing in the interaction of laser beam and plasma with periodical density ripple has been studied by the applied WKB approximation and higher-order paraxial theory. The result shows that under the influence of relativistic nonlinear effect, the dielectric function shows the fierce oscillational variation with similar periodicity, which then leads to the intense relativistic beam self-focusing along the propagation distance, such self-focusing also presents similar periodic variation. Besides, in the plasma with periodical density ripple, the initial density and the density ripple amplitude have obvious influence on self-focusing. When the two factors increase, then there will be more strength self-focusing. Choosing the appropriate initial density and the periodic density parameter is benefit to the formation of the more stable self-focusing.

High-energy-density-science capabilities at the Facility for Antiproton and Ion Research

The Facility for Antiproton and Ion Research (FAIR) will employ the World's highest intensity relativistic beams of heavy nuclei to uniquely create and investigate macroscopic (millimeter-sized) quantities of highly energetic and dense states of matter. Four principal themes of research have been identified: properties of materials driven to extreme conditions of pressure and temperature, shocked matter and material equation of state, basic properties of strongly coupled plasma and warm dense matter, and nuclear photonics with a focus on the excitation of nuclear processes in plasmas, laser-driven particle acceleration, and neutron production. The research program, principally driven by an international collaboration of scientists, called the HED@FAIR collaboration, will evolve over the next decade as the FAIR project completes and experimental capabilities develop. The first programmatic research element, called “FAIR Phase 0, officially began in 2018 to test components, detectors, and experimental techniques. Phase-0 research employs the existing and enhanced infrastructure of the GSI Helmholtzzentrum für Schwerionenforschung (GSI) heavy-ion synchrotron coupled with the PHELIX high-energy, high-intensity laser. The “FAIR Day one” experimental program, presently scheduled to begin in 2025, commences the use of FAIR's heavy-ion synchrotron, coupled to new experimental and diagnostic infrastructure, to realize the envisaged high-energy-density-science research program.

Formation of Intense Quasicylindrical Charged-Particle Beams

2D and 3D problems of the formation of intense relativistic charged-particle beams are discussed for different geometrical configurations. Both the exact solutions in the closed form and the results of the paraxial approximation are investigated. The model of elliptic beams is analyzed, and the conclusion is drawn that classical conceptions do not correspond to practical tasks of the formation and transport of these objects.

Modeling polar region atmospheric ionization induced by the giant solar storm on 20 January 2005

AbstractIonization in Earth's troposphere is mainly due to Galactic cosmic rays. Occasionally, solar storms produce intense relativistic ion beams that significantly increase such ionization. One of the largest recorded solar radiation storms, on 20 January 2005, resulted in up to 55‐fold increases in the count rates of ground‐based particle detectors in polar regions. We use McMurdo and Inuvik neutron monitor data to estimate accurate time profiles of ion energy spectra above the atmosphere at each location. Using data‐driven atmospheric models, we perform Monte Carlo simulations of particle‐air interactions and calculate atmospheric ionization and potential biological dosage versus altitude and time for each location. We found that if airplane passengers had traversed the south polar region, they could have been exposed to the typical annual cosmic radiation dosage at sea level within 1 h. These techniques can help evaluate possible influences of solar activity on atmospheric properties.

On the Road to FAIR: 1stOperation of AGATA in PreSPEC at GSI

The Facility for Antiproton and Ion Research (FAIR), under construction at Darmstadt will provide intense relativistic beams of exotic nuclei at its Superconducting-FRagment Separator. High-resolution in-beam γ-ray spectroscopy will be performed in the HISPEC experiment, using the European Advanced GAmma-ray Tracking Array (AGATA). The PreSPEC-AGATA campaign is the predecessor of HISPEC and runs from 2012 to 2014 at GSI Helmholtzzentrum für Schwerionenforschung GmbH. Up to19 AGATA modules were used at GSI's F Ragment Separator in 2012. We report on the status of the experiment including preliminary results from performance commissioning.

Spatially resolved quantum nano-optics of single photons using an electron microscope.

We report on the experimental demonstration of single-photon state generation and characterization in an electron microscope. In this aim we have used low intensity relativistic (energy between 60 and 100keV) electrons beams focused in a ca. 1nm probe to excite diamond nanoparticles. This triggered individual neutral nitrogen-vacancy centers to emit photons which could be gathered and sent to a Hanbury Brown-Twiss intensity interferometer. The detection of a dip in the correlation function at small time delays clearly demonstrates antibunching and thus the creation of nonclassical light states. Specifically, we have also demonstrated single-photon states detection. We unveil the mechanism behind quantum states generation in an electron microscope, and show that it clearly makes cathodoluminescence the nanometer scale analog of photoluminescence. By using an extremely small electron probe size and the ability to monitor its position with subnanometer resolution, we also show the possibility of measuring the quantum character of the emitted beam with deep subwavelength resolution.

Off-axis stability of intense continuous relativistic beams

This paper investigates the stability of off-axis continuous intense relativistic beams propagating inside a circular conducting pipe. The equations of motion for the centroid and the envelope of slightly off-axis beams are derived and used to determine equilibrium and stability conditions for the beam transport. It is shown that depending on the parameters of the system, beams propagating along the pipe axis may become unstable due to the presence of the wall, imposing a fundamental limitation in the effective area that an equilibrium beam can occupy inside the conductor.

Feasibility Study of Axially- Extracted Virtual Cathode Oscillator

In this paper, we have analyzed the design parameters of the axially - extracted virtual cathode oscillator, which is high-power microwave source based on the concept of the virtual cathode associated with the intense relativistic electrons beam oscillations in the electrostatic potential well. The microwave emission by the virtual cathode oscillator results from both the space and time oscillations of virtual cathode and reflexing electrons trapped in the potential well between the virtual and real cathodes. In the X-band frequency spectrum 700 MW microwave peak power has been obtained analytically by the solid electron beam of 300 kV and 20 kA for feasible design parameters. The analysis has been performed by 2-dimensional, relativistic, electromagnetic particle-in-cell simulation code XOOPIC.

Space-charge limiting currents for magnetically focused intense relativistic electron beams

The self-consistent differential equations, which describe a laminar-flow equilibrium state in a magnetically focused intense relativistic electron beam propagating inside a conducting waveguide, are presented. The canonical angular momentum, pθ, defined under the conditions at the source, uniquely determines the possible solutions of these equations. By numerically solving these equations, the space-charge limited current and the externally applied magnetic field are obtained in a solid beam and a hollow beam in two cases of pθ = 0 (magnetically shielded source) and pθ = const. (immersed source) separately. It is shown that the hollow beam is more beneficial to the propagation of the intense relativistic beam through a drift tube than the solid beam.

Resonant coherent excitation of relativistic nuclei in aligned crystals: New experimental perspectives at FAIR

A short overview of the status of nuclear resonant coherent excitation (RCE) of relativistic nuclei in aligned crystals is presented. The planned GSI accelerator facility FAIR, which will provide intense relativistic heavy-ion beams, will offer new experimental perspectives to study nuclear RCE. Unique opportunities will arise from the availability of bare ions up to uranium with relativistic energies up to 30GeV/u. Synchrotron accelerators, which allow for fine-tuning of the extraction energy, provide ideal conditions for nuclear RCE experiments. Calculations of electromagnetic excitation cross-sections of projectile nuclei in relativistic collisions with individual target atoms are presented, estimates of the nuclear RCE probability in a crystal, a list of candidate nuclei for nuclear RCE experiments, as well as possible experimental schemes at FAIR.

Space-charge limiting currents in magnetically focused intense relativistic beams with an ion channel

The intense relativistic beam propagation through the drift tube filled with background plasma is investigated. The self-consistent differential equations, which describe the laminar-flow equilibria state in magnetically focused relativistic beams with an ion channel, are presented. By solving these equations using the Runge-Kutta method, the azimuthal velocity, the axial velocity, and the electron beam density, which are functions of radial position, can be calculated. Then the space-charge limiting current and the externally applied magnetic field can be obtained for solid beams and hollow beams. In the case of plasma fill, the axial velocity of the laminar flow is a nonuniform radial profile. The simulated results show that the background plasma can increase the space-charge limiting current, reduce the externally applied magnetic field, and improve the electron beam propagation through the drift tube.

Challenges and opportunities for atomic physics at FAIR: The new GSI accelerator project

We present a short overview of the current status of the new accelerator project FAIR at GSI with the new double synchrotron rings and the multi-storage rings. The key features of the new facility, which provides intense relativistic beams of stable and unstable nuclei, are introduced and their relation to the anticipated experimental programs in nuclear structure physics and antiproton physics is shown. The main emphasis in this overview is given to the atomic physics program with unique opportunities which will be provided e.g. by bare U92+ ions with kinetic energies continuously variable between relativistic energies corresponding to γ up to ≅35 down to kinetic energies of such ions in traps corresponding to fractions of a Kelvin.

Three-dimensional wakes driven by intense relativistic beams in gas targets

Three-dimensional (3-D) particle-in-cell (PIC) simulations of intense laser pulses and intense relativistic electron beams, propagating in gas targets are presented. As these beams propagate, the background gas is tunnel ionized, and the beam drives a wake, which sustains 1-100 GV/cm electric fields and propagates at the velocity of the driver. Such wakes can accelerate electrons to gigaelectronvolt energies in cm- length scale plasmas.

Longitudinal self-modulation of an intense relativistic electron beam in a two-cavity system

Self_modulation may appear on an intense relativistic electron beam(IREB) trave rsing a two_cavity klystron system. It is caused by the intense relativistic eff ect. RF output can be obtained without RF input. Based on this mechanism, a new type of high_power microwave source is suggested. The oscillation condition of t he intense relativistic election beam, traverse mechanism and PIC simulation are presented. After optimization design, a 800MW output peak microwave power was o bserved at a frequency of 099GHz, while an electron beam of voltage 500kV, cur rent 4kA is injected. The efficiency is about 40%.

Density measurements of heavy-ion-beam-induced stress waves in solid matter by a sensitive laser deflection technique

We present a sensitive density diagnostic based on the deflection of a laser beam by refractive index gradients. The method is used to investigate stress waves in plexiglass, created by the irradiation of multilayered metal–plexiglass targets with intense relativistic heavy-ion beams. Measured laser deflection angles are of the order of 1 mrad, with a resolution of the apparatus of 50 μrad. Results are in excellent agreement with interferometric measurements. The deflection technique is superior to an imaging interferometer in terms of simplicity and sensitivity.

Studies of high energy density in matter driven by heavy ion beams in solid targets

By the interaction of intense (1010 particles/500 ns) relativistic (∼300 MeV/amu) heavy ion beams with solid targets, large volumes (several cubic millimeters) of strongly coupled plasmas are produced at solid-state densities and temperatures of up to 1 eV, with relevance for equation-of-state (EOS) studies of matter at high energy density and heavy ion-beam-driven inertial confinement fusion (ICF). The time and space profile of the ion beams, focused by the plasma lens to diameters of a minimum of 0.5 mm in order to obtain specific energy depositions of up to about 4 kJ/g, were measured to calculate the energy deposition in the target. In the present work, the plasmas created by ion beam interaction with cryogenic gas crystals and metallic targets are studied, among other methods, by backlighting shadowgraphy and electrical conductivity measurements. The experiments are coupled with two-dimensional hydrodynamic simulations.

Gigavolt pulsed power by magnetic levitation

A magnetically levitated and insulated torus of meter-size dimensions can be charged up to gigavolt potentials. Discharging the torus through a breach made by a plasma jet or spark gap, an intense relativistic ion beam can be extracted from a magnetically insulated diode. Because of its self-magnetic field, the beam can be transported over large distances, a property well suited for thermonuclear microexplosion ignition.

Electron beam probing of strong Langmuir fields in an intense beam-plasma system

Strong Langmuir turbulence fields driven by an intense relativistic beam were probed using a weak electron beam after the intense beam passed through a plasma. Persistence of the strong Langmuir turbulence state was proved by observing broadening of the profile of the probe beam after it traversed the plasma column.