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Numerical simulation is used to compare two methods for measuring power of wideband electromagnetic noise in experimental facilities with high-current relativistic electron beams formed by explosive-emission cathodes. The simulation shows that the difference in the experimental results by two orders of magnitude—several megawatts for pulses with a duration of few nanoseconds and tens of kilowatts for pulses with a duration of hundreds of nanoseconds—arises from the nature of the noise itself at different stages of the explosive-emission cathode operation rather than from difference of the measurement methods.

We report experimental results on relativistic electron beam (REB) transport in a set of cold and shock-heated carbon samples using the high-intensity kilojoule-class OMEGA EP laser. The REB energy distribution and transport were diagnosed using an electron spectrometer and x-ray fluorescence measurements from a Cu tracer buried at the rear side of the samples. The measured rear REB density shows brighter and narrower signals when the targets were shock-heated. Hybrid PIC simulations using advanced resistivity models in the target warm-dense-matter (WDM) conditions confirm this observation. We show that the resistivity response of the media, which governs the self-generated resistive fields, is of paramount importance to understand and correctly predict the REB transport.

A project for a submillimeter free electron laser (FEL) based on a relativistic electron beam (REB) generated in a linear induction accelerator (LIA) is proposed for the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, and the Institute of Applied Physics, Russian Academy of Sciences. A theoretical analysis shows that the electron beam generated in the LIA (energy MeV, current kA, normalized emittance ~ 1100 π mm mrad) is a suitable driver for generating subgigawatt pulses of coherent EM radiation in the submillimeter range of wavelengths (0.3–1 THz). The main proposals for developing a FEL based on the electron beam generated in a linear induction accelerator are presented, the main project tasks are outlined, and proposed ways of solving them are described. Results from electron-optical experiments on the formation of an electron beam intended for FEL applications are presented.

The long-distance stable transport of relativistic electron beams (REBs) in plasmas is studied by full three-dimensional particle-in-cell simulations. Theoretical analysis shows that the beam transport is mainly influenced by three transverse instabilities, where the excitation of self-modulation instability, and the suppression of the filamentation instability and the hosing instability are important to realize the beam stable transport. By modulating the transport parameters such as the electron density ratio, the relativistic Lorentz factor, the beam envelopes and the density profiles, the relativistic bunches having a smooth density profile and a length of several plasma wave periods can suppress the beam-plasma instabilities and propagate in plasmas for long distances with small energy losses. The results provide a reference for the research of long-distance and stable transport of REBs, and would be helpful for new particle beam diagnosis technology and space active experiments.

The paper studies the interaction between the relativistic electron beam and electromagnetic resonances in the Cherenkov generator with the single-section slow-wave structure using the 2.5D hybrid particle-in-cell code. In numerical simulation, the tubular beam current of ≤ 25 kA and ≤ 490 keV energy are used to inject the electron beam into a homogeneous slow-wave structure of a diameter 40 mm with and without a diffraction reflector. The frequency range is 362 to 367 GHz. Parameter ranges are obtained for the stable radiation generation with synchronization of electromagnetic resonances by the electron beam and self-modulation of radiation power. With the diffraction reflector, the total power of stable radiation is 400 MW with the forward radiation power of 90%, regardless of power ohmic losses. Resonance magnification modes are detected for the radiation power in the narrow range of the electron energy, which match the radiation frequency near the third-order electromagnetic resonance with no electron beam.

The interaction of a relativistic electron beam with an energy of 280–1500 keV and electromagnetic resonances in a multiwave Cherenkov generator with a diffraction reflector is studied using a 2.5D hybrid code. The main calculations are performed with a 5 kA tubular beam current injected into an electrodynamic system with a diameter of 40 mm. The frequencies are varied within 358–368 GHz. The parameter regions of stable radiation generation during synchronization of electromagnetic resonances by an electron beam and the power self-modulation mode are found. The total radiation power in the calculations, excluding ohmic losses, reaches 2.32 GW with a generation efficiency of 42%. The radiation power decreases by two orders of magnitude with an increase in the electron energy from 1100 keV to 1150 keV. The optimal beam and electrodynamic system parameters in the electron energy range up to 500 keV are found.

A hybrid reduced model for relativistic electron beam transport based on the angular moments of the relativistic kinetic equation with a special closure is presented. It takes into account collective effects with the self-generated electromagnetic fields as well as collisional effects with the slowing down of the relativistic electrons by plasmons, bound and free electrons and their angular scattering on both ions and electrons. This model allows for fast computations of relativistic electron beam transport while describing their energy distribution evolution. Despite the loss of information concerning the angular distribution of the electron beam, the model reproduces analytical estimates in the academic case of a monodirectional and monoenergetic electron beam propagating through a warm and dense plasma and hybrid particle-in-cell simulation results in a realistic laser-generated electron beam transport case.

AbstractThe destruction of an energetic condensed system based on glycerol trinitrate, polyether urethane, and aluminum powder upon exposure to a relativistic electron beam with a maximum energy of 310 keV, a total duration of 170–180 ns, and an average flux density of 200–215 J/cm2 was studied by nanosecond electron-optical chronography, scanning electron microscopy, and energy dispersive analysis. The effect of the generation of pulsed electric fields and shock-wave loads accompanying relativistic electron beam absorption on the mechanical damage to samples of energetic condensed systems is discussed.

Particle accelerators driven by laser-generated terahertz (THz) pulses promise unprecedented control over the energy–time phase space of particle bunches compared with conventional radiofrequency technology. Here we demonstrate acceleration of a relativistic electron beam in a THz-driven linear accelerator. Narrowband THz pulses were tuned to the phase-velocity-matched operating frequency of a rectangular dielectric-lined waveguide for extended collinear interaction with 35 MeV, 60 pC electron bunches, imparting multicycle energy modulation to chirped (6 ps) bunches and injection phase-dependent energy gain (up to 10 keV) to subcycle (2 ps) bunches. These proof-of-principle results establish a route to whole-bunch linear acceleration of subpicosecond particle beams, directly applicable to scaled-up and multistaged concepts capable of preserving beam quality, thus marking a key milestone for future THz-driven acceleration of relativistic beams.Relativistic 35 MeV electron bunches with charges of 60 pC are accelerated in a terahertz-wave-driven dielectric waveguide. When the terahertz pulse energy is 0.8 μJ, an accelerating gradient of 2 MeV m−1 and energy gain of 10 keV are achieved.

AbstractThe dependence of the angular density and the photon yield of collimated diffracted transition radiation (DTR) generated in a thin single-crystal plate by a beam of relativistic electrons on the beam divergence are studied. An expression describing the DTR angular density averaged over all the rectangular trajectories of electrons in the beam is derived. For the averaging, the two-dimensional Gaussian distribution is used. A significant dependence of the angular density of collimated DTR photons on the electron-beam divergence is shown. An expression describing the number of collimated DTR photons is obtained. The significant dependence of the photon number of the collimated DTR is shown.