Relativistic Particle Beam Research Articles

Magnetic pinching of relativistic particle beams: a new approach to strong-field QED physics

Quantum electrodynamics (QED) is a foundation of modern physics, yet access to the strong-field QED regime in the laboratory remains a formidable challenge. Currently, high-power lasers at the multi-petawatt level and above are generally believed to be an important approach to test QED physics. Here, we present a different approach by use of an electron beam self-pinched to near-solid-density. The beam self-pinching is realized while it transports through a properly designed hollow cone target, where strong azimuthal magnetic fields are generated by the beam-induced plasma return currents at the inner surface of the cone target. In this way, the beam diameter can be reduced by more than an order of magnitude down to submicron and its density is increased by hundreds of times. The produced ultradense electron beams can unlock a new regime of QED-dominated beam–plasma interactions, for example, more than 60% of the beam energy can be converted into GeV gamma-rays with unprecedented brilliance when such a beam passes through a thin solid foil. Moreover, with proper parameter design, this beam-focusing scheme can also be applied to positron beams and thus may find applications in broad areas, such as particle colliders and strong-field physics.

Relativistic space-charge field calculation by interpolation-based treecode

Space-charge effects are of great importance in particle accelerator physics. In the computational modeling, tree-based methods are increasingly used because of their effectiveness in handling non-uniform particle distributions and/or complex geometries. However, they are often formulated using an electrostatic force which is only a good approximation for low energy particle beams. For high energy, i.e., relativistic particle beams, the relativistic interaction kernel may need to be considered and the conventional treecode fails in this scenario. In this work, we formulate a treecode based on Lagrangian interpolation for computing the relativistic space-charge field. Two approaches are introduced to control the interpolation error. In the first approach, a modified admissibility condition is proposed for which the treecode can be used directly in the lab-frame. The second approach is based on the transformation of the particle beam to the rest-frame where the conventional admissibility condition can be used. Numerical simulation results using both methods will be compared and discussed.

SPACE: 3D parallel solvers for Vlasov-Maxwell and Vlasov-Poisson equations for relativistic plasmas with atomic transformations

A parallel, relativistic, three-dimensional particle-in-cell code SPACE has been developed for the simulation of electromagnetic fields, relativistic particle beams, and plasmas. In addition to the standard second-order Particle-in-Cell (PIC) algorithm, SPACE includes efficient novel algorithms to resolve atomic physics processes such as multi-level ionization of plasma atoms, recombination, and electron attachment to dopants in dense neutral gases. SPACE also contains a highly adaptive particle-based method, called Adaptive Particle-in-Cloud (AP-Cloud), for solving the Vlasov-Poisson problems. It eliminates the traditional Cartesian mesh of PIC and replaces it with an adaptive octree data structure. The code's algorithms, structure, capabilities, parallelization strategy, and performance have been discussed. Typical examples of SPACE applications to accelerator science and engineering problems are described.

Measurement of ionization loss of 50 GeV protons in silicon with smoothly tunable up to 1 cm thickness using a single flat detector

Research of the ionization loss of 50 GeV protons, the path of which in the depleted layer of the silicon detector was smoothly regulated in the range from 0.3 to 10 mm, is presented. In the experiment, we used a flat silicon detector with a fixed thickness of the depleted layer of 300 μm. The smooth regulation of the path was realized due to the variation of the angle between the surface of the detector and the incident proton beam. The comparison of experimental data and theoretical calculations of the ionization loss demonstrates agreement in all range of thicknesses. Results of the research can be used in order to control the angle between the surface of the detector and the incident beam of relativistic particles. Besides, the results can be used in the analysis of data from astrophysical silicon detectors of charged particles if high-energy particles crossed flat detectors at arbitrary angle.

Formation of Optical Images with Synchrotron Radiation Flux of Relativistic Electrons in the X-Ray Generator "Nestor"

When setting up physical experiments involving the use of the polarization properties of synchrotron radiation (SR) or a monoenergetic photon beam, detailed calculation of the spectral angular distribution of SR and its polarization components is of interest. Consideration of the electron beam size shows that in real conditions the radiation propagating in the plane of the equilibrium orbit will not be completely polarized, and the shape and dimensions of the angular distribution of radiation will be distorted. The motion of electrons in the uniform magnetic field and SR of the beam of relativistic particles in the storage ring of "NESTOR" are considered. The effect of the size of the electron beam with the energy of E=225 MeV in the 6-dimensional space on the formation of images of the flux of quanta of SR is analyzed. It is shown that the main contribution to the formation of images is made by the two-dimensional distribution of particles along the vertical direction axis and vertical oscillations. A software simulation code has been developed, the use of which made it possible to simulate the process of optical image formations by the flux of SR quanta (Этого предложения нет в русской аннотации). The formation of images of the radiation of electrons with an energy of E=225 MeV with change in the longitudinal distance L to the registration plane is considered. It is determined that at small longitudinal distances the main contribution to the image is made by the vertical distribution of particles in the beam. With an increase in the basic distance L, the contribution of the distribution of particles over vertical oscillations increases, which becomes decisive for large L value. Numerical simulation of image formation has been carried out. For the base distance of 300 cm and beam parameters with the vertical root mean square size of 0.2 mm and a vertical root mean square size of 0.15 mrad, the family of angular distributions is presented in the form of two-dimensional histograms for wavelengths , , , where , is the critical wavelength of SR. The dimensions of the optical window are obtained, the size of which makes it possible to reliably register the entire flux of SR quanta for the indicated registration characteristics.

An Active Plasma Beam Dump for EuPRAXIA Beams

Plasma wakefields driven by high power lasers or relativistic particle beams can be orders of magnitude larger than the fields produced in conventional accelerating structures. Since the plasma wakefield is composed not only of accelerating but also of decelerating phases, this paper proposes to utilize the strong decelerating field induced by a laser pulse in the plasma to absorb the beam energy, in a scheme known as the active plasma beam dump. The design of this active plasma beam dump has considered the beam output by the EuPRAXIA facility. Analytical estimates were obtained, and compared with particle-in-cell simulations. The obtained results indicate that this active plasma beam dump can contribute for more compact, safer, and greener accelerators in the near future.

ПЕРЕТВОРЕННЯ ЗОБРАЖЕНЬ ЕМІСІІ РЕЛЯТИВІСТСЬКИХ ЕЛЕКТРОНІВ І МЕТРОЛОГИЧНІ ХАРАКТЕРИСТИКИ ПОТОКУ ФОТОНІВ В КАНАЛІ ВИВОДУ СИНХРОТРОННОГО ВИПРОМІНЮВАННЯ НАКОПИЧУВАЧА "НЕСТОР" ННЦ ХФТІ

При постановке экспериментов, связанных с использованием поляризационных свойств синхротронного излучения (СИ), представляет интерес детальный расчет спектрального углового распределения СИ и его поляризационных компонент. Учет размеров пучка показывают, что в реальных условиях излучение не будет полностью поляризованным, а форма и размеры углового распределения излучения будут искажены. Рассмотрено движение электронов в однородном магнитном поле и СИ пучка релятивистских частиц в накопителе "НЕСТОР" Национального Научного Центра «Харьковский Физико- Технический Институт» (ННЦ ХФТИ). Проанализировано влияние на формирование изображений потока квантов СИ размеров пучка электронов с энергией Е=225 МэВ. Показано, что в формирование изображений основной вклад вносит двумерное распределение частиц по вертикали и по вертикальным колебаниям. Разработано программное обеспечение, использование которого дало возможность промоделировать процесс формирования оптических изображений потоком квантов СИ. Рассмотрено формирование изображений излучения электронов с энергией Е=225 МэВ при изменении продольного расстояния L до плоскости регистрации. Определено, что на малых продольных расстояниях основной вклад в изображении вносит вертикальное распределение частиц. С увеличением расстояния возрастает вклад распределения частиц по вертикальным колебаниям, который для больших L становится определяющим. Проведено численное моделирование формирования изображений. Приведено семейство угловых распределений плотности потоков σ- и π-компонент поляризации, рассчитанных для одного из каналов вывода СИ накопителя"НЕСТОР". Зависимости оформлены в виде двумерных гистограмм для длины Lmax=300 см, вертикальных среднеквадратичных параметров пучка и разных длин волн излучения, а также для разных дисперсий L σ электронного сгустка. Получены размеры оптического люка, величина которых позволяет гарантированно регистрировать весь поток квантов СИ для указанных характеристик регистрации.

Physics-Informed Neural Network Method for Space Charge Effect in Particle Accelerators

The electromagnetic coupling of a charged particle beam with vacuum chambers is of great interest for beam dynamics studies in the design of a particle accelerator. A deep learning-based method is proposed as a mesh-free numerical approach for solving the field of space charges of a particle beam in a vacuum chamber. Deep neural networks based on the physical model of a relativistic particle beam with transversally nonuniform charge density moving in a vacuum chamber are constructed using this method. A partial differential equation with the Lorentz factor, transverse charge density, and boundary condition is embedded in its loss function. The proposed physics-informed neural network method is applied to round, rectangular, and elliptical vacuum chambers. This is verified in comparison with analytical solutions for coupling impedances of a round Gaussian beam and an elliptical bi-Gaussian beam. The effects of chamber geometries, charge density, beam offset, and energy on the beam coupling impedance are demonstrated.

High-intensity laser-driven secondary radiation sources using the ZEUS 45 TW laser system at the Institute of Plasma Physics and Lasers of the Hellenic Mediterranean University Research Centre

Abstract The rapid development of high-intensity laser-generated particle and photon secondary sources has attracted widespread interest during the last 20 years not only due to fundamental science research but also because of the important applications of this developing technology. For instance, the generation of relativistic particle beams, betatron-type coherent X-ray radiation and high harmonic generation have attracted interest from various fields of science and technology owing to their diverse applications in biomedical, material science, energy, space, and security applications. In the field of biomedical applications in particular, laser-driven particle beams as well as laser-driven X-ray sources are a promising field of study. This article looks at the research being performed at the Institute of Plasma Physics and Lasers (IPPL) of the Hellenic Mediterranean University Research Centre. The recent installation of the ZEUS 45 TW laser system developed at IPPL offers unique opportunities for research in laser-driven particle and X-ray sources. This article provides information about the facility and describes initial experiments performed for establishing the baseline platforms for secondary plasma sources.

Design and characterisation of frequency selective conductive materials for electromagnetic fields control

To prevent the electromagnetic (EM) wakefields excitation, protect detectors from damage at a range of installations and facilities including particle accelerators the EM field control is required. Conductive foils or wires providing EM protection and required thermal and mechanical properties are normally used. We suggest novel composite materials with uniquely designed frequency selective conductivity enabling them to overcome the properties of the conventional materials, protect from EM fields and supress undesirable phenomena. Theoretical and experimental investigations are carried out and the conductivity of designed and composite (dual-layer) aluminium/graphene metamaterials as well as graphene and aluminium foils is studied. The EM properties of these materials are compared, and conditions of full and partial electromagnetic transparency are discussed. Results observed allow engineering materials capable of EM field control, instability suppression including those observed in high-intensity particle accelerators and enabling control of an EM field generating media including relativistic charge particle beams.

Measuring vacuum component impedance for the Argonne Advanced Photon Source upgrade

The Advanced Photon Source plans to upgrade to a multibend achromat (MBA) lattice that will dramatically decrease the electron beam emittance, thereby enhancing the x-ray brightness by two to three orders of magnitude. Electron beam focusing in the MBA requires small-aperture vacuum components that must also have a small impedance so as to minimize rf-heating and collective instabilities. As part of this effort, this paper focuses on coupling impedance measurements and analysis of certain critical Advanced Photon Source Upgrade vacuum components. Impedance measurements of accelerator components have traditionally been done with the coaxial wire method, which is based on the fact that the Transverse Electro-Magnetic (TEM) mode of the coaxial cable can mimic the Coulomb field of a particle beam; however this measurement technique has various limitations. This paper describes our approach to measure the coupling impedance using a Goubau line (G-line), which is essentially a single wire transmission line designed to propagate Sommerfeld-like surface waves whose fundamental Transverse Magnetic (TM) mode mimics the Coulomb field of a relativistic particle beam. We describe in detail the measurement procedure that we have developed for the G-line, including the measurement setup and proper definition of a reference, measurement procedure and advantages, and our experience regarding how to reduce systematic experimental error that we learned over the course of the measurements. Starting with our initial suite of measurements and simulations designed to benchmark and validate the novel G-line based measurement technique, we present the measured results for several Advanced Photon Source Upgrade vacuum components, including those of two rf-gasket designs and the beam position monitor-bellows assembly.

Scaling laws for the depolarization time of relativistic particle beams in strong fields

The acceleration of polarized electrons and protons in strong laser and plasma fields is a very attractive option to obtain polarized beams in the GeV range. We investigate the feasibility of particle acceleration in strong fields without destroying an initial polarization, taking into account all relevant mechanisms that could cause polarization losses, i.e. the spin precession described by the T-BMT equation, the Sokolov-Ternov effect and the Stern-Gerlach force. Scaling laws for the (de-)polarization time caused by these effects reveal that the dominant polarization limiting effect is the rotation of the single particle spins around the local electromagnetic fields. We compare our findings to test-particle simulations for high energetic electrons moving in a homogeneous electric field. For high particle energies the observed depolarization times are in good agreement with the analytically estimated ones.

Fields of a relativistic beam of charged particles between parallel planes: Exact two-dimensional solutions obtained by the method of images

We calculate exact two-dimensional analytic expressions for the electric and magnetic fields and their potentials generated by a linear beam of relativistic charged particles between infinite ideally conducting planes and ferromagnetic poles. We use the method of summing an infinite sequence of fields of linear image charges and image currents to obtain solutions and also calculate the density distribution of the electric charge on the conductor surface induced by the charged particle beam. We obtain new formulas for the linear approximation of the fields near the beam and discuss the mathematical features of the exact solutions and the applicability constraints for the linear approximations.

Control of the Trajectories of Positively and Negatively Charged Particles by Reflection from a Chain of Bent Single Crystals

A fast algorithm of calculating the passage of particles through a chain of bent single crystals is proposed based on the phenomenon of reflection of a relativistic-particle beam from crystal atomic planes. The results of calculating the passage of particles through a sequence of eight bent crystals are compared with the experimental data.

Detector response and performance of a 500 μm thick GaAs attached to Timepix3 in relativistic particle beams

The performance and response of a Timepix3 detector with a 500 μm thick GaAs:Cr sensor layer was investigated in different radiation fields. The sensor resistivity was ρ ≈ 109 Ω cm. Fitting different modified Hecht functions, which take the small pixel effect into account, the mobility-lifetime products of μeτe = (0.773 ± 0.018) × 10−4 cm2V−1 and μeτe = (0.996 ± 0.056) × 10−4 cm2V−1 were determined. Hereby, the latter value is favored due to the better agreement of fit and data. In a measurement in a 40 GeV/c pion beam, the drift times and charge collection efficiencies were studied as a function of the interaction depth. We present the measured drift velocity as a function of the electric field strength and compare the determined dependence with a model. In a measurement in a mixed ion beam, we study the capability of the detector to separate different ion species. We show the detector response in the form of tracks and discuss heavy ion track features.

Two-axis dielectric laser acceleration using two orthogonal laser pulses in a dual-grating base structure

In this paper, two-axis dielectric laser acceleration is proposed by introducing a dual-grating base laser accelerator structure excited with two orthogonal propagating ultrashort laser pulses. A 2D periodic structure is designed that provides phase synchronicity between the relativistic particle beam and orthogonal propagating laser pulses. In this way, the particle beam can gain energy from both laser pulses simultaneously. It is numerically demonstrated that utilizing this method increases both the acceleration gradient and acceleration factor up to 90% in comparison with dual-grating dielectric laser acceleration. Also, deflecting force elimination, particle beam quality, and bunch acceleration efficiency can be improved using this method.

Noninvasive Micrometer-Scale Particle-Beam Size Measurement Using Optical Diffraction Radiation in the Ultraviolet Wavelength Range

We present recent achievements in the application of optical diffraction radiation (ODR) to the measurement of the transverse beam size of a 1.3 GeV micrometer-size electron beam performed with an instrument installed in the extended extraction line of the KEK Accelerator Test Facility. ODR is a recent technique for the measurement of the transverse size and emittance of highly relativistic particle beams. ODR has the advantage of being a noninvasive and relatively inexpensive technique and is a candidate for the operation of linear particle accelerators, where no simple alternatives (e.g., synchrotron radiation) are available. In an effort to improve the resolution and performance, we establish an alternative target microfabrication technology, adopt solutions to improve the signal-to-noise ratio, and perform an experiment in the UV spectrum at 250 nm. With such a configuration, a transverse beam size as low as $3\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$ is measured, drastically improving on past measurements reported in the literature. In light of these results, ODR, when combined with a high-resolution optical-transition-radiation monitor, represents a credible diagnostics solution for low-emittance high-intensity particle beams.

FIELDS OF AN ULTRA-RELATIVISTIC BEAM OF CHARGED PARTICLES BETWEEN PARALLEL PLATES. EXACT TWO-DIMENSIONAL SOLUTIONS BY THE METHOD OF IMAGES AND APPLICATIONS TO THE HL-LHC

Exact 2D analytic expressions for E and B fields and their potentials created by a linear beam of relativistic charged particles between infinite perfectly conductive plates and ferromagnetic poles are derived. The solutions are obtained by summing an infinite sequence of fields from linear charge-images and current-images in complex space. Knowledge of the normal component of the E field on the conductor surface makes it possible to calculate the induced electric charge surface density. In addition, we derive within an improved linear approximation new analytical expressions for fields near the beam in the case of an arbitrary beam offset from the median plane. The mathematical features of exact solutions and limitations for the applicability of linear approximations are specified.The primary goals of the future high-luminosity p-p and heavy-ion LHC programme are the search for yet unobserved effects of physics beyond the SM, searches for rare or low-sensitivity processes in the Higgs sector, and probing in more detail the mechanism of EW symmetry breaking. This programme relies on the stable operation of the accelerator. However, as the beam luminosity increases, a number of destabilizing phenomena occur, in particular field emission, enhancing the electron cloud effect. For the case of a proton beam, we apply the exact 2D solution for estimating the intensity of electron field emission activated by the electric field of the beam in collimators of the future high-luminosity LHC. Calculation shows that the field emission intensity is very sensitive to a collimator surface roughness. In addition, with a relatively small and accidental beam displacement from the median path, about 20% of the collimator half-gap, the emission intensity increases by a factor of 1.E+7. This will partially neutralize the beam space charge, violating acceleration dynamics and enhancing instability effects.

Управление траекториями положительно и отрицательно заряженных частиц с помощью отражения на цепочке изогнутых монокристаллов

A fast algorithm for calculating the passage of particles through a chain of curved single crystals is proposed, based on the phenomenon of reflection of a beam of relativistic particles from the atomic planes of the crystal. The results of calculating the passage of particles through a sequence of eight curved crystals are compared with experimental data.

Relativistic Particle Beams as a Resource to Solve Outstanding Problems in Space Physics

The Sun’s connection with the Earth’s magnetic field and atmosphere is carried out through the exchange of electromagnetic and mass flux and is regulated by a complex interconnection of processes. During space weather events, solar flares or fast streams of solar atmosphere strongly disturb the Earth’s environment. Often the electric currents that connect the different parts of the Sun-Earth system become unstable and explosively release the stored electromagnetic energy in one of the more dramatic expressions of space weather – the auroral storm and substorm. Some aspects of the magnetosphere-ionosphere connection that generates auroral arcs during space weather events are well-known. However, several fundamental problems remain unsolved because of the lack of unambiguous identification of the magnetic field connection between the magnetosphere and the ionosphere. The correct mapping between different regions of the magnetosphere and their foot-points in the ionosphere, coupled with appropriate distributed measurements of plasma and fields in focused regions of the magnetosphere, is necessary to establish unambiguously that a given magnetospheric process is the generator of an observed arc. The three most important problems for which the correct magnetic field mapping would provide closure to are the substorm growth phase arcs, the expansion phase onset arcs and the system of arcs that emerge from the magnetosphere-ionosphere connection during the development of the early substorm expansion phase phenomenon known as substorm current wedge (SCW). Energetic electron beams, used as magnetic field tracers, can enable the closure needed. However, the application of beams as tracers require demonstration that the beams can be injected into the loss cone, that the spacecraft potentials induced by the beam emission are manageable, and that sufficient electron flux reaches the atmosphere to be detectable by optical or radio means after the beam has propagated thousands of kilometers under competing effects of beam spread and constriction as well as effects of beam-induced instabilities. In this communication we provide a review of the latest results of synergistic research carried out under the NSF INSPIRE program to address these challenges and discuss the next steps toward the realization of active experiments in space using relativistic electron beams.