Bunch Of Particles Research Articles

Photoinjector complex in IAP RAS: design parameters and current state of realization

The calculated parameters of the photoinjector electron accelerator currently being implemented at the Institute of Applied Physics are presented, and the current state of work is described. The complex provides a step-by-step increase of the average energy of particles in dense electron bunches up to 20 MeV, which opens possibilities for the implementation on its basis of a wide class of electromagnetic radiation sources.

Toward a Laser-Driven Traveling-Wave Linac on a Chip

Restricted by pulse dispersion, dephasing, and bunch deflection, it has been a challenging task to realize high-gain particle acceleration and bunch focusing by using an ultrashort-pulse laser to drive an integrable acceleration structure, which is necessary to develop an on-chip particle accelerator for practical applications. Here we propose a laser-driven traveling-wave linac (linear accelerator), which uses the cascade reflection and refraction of an ultrashort laser pulse on a microscale dielectric structure to achieve long-range laser-particle interaction, avoiding waveguide dispersion, and enhancing sustainable acceleration gradient. It is scalable and extensible, and can realize full-course particle acceleration by using a single laser source via the inverse Cherenkov effect. With this accelerator scheme, we further propose a dynamic synchronization and focusing method, which not only counteracts dephasing but also restrains the bunch spread and deflection caused by space-charge and emittance effects, realizing stable bunch transport and acceleration in a tiny-size bunch channel without resorting to the need for external focusing equipment. This accelerator scheme paves the way toward a high-efficiency laser-driven all-dielectric on-chip particle accelerator for practical applications.

Up-sampling of electron beam simulation particles with addition of shot-noise

An algorithm and numerical code for the up-sampling of a system of particles, from a smaller to a larger number, is described. The method introduces a Poissonian ‘shot-noise’ to the up-sampled distribution, typical of the noise statistics arising in a bunch of particles generated by a particle accelerator. The algorithm is applied to a 6-Dimensional phase-space distribution of relatively few simulation particles, representing an electron beam generated by particle accelerator modelling software, for subsequent injection into an Free Electron Laser (FEL) amplifier which is used here to describe the model. A much larger number of particles is usually required to model the FEL lasing process than is required to model the electron beam accelerators that drive it. A numerical code developed from the algorithm was then used to generate electron bunches for injection into to an unaveraged 3D FEL simulation code, Puffin. Results show good qualitative and quantitative agreement with analytical theory. The program and user manual is available for download.

Towards an electrostatic storage ring for fundamental physics measurements

We describe a new table-top electrostatic storage ring concept for 30 keV polarized ions with fixed spin orientation. The device will ultimately be capable of measuring magnetic fields with a resolution of 10−20 T with sub-mHz bandwidth. With the possibility to store different kinds of ions or ionic molecules and access to prepare and probe states of the systems using lasers and SQUIDs, it can be used to search for electric dipole moments (EDMs) of electrons and nucleons, as well as axion-like particle dark matter and dark photon dark matter. Its sensitivity potential stems from several hours of storage time, comparably long spin coherence times, and the possibility to trap up to 109 particles in bunches with possibly different state preparations for differential measurements. As a dark matter experiment, it is most sensitive in the mass range of 10−10 to 10−19 eV, where it can potentially probe couplings orders of magnitude below current and proposed laboratory experiments.

A beam position monitor for electron bunch detection in the presence of a more intense proton bunch for the AWAKE Experiment

The Advanced Proton Driven Plasma Wakefield Experiment (AWAKE) at CERN uses 6 cm long proton bunches extracted from the Super Proton Synchrotron (SPS) at 400 GeV beam energy to drive high gradient plasma wakefields for the acceleration of electron bunches to 2 GeV within a 10 m length. Knowledge and control of the position of both copropagating beams is crucial for the operation of the experiment. Whilst the current electron beam position monitoring system at AWAKE can be used in the absence of the proton beam, the proton bunch signal dominates when both particle bunches are present simultaneously. A new technique based on the generation of Cherenkov diffraction radiation (ChDR) in a dielectric material placed in close proximity to the particle beam has been designed to exploit the large bunch length difference of the particle beams at AWAKE, 200 ps for protons versus a few ps for electrons, such that the electron signal dominates. Hence, this technique would allow for the position measurement of a short electron bunch in the presence of a more intense but longer proton bunch. The design considerations, numerical analysis and plans for tests at the CERN Linear Electron Accelerator for Research (CLEAR) facility are presented.

О роли кулоновских полей в формировании эмиттанса в фотопушках

A theoretical analysis is made of the formation of longitudinal and transverse emittance of beams of charged particles in photoguns under the influence of repulsive forces of Coulomb fields. In numerical calculations, the characteristics of bunches of charged particles with uniform and Gaussian charge density distributions are compared. The efficiency of the proposed numerical-analytical model is compared with calculations using the Astra program. The obtained numerical and analytical results can be useful in the design of photoinjectors to select the optimal parameters that determine the main characteristics of photoguns.

Study of hydrodynamic-tunnelling effects induced by high-energy proton beams in graphite

The design and assessment of machine-protection systems for existing and future high-energy accelerators comprises the study of accidental beam impact on machine elements. In case of a direct impact of a large number of high-energy particle bunches in one location, the damage range in the material is significantly increased due to an effect known as hydrodynamic tunnelling. The effect is caused by the beam-induced reduction of the material density along the beam trajectory, which allows subsequent bunches to penetrate deeper into the target. The assessment of the damage range requires the sequential coupling of an energy-deposition code, like FLUKA, and a hydrodynamic code, like Autodyn. The paper presents the simulations performed for the impact of the nominal LHC beam at 7 TeV on a graphite target. It describes the optimisation of the simulation setup and the required coupling workflow. The resulting energy deposition and the evolution of the target density are discussed.

Erratum: “Adiabatic matching of particle bunches in a plasma-based accelerator in the presence of ion motion” [Phys. Plasmas 28, 053102 (2021)

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Three-dimensional acoustic monitoring of laser-accelerated protons in the focus of a pulsed-power solenoid lens

Abstract The acoustic pulse emitted from the Bragg peak of a laser-accelerated proton bunch focused into water has recently enabled the reconstruction of the bunch energy distribution. By adding three ultrasonic transducers and implementing a fast data analysis of the filtered raw signals, I-BEAT (Ion-Bunch Energy Acoustic Tracing) 3D now provides the mean bunch energy and absolute lateral bunch position in real-time and for individual bunches. Relative changes in energy spread and lateral bunch size can also be monitored. Our experiments at DRACO with proton bunch energies between 10 and 30 MeV reveal sub-MeV and sub-mm resolution. In addition to this 3D bunch information, the signal strength correlates also with the absolute bunch particle number.

Radiation of a charged particle bunch passing through a deeply corrugated structure with a relatively small period

We analyze electromagnetic radiation from a bunch passing through a corrugated conductive planar structure. The wavelengths of the radiation are assumed to be much greater than the corrugation period. Under this approximation, the corrugated structure can be replaced with a smooth surface on which the so-called equivalent boundary conditions (EBC) are fulfilled. Here, we also assume that the structure is deeply corrugated, i.e. the structure depth is of the same order as an inverse wavenumber. Using the EBC we obtain a general solution and investigate it asymptotically. It is shown that two types of radiation are generated: volume radiation and surface waves. Both types of the radiations are analyzed in detail. In particular, we demonstrate that the radiation is highly sensitive to the structure depth. Phenomena under investigation can be useful for generating the electromagnetic radiation and for particle bunch diagnostics.

Controlled Growth of the Self-Modulation of a Relativistic Proton Bunch in Plasma.

A long, narrow, relativistic charged particle bunch propagating in plasma is subject to the self-modulation (SM) instability. We show that SM of a proton bunch can be seeded by the wakefields driven by a preceding electron bunch. SM timing reproducibility and control are at the level of a small fraction of the modulation period. With this seeding method, we independently control the amplitude of the seed wakefields with the charge of the electron bunch and the growth rate of SM with the charge of the proton bunch. Seeding leads to larger growth of the wakefields than in the instability case.

Stampedes I: fishnet OPE and octagon Bootstrap with nonzero bridges

Some quantities in quantum field theory are dominated by so-called leading logs and can be re-summed to all loop orders. In this work we introduce a notion of stampede which is a simple time-evolution of a bunch of particles which start their life in a corner — on the very right say — and hop their way to the opposite corner — on the left — through the repeated action of a quantum Hamiltonian. Such stampedes govern leading logs quantities in certain quantum field theories. The leading euclidean OPE limit of correlation functions in the fishnet theory and null double-scaling limits of correlators in mathcal{N} = 4 SYM are notable examples. As an application, we use these results to extend the beautiful bootstrap program of Coronado [1] to all octagons functions with arbitrary diagonal bridge length.

Tensile Strength and Morphological Behavior of Treated Oil Pam Empty Fruit Bunch Particle Reinforced Polymeric Composite

Numerous literatures have suggested that the use of natural fiber as filler can improve the mechanical properties of a polymer composite. Oil palm empty fruit bunch fibers (OPEFB) are no exception and have shown to exhibit good mechanical properties, with the potential to produce environmentally friendlier composites. In this study, the tensile strengths and morphologies of micro OPEFB filled composites with varying loadings (0.3125 wt% to 10 wt%) were investigated. It was found that increasing content of OPEFB reduces the translucency of the composite almost linearly. It was also revealed that the addition of 0.3125 wt% to 2.5 wt% has a reinforcing effect, observing improvement up to 17.4% compared to its neat condition. Such findings would facilitate the development of an effective OPEFB reinforced polymeric nanocomposite.

Diffraction at the Open End of Dielectric-Lined Circular Waveguide

A rigorous approach for solving canonical circular open-ended dielectric-lined waveguide diffraction problems is presented. This is continuation of our recent paper [1] where a simpler case of uniform dielectric filling has been considered. Here we deal with the case of an open-ended circular waveguide with layered dielectric filling which is closer to potential applications. The presented method uses the solution of corresponding Wiener-Hopf-Fock equation and leads to an infinite linear system for reflection coefficients (S-parameters) of the waveguide, the latter can be efficiently solved numerically using the reducing technique. As a specific example directly applicable to beam-driven radiation sources based on dielectric-lined capillaries, diffraction of a slow TM symmetrical mode at the open end of the described waveguide is considered. A series of such modes forms the wakefield (Cherenkov radiation field) generated by a charged particle bunch during its passage along the vacuum channel axis. Calculated S-parameters were compared with those obtained from COMSOL simulation and an excellent agreement was shown. This method is expected to be very convenient for analytical investigation of various electromagnetic interactions of Terahertz (THz) waves (both free and guided) and charged particle bunches with slow-wave structures prospective in context of modern beam-driven THz emitters, THz accererators and THz-based bunch manipulation and bunch diagnostic systems.

Limiting effects in drive bunch beam dynamics in beam-driven accelerators: instability and collective effects

In a collinear beam-driven wakefield accelerator, a bunch of charged particles is accelerated by a strong electric field that is generated in a medium by a preceding high-charge drive bunch. Multiple beam-driven acceleration concepts have been proposed and demonstrated in proof-of-principle experiments. In some concepts, the medium is plasma where very strong electric fields are created due to the motion of ions and electrons with respect to each other. In other configurations, the medium is a slow-wave electromagnetic structure made of dielectric and/or metal, and high gradients are achieved due to the very short duration of the electromagnetic pulse excited in the structure by the drive bunch. Because of the high charge, and consequently long length of the drive bunch, wakefields excited by the leading particles of the drive bunch affect the trailing particles in the same bunch and result in beam-driven instabilities obstructing the drive bunch's stable propagation and extended interactions with the witness bunch, ultimately terminating the energy transfer process. This paper presents an overview of the drive-bunch beam dynamics in beam-driven structure- and plasma-based accelerators with a focus on beam instabilities that limit stable propagation of the drive bunch, such as the beam break-up instability and transverse defocusing and deflection in cases of cylindrical and planar structures and plasma waveguides. Possible mitigation techniques are discussed.

Start-to-end simulations of plasma-wakefield acceleration using the MAX IV Linear Accelerator

Plasma-wakefield acceleration (PWFA) relies on the interaction between intense particle bunches and plasma for reaching higher accelerating gradients than what is possible with conventional radio-frequency technology. Using ultra-relativistic beam drivers allows for long acceleration lengths and have potential applications such as energy booster stages for synchrotron light sources or linear colliders and generating ultra-high-brightness beams from the background plasma. In this article, we present start-to-end simulations of the MAX IV Linear Accelerator as part of our investigations into the feasibility of using the linac for a PWFA experiment. We find that PWFA appears to be a viable application for the linac. A part of this conclusion is based on our finding that the general properties of the bunch compressor type employed in the MAX IV linac are well-suited for efficient generation of PWFA-optimized bunch current profiles, both for single- and double-bunch beams.

Recovery time of a plasma-wakefield accelerator

The interaction of intense particle bunches with plasma can give rise to plasma wakes1,2 capable of sustaining gigavolt-per-metre electric fields3,4, which are orders of magnitude higher than provided by state-of-the-art radio-frequency technology5. Plasma wakefields can, therefore, strongly accelerate charged particles and offer the opportunity to reach higher particle energies with smaller and hence more widely available accelerator facilities. However, the luminosity and brilliance demands of high-energy physics and photon science require particle bunches to be accelerated at repetition rates of thousands or even millions per second, which are orders of magnitude higher than demonstrated with plasma-wakefield technology6,7. Here we investigate the upper limit on repetition rates of beam-driven plasma accelerators by measuring the time it takes for the plasma to recover to its initial state after perturbation by a wakefield. The many-nanosecond-level recovery time measured establishes the in-principle attainability of megahertz rates of acceleration in plasmas. The experimental signatures of the perturbation are well described by simulations of a temporally evolving parabolic ion channel, transferring energy from the collapsing wake to the surrounding media. This result establishes that plasma-wakefield modules could be developed as feasible high-repetition-rate energy boosters at current and future particle-physics and photon-science facilities.

Experimental Setup for Irradiation of Cell Cultures at L2A2

Laser–plasma proton sources and their applications to preclinical research has become a very active field of research in recent years. In addition to their small dimensions as compared to classical ion accelerators, they offer the possibility to study the biological effects of ultra-short particle bunches and the correspondingly high dose rates. We report on the design of an experimental setup for the irradiation of cell cultures at the L2A2 laboratory at the University of Santiago de Compostela, making use of a 1.2 J Ti: Sapphire laser with a 10 Hz repetition rate. Our setup comprises a proton energy separator consisting of two antiparallel magnetic fields realized by a set of permanent magnets. It allows for selecting a narrow energy window around an adaptable design value of 5 MeV out of the initially broad spectrum typical for Target Normal Sheath Acceleration (TNSA). At the same time, unwanted electrons and X-rays are segregated from the protons. This part of the setup is located inside the target vessel of the L2A2 laser. A subsequent vacuum flange sealed with a thin kapton window allows for particle passage to external sample irradiation. A combination of passive detector materials and real-time monitors is applied for measurement of the deposited radiation dose. A critical point of this interdisciplinary project is the manipulation of biological samples under well-controlled, sterile conditions. Cell cultures are prepared in sealed flasks with an ultra-thin entrance window and analysed at the nearby Fundación Pública Galega Medicina Xenómica and IDIS. The first trials will be centred at the quantification of DNA double-strand breaks as a function of radiation dose.

Structurally and morphologically engineered single-pot biogenic synthesis of NiO nanoparticles with enhanced photocatalytic and antimicrobial activities

The cumulative aquatic contamination and contagious diseases in the present modernity are revealing the high demand for many savior revolutionary materials in the future. In this regard, the potential for green synthesis of NiO NPs has been efficiently investigated for future engineering and medical concerns. Authors employ a facile green route for the synthesis of nickel oxide nanoparticles (NiO NPs) using Piper betle leaves extract as a capping and reducing agent. Synthesized NPs have been analysed by several spectroscopic and microscopic techniques, such as UV–visible spectroscopy, Fourier infrared transform (FTIR), X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-rays (EDX), and transmission electron microscopes (TEM). NiO NPs show a redshift in the absorption energy spectrum with a band gap energy of 2.50 eV. The FTIR spectrum confirms the presence of O–H bonds, O = C = O bonds, C–H bonds, N–C bonds and C = C bonds on the surface of the NiO NPs. XRD study reveals the rhombohedral crystal structure of the NiO NPs. Crystallite size is verified by Debye Scherrer, Williamson–Hall and the Modified Debye Scherrer calculations. SEM/EDX shows bunches of particles distributed over a large area with a non-agglomerated state and atomic percentage of the elements. The organic moieties of Piper betle lead to the generation of various shapes of NiO NPs as observed in high magnification TEM images. The synthesized NiO NPs embrace the extraordinary potential for photocatalytic decolorization of the RR141 dye with 99% efficiency and a high dye degradation rate of 0.03161 min−1. Additionally, the synthesized NiO NPs have shown high antimicrobial activity against the E. coli (gram negative) and B. subtilis (gram positive) microorganisms. This work demonstrates an efficient method for employing synthesized NiO as an effective photocatalyst for the degradation of RR141 dye and as a bactericidal agent for gram-positive and gram-negative bacteria.

Radiation of a charged particle bunch moving along a deeply corrugated structure with a relatively small period

We investigate electromagnetic radiation from a bunch moving along a corrugated conductive planar structure. The radiation is analyzed at wavelengths which are much greater than the period of the corrugation. In this case, the theoretical solution can be obtained by the use of equivalent boundary conditions (EBC). Here, we consider the case of deep corrugation, i.e. we assume that the depth of the structure is of the same order as an inverse wavenumber. Using the EBC method we obtain the general solution of the problem and investigate it asymptotically. It is shown that the bunch generates surface waves propagating in the plane of the structure, whereas volume radiation is absent at the frequencies under consideration. The surface radiation is analyzed in detail. In particular, it is demonstrated that, under certain conditions, the properties of the surface waves can be used for the determination of the bunch size. In addition, we consider the energy losses of the bunch. Typical dependences of the energy losses on the corrugation parameters are obtained and analyzed.