Bunch Of Particles Research Articles

Polarization of diffraction radiation of a bunch of charged particles on a metal sphere

Polarization of diffraction radiation of a bunch of charged particles on a metal sphere

Non-destructive characterization of individual particle bunches by a resistive-cooling measurement in a Penning trap

We have developed and operated an electronic system for the non-destructive detection and cooling of charged-particle bunches that are captured and confined in a Penning trap, together with methods for the evaluation of corresponding measurements that allow for a detailed characterization of each individual particle bunch. Once calibrated, from a single measurement of the particles’ induced electronic signal as a function of time directly upon capture, the setup and method allow for a fast determination of the initial and final absolute particle energies, of the cooling rate, and of the absolute number of particles in the bunch. We demonstrate this with highly charged ions (Ne8+) that are injected into the Penning trap of the HILITE experiment.

Dose increment in ultrashort particle irradiations via coherent stopping power

We present a relativistic self-consistent theory of the coherent stopping power (CSP) of ultradense charged particle beams propagating in a dense matter. CSP corresponds to a collective inelastic collision which adds to the ordinary stopping power of individual particles. Unlike the latter, which depends only on the particles' energy, CSP depends upon many more parameters such as the total charge of the ensemble and its charge density and shape. This paves the way for a broad variety of novel methods to tailor particle absorption and penetration in a dense matter. CSP losses can be explained both by collective excitations of single or multiple molecules and by the emission of coherent Cherenkov radiation. Here we demonstrate that the former mechanism is more relevant than the latter. We find that the coherent energy absorption of subpicosecond particle bunches in water occurs exciting a broad Debye process in the GHz range and an intermolecular stretching vibration mode in the THz region. We generalize the Bethe-Bloch stopping power formula to coherent effects including self-forces, dielectric screening, and absorption by the dense matter. For the sake of a self-consistent dynamical theory including phase space evolution, we have also generalized the Fermi-Eyges theory of particle diffusion to the presence of forces. Nonlinear dynamics is demonstrated, inducing nonlinear dose release, beam self-focusing, and self-enhancement of coherent losses. Given the advent of ultraintense particle sources and their use for biomedical and other relevant applications, our results may be of paramount importance for contemporary and future developments of science and technology. Published by the American Physical Society 2024

Polarization of Diffraction Radiation of a Bunch of Charged Particles on a Metal Sphere

Polarization of Diffraction Radiation of a Bunch of Charged Particles on a Metal Sphere

Experimental Observation of Space-Charge Field Screening of a Relativistic Particle Bunch in Plasma.

The space-charge field of a relativistic charged bunch propagating in plasma is screened due to the presence of mobile charge carriers. We experimentally investigate such screening by measuring the effect of dielectric wakefields driven by the bunch in a uncoated dielectric capillary where the plasma is confined. We show that the plasma screens the space-charge field and therefore suppresses the dielectric wakefields when the distance between the bunch and the dielectric surface is much larger than the plasma skin depth. Before full screening is reached, the effects of dielectric and plasma wakefields are present simultaneously.

5D tomographic phase-space reconstruction of particle bunches

We propose a new beam diagnostics method to reconstruct the phase space of charged particle bunches in five dimensions, which consist of the horizontal and vertical positions and divergences as well as the time axis. This is achieved by combining a quadrupole-based transverse phase-space tomography with the adjustable streaking angle of a polarizable X-band transverse deflection structure. We demonstrate with detailed simulations that the method is able to reconstruct various complex phase-space distributions and that the quality of the reconstruction depends on the number of input projections. This method allows for the identification and visualization of previously unnoticed detailed features in the phase-space distribution and can thereby be used as a tool toward improving the performance of particle accelerators or performing more accurate simulation studies. Published by the American Physical Society 2024

Laser-driven pointed acceleration of electrons with preformed plasma lens

The simultaneous laser-driven acceleration and angular manipulation of the fast electron beam are experimentally demonstrated. The bunch of multi-MeV energy charged particles is generated during the propagation of the femtosecond laser pulse through the near-critical plasma slab accompanied by plasma channeling. Plasma is formed by the controlled breakdown of a thin-tape target by a powerful nanosecond prepulse. The electron beam pointing approach is based on the refraction of a laser pulse in the presence of a strong radial density gradient in the breakdown of the tape with a small displacement of the femtosecond laser beam relative to the breakdown symmetry axis. A shift of several micrometers makes it possible to achieve beam deflection by an angle up to 10° with acceptable beam charge and spectrum conservation. This opens up opportunities for applications for scanning objects with an electron beam and the multistage electron beam energy gain in consecutive laser accelerators without bulk magnetic optics for particles. Experimental findings are supported by numerical particle-in-cell calculations of laser-plasma acceleration and hydrodynamic simulations. Published by the American Physical Society 2024

Electro-optic 3D snapshot of a laser wakefield accelerated kilo-ampere electron bunch

Laser wakefield acceleration, as an advanced accelerator concept, has attracted great attentions for its ultrahigh acceleration gradient and the capability to produce high brightness electron bunches. The three-dimensional (3D) density serves as an evaluation metric for the particle bunch quality and is intrinsically related to the applications of an accelerator. Despite its significance, this parameter has not been experimentally measured in the investigation of laser wakefield acceleration. We report on an electro-optic 3D snapshot of a laser wakefield electron bunch at a position outside the plasma. The 3D shape of the electron bunch was detected by simultaneously performing optical transition radiation imaging and electro-optic sampling. Detailed 3D structures to a few micrometer levels were reconstructed using a genetic algorithm. The electron bunch possessed a transverse size of less than 30 micrometers. The current profile shows a multi-peak structure. The main peak had a duration of < 10 fs and a peak current > 1 kA. The maximum electron 3D number density was ~ 9 × 1021 m -3. This research demonstrates a feasible way of 3D density monitoring on femtosecond kilo-ampere electron bunches, at any position of a beam transport line for relevant applications.

Hosing of a Long Relativistic Particle Bunch in Plasma.

Experimental results show that hosing of a long particle bunch in plasma can be induced by wakefields driven by a short, misaligned preceding bunch. Hosing develops in the plane of misalignment, self-modulation in the perpendicular plane, at frequencies close to the plasma electron frequency, and are reproducible. Development of hosing depends on misalignment direction, its growth on misalignment extent and on proton bunch charge. Results have the main characteristics of a theoretical model, are relevant to other plasma-based accelerators and represent the first characterization of hosing.

Longitudinal splitting of bunches with variable energies in synchrotron

The ever-enriching beam application has put for-ward more demands on accelerators. If multiple bunches of different energies can be extracted for FLASH point scanning in a short time (< 500 ms), the spatial dose distribution advantage of proton Bragg peak can be combined with the temporal effect ad-vantage of FLASH. This paper provides three methods for generating short bunches in synchrotron. By adjusting the pulse parameters of the barrier voltages in the induction synchrotron, the short bunches can be easily generated. The short bunches can be kicked out of the beam reference orbit by kickers. When the pro-cess is repeated for many times, and the energy-changing process is added to the time interval during which the short bunches are continuously generated, the short bunches of multiple energies can be extracted in one working cycle. By finely controlling the changes of rectangular pulses, the number of particles in the short bunches can be better controlled, making an important contribution to further enriching the application of synchrotron.

Analysis of the piezo- and pyroelectric response of PVDF foils as fast particle detectors in pulsed supersonic jets.

We report the design and performance of a new, rugged, general-purpose particle detector consisting of a stretched foil of polyvinylidene difluoride. Several detectors have been built and evaluated for applications in pulsed supersonic jet experiments where, e.g., particle density shall be measured with high time resolution. The working principle is that a directed bunch of particles, moving in vacuum, collides with the sensitive detector area and generates an electric charge. This charge generation is due to both the piezo- and the pyroelectric effect and results in a very fast detector response. In our detailed analysis of the detected signal, the piezoelectric contribution is defined by the constitutive equations of piezoelectricity, which are used in combination with the concept of a driven damped circular membrane allowing to obtain an analytic solution. The pyroelectric contribution is described via the exchanged energy between the impinging particle pulse and the detector foil. Because both the piezo- and the pyroelectric effects can be exploited, additional information about the particle impact such as the coefficient of energy accommodation or the coefficient of restitution can be determined experimentally.

A compact dielectric grating-based charged particle bunch length diagnostic device at ARES

Dielectric gratings are already used in Dielectric Laser Acceleration due to their high damage thresholds at high acceleration gradients. When an electron bunch passes close to one of these gratings, it emits radiation, and the features of this radiation will be dependent upon the beam position relative to the grating, the bunch charge, and the bunch length. A compact high-resolution diagnostics device will be developed that consists of multiple gratings with different periods; these types of devices are required for the accurate operation of future compact accelerators which are currently undergoing development and testing. ARES linac at DESY is able to provide sub-fs electron bunches and has a range of high-resolution diagnostic devices installed, such as the PolariX Transverse Deflecting Structure, which will allow for performance verification of a new diagnostic. The electron bunches can be altered, allowing for the measurement and analysis of the emitted radiation for different bunch lengths and charges. This work will present the current progress in this area, including the presentation and discussion of simulations, and a discussion of the planned experiments at ARES.

Position-sensitive non-destructive detection of charged-particle bunches in low-energy beamlines

We have developed and operated an electronic detection system for the non-destructive single-pass detection of bunches of charged particles in a beamline that allows for a measurement of their lateral position with respect to the central beamline axis on a shot-to-shot basis. It provides all features of our related development reported in Kiffer et al. (Rev Sci Instrum 90:113301, 2019), namely single-pass measurement of bunch length, kinetic energy and absolute charge, and is additionally designed to provide the lateral position of bunches with sub-mm accuracy. We show the setup, associated methods and provide characterizing measurements with bunches of highly charged ions in the keV regime of kinetic energy that demonstrate the capabilities and show a typical application.

Coherent Cherenkov Radiation by Bunches in Fast Radio Bursts

Fast radio bursts (FRBs) are extragalactic radio transients with extremely high brightness temperature, which strongly suggests the presence of coherent emission mechanisms. In this study, we introduce a novel radiation mechanism for FRBs involving coherent Cherenkov radiation (ChR) emitted by bunched particles that may originate within the magnetosphere of a magnetar. We assume that some relativistic particles are emitted from the polar cap of a magnetar and move along magnetic field lines through a charge-separated magnetic plasma, emitting coherent ChR along their trajectory. The crucial condition for ChR to occur is that the refractive index of the plasma medium, denoted as n r , must satisfy the condition . We conduct comprehensive calculations to determine various characteristics of ChR, including its characteristic frequency, emission power, required parallel electric field, and coherence factor. Notably, our proposed bunched coherent ChR mechanism has the remarkable advantage of generating a narrower-band spectrum. Furthermore, a frequency downward-drifting pattern and ∼100% linearly polarized emission can be predicted within the framework of this emission mechanism.

Pickering Emulsion Properties Generated by Nanofibrillated Cellulose Isolated from Oil Palm Fruit Bunch (OPEFB) as a Stabilizer

This study aims to find the optimal nanofibrillated cellulose (NFC) concentration isolated from oil palm empty fruit bunch (OPEFB) particles to form stable pickering emulsions against creaming and coalescence. The emulsification process is based on a combination of homogenizer and ultrasonication. Pickering emulsion was prepared by mixing the dispersed phase (palm oil) and the dispersing phase (NFC concentration of 0.05 - 0.7 w/v%) at the ratio of 10:90. Fresh emulsion has a milky white appearance and is homogeneous. However, some samples' creaming process occurred on the 30th day of storage. Microscopic observations show that the droplets are round with various sizes. Differences in NFC concentrations significantly affect droplet size, zeta potential, rheology, and emulsion stability. Increasing the NCF concentration resulted in smaller droplet sizes, viscosity, zeta potential, and pickering emulsion stability. The emulsion has high stability against coalescence and creaming. NFC at 0.7 w/v% generates an emulsion with the best characteristics and high stability against creaming and coalescence. OPEFB-based NFC has the potential as a pickering emulsion stabilizer particle that can be applied to the food and non-food industries.

Diffraction of a symmetric TM mode at an open-ended deeply corrugated waveguide with a small period

We investigate the diffraction of a symmetric TM mode at an open-ended corrugated cylindrical waveguide with a flange. This mode can be generated, in particular, by a charged particle bunch moving along the waveguide axis. We analyze the so-called “longwave” range when the wavelengths and the waveguide radius are much greater than the corrugation period. In this case, the corrugated waveguide wall can be replaced with a smooth one on which the so-called equivalent boundary conditions (EBC) are fulfilled. Here, we also assume that the wall is deeply corrugated, i.e. the corrugation depth is of the same order as an inverse wavenumber. The approach applied uses the solution of the corresponding Wiener–Hopf–Fock equation. This solution is in turn utilized to construct an infinite linear system for reflection coefficients which can be solved numerically using the reduction technique. Integral representations for the components of the electromagnetic field are obtained. Typical radiation patterns are presented and analyzed.

Measurements in pulsed neutron fields.

Dosimetry in pulsed and mixed radiation fields represents an important challenge in radiation measurements, because in several accelerator technologies, the acceleration occurs in bunches of particles with short time duration, producing intense radiation pulses spaced by a relatively long time of beam off. The stray mixed radiation field generated around these installations maintains the same time structure as the primary beam and causes a problem in workplace fields' monitoring. Active neutron detectors normally used in steady neutron fields, specifically REM-counters and Bonner sphere spectrometers, can suffer pulsed fields because of the high dead time losses during the bursts and are often inadequate for pulsed field monitoring. This work reviews the efforts of European Radiation Dosimetry Group (EURADOS), and in particular of the Working Group 11 'High Energy Radiation Fields', to define the problem, characterize instrumentation and to propose solutions to the issue of pulsed and mixed radiation fields. Despite the EURADOS initiative, several open issues still remain. A metrological traceability for pulsed neutron fields is missing. There is still room for the optimization and better characterization of available instruments. Initiatives of education and training are required.

Linear colliders based on laser-plasma accelerators

Laser-plasma accelerators are capable of sustaining accelerating fields of 10–100 GeV/m, 100–1000 times that of conventional technology and the highest fields produced by any of the widely researched advanced accelerator concepts. Laser-plasma accelerators also intrinsically accelerate short particle bunches, several orders of magnitude shorter than that of conventional technology, which leads to reductions in beamstrahlung and, hence, savings in the overall power consumption to reach a desired luminosity. These properties make laser-plasma accelerators a promising accelerator technology for a more compact, less expensive high-energy linear collider providing multi-TeV polarized leptons. In this submission to the Snowmass 2021 Accelerator Frontier, we discuss the motivation for a laser-plasma-accelerator-based linear collider, the status of the field, and potential linear collider concepts up to 15 TeV. We outline the research and development path toward a collider based on laser-plasma accelerator technology, and highlight near-term and mid-term applications of this technology on the collider development path. The required experimental facilities to carry out this research are described. We conclude with community recommendations developed during Snowmass.

A beamline to control longitudinal phase space whilst transporting laser wakefield accelerated electrons to an undulator

Laser wakefield accelerators (LWFAs) can produce high-energy electron bunches in short distances. Successfully coupling these sources with undulators has the potential to form an LWFA-driven free-electron laser (FEL), providing high-intensity short-wavelength radiation. Electron bunches produced from LWFAs have a correlated distribution in longitudinal phase space: a chirp. However, both LWFAs and FELs have strict parameter requirements. The bunch chirp created using ideal LWFA parameters may not suit the FEL; for example, a chirp can reduce the high peak current required for free-electron lasing. We, therefore, design a flexible beamline that can accept either positively or negatively chirped LWFA bunches and adjust the chirp during transport to an undulator. We have used the accelerator design program MAD8 to design a beamline in stages, and to track particle bunches. The final beamline design can produce ambidirectional values of longitudinal dispersion (R_{56}): we demonstrate values of + 0.20 mm, 0.00 mm and − 0.22 mm. Positive or negative values of R_{56} apply a shear forward or backward in the longitudinal phase space of the electron bunch, which provides control of the bunch chirp. This chirp control during the bunch transport gives an additional free parameter and marks a new approach to matching future LWFA-driven FELs.

ANALYSIS OF ACOUSTIC AND PHYSICAL PROPERTIES OF OIL PALM EMPTY FRUIT BUNCH PARTICLE COMPOSITE BOARDS FABRICATED WITH VARYING ADHESIVE CONTENT

A study was performed to analyze the sound intensity level and physical properties of a composite board made from oil palm empty fruit bunch (OPEFB) particles mixed with polyvinyl acetate (PVAc) adhesive. The composite boards were fabricated with various concentrations of adhesive, namely 8%, 10%, 12%, 14%, and 16%. The intensity level was measured at sound wave frequencies of 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz. The results showed that the highest sound intensity level, 74,2 dB at a frequency of 500 Hz, was found in the composite board with an 8% adhesive concentration. This composite board is categorized as a low-density composite board. The lowest sound intensity level, 58,6 dB at a frequency of 125 Hz, was found in the composite board produced with 16% adhesive concentration. This composite board is categorized as a high-density composite board. The physical property test results for all adhesive concentration variations showed that the resulting composite board density was 0,705-0,723 g/cm3, and the moisture content was 8,36%-9,66%. These values met the requirements of SNI 03-2105-2006.