Charged Particles Research Articles

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

Aggregation of positively charged poly(methyl methacrylate) latex particles in the presence of trifluoromethanesulfonate anion

Abstract We investigated the unique aggregation behavior of 3 types of positively charged poly(methyl methacrylate) (PMMA) latex particles in the presence of a trifluoromethanesulfonate (triflate) anion. The particles were prepared based on surfactant-free emulsion polymerization using azo radical initiators. The triflate anion was strongly adsorbed to surfaces of positively charged PMMA latex particles, as confirmed by electrophoresis. Additionally, its presence significantly reduced the critical coagulation concentration of the cationic PMMA latex particles compared with other anions.

In vitro and ex vivo evaluation of chitosan gel containing metformin-loaded polymeric nanoparticles for topical treatment of melanoma

Objective The purpose of this study was to prepare and evaluate chitosan (CS) gel containing metformin hydrochloride (MET)-loaded polycaprolactone (PCL) nanoparticles (NPs) for topical treatment of melanoma. Significance Topical administration of MET-PCL NPs-CS gel improves penetration of drug, decreases side effects, and increases efficacy of treatment. Methods MET-PCL NPs were prepared by double emulsion method. Particle size, charge, encapsulation efficiency (EE), release, and morphology were evaluated. MET-PCL NPs-CS gel formulation was characterized in terms of organoleptic properties, pH, gelling time, viscosity, spreadability, release, and morphology. Cytotoxicity was performed on B16F10 cells. Ex vivo permeability was done with pig skin. Results The size, charge, and EE were found to be 180 ± 10 nm, −11.4 mV, and 93%. SEM images showed that NPs were spherical and smooth. An initial burst release followed by a slower release was observed. MET-PCL NPs-CS gel was found to be transparent. The pH was 4.9 ± 0.05. The gelation time was 1.6 ± 0.2 min. The viscosity results confirm pseudoplastic behavior of gel. The spreadability by % area was 392 ± 6.4 cm. The images showed that gelling network of CS gel was composed of suspended NPs. The viscosity was between 554 and 3503 cP. MET-PCL NPs-CS gel showed prolonged release up to 72 h. On B16F10 cells, gel showed higher cytotoxicity compared to MET solution. MET-PCL NPs-CS gel had twofold higher permeability in pig skin compared with MET-CS gel. Conclusion Topical administration of MET-PCL NPs-CS gel into the skin resulted in improved dermal penetration and this promising approach may be of value in effective treatment of melanoma and other skin cancers.

Fast Optimization of Charged Particle Dynamics with Damping

Fast Optimization of Charged Particle Dynamics with Damping

Energetic Charged Particle Measurements During Juno's Two Close Io Flybys

AbstractOn days 2023‐364 and 2024‐034, the Juno spacecraft made close passages of Jupiter's moon Io, at altitudes of about 1,500 km. Data obtained from the first flyby, when the spacecraft was on magnetic field lines connected to both Jupiter and Io, revealed deep flux decreases. In addition, Juno's energetic particle detectors observed tens to hundreds of keV electron and proton beams. Such beams could be generated near Jupiter on field lines associated with Io. The second encounter occurred in the plasma wake and a more modest flux decrease was observed. Furthermore, data from both encounters suggest a spatially extensive decrease in >1 MeV electrons that includes regions inward of Io's orbit. In the immediate vicinity of Io, signatures of absorption likely dominate the data whereas diffusion and wave‐particle interactions are expected to be needed to understand MeV electron data in the wider spatial region around Io.

Photoelectric charging and lofting of dust particles on a conducting surface with external electric fields

We present a laboratory study of photoelectric charging of dust particles and their lofting on a conducting surface in the presence of external electric fields. Insulating particles with diameter <45 μm are dispersed on a conducting surface exposed to ultraviolet (UV) light. In addition to the UV exposure, a positive or negative external electric field is applied. Independent of the orientation of the external electric field, the dust particles are found to be positively charged but with different mechanisms. It is shown that the orientation of the external electric field controls the dynamics of photoelectrons emitted from the dust particles and the conducting substrate surface. Distinctly different lofting results are shown between these two electric field cases. The results provide insight for understanding dust charging and release and helping develop mitigation solutions in particle accelerators, semiconductor manufacturing, fusion reactors, and space exploration to planetary bodies.

Applications of Fast Magnetic Reconnection Models to the Atmospheres of the Sun and Protoplanetary Disks

Partially ionized plasmas consist of charged and neutral particles whose mutual collisions modify magnetic reconnection compared with the fully ionized case. The collisions alter the rate and locations of the magnetic dissipation heating and the distribution of energies among the particles accelerated into the nonthermal tail. We examine the collisional regimes for the onset of fast reconnection in two environments: the partially ionized layers of the solar atmosphere, and the protoplanetary disks that are the birthplaces for planets around young stars. In both these environments, magnetic nulls readily develop into resistive current sheets in the regime where the charged and neutral particles are fully coupled by collisions, but the current sheets quickly break down under the ideal tearing instability. The current sheets collapse repeatedly, forming magnetic islands at successively smaller scales, until they enter a collisionally decoupled regime where the magnetic energy is rapidly turned into heat and charged-particle kinetic energy. Small-scale, decoupled fast reconnection in the solar atmosphere may lead to preferential heating and energization of ions and electrons that escape into the corona. In protoplanetary disks such reconnection causes localized heating in the atmospheric layers that produce much of the infrared atomic and molecular line emission observed with the Spitzer and James Webb Space Telescopes.

Discharge mode and particle transport in radio frequency capacitively coupled Ar/O2 plasma discharges

Abstract In this study, simulations are conducted on capacitively coupled Ar/O2 mixed gas discharges employing a one-dimensional fluid coupled with an electron Monte Carlo (MC) model. The research explores the impact of different O2 ratio and pressures on the discharge characteristics of Ar/O2 plasma. At a fixed Ar/O2 gas ratio, with the increasing pressure, higher ion densities, as well as a slight increase in electron density in the bulk region can be observed. The discharge remains dominated by the Drift-Ambipolar (DA) mode, and the flux of O(3P) at the electrode increases with the increasing pressure due to higher background gas density, while the fluxes of O(1D) and Ar* decrease due to the pronounced loss rate. With the increasing proportion of O2, a change in the dominant discharge mode from α mode to DA mode can be detected, and the O2-associated charged particle densities are significantly increased. However, Ar+ density shows a trend of increasing and then decreasing, while for neutral fluxes at the electrode, Ar* flux decreases, and O(3P) flux increases with the reduced Ar gas proportion, while trends in O(1D) flux show slight differences. The evolution of the densities of the charged particle and the neutral fluxes under different discharge parameters are discussed in detail using the ionization characteristics as well as the transport properties. Hopefully, more comprehensive understanding of Ar/O2 discharge characteristics in this work will provide a valuable reference for the industry.

FTIR, Raman spectroscopic, microstructure and neutron-particle interaction properties of Mo3+ doped cadmium zinc lithium-borate glasses

The application of different glass materials in the area of radiation shielding and charge particle attenuation has necessitated a comprehensive study of glass materials doped with special elements to examine the impact of the special element on the microstructure and shielding capabilities of resultant glass materials. In this study, the optical absorption spectra of Mo3+ doped cadmium zinc lithium borate glasses (BCZLMx) was investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopic methods to ascertain the suitability of BCZLMx glass microstructure to neutron and charge particle attenuation. Results show that the absorption cross-section is the dominant contributor to the total cross section for all samples, ranging from 110.9 cm−1 to 111.7 cm−1. BCZLM1 glass sample appears to be slightly more effective at removing fast neutrons from the beam while BCZLM5 glasses are effective at stopping electrons, protons, alpha particles, and carbon ions when compared to the other BCZLMx glasses samples. This implies that doping cadmium zinc lithium borate glasses with Mo3+ reduces fast and thermal neutrons shielding potential and increased charge particles interaction of the BCZLMx glass system.

Interactions of cosmic rays with the primordial photons of the Universe

Understanding the physical processes involved in the propagation of cosmic rays in the intergalactic media is one of the biggest problems in astrophysics today. It is an important topic because one first tries to identify the sources and later to understand the physical processes that occur when the particles are accelerated to ultra-high energies (E>1018eV). And because cosmic rays are charged particles, they are deflected in the existing magnetic fields as they propagate to Earth, making it very difficult to correlate their direction of arrival with astrophysical sources. Moreover, cosmic rays consist mainly of atomic nuclei interacting with the cosmic microwave background (CMB) and the extragalactic background light (EBL) during their propagation, and a significant part of their energy is consumed in these processes (for a proton with E∼1021 eV, its energy is approximately halved over a distance of 20 Mpc). In this article, we describe the main processes between background photons and ultrahigh-energy cosmic rays. We have also used the equations for comparison with the most commonly used programme in this field to illustrate the physical processes addressed. We conclude that the result of the equations leads to well-established results in the field, such as the importance of EBL for the process of photodesintegration (Allard, 2012).

Charged particle reflection in a magnetic mirror

We study the reflection of electrons in a magnetic field mirror. It is a field with a gradient from a lowest value B0 to a largest one Bm. With this purpose, Montecarlo simulations are made. We use a number of 5,000 particles with random pitch angles. The frequency distribution of these random values follows a Gaussian distribution centered at \theta = 0 and with standard deviation \sigma. Various values of \sigma and also different values of the B0 /Bm ratio are used in the simulations. The simulations show that \sigma has an important influence on the confinement of charged particles, for the different B0 /Bm ratios here studied. However, the percent of reflected particles differs from a B0 /Bm ratio to another in the whole range of \sigma, although for \sigma = 10 the differences between different ratios are small (<5%). The number of reflected particles increases very rapidly with \sigma, in the range of 10° to 40°. For the \sigma range from 20° to 40°, the percent of reflected particles is \leq 20% larger for B0 /Bm = 0.10 than for the 0.55 ratio.

Broken symmetries in quasi-2D charged systems via negative dielectric confinement

We report spontaneous symmetry breaking (SSB) phenomena in symmetrically charged binary particle systems under planar nanoconfinement with negative dielectric constants. The SSB is triggered solely via the dielectric confinement effect, without any external fields. The mechanism of SSB is found to be caused by the strong polarization field enhanced by nanoconfinement, giving rise to charge/field oscillations in the transverse directions. Interestingly, dielectric contrast can even determine the degree of SSB in transverse and longitudinal dimensions, forming charge-separated interfacial liquids and clusters on square lattices. Furthermore, we analytically show that the formed lattice constant is determined by the dielectric mismatch and the length scale of confinement, which is validated via molecular dynamics simulations. The novel broken symmetry mechanism may provide new insights into the study of quasi-2D systems and the design of future nanodevices.

Complex shock structure in multi-species dusty plasma with nonextensive electrons and two-temperature nonthermal ions

A theoretical investigation has been made to explore the behavior of nonplanar (cylindrical and spherical) electrostatic shock waves in a dusty plasma system that consists of arbitarily charged dust particles, negatively charged heavy ions following Cairn’s distribution, positively charged ions with two different temperatures, and nonextensive electrons. The reductive perturbation technique is used to derive a modified Burgers equation analytically. Analytical analysis shows that the characteristics of the nonplanar shock waves, including their polarity, amplitude, width, and phase speed, undergo significant alterations due to factors such as the charges on dust particles, the number density of particles, the temperatures of heavy and light ions, nonextensive electron behavior, and dust kinematic viscosity. Furthermore, this study found shock structures with either a positive or negative potential, depending on the critical value of the proportion of ions to the density of dust particles. The findings maybe useful in understanding the characteristics of shock waves both in space plasma environments and laboratory plasmas.

Reinforcements of cationic polyvinyl alcohol with low dosage for secondary fibre

ABSTRACT The effect of polyvinyl alcohol, a green water-soluble polymer, usually is not satisfied as a secondary-fiber reinforcing agent in pulp and paper-making industry due to the same negative charges of PVA and pulp fiber. In this study, 3-chloro-2-hydroxypropyltrimethylammonium chloride was used as an etherifying agent to prepare cationic modification of polyvinyl alcohol (CPVA) with degree of etherification of 0.059 under a reaction time of 4 hours and n(PVA : etherifying agent) = 1 : 0.5. Compared with PVA, CPVA exhibits positive charge and smaller particle size, enabling it to effectively combine with negatively charged fibers and get in between the fibers. As a result, CPVA demonstrates a remarkable ability to improve the paper’s physical properties. With a dosage of only 0.2% CPVA (based on the absolute dry pulp), which is merely 1/10 of the dosage of PVA, CPVA increases the paper’s tensile index by 54.09%, burst index by 25.96%, and tear index by 21.09%. CPVA as a reinforcing agent for secondary fiber pulps, which can be attributed to the alteration in charge, to enhance CPVA’s affinity for the electrostatic interaction of the fibers. Consequently, CPVA emerges as a viable and eco-friendly enhancement solution, demonstrating significant potential in secondary fiber reuse.

Interacting dust grains in complex plasmas: Ion wake formation and the electric potential

Dust grains have been used as minimally invasive probes to determine plasma parameters including the plasma density, temperature, and electric field in a plasma discharge. However, the dust grains in a plasma generate local potential disturbances due to the collection of charge and the subsequent electrostatic interactions between the dust and charged plasma particles. Dust grains in close proximity to one another exhibit interesting non-reciprocal interactions and self-organize into structures such as one-dimensional filamentary chains, two-dimensional “zigzags,” and three-dimensional helices, among others. The formation of these structures suggests that although the dust grains may be less invasive than traditional plasma probes, the disturbance to the local plasma environment introduced by dust grains is non-trivial. Commonly used analytic forms of the electric potential describing complex plasmas have failed to resolve the near-dust region, and as a result are insufficient to provide insight about the formation of complex dust structures. Here, we use an N-body simulation to compute the electric potential from ion densities near various dust grain configurations. We provide an alternative description to the standard analytic model for the electric potential of dust and ion wakes based on a Gaussian shaped cloud of ions. The electric potential obtained from simulations is used to identify minimum energy configurations for two and three dust grains. It is further demonstrated that the minimum potential region identified for N dust grains and their associated ion wakes does not predict the minimum-energy configuration of N + 1 dust grains.

First quantitative characterization of the Martian dust devil dimensions determined from InSight data

In a pioneer study, the dimensions height H and width D of Martian dust devils are determined considering a simple model, in which the principal contribution to the magnetic field generated by a dust devil, comes from the swirling motion of their negatively charged lighter particles. Finally, a linear relation between H/D and the pressure drop associate to the dust devils is found. This relationship is a new and very conspicuous result determined in the present study. The reliability of this result should be assured revisiting this work with the data provided by future missions, as the Exobiology on Mars (ExoMars) project, when these data sets be available.

Electromagnetic fields with symmetry

We show that if an electromagnetic field is invariant under translations or rotations, three of the six components of the field can be expressed in terms of a (gauge-invariant) scalar potential which is also invariant under these transformations. This scalar potential appears in the constant of motion associated with this symmetry for a charged test particle in this field. We also show that the Cartesian components of the electromagnetic field can be combined to form two SO(2, 1) vectors

Highly stable, fluorescent, artificial lipoprotein nanoparticles.

Here, we report a novel kind of protein nanoparticles of 11 nm in size, which have a central protein core surrounded by two layers of lipid. One layer of the lipid was covalently attached to the protein, while the other layer has been physically assembled around the protein core. Particle synthesis is highly modular, while both the size and charge of the protein nanoparticles are controlled in a predictable manner. Circular dichroism studies of the conjugate showed that the protein secondary structure is retained, while biophysical characterizations indicated the particle purity, size, and charge. The conjugate had a high thermal stability to steam sterilization conditions at 121°C (17 psi). After labeling the protein core with few different fluorescent dyes, they were strongly fluorescent with the corresponding colors independent of their size, unlike quantum dots. They are readily digested by proteases, and these water-soluble, non-toxic, highly stable, biocompatible, and biodegradable conjugates are suitable for cell imaging and drug delivery applications.

Eco-friendly three-phase-gel foam with novel particle-gel crosslinking enhancing stabilization and fire extinguishing

To address the instability and limited fire-suppression effectiveness of foam agents, a three-phase gel foam incorporating α-olefin sulfonate (AOS), alkylphenol ethoxylates (OP-10), modified bentonite, and cellulose gel was developed. The foam formula was optimized by using response surface method. Combined with Zeta potential and FTIR, the intrinsic interaction between materials was analyzed. The foam decay process, liquid discharge regularity, and viscosity change under different additives were compared. The enhancement of its fire extinguishing ability was explored. Results show that: The optimized foam achieves optimal foaming volume and half-life. Surfactant adsorption reduces the surface charge of particles and stabilizes their dispersion in liquid membrane. Cellulose is wound between particles to form a stable absorbent skeleton and delay decay of foam. Foam adheres stably to solids and covers them with barrier, inhibiting wood burning. The time to extinguish wood stack fire was 84 s, a 36.84% improvement over Class A foam extinguishing agents.

Influence of beam content composition on testbeam studies of hadron calorimeters

Abstract Hadron calorimeters are one of the most important detectors in the contemporary nuclear and particle physics experiments. Their construction and verification process takes years in designing, testing and data analysis of prototypes. Crucial step for the prototypes are tests performed by exposing the detectors to charge particle beams. Here we study the impact of the different beam content composition to one of the main properties of the hadron calorimeters – their energy resolution. We implement a test detector - Metal Hadronic Calorimeter (MACA) in GEANT4 environment and we perform different simulations to study the influence to the main energy resolution parameters.