Velocity Of Charged Particles Research Articles

Еdgе fiеld of dеflеctorplаtes with expanding screens

Deflector plates consist of two parallel conductive plates that create a deflecting electric field. They can be used to control the flow of charged particles ― electrons or ions. The effect of the еdgе fiеld of deflector plates leads to a change in the velocity of charged particles in the longitudinal and transverse directions, consequently of which their real trajectories change, deviating from ideal ones, which violates the space-time resolution of corpuscular optical devices in which they are used. Apart from that, the electric field at the input to the plates of deflector can vary over time, which must also be taken into account when the deflector diverts the beam of charged particles. Thus, in many cases, the use of deflector plates with open ends is inappropriate, since uncontrolled scattering fields are formed. In this article, we can consider the field of deflector plates with expanded screens at the output, so that deflecting beams of charged particles can be used at the output of deflector plates. Using the methods of the theory of complex variable functions, analytical expressions for the edge field of deflector plates with grounded screens were obtained. Firstly, by grounding the screens and shielding the plates from the deflection field, we can localize the edge electric field and reduce the uncontrolled scattering fields, and secondly, such a field can be accurately calculated analytically.

A comparison of single and twin tungsten electrode – wire electrode IAW

ABSTRACT Twin tungsten electrode – wire electrode indirect arc welding (TTW IAW) was a novel welding method. In this paper, the wettability and spreading of weld bead of TTW IAW were investigated by comparing with single tungsten electrode – wire electrode indirect arc welding (STW IAW). Results showed that compared to STW IAW, TTW IAW possessed larger arc width and greater arc heat distribution range with smaller variation gradient, due to the lower velocity of charged particles toward the arc center, caused by the smaller electromagnetic force acting on the arc plasma. So did the temperature distribution of weld pool of TTW IAW. Moreover, the process stability of TTW IAW was better. Besides, at the molten pool front, the transverse convection of the melted metal of TTW IAW was adequate, because of the superior wettability and long flow duration of the melted metal; at the molten pool rear, the inward convection of the melted metal of TTW IAW was weak mainly owing to the low Marangoni force. Therefore, the weld bead width of TTW IAW increased by about 25.0% and the wetting angle of the weld bead decreased by about 25.7% compared to STW IAW, which indicated that the weld bead spreading of TTW IAW was better.

Special Relativity Search: A novel metaheuristic method based on special relativity physics

In this work, a novel metaheuristic optimization algorithm called Special Relativity Search (SRS) is proposed. The SRS is inspired by the interaction of particles in an electromagnetic field. Particle interactions are calculated using the Lorentz force, and the equation of motion is developed using angular frequency. The magnetic force between particles is perpendicular to the velocity of charged particles and the magnetic field, which causes particles to move in a circular trajectory. In this method, for the first time, the theory of special relativity physics is utilized to determine the coordinates of charged particles in each rotation. The SRS main step equation is developed using the two phenomena of length contraction and time dilation. Charged particles are members of the initial population that is randomly generated, and their charge is determined based on their fitness. To show the efficiency and robustness of the SRS in solving optimization problems, 83 benchmark functions, which are a wide range of mathematical problems, are selected and optimized based on the values of Best, Mean, Median, and Standard Deviation (SD). The statistical test of the Wilcoxon Signed Ranks (WSR) is performed to fairly compare the results of this new method with other popular metaheuristic algorithms. The test results show that in most cases SRS is superior to other methods from the state-of-the-art. The results of evaluated optimization problems show that SRS is more effective and efficient compared to some other well-known metaheuristic methods in solving optimization problems.

Two-fluid simulations of Rayleigh-Taylor instability in a magnetized solar prominence thread

Solar prominences are formed by partially ionized plasma with inter-particle collision frequencies, which generally warrant magnetohydrodynamic treatment. In this work, we explore the dynamical impacts and observable signatures of two-fluid effects in the parameter regimes when ion-neutral collisions do not fully couple the neutral and charged fluids. We performed 2.5D two-fluid (charge – neutrals) simulations of the Rayleigh-Taylor instability (RTI) at a smoothly changing interface between a solar prominence thread and the corona. The purpose of this study is to deepen our understanding of the RTI and the effects of partial ionization on the development of the RTI using nonlinear two-fluid numerical simulations. Our two-fluid model takes into account viscosity, thermal conductivity, and collisional interaction between neutrals and charge: ionization or recombination, energy and momentum transfer, and frictional heating. In this paper, we explore the sensitivity of the RTI dynamics to the prominence equilibrium configuration, including the impact of the magnetic field strength and shear supporting the prominence thread, and the amount of prominence mass-loading. We show that at small scales, a realistically smooth prominence-corona interface leads to qualitatively different linear RTI evolution than that which is expected for a discontinuous interface, while magnetic field shear has the stabilizing effect of reducing the growth rate or eliminating the instability. In the nonlinear phase, we observe that in the presence of field shear the development of the instability leads to formation of coherent and interacting 2.5D magnetic structures, which, in turn, can lead to substantial plasma flow across magnetic field lines and associated decoupling of the fluid velocities of charged particles and neutrals.

Particle dynamics around the black string

In this paper, some dynamical properties of neutral and charged particles around a weakly magnetized five-dimensional static black string have been studied. The perturbation method was also used to calculate the innermost stable circular orbit (ISCO) of this metric in the presence of a magnetic field. The escape velocity of neutral and charged particles around the black string was derived. In the next step, the analytical solutions of the equations of motion were discussed and some possible orbits for particles in the black string space–time were plotted. Interestingly, it was found that adding an extra dimension has a slight influence on the effective potential and one term of the effective force. The magnitude of the new constant of motion (J) affects both the shape of the potential and existence of the stable circular orbits. In conclusion, by comparing a black hole and a black string, it is realized that the value of a new constant of motion causes slight but interesting differences.

Toroidicity effects on the absorption of IC waves by electrons

Poloidal modulation of the parallel velocity of charged particles in a tokamak magnetic field modifies the strength of electron absorption of the compressional wave in the ion cyclotron range of frequencies. We have developed a model of this effect which is sufficiently simple to be numerically tractable, and we have implemented it in TORIC full-wave code, which solves the wave equation in toroidal axisymmetric geometry. We find that the effect is normally negligible in present-day devices, but its importance increases with the dimensions and the temperature of the plasma, and should be taken into account when estimating the competition between electron and ion heating and the efficiency of the current drive in future reactor-grade plasmas.

Tapered image charge detector for measuring velocity distributions of submicrometer particle scattering.

A novel detector for measuring the post-impact velocities (trajectory and speed) of charged submicrometer particles is presented. A stack of tapered cylindrically symmetric electrodes connected to a set of image charge detection circuits is used in conjunction with an image-charge-sensitive target to measure the incident velocity and scattered trajectories of charged particles following impact with the target. This particle detector is used in conjunction with a mass, charge, and energy-selected source of collimated charged particles. Polystyrene latex spheres were used to characterize the performance of the detector, and examples of scattering trajectories are analyzed to demonstrate detector functionality. Measurements of the coefficient of restitution for 500 nm diameter tin particles are also reported and compared with previous measurements performed with a simpler image-charge detector. Finally, the angular distribution for 500 nm tin particles scattering from highly polished molybdenum at an incident velocity of 150 m/s is reported.

Quasi-monochromatic THz pulse generation using Cherenkov radiation from a spatially modulated electron beam

Cherenkov radiation forms a wave front in a direction that depends on the density of the medium and the velocity of charged particles; therefore, ordinary electron bunches do not generate coherent radiation unless they are sufficiently compressed. In this work, we present the generation of a quasi-monochromatic THz pulse using an electron bunch with a periodic structure generated from a small rf gun. A coherent THz pulse was generated by matching the tilt angle of the electron bunch and Cherenkov radiation angle with a rf deflector. Furthermore, we attempted to render the THz pulse quasi-monochromatic by adding a periodic structure to the electron bunch using a multi-slit. Finally, using several band-pass filters, we successfully confirmed that the quasi-monochromatic operation was performed at frequencies of 0.2 and 0.3 THz.

On the Poynting vector and the curvature of a charged particle travelling in the electro-magnetic field

The aim of this paper is to represent the trajectory’s curvature related to the power density of the electromagnetic wave that has been widely described as the Poynting vector. The paper starts from the infinitesimal work equation and transformed by using the vector identities and Maxwell’s equations. The result of this transformation leads to a decoupled representation of the Poynting vector as a separate contribution of the electrical and magnetic fields. The decoupled form of the Poynting vector is emphasized by the presence of the charged particle velocity and its curvature. The discussion is conducted symbolically in order to conclude that the power density produced by a charged particle traveling in an electromagnetic field will decrease as the trajectory’s curvature increases.

Numerical Analysis of Charged Particles Transport in Air Based on Vortex Rings

Charged particles are widely used in the fields of defogging, haze removal and artificial rainfall. A novel transport strategy of charged particles based on the vortex rings is presented in this paper, to expand the effective action region and enhance the effect of charged particles. Transport distance and transport velocity (TV) of charged particles are the crucial two evaluation indexes. For the vortex rings generated by a piston-cylinder device, the transport velocity is closely related to Reynolds number and formation time. Based on the k-ω turbulence model, this paper verifies the relationship between vortex ring circulation, transport velocity and Formation Number in air by finite element methods, and studies the influence on the formation of vortex rings of an insulating bell mouth placed at the outlet of cylinder. The simulation results show that the Formation Number of vortex rings in the air is 4.0 ~ 5.0, and the growth rate of transport velocity of vortex ring slows down when the formation time is larger than Formation Number. The study also indicates that the bell mouth has little effect on the velocity of the vortex ring, when the bell mouth angle is greater than 45° and the length of generatrix is between 0.2 m and 1.0 m. Therefore, the research results can provide a reference for the design and optimization of a vortex ring generator for transporting charged particles to a certain target area.

Charge-particles transport in semiconductors characterized by a generalized Langevin equation with a fractional noise

From the view of intrinsic noise in semiconductors, the model of charge-particles transport in one-dimensional semiconductors described by a generalized Langevin equation (GLE) driven by a intrinsic fractional Gaussian noise is proposed in this paper. The analytical expression of the average charged particle velocity, the differential mobility, the conductivity of charge-particles, the two-time correlation function of the velocity fluctuation and the power spectral of total current density fluctuation have been derived. Furthermore, the model of motion for the charge-particle subjected to an electric field and a magnetic field governed by GLE is introduced. The expressions of mean values and variances of charged particle velocity, Fokker–Planck equation of charge-particle motion, the asymptotic behaviors of the relaxation functions have been obtained. Under the Hall effect, the Hall angle, the Hall coefficient, as well as the electrical resistivity also have been studied.

Search for heavy charged long-lived particles in the ATLAS detector in 36.1 fb−1 of proton-proton collision data at s=13 TeV

A search for heavy charged long-lived particles is performed using a data sample of 36.1 fb$^{-1}$ of proton-proton collisions at $\sqrt{s} = 13$ TeV collected by the ATLAS experiment at the Large Hadron Collider. The search is based on observables related to ionization energy loss and time of flight, which are sensitive to the velocity of heavy charged particles traveling significantly slower than the speed of light. Multiple search strategies for a wide range of lifetimes, corresponding to path lengths of a few meters, are defined as model-independently as possible, by referencing several representative physics cases that yield long-lived particles within supersymmetric models, such as gluinos/squarks ($R$-hadrons), charginos and staus. No significant deviations from the expected Standard Model background are observed. Upper limits at 95% confidence level are provided on the production cross sections of long-lived $R$-hadrons as well as directly pair-produced staus and charginos. These results translate into lower limits on the masses of long-lived gluino, sbottom and stop $R$-hadrons, as well as staus and charginos of 2000 GeV, 1250 GeV, 1340 GeV, 430 GeV and 1090 GeV, respectively.

Studying the effect of charged particle’s flow velocity on the relative complex permittivity of dusty plasma

In this paper, the expression of relative complex permittivity is deduced based on considering the effect of charged particle’s (electrons and ions) flow velocity. The theoretical deduction manifests that the relative complex permittivity is related to temperature, pressure and frequency, especially the flow velocity of charged particles. In further discussion, it is found that there is a turning point in the depended relation between the relative complex permittivity and the flow velocity. In particular, the involved results manifest that the turning point only changes with the temperature at a certain frequency. Besides, some physical explanations for the above phenomenon are also proposed. In a word, the involved study can provide some reference for the electromagnetic characteristics of dusty plasma.

MCP-PMT production for Belle II TOP detector and further R&D

Abstract We have developed 1-inch square-shaped Micro-Channel-Plate PMT (MCP-PMT) for the barrel particle identification detector, named Time-Of-Propagation (TOP) detector, at the Belle II experiment. The TOP detector utilizes the precise timing measurement to reconstruct the charged particle velocity through the Cherenkov ring image and the time-of-flight information. The MCP-PMT realizes the timing measurement with 40 ps precision for single photon detection. We have tested over 600 MCP-PMTs including spares, and installed 512 of those into the Belle II TOP detector. Along with the mass production, we have studied to improve the MCP-PMT photocathode lifetime. By applying Atomic-Layer-Deposition (ALD) technique on MCP and further residual gas reduction process, the lifetime have improved significantly. The improved PMTs are also installed. To understand the mechanism of photocathode deterioration, we have measured feed-backed ion’s signals using developed MCP-PMTs and studied the correlation between the rate and the lifetime.

Study on the factors affecting the electrical conductivity of dusty plasma

Electrical conductivity is one of the important parameters of dusty plasma. The factors, which could affect it, are worth to be well studied. In this paper, on the basis of considering the effect of flow velocity of charged particles (electrons and ions), the electrical conductivity of dusty plasma is discussed. The involved results indicate that the electrical conductivity appears a minimum on the relation with flow velocity, for which the physical and mathematical explanations are proposed. In further, a ratio is reintroduced to investigate the dependence of electrical conductivity on flow velocity. Based on which, it is found that the ratio where the minimal electrical conductivity appears does not vary with the angular frequency and pressure, only changes with the temperature of dusty plasma. Finally, the physical reason and verification are discussed, and the potential benefit of this study is also proposed.

Mechanical properties and electromagnetic radiation characteristics of concrete specimens after exposed to elevated temperatures

Experiments on electromagnetic radiation (EMR) from coal and rock under different loading modes have been conducted in laboratories and in the field, but there are few reports about EMR from concrete after it has been exposed to high temperatures. To determine the feasibility of using EMR to evaluate the condition of concrete after high temperature events, like structure fires, three groups of concrete specimens were tested by uniaxial compression after being heated to elevated temperatures; the EMR signals were recorded and analyzed. The results show that the compressive strength decreases with exposure temperature higher than 100 °C and the modulus of elastic is generally inversely proportional to exposure temperature. Low frequency EMR (∼10.9–131.5 kHz) was observed during loading. The EMR impulses respond well to the stress, so they should reflect the stress state in the specimens. In our experiments, a large EM signal arrives that nearly coincides with the main fracture and then the signal rapidly attenuates; a series of low-amplitude oscillations follow. For specimens after being heated to different temperatures, the EMR waveforms are similar in shape but differ in intensity. The principal frequency and the corresponding maximum amplitude in the EMR spectra increase with the exposure temperature. Based on the exclusion method, piezoelectric effects and motion from the variable velocity of charged particles are believed to be the probable mechanisms causing EMR to be generated from the specimens.

A supplemental device to return escaping particles to a magnetic mirror reactor

Cyclotron resonance is now applied as one of the important means for heating plasma in a fusion reactor. We examined this phenomenon from the viewpoint of electron gyration orbits through a solution of the linearized relativistic equation of motion. We found a powerful term that accelerates a relativistic charged particle largely at a resonance point when a magnetic field strength is very large. In this study, aiming an effect of this term, we consider applying a resonance phenomenon to reducing the number of charged particles that escape from a magnetic mirror reactor. We install a long supplemental device at the exit of a main magnetic bottle and make a cyclotron resonance space within the device, as shown in Fig. 7. If velocities (perpendicular to a magnetic field) of charged particles are accelerated largely within the cyclotron resonance space, the reflection efficiency of a magnetic mirror behind the resonance space ought to be improved. Based on this idea, we discuss such a supplemental device for recovering the maximum number of escaping charged particles.

Generation of Suprathermal Electrons by Collective Processes in Collisional Plasma

Abstract The ubiquity of high-energy tails in the charged particle velocity distribution functions (VDFs) observed in space plasmas suggests the existence of an underlying process responsible for taking a fraction of the charged particle population out of thermal equilibrium and redistributing it to suprathermal velocity and energy ranges. The present Letter focuses on a new and fundamental physical explanation for the origin of suprathermal electron velocity distribution function (EVDF) in a collisional plasma. This process involves a newly discovered electrostatic bremsstrahlung (EB) emission that is effective in a plasma in which binary collisions are present. The steady-state EVDF dictated by such a process corresponds to a Maxwellian core plus a quasi-inverse power-law tail, which is a feature commonly observed in many space plasma environments. In order to demonstrate this, the system of self-consistent particle- and wave-kinetic equations are numerically solved with an initially Maxwellian EVDF and Langmuir wave spectral intensity, which is a state that does not reflect the presence of EB process, and hence not in force balance. The EB term subsequently drives the system to a new force-balanced steady state. After a long integration period it is demonstrated that the initial Langmuir fluctuation spectrum is modified, which in turn distorts the initial Maxwellian EVDF into a VDF that resembles the said core-suprathermal VDF. Such a mechanism may thus be operative at the coronal source region, which is characterized by high collisionality.

The Influence of Primary Electrons on the Emissive Properties of Plasma

An expression is derived for the directed velocities of charged particles at the boundary of plasma containing a large number of primary electrons. Special cases of the expression are analyzed and the velocities of ions and electrons escaping from plasma in different situations are determined.

19pAK-13 AdS/CFT対応を用いた非平衡定常系における荷電粒子の特性速度

19pAK-13 AdS/CFT対応を用いた非平衡定常系における荷電粒子の特性速度