Acceleration Of Charged Particles Research Articles

Major X-Class Solar Flare from Earth-Facing Active Region AR12887 on October 28, 2021 and First Cosmic Ray GLE 73 in Solar Cycle 25

A phenomenological study of the new Ground Level Enhancement GLE 73 of cosmic rays (CRs) on October 28, 2021 is presented in this work. The investigated GLE 73 appears as one of the first major events of the Sun in the new solar cycle 25 (2019–2030). The recent GLE 73 occurred as a result of an X-class solar flare and was measured on the surface of both the Earth (by Neutron Monitors) and PAMELA satellite-borne instruments. This GLE occurs as a result of massive acceleration of charged particles in the solar corona and interplanetary space. Usually such event provides quite a soft spectrum of energetic particles, but sometimes the spectrum is sufficiently hard so that the initial solar protons can generate secondary nucleons that can be detected as an increase in the cosmic ray flux at ground level. Such exceptional event represents the studied GLE 73. These GLEs of cosmic rays are numbered consecutively from the first events that were detected on February 28, 1942 (GLE 1) and March 7, 1942 (GLE 2) J exactly 80 years ago. During the past 80 years of GLE studies some fundamental results of space physics have been achieved. Analyzing the list of all GLEs registered until now in the period (1942–2021) some characteristics that are important parameters can be determined. The quantification of GLEs in different solar cycles is presented by calculating the frequency of GLE occurrence in solar cycles 17–25.

In Situ Measurement of the Energy Fraction in Suprathermal and Energetic Particles at ACE, Wind, and PSP Interplanetary Shocks

Abstract The acceleration of charged particles by interplanetary shocks (IPs) can drain a nonnegligible fraction of the plasma pressure. In this study, we have selected 17 IPs observed in situ at 1 au by the Advanced Composition Explorer and the Wind spacecraft, and 1 shock at 0.8 au observed by Parker Solar Probe. We have calculated the time-dependent partial pressure of suprathermal and energetic particles (smaller and greater than 50 keV for protons and 30 keV for electrons, respectively) in both the upstream and downstream regions. The particle fluxes were averaged for 1 hr before and 1 hr after the shock time to remove short timescale effects. Using the MHD Rankine–Hugoniot jump conditions, we find that the fraction of the total upstream energy flux transferred to suprathermal and energetic downstream particles is typically ≲16%, in agreement with previous observations and simulations. Notably, by accounting for errors on all measured shock parameters, we have found that for any given fast magnetosonic Mach number, M f < 7, the angle between the shock normal and average upstream magnetic field, θ Bn, is not correlated with the energetic particle pressure; in particular, the partial pressure of energized particles does not decrease for θ Bn ≳ 45°. The downstream electron-to-proton energy ratio in the range ≳ 140 eV for electrons and ≳ 70 keV for protons exceeds the expected ∼1% and nears equipartition (>0.1) for the Wind events.

Constraints on Cosmic Ray Acceleration Capabilities of Black Holes in X-ray Binaries and Active Galactic Nuclei

Rotating black holes (BHs) are likely the largest energy reservoirs in the Universe as predicted by BH thermodynamics, while cosmic rays (CRs) are the most energetic among particles detected on Earth. Magnetic fields surrounding BHs combined with strong gravity effects, thanks to the spacetime symmetries, turn the BHs into powerful accelerators of charged particles. At the same time, in the age of multi-wavelength and multi-messenger astronomy, BHs and their environments have not yet been probed with CR messengers, despite being observed across most of the electromagnetic spectrum, and neutrino and gravitational waves. In this paper, we probe the acceleration capabilities of BHs in 8 galactic X-ray binaries and 25 local active galactic nuclei (AGNs) within 100 Mpc, based on the ultra-efficient regime of the magnetic Penrose process of a BH energy extraction combined with observational data. We find that the maximum energy of the galactic BHs can reach only up to the knee of the CR spectrum, including supermassive BH Sgr A* at the Galactic Center. On the other hand, for supermassive BHs in AGNs, we find that the mean energy of primary CRs is of the order of 1019 eV. It is therefore likely that local supermassive BHs give sufficient contribution to the ankle—a sharp change in the slope of the cosmic ray spectrum around 1018.6 eV energy. We also discuss the energy losses of primary CRs close to the acceleration zones. In the galactic BH cases, it is likely dominated by synchrotron radiation losses.

Effect of the film thickness on pumping properties of Ti–Zr–V coating

Non-evaporable getter (NEG) coating is widely used for vacuum system of charged particle accelerators. The RF surface resistance of NEG coating is increasing with its thickness. Therefore, knowing how NEG coating properties depend on its thickness is essential for vacuum system design of accelerators. This paper describes the results of studying the pumping properties of Ti–Zr–V NEG films deposited from an alloy target for thicknesses in the range between 0.1 and 1μm. Good pumping properties for H2 and CO have been demonstrated after activation to 140 °C. It has been demonstrated that initial CO sticking probability does not depend on thickness, however, initial H2 sticking probability and CO sorption capacity are almost proportional to NEG thickness. The NEG coating degradation with a number of activations has been observed, the thinner NEG film the stronger the degradation.

Medical cyclotron: Operational aspects and its clinical utility

Cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1930 at the University of California, Berkeley and patented in 1932. Lawrence was awarded the Nobel Prize in Physics 1939 for this invention. It is based on a combination of radiofrequency acceleration and bending of charged particles in a magnetic field. This way the same electrode is used over and over again to give acceleration to the particles. Lawrence built the first cyclotron in 1931 and it produced Protons of 1.25 MeV. In a conventional Cyclotron, the charged particles move in two semicircular metal containers called Dees (because of the D-shaped electrodes). In most of the modern medical cyclotrons, there are four gaps with four pie-shaped Dees instead of two. The particles pass through the same acceleration gap many times with increasing radius before they acquire the desired energy. The entire accelerating system is maintained at high vacuum (10-6 to 10-8 Torr), and the Dees are housed in a vacuum chamber. Hydrogen gas is passed through an arc current to produce the ion source for the acceleration in the cyclotron. The ion source is pulled toward the center of Dee structure by applying a positive bias voltage. A high voltage (>36 kV) is applied to the Dee structure with the help of an oscillator. The ion located at the center is thus attracted toward a Dee that happens to be at the opposite potential at that particular moment. As the magnetic and electric fields (in Dees) in the cyclotron are at right angles to each other the ion beam moves in a circular path inside the hollow Dees. In the present scenario, negative ion cyclotron accepted everywhere in the medical field. The objective of this article is to educate the new generation of physicians and share the knowledge of medical cyclotron and its integrity mainly among our colleague apart from nuclear medicine. Hence, that they can understand about this complex and complicated equipment and its medical utility for patients benefit.

Modulated Laser-Induced Acceleration of a Relativistic Charged Particle

Modulated Laser-Induced Acceleration of a Relativistic Charged Particle

Technique for obtaining an integral characteristic of the structure of a loaded composite material based on microtomographic research data

Composite materials are characterized by an uneven distribution of the density value in the volume. Under mechanical loading, the parameters of the density distribution over the volume change, which leads to qualitative changes in the structure up to the formation of discontinuities, and the shock-wave sensitivity also changes accordingly. The exact distribution of regions with different density values in the bulk of the material is established by means of X-ray microtomography.The purpose of the work was to develop a technique for obtaining an integral characteristic of the structure of a loaded composite material based on microtomographic examination data. Samples of a carbon composite material in the initial state and subjected to loading with various degrees of deformation were used as objects of study. Synchrotron radiation from a VEPP-3 charged particle accelerator (Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia) was used as an X-ray source for microtomographic studies.To extract the indicated integral characteristic of the structure from the density matrices of the material, an image analysis technique was developed based on sequential image filtering in order to select regions with a given range of gray shades from the total matrix. To decompose the general matrix into derivatives and their subsequent analysis, the universal software ImageJ-FiJi was used.Based on the processing results, a dependence was obtained that characterizes the ratio of the size of the local region of the structure with a characteristic density value to the distance between these regions, that is, the desired integral characteristic from the conditional density range of the analyzed regions.

OPTICAL SYSTEM DESIGN OF THE DETECTOR FOR SOLAR TERAHERTZ EMISSION MEASUREMENTS

The objectives and scientific tasks of the planned space experiment “Solntse-Terahertz” to be performed onboard the ISS Russian Segment are briefly described in the paper. In particular, the aim of the experiment is to study uninvestigated solar electromagnetic emission in the terahertz domain, in ~ 1012 – 1013 Hz (300-30 µm) frequency range. It is expected to obtain new data on solar active region emission including solar flare emission. These data are necessary to clarify the nature of solar activity and construct physical model of charged particle acceleration in active regions during solar flares and other astrophysical objects. We focus on the telescope optical system design and evaluation of main characteristics of this system. Results of simulations and comparison with the experimental verification of obtained characteristics are presented. A close correlation of the estimations and experimental results was obtained. As a result, main parameters of the telescope optical system of experimental hardware “Solntse-Terahertz” were determined. Key words: Sun, solar flares, terahertz emission, optical system.

Comparative Study of Electric Currents and Energetic Particle Fluxes in a Solar Flare and Earth Magnetospheric Substorm

Abstract Magnetic field line reconnection is a universal plasma process responsible for the conversion of magnetic field energy to plasma heating and charged particle acceleration. Solar flares and Earth's magnetospheric substorms are two of the most investigated dynamical systems where global magnetic field reconfiguration is accompanied by energization of plasma populations. Such a reconfiguration includes formation of a long-living current system connecting the primary energy release region and cold dense conductive plasma of the photosphere/ionosphere. In both flares and substorms the evolution of this current system correlates with the formation and dynamics of energetic particle fluxes (although energy ranges can be different for these systems). Our study is focused on the similarity between flares and substorms. Using a wide range of data sets available for flare and substorm investigations, we qualitatively compare the dynamics of currents and energetic particle fluxes for one flare and one substorm. We show that there is a clear correlation between energetic particle precipitations (associated with energy release due to magnetic reconnection seen from riometer and hard X-ray measurements) and magnetic field reconfiguration/formation of the current system, whereas the long-term current system evolution correlates better with hot plasma fluxes (seen from in situ and soft X-ray measurements). We then discuss how data sets of in situ measurements of magnetospheric substorms can help interpret solar flare data.

A Brief Introduction to Beam Position Monitors for Charged Particle Accelerators

While charged particle accelerators have their origin in the research related to fundamental and high-energy physics, they expanded their applications to many other fields of applied research in physics, material science, biology, chemistry, and medical science, including the treatment of patients, to name some. However, in all types of accelerators assembles of charged particles, e.g., electrons, protons, ions, sometimes their antimatter partners positrons or p-bars (anti-protons) are accelerated to a desired energy, typically in an evacuated, metallic tube, called beam pipe. The acceleration is performed by providing an electric field of high gradient to the charged particle assemble in the direction of motion. In most cases this is performed by resonant radio-frequency (RF) cavities, which are fed by a high-power RF source. However, new acceleration schemes using high power lasers, plasma wakefields, etc. are also studied these days. A guide-field along the accelerator, typically provided by sets of different types of magnets, ensures the charged particles stay within the transverse boundaries of the beam pipe, near its center, travelling on the wanted trajectory. Accelerating elementary particles, like electrons, or quasi-elementary particles, like protons, to very high energies (GeV range) results their velocity $v$ to be close to speed-of-light $c$ , typically expressed as relative velocity $\beta=v/c\approx 1$ , and any further acceleration manifests in a gain of momentum $p=\gamma m_{0}v$ , with $\gamma=1/\sqrt{1-\beta^{2}}$ being the Lorentz factor and $m_{0}$ being the mass of the particle at rest, 0.511 MeV and 938.26 MeV for electron and proton, respectively. The use of resonant RF cavities for the acceleration, causes the particles to form bunches, which fill a longitudinal range of typically a few millimeters up to some meters, depending on $f_{RF}, \gamma$ and other factors. This means, the large number of charged particles in the accelerator are not uniformly distributed along the beam-line but appear in bunches of typical $N=10^{8}-10^{11}$ particles per bunch, and the minimum space between the center of those bunches is defined by the RF bucket length, given by the wavelength $\lambda_{RF}=v/f_{RF}$ of the RF system.

Multi-spacecraft observations of the structure of the sheath of an interplanetary coronal mass ejection and related energetic ion enhancement

Context. Sheath regions ahead of coronal mass ejections (CMEs) are large-scale heliospheric structures that form gradually with CME expansion and propagation from the Sun. Turbulent and compressed sheaths could contribute to the acceleration of charged particles in the corona and in interplanetary space, but the relation of their internal structure to the particle energization process is still a relatively little studied subject. In particular, the role of sheaths in accelerating particles when the shock Mach number is low is a significant open research problem. Aims. This work seeks to provide new insights on the internal structure of CME-driven sheaths with regard to energetic particle enhancements. A good opportunity to achieve this aim was provided by multi-point, in-situ observations of a sheath region made by radially aligned spacecraft at 0.8 and ∼1 AU (Solar Orbiter, the L1 spacecraft Wind and ACE, and BepiColombo) on April 19−21, 2020. The sheath was preceded by a weak and slowly propagating fast-mode shock. Methods. We apply a range of analysis techniques to in situ magnetic field, plasma and particle observations. The study focuses on smaller scale sheath structures and magnetic field fluctuations that coincide with energetic ion enhancements. Results. Energetic ion enhancements were identified in the sheath, but at different locations within the sheath structure at Solar Orbiter and L1. Magnetic fluctuation amplitudes at inertial-range scales increased in the sheath relative to the solar wind upstream of the shock, as is typically observed. However, when normalised to the local mean field, fluctuation amplitudes did not increase significantly; magnetic compressibility of fluctuation also did not increase within the sheath. Various substructures were found to be embedded within the sheath at the different spacecraft, including multiple heliospheric current sheet (HCS) crossings and a small-scale flux rope. At L1, the ion flux enhancement was associated with the HCS crossings, while at Solar Orbiter, the ion enhancement occurred within a compressed, small-scale flux rope. Conclusions. Several internal smaller-scale substructures and clear difference in their occurrence and properties between the used spacecraft was identified within the analyzed CME-driven sheath. These substructures are favourable locations for the energization of charged particles in interplanetary space. In particular, substructures that are swept from the upstream solar wind and compressed into the sheath can act as effective acceleration sites. A possible acceleration mechanism is betatron acceleration associated with a small-scale flux rope and warped HCS compressed in the sheath, while the contribution of shock acceleration to the latter cannot be excluded.

Investigation of (p,xd) reaction on 120Sn nucleus at proton energy of 30 MeV

For the first time, the double-differential and integral cross-sections of the reaction (p,xd) on the 120Sn nucleus were measured at the energy of the bombarding protons of 30 MeV. Tin is the structural material of the nuclear power plants being designed, in particular, the promising ADS (Accelerator Driven System) hybrid electro-nuclear installations consisting of a high-energy proton accelerator and a deeply subcritical nuclear reactor. The main idea is to use high-energy charged particle accelerators to produce neutrons in heavy element targets. For registration and identification of reaction products, the dE-E method was used, where two parameters of the detected particle are registered: specific ionization and total energy. The total error of the measured double-differential cross sections did not exceed 20%. After integrating the double-differential cross sections by angle, the integral energy spectrum was determined. The theoretical analysis is carried out within the framework of the TALYS calculation code, which is based on modern theoretical models of nuclear decay. The mechanisms of nuclear reactions responsible for the formation of the energy spectrum of outgoing deuterons are determined. The obtained experimental results fill in the missing values of the cross-sections of the studied reactions and can be used in the development of new approaches to the theory of nuclear reactions, as well as in the design of hybrid nuclear power plants.

Charged particles energization during magnetic reconnection in the Earth’s magnetosphere by double layers: an analytical approach

ABSTRACT Charged particles energization at the magnetic reconnection sites in the Earth’s magnetosphere is a subject of active debate in space plasma, specifically in magnetopause and magnetotail regions. In the proximity of the reconnection region, Magnetospheric Multiscale (MMS) and other satellite missions have confirmed the existence of electron acceleration ranging from 100 keV to MeV. There is also evidence of cold ions acceleration in the separatrix region of the Earth’s magnetopause. An important candidate responsible for charged particles acceleration is believed to be the double layer (DL) structures, and which were first observed by the Cluster satellite in the separatrix region of the Earth’s magnetosphere. Moreover, the MMS mission also observed parallel electric field fluctuations up to 100 mV/m carried by DL at the magnetic reconnection site in the Earth’s magnetosphere. Motivated by the reported literature, we investigate the DL and its associated electric field at the magnetopause magnetic reconnection site by using a simple analytical model in which the DLs associated with kinetic Alfvén waves are studied in a low- $\beta$ electron-ion plasma with Tsallis distributed electrons and fluid ions using the Sagdeev potential technique. The non-extensive parameter (superthermality) of the Tsallis distribution has a pronounced effect on the DL’s strength (as defined by the potential drop) and its associated parallel electric field. Our results are consistent with the earlier studies on DLs in Earth’s magnetosphere. Additionally, we discuss the implications of our findings on charged particle energization in the separatrix region of the Earth’s magnetopause during magnetic reconnection.

Effects of the bounded geometry on the ion-acoustic waves

We translate three-dimensional magnetohydrodynamic equations describing the bounded plasma into a one-dimensional case and obtain an equivalent damping force that resulted from both the bounded geometry and the viscosity of the plasma by averaging all the physical quantities on the cross section, which is perpendicular to the wave propagation direction. A damping solitary wave propagating in a viscous bounded plasma is also verified by the particle-in-cell simulation method. The results in the present paper may be useful in the study of charged beam and particle acceleration, etc. Moreover, we can devise an experiment to obtain the viscosity coefficient of the plasma by measuring the ratio of two amplitudes at two different points.

Electrodynamic Contributions to the Hall‐ and Parallel Electric Fields in Collisionless Magnetic Reconnection

AbstractIn collisionless magnetic reconnection, the Hall electric field and the parallel electric field play important roles because they are responsible for acceleration of charged particles, especially electrons. Using particle‐in‐cell simulations, we study electrodynamic nature of the two electric fields in two‐dimensional collisionless reconnection. We find that the Hall electric field is predominantly () electrostatic; its electromagnetic (induced) component is small but nonzero (). The parallel electric field or potential is contributed comparably by its electrostatic and induced components. In the electron inflow region, along the separatrix, and at the X‐line, the electrostatic component of the parallel electric field (or potential) is larger; while in the electron outflow region, the electromagnetic (induced) component is larger. An initial guide field does not change the electrodynamic nature of the Hall electric field but does change that of the parallel electric field. In the guide field case, the parallel electric field is contributed predominantly by the electromagnetic component from the electron inflow region to the X‐line and by the electrostatic component in the electron outflow region.

Experimental installation for studying cathode plasma processes in vacuum gap of pulsed electron accelerator with gas or liquid injection

One of the directions of using plasma sources is the formation of plasma emitters for electron beams as part of direct-action charged particle accelerators. The parameters of the accelerator generators require mutual matching with the characteristics of the plasma emitters. The paper describes the design, composition and diagnostic equipment of an experimental stand based on a vacuum chamber of a pulsed electron accelerator for testing plasma sources of pulsed electron beams. The stand includes a vacuum volume with a high-voltage bushing, pumping out pipes, diagnostic windows along the perimeter and a mounting flange of a complex device for diagnosing the characteristics of pulsed electron beams. The stand provides the possibility of controlled supply of gas and liquid to the formation region of the plasma emitter of electrons under the influence of an accelerating voltage pulse. The location of the diagnostic windows and flanges of the stand allows direct optical observations of the plasma formation region in the frontal and profile directions. The use of the stand will make it possible to determine the characteristics of the tested plasma emitters for their operation as part of a vacuum diode of pulsed electron accelerator.

Penrose Process: Its Variants and Astrophysical Applications

We present a review of the Penrose process and its modifications in relation to the Kerr black holes and naked singularities (superspinars). We introduce the standard variant of this process, its magnetic version connected with magnetized Kerr black holes or naked singularities, the electric variant related to electrically charged Schwarzschild black holes, and the radiative Penrose process connected with charged particles radiating in the ergosphere of magnetized Kerr black holes or naked singularities. We discuss the astrophysical implications of the variants of the Penrose process, concentrating attention to the extreme regime of the magnetic Penrose process leading to extremely large acceleration of charged particles up to ultra-high energy E∼1022 eV around magnetized supermassive black holes with mass M∼1010M⊙ and magnetic intensity B∼104 G. Similarly high energies can be obtained by the electric Penrose process. The extraordinary case is represented by the radiative Penrose process that can occur only around magnetized Kerr spacetimes but just inside their ergosphere, in contrast to the magnetic Penrose process that can occur in a more extended effective ergosphere determined by the intensity of the electromagnetic interaction. The explanation is simple, as the radiative Penrose process is closely related to radiated photons with negative energy whose existence is limited just to the ergosphere.

The in-situ exploration of Jupiter’s radiation belts

Jupiter has the most complex and energetic radiation belts in our Solar System and one of the most challenging space environments to measure and characterize in-depth. Their hazardous environment is also a reason why so many spacecraft avoid flying directly through their most intense regions, thus explaining how Jupiter’s radiation belts have kept many of their secrets so well hidden, despite having been studied for decades. In this paper we argue why these secrets are worth unveiling. Jupiter’s radiation belts and the vast magnetosphere that encloses them constitute an unprecedented physical laboratory, suitable for interdisciplinary and novel scientific investigations: from studying fundamental high energy plasma physics processes which operate throughout the Universe, such as adiabatic charged particle acceleration and nonlinear wave-particle interactions, to exploiting the astrobiological consequences of energetic particle radiation. The in-situ exploration of the uninviting environment of Jupiter’s radiation belts presents us with many challenges in mission design, science planning, instrumentation, and technology. We address these challenges by reviewing the different options that exist for direct and indirect observations of this unique system. We stress the need for new instruments, the value of synergistic Earth and Jupiter-based remote sensing and in-situ investigations, and the vital importance of multi-spacecraft in-situ measurements. While simultaneous, multi-point in-situ observations have long become the standard for exploring electromagnetic interactions in the inner Solar System, they have never taken place at Jupiter or any strongly magnetized planet besides Earth. We conclude that a dedicated multi-spacecraft mission to Jupiter is an essential and obvious way forward for exploring the planet’s radiation belts. Besides guaranteeing numerous discoveries and huge leaps in our understanding of radiation belt systems, such a mission would also enable us to view Jupiter, its extended magnetosphere, moons, and rings under new light, with great benefits for space, planetary, and astrophysical sciences. For all these reasons, in-situ investigations of Jupiter’s radiation belts deserve to be given a high priority in the future exploration of our Solar System. This article is based on a White Paper submitted in response to the European Space Agency’s call for science themes for its Voyage 2050 programme.

Center of mass energy of charged particles about Reissner–Nordström black hole

We study the acceleration of charged particles by Reissner Nordström black hole by taking into account the term appearing in the formula of the center of mass energy due to charge of the particle. We consider that the particle is radially falling towards the black hole, i.e., [Formula: see text]. It is found that the center of mass energy is infinitely large at the outer horizon without any constraint.

Testing for the continuous spectrum of x rays predicted to accompany the photoejection of an atomic inner-shell electron

Echoing classical physics, quantum electrodynamics predicts the release of a spectral continuum of electromagnetic radiation upon the sudden acceleration of charged particles in quantum matter. Despite apparent theoretical success in describing sister nuclear processes, known as internal bremsstrahlung, following nuclear beta decay and K capture, the situation of the photoejection of an electron from an inner shell of an atom, intraatomic bremsstrahlung (IAB), is far from settled. In this paper we present fresh measurements which rely on contemporary signal processing as well as the high flux available from a synchrotron radiation source to revisit the problem by photoejecting electrons from the innermost shell of copper. For the first time we have sufficient sample statistics to measure the expected spectra at the level expected by contemporary theory. Furthermore, we employ sufficiently thin targets to overcome secondary scattering artifacts. Our approach applies the fluorescence coincidence method to guard against extraneous scattering and multiple incident photon processes. Our observations set a severe upper limit on the rate for IAB: We conclude that current theory overpredicts, by at least 5 sigma, the measured rate for K shell IAB in copper in the range of detected energies below the K fluorescence energy.