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Terrestrial particle accelerators collide charged particles, then watch the trajectory of outgoing debris – but they cannot manipulate dark matter. Fortunately, dark matter is the main component of galaxy clusters, which are continuously pulled together by gravity. We show that galaxy cluster mergers can be exploited as enormous, natural dark matter colliders. We analyse hydrodynamical simulations of a universe containing self-interacting dark matter (SIDM) in which all particles interact via gravity, and dark matter particles can also scatter off each other via a massive mediator. During cluster collisions, SIDM spreads out and lags behind cluster member galaxies. Individual systems can have quirky dynamics that makes them difficult to interpret. Statistically, however, we find that the mean or median of dark matter's spatial offset in many collisions can be robustly modelled, and is independent of our viewing angle and halo mass even in collisions between unequal-mass systems. If the SIDM cross-section were σ/ m  = 0.1 cm2 g−1 = 0.18 barn GeV−1, the 'bulleticity' lag would be ∼5 per cent that of gas due to ram pressure, and could be detected at 95 per cent confidence level in weak lensing observations of ∼100 well-chosen clusters. [ABSTRACT FROM AUTHOR]

Purpose: Most current research toward ultra‐high dose rate (FLASH) radiation is conducted with advanced proton and electron accelerators, which are of limited accessibility to basic laboratory research. An economical alternative to charged particle accelerators is to employ high‐capacity rotating anode x‐ray tubes to produce kilovoltage x‐rays at FLASH dose rates at short source‐to‐surface distances (SSD). This work describes a comprehensive dosimetric evaluation of a rotating anode x‐ray tube for potential application in laboratory FLASH study. Methods and materials: A commercially available high‐capacity fluoroscopy x‐ray tube with 75 kW input power was implemented as a potential FLASH irradiator. Radiochromic EBT3 film and thermoluminescent dosimeters (TLDs) were used to investigate the effects of SSD and field size on dose rates and depth‐dose characteristics in kV‐compatible solid water phantoms. Custom 3D printed accessories were developed to enable reproducible phantom setup at very short SSD. Open and collimated radiation fields were assessed. Results: Despite the lower x‐ray energy and short SSD used, FLASH dose rates above 40 Gy/s were achieved for targets up to 10‐mm depth in solid water. Maximum surface dose rates of 96 Gy/s were measured in the open field at 47 mm SSD. A non‐uniform high‐to‐low dose gradient was observed in the planar dose distribution, characteristic of anode heel effects. With added collimation, beams up to 10‐mm diameter with reasonable uniformity can be produced. Typical 80%–20% penumbra in the collimated x‐ray FLASH beams were less than 1 mm at 5‐mm depth in phantom. Ramp‐up times at the maximum input current were less than 1 ms. Conclusion: Our dosimetric characterization demonstrates that rotating anode x‐ray tube technology is capable of producing radiation beams in support of preclinical FLASH radiobiology research. [ABSTRACT FROM AUTHOR]

The dynamics of spin in external electromagnetic, gravitational, and axion fields is analyzed in the framework of the gravitoelectromagnetism approach in Einstein's general relativity theory. We consistently extend the recent studies from the flat Minkowski geometry to the curved spacetime manifolds, contributing to the discussion of the possible new role of a precessing spin as an "axion antenna" that can be used to detect the hypothetical axion-like dark matter. The formalism developed helps to clarify the subtle influence of the gravitational/inertial and axion fields in the ultra-sensitive high-energy spin experiments with charged particles and neutrons at accelerators and storage rings devoted to testing fundamental physical symmetries, including attempts to establish the nature of dark matter in the Universe. [ABSTRACT FROM AUTHOR]

Long-duration space exploratory missions to the Earth's moon and the planet Mars are actively being planned. Such missions will require humans to live for prolonged periods beyond low earth orbit where astronauts will be continuously exposed to high energy galactic cosmic rays (GCRs). A major unknown is the potential impact of GCRs on the risks of developing degenerative cardiovascular disease, which is a concern to NASA. A ground-based rat model has been used to provide a detailed characterization of the risk of long-term cardiovascular disease from components of GCRs at radiation doses relevant to future human missions beyond low earth orbit. Six month old male WAG/RijCmcr rats were irradiated at a ground-based charged particle accelerator facility with high energy ion beams broadly representative of GCRs: protons, silicon and iron. Irradiation was given either as a single ion beam or as a combination of three ion beams. For the doses used, the single ion beam studies did not show any significant changes in the known cardiac risk factors and no evidence of cardiovascular disease could be demonstrated. In the three ion beam study, the total cholesterol levels in the circulation increased modestly over the 270 day follow up period, and inflammatory cytokines were also increased, transiently, 30 days after irradiation. Perivascular cardiac collagen content, systolic blood pressure and the number of macrophages found in the kidney and in the heart were each increased 270 days after irradiation with 1.5 Gy of the three ion beam grouping. These findings provide evidence for a cardiac vascular pathology and indicate a possible threshold dose for perivascular cardiac fibrosis and increased systemic systolic blood pressure for complex radiation fields during the 9 month follow up period. The development of perivascular cardiac fibrosis and increased systemic systolic blood pressure occurred at a physical dose of the three ion beam grouping (1.5 Gy) that was much lower than that required to show similar outcomes in earlier studies with the same rat strain exposed to photons. Further studies with longer follow up periods may help determine whether humans exposed to lower, mission-relevant doses of GCRs will develop radiation-induced heart disease. [ABSTRACT FROM AUTHOR]

The features of the processes of initiation and development of spark discharges in microstructural gas detectors of ionizing radiation in laboratory conditions and on charged-particle beams in accelerators are considered. Such aspects as the Raether charge limit, secondary electron emission, avalanche cross-overlap, positive ion feedback, explosive electron emission, cascading of detectors, and the charge density have been analyzed in detail. The better understanding of these effects will make it possible to make a further step in the development of new-type position-sensitive gas detectors. [ABSTRACT FROM AUTHOR]

Coupled-cavity traveling wave tube (CCTWT) is a high power microwave vacuum electronic device used to amplify radio frequency signals. CCTWTs have numerous applications, including radar, radio navigation, space communication, television, radio repeaters, and charged particle accelerators. Microwave-generating interactions in CCTWTs take place mostly in coupled resonant cavities positioned periodically along the electron beam axis. Operational features of a CCTWT, particularly the amplification mechanism, are similar to those of a multicavity klystron. We advance here a Lagrangian field theory of CCTWTs with the space being represented by one-dimensional continuum. The theory integrates into it the space-charge effects, including the so-called debunching (electron-to-electron repulsion). The corresponding Euler–Lagrange field equations are ordinary differential equations with coefficients varying periodically in the space. Utilizing the system periodicity, we develop instrumental features of the Floquet theory, including the monodromy matrix and its Floquet multipliers. We use them to derive closed form expressions for a number of physically significant quantities. Those include, in particular, dispersion relations and the frequency dependent gain foundational to the RF signal amplification. Serpentine (folded, corrugated) traveling wave tubes are very similar to CCTWTs, and our theory applies to them also. [ABSTRACT FROM AUTHOR]

The paper considers the formation mechanisms of triniobium tin coatings during their deposition by magnetron sputtering using a stoichiometric target. The optimum mode is identified for the magnetron source operation. Investigated are the elemental and phase compositions, coating microstructure, and its change during the high-temperature annealing. It is found that magnetron sputtering coatings deposited in the vacuum chamber at 0.3 Pa and annealed at 800°C, possess the optimum elemental and phase compositions. [ABSTRACT FROM AUTHOR]

The analysis of superconducting nanowires placed in different electromagnetic environments is presented in the framework of Ginzburg-Landau model. First domain of application of conducted analysis is noninvasive superconducting detectors of charged particles and robust field induced Josephson junctions. Robust field induced Josephson junctions (rFIJJs) made by polarization of superconducting nanostructures by external magnetic fields are presented in one dimensional model. The analytical methodology of modeling of rFIJJs in one dimensional cases is introduced and possible implementations are pointed by reference to the principle of minimization of magnetic field energy that is preimposing the space dependence of the screening currents. The presented schemes have potential in description both classical and quantum computers with use of topological defects of superconducting order parameter and artificial evolution. Scheme of testing new topologies and working parameters of circuits is given what shall imply enhancement of already known circuit schemes. Furthermore concept of noninvasive superconducting detectors is given as sensing device for moving charged particles as in accelerator beam or in nano-accelerator beam. Obtained results are refereeing to functionalization of superconducting nanowires topology with reference to various programmable biasing magnetic fields that incorporates the concept of programmable superconducting matter. The presented conceptual scheme can also be used for designing the experiments, where Bose-Einstein condensate is being biased with various class of topologies of magnetic fields coming from three dimensional meta-lattice of superconducting nanowires. [ABSTRACT FROM AUTHOR]

The efficiency of deflection of high-energy negatively charged particles by a bent crystal using planar channeling and stochastic deflection mechanism is compared. The comparison is carried out on the example of antiprotons with kinetic energy from 1 to 14 GeV, which will be achievable on accelerators of the Facility for Antiproton and Ion Research. The comparison showed that both deflection mechanisms make it possible to deflect a part of the antiproton beam in the specified energy range by angles of the order of several hundred microradians, which significantly exceed the critical angle of planar channeling. At the same time, the stochastic deflection mechanism makes it possible to deflect particles at much larger angles than planar channeling. [ABSTRACT FROM AUTHOR]

A previously developed improved photoemission model is applied to a detailed analysis of the high-brightness electron bunch formation in an RF photogun. Space charge-dominated photoemission has a significant influence on the formation of transverse emittance, as well as on the energy distribution within the emitted electron bunch. [ABSTRACT FROM AUTHOR]

Extractive chromatography for radiochemical separation of 111In from Cd targets irradiated from charged particle accelerator was developed using D2EHPA-St-DVB extractant impregnated resin which was prepared from D2EHPA (bis (2-ethylhexyl) phosphoric acid), St(styrene) and DVB (divinyl benzene). For the separation of 111In from Cd by the extractant impregnated resin, the separability of 111In from natural metal cadmium targets has been evaluated by determining the extraction equilibrium constant and the adsorption band movement rate of those elements. The target sample solution (HNO3 conc.; 2 mol·L−1) was adsorbed onto the column which was filled with synthesized D2EHPA-St-DVB extractant impregnated resin. The column was washed with HNO3 solution (conc.; 1 mol·L−1) for removing Cd and 111In was stripped with HCl solution (conc.; 6 mol·L−1). The nuclear purity of the separated 111In was measured as 99.2% by gamma spectrometry and conformed to the requirements of nuclear pharmaceutical. [ABSTRACT FROM AUTHOR]

Different from most of the previous studies using light or photons, we use highly charged ions as projectiles to activate proton migration in the smallest saturated and unsaturated hydrocarbon molecules, i.e., CH4 and C2H2. The H 3 + formation channel ( H 3 + + CH+) and isomerization channel (C+ + C H 2 + ), serving as indicators of proton migration, are observed in the fragmentation of CH4 and C2H2 dications. Corresponding kinematical information, i.e., kinetic energy release, is for the first time obtained in the collisions with highly charged ions. In particular, for the C+ + C H 2 + channel, a new pathway is identified, which is tentatively attributed to the isomerization on high-lying states of acetylene dication. The kinetic energy release spectra for other two-body breakup channels are also determined and precursor dication states could thus be identified. [ABSTRACT FROM AUTHOR]

In this study, we experimentally investigated the effect of charged particles generated from an alternating current glow discharge in liquids and the ability of these particles to synthesize silver nanoparticles. The measurement of the pH and electrical conductivity in liquids was performed to study the interface reactions and transfer of species from plasmas to liquids. Solutions of sodium hydroxide, de-ionized water, sodium nitrate, and silver nitrate were used in this study. We determined that the pH of de-ionized water and sodium hydroxide solutions was reduced to 4.0 during the discharge. However, the pH of nitrate salts evolved in two opposite stages, with an initial reduction within 3 min from the start of the discharge and a subsequent increase to alkaline values. The results also showed that spherical silver nanoparticles were generated in the silver nitrate solutions under the discharge. These results indicate that alternating current glow discharge generates both positive ions and free electrons when in contact with a liquid, leading to complex chemical transformations. This suggests that the proposed approach can be used for noble nanoparticle synthesis. [ABSTRACT FROM AUTHOR]

One of the charged-particle accelerators with relatively low energy and relatively high current is the vacuum-insulated tandem accelerator proposed for boron neutron capture therapy and planned for use in a number of other applications requiring a more remote location of the neutron-generating target from the accelerator. In this work, the phase portrait of the ion beam and its dependence on the ion beam current and the strength of the magnetic lens focusing the beam of negative hydrogen ions on the input of the accelerator are measured. It is shown that the modernization of the magnetic lens contributed to the reduction of the spherical aberration of the lens and improved the quality of the negative ion beam. It has been established that the ion beam emittance increases with increasing current, and the space charge affects the phase portrait of the ion beam in the low energy transport path. To compensate for the action of the space charge on the phase portrait of the proton beam, the strength of the magnetic lens is changed. The obtained experimental data indicate that the proton beam can be transported to the site of the planned location of the neutron-generating target without adding focusing elements. [ABSTRACT FROM AUTHOR]

A methodology for electrochemical preparation of nickel layers intended to be used as targets for charged particle accelerators is proposed. The goal is to deposit the majority of metal dissolved in the electrolytic bath during a reasonable time (no longer than several hours) providing an acceptable quality of the deposits in terms of purity, surface roughness, compact and crack-free structure and mechanical stability. The electrodeposition is carried out from novel aqueous baths prepared by dissolution of a metal powder in a HNO3-free solution due to the limited availability of isotopically enriched nickel concentration of the metal in the bath is low or moderate. This factor combined with the requirement of deposition of all dissolved metal makes serious differences between the target deposition and regular industrial plating. The impact of the electrolytic bath pH and the plating current density is analysed in order to optimise deposition parameters. The pH was varied from 3.8 to 5.3 while the applied current density ranged from 30 to 240 mA cm−2. Progress in the deposition process was analysed using in situ UV–vis spectroscopy while a scanning electron microscope was applied to study the morphology of the deposits. Optimal electroplating conditions, which allow relatively fast deposition (up to ca. 7.2 h) of good quality metallic deposits containing most of the metal present in the bath (≥ 95%), are suggested. [ABSTRACT FROM AUTHOR]

A propulsion concept in which a spacecraft interacts with both a stream of high-velocity macroscopic pellets and the mass of the interplanetary or interstellar medium is proposed. Unlike previous pellet-stream propulsion concepts, the pellets are slower than the spacecraft and are accelerated backwards as they are overtaken by it, imparting a forward acceleration on the spacecraft. This maneuver is possible due to the interaction with a fixed medium (e.g., interstellar medium); as the spacecraft travels through the medium, it is able to extract power from the relative wind blowing over the spacecraft. As viewed from the rest frame, the kinetic energy of the pellets is transferred to the spacecraft; the source of energy for the propulsive maneuver (i.e., whether the source is the pellets or the wind) is thus reference-frame dependent. This concept relies upon the relative velocities (or shear) between the pellet stream and the fixed medium in order to concentrate the energy of the pellets into the spacecraft and is therefore termed wind–pellet shear sailing. The equations governing the mass ratio of pellets to the spacecraft and its dependence on the final spacecraft velocity are derived, analogous to the classical rocket equation; the critical role of the efficiency of the power extraction and transfer process is identified. Natural sources of energy (photon and particle fluxes from the sun) are considered as a means to accelerate the pellets, produced from in-situ sources of material in the solar system, to velocities of 1000 to 6000 km/s. Techniques for onboard generation of power via electromagnetic interaction with the interstellar medium (ISM) are reviewed, with a repetitively stroked plasma magnet being identified as a promising approach. The necessity of the spacecraft to detect and track the pellets as they are overtaken dictates the desired properties of the pellets. Pellet pushers (i.e., accelerators) on board the spacecraft are also preliminarily explored in their engineering considerations, with electric field accelerators of charged nanometric particles, Lorentz-force accelerated ionized pellets, or expansion of vaporized pellets via a nozzle being highlighted as potential approaches. A preliminary mission profile is defined in which a 500-kg scientific payload is delivered to orbit about α -Centauri, using wind–pellet shear sailing as the intermediate stage to bring the spacecraft from 2% to 5.5% of c , with a total mission duration (launch to arrival) of 27 years. The concept design illustrates the potential for synergy at the low-velocity end with advanced solar photon or solar-wind sailing and at the high-velocity end with the q -drive concept. • A new concept is proposed: a spacecraft overtakes pellets, transferring their energy to the spacecraft. • The concept exploits the use of free energy sources available in space. • Analysis suggests spacecraft may be accelerated from 2% to 5% of the speed of light. • The technique may be combined with other propulsion devices to achieve greater speeds. • A mission to return data from nearby stars within 30 years of launch may be possible. [ABSTRACT FROM AUTHOR]

Multicavity Klystron (MCK) is a high power microwave vacuum electronic device used to amplify radio frequency (RF) signals. MCKs have numerous applications, including radar, radio navigation, space communication, television, radio repeaters, and charged particle accelerators. The microwave-generating interactions in klystrons take place mostly in coupled resonant cavities positioned periodically along the electron beam axis. Importantly, there is no electromagnetic coupling between cavities. The cavities are coupled only by the flow of bunched electrons drifting from one cavity to the next. We advance here a Lagrangian field theory of MCKs with the space being represented by a one-dimensional continuum. The theory integrates into it the space-charge effects, including the so-called debunching (electron-to-electron repulsion). The corresponding Euler–Lagrange equations are ordinary differential equations with coefficients varying periodically in the space. Utilizing the system periodicity, we develop the instrumental features of the Floquet theory, including the monodromy matrix and its Floquet multipliers. We use them to derive closed form expressions for a number of physically significant quantities. Those include, in particular, the dispersion relations and the frequency dependent gain foundational to the RF signal amplification. We assume that MCKs operate in the voltage amplification mode associated with the maximal gain. [ABSTRACT FROM AUTHOR]

A large number of experiments carried out at charged particle accelerators indicate that the radiation dose accumulated by the scintillation materials contained in detectors is significant. For example, in experiments at the Large Hadron Collider, the radiation dose in scintillation detectors can reach 10 Mrad and will increase in the future. In this connection, the search for new radiation-resistant scintillation materials is especially important. Irradiation can significantly alter the characteristics of the scintillator material. The aim of this work was to study the features of possible radiation damage and transformations in composite scintillators under the action of ionizing radiation. We focused on composite scintillators, which are transparent non-luminescent gel-compositions containing grains of scintillation oxide single crystals. A comparative analysis of the spectra of the relative light yield, transmission, and luminescence, as well as their dependence on the accumulated dose for various composite scintillators, has been carried out. Possible mechanisms of radiation changes occurring in scintillators under irradiation are proposed and the influence of these processes on the radiation resistant of composite scintillators is analyzed. In this work, as in previous works in this series, we irradiated composite scintillators on a linear electron accelerator. The electron energy was 10 MeV. We irradiated with a low (0.2 Mrad/h) and a high (1500 Mrad/h) dose rate. At low dose rate, cracking occurs at lower radiation dose values (about 100–200 Mrad) than under irradiation at a high dose rate (up to 500 Mrad). The luminescent characteristics of the scintillator changed insignificantly until the gel composition fixing single-crystal grains cracked. After destruction of the gel composition, an abrupt deterioration in the properties of the sample took place. [ABSTRACT FROM AUTHOR]

To very good approximation, particularly for hadron machines, charged-particle trajectories in accelerators obey Hamiltonian mechanics. During routine storage times of eight hours or more, such particles execute some 10 8 revolutions about the machine, 10 10 oscillations about the design orbit, and 10 13 passages through various bending and focusing elements. Prior to building, or modifying, such a machine, we seek to identify accurately the long-term behaviour and stability of particle orbits over such large numbers of interactions. This demanding computational effort does not yield easily to traditional methods of symplectic numerical integration, including both explicit Yoshida-type and implicit Runge–Kutta or Gaussian methods. As an alternative, one may compute an approximate one-turn map and then iterate that map. We describe some of the essential considerations and techniques for constructing such maps to high order and for realistic magnetic field models. Particular attention is given to preserving the symplectic condition characteristic of Hamiltonian mechanics. [ABSTRACT FROM AUTHOR]

Emission of short electron bunches with high charge in RF guns is considered. The emission mechanism in the case of picosecond laser pulses and the presence of a strong electric field at the cathode is quite different from the traditional one limited by the space charge of emitted particles. In this case, it is necessary to take into account the influence of positive charge dynamically formed on the cathode surface related to the difference of velocities of photoelectrons leaving the semiconductor film of the photocathode and velocities of electrons entering the emission region. The comparison of the numerical results and experimental data obtained at the facility for testing photoinjectors at PITZ (DESY, Zeuthen, Germany) demonstrated good agreement. [ABSTRACT FROM AUTHOR]

A small deformation to the Schwarzschild metric controlled by four free parameters could be referred to as a nonspinning black hole solution in alternative theories of gravity. Since such a non-Schwarzschild metric can be changed into a Kerr-like black hole metric via a complex coordinate transformation, the recently proposed time-transformed, explicit symplectic integrators for the Kerrtype spacetimes are suitable for a Hamiltonian system describing the motion of charged particles around the non-Schwarzschild black hole surrounded with an external magnetic field. The obtained explicit symplectic methods are based on a time-transformed Hamiltonian split into seven parts, whose analytical solutions are explicit functions of new coordinate time. Numerical tests show that such explicit symplectic integrators for intermediate time steps perform well long-term when stabilizing Hamiltonian errors, regardless of regular or chaotic orbits. One of the explicit symplectic integrators with the techniques of Poincaré sections and fast Lyapunov indicators is applied to investigate the effects of the parameters, including the four free deformation parameters, on the orbital dynamical behavior. From the global phase-space structure, chaotic properties are typically strengthened under some circumstances, as the magnitude of the magnetic parameter or any one of the negative deformation parameters increases. However, they are weakened when the angular momentum or any one of the positive deformation parameters increases. [ABSTRACT FROM AUTHOR]

The characteristic features of plasma acceleration in the current sheets are discussed on the basis of an analysis of the structure of electrodynamic forces at successive stages of the evolution of the current sheets formed in the plasma with helium ions. Of particular interest is the generation of reverse currents at the side edges of the sheet and the appearance of forces, which are braking previously accelerated plasma flows. [ABSTRACT FROM AUTHOR]

Shielding the bias applied to the probe by the sheath formed around it and determination of parameters of unperturbed plasmas are in the basis of the probe diagnostics. The results from a two-dimensional model of a discharge with a probe inserted in it show that the probe influences the spatial distribution of the plasma parameters in the entire discharge. The increase (although slight) in the electron temperature, due to the increased losses of charged particles on the additional wall in the discharge (mainly the probe holder), leads to redistribution of the plasma density and plasma potential, as shown by the results obtained at the floating potential of the probe. The deviations due to the bias applied to the probe tip are stronger in the ion saturation region of the probe characteristics. The pattern of the spatial redistribution of the plasma parameters advances together with the movement of the probe deeper in the discharge. Although probe sheaths and probe characteristics resulting from the model are shown, the study does not aim at discussions on the theories for determination of the plasma density from the ion saturation current. Regardless of the modifications in the plasma behavior in the entire discharge, the deviations of the plasma parameters at the position of the probe tip and, respectively, the uncertainty which should be added as an error when the accuracy of the probe diagnostics is estimated do not exceed 10%. Consequently, the electron density and temperature obtained, respectively, at the position of the plasma potential on the probe characteristics and from its transition region are in reasonable agreement with the results from the model of the discharge without a probe. Being in the scope of research on a source of negative hydrogen ions with the design of a matrix of small radius inductive discharges, the model is specified for a low-pressure hydrogen discharge sustained in a small-radius tube. [ABSTRACT FROM AUTHOR]

In electrostatic tandem charged particle accelerators, gas stripping targets are used to convert negative ions into positive ones. Partial ionization of the gas by ions leads to the formation of an undesirable beam of stripping gas ions in the accelerating channels. In this work, the current of a beam of argon ions produced in a tandem accelerator with vacuum insulation was measured by mass spectroscopy. It is shown that the current of argon ions is 2000 times smaller than the current of the proton beam. The reliability of the measurements is provided by visualization of an argon ion beam on the surface of a lithium target and is also confirmed by an experiment with increased gas injection and an estimate of the possible contribution of the proton beam. It is shown that such a small value of the argon ion current does not pose a danger either as a source of additional heating of a lithium target, or as an additional load of a high-voltage power supply, and therefore does not require the previously proposed means for its suppression. [ABSTRACT FROM AUTHOR]

The equivalence between particles under rotation and charged particles in a magnetic field relates phenomena as diverse as spinning atomic nuclei, weather patterns, and the quantum Hall effect. For such systems, quantum mechanics dictates that translations along different directions do not commute, implying a Heisenberg uncertainty relation between spatial coordinates. We implement squeezing of this geometric quantum uncertainty, resulting in a rotating Bose-Einstein condensate occupying a single Landau gauge wave function. We resolve the extent of zero-point cyclotron orbits and demonstrate geometric squeezing of the orbits’ centers 7 decibels below the standard quantum limit. The condensate attains an angular momentum exceeding 1000 quanta per particle and an interatomic distance comparable to the cyclotron orbit. This offers an alternative route toward strongly correlated bosonic fluids. [ABSTRACT FROM AUTHOR]

The interaction of a charged particle and a rotating fullerene molecule in a fullerite crystal is investigated. The mathematical model was constructed and implemented for fullerene rotation frequencies up to 1014 Hz and velocities of an incident charged particle of the order of 103 m s−1. The study was carried out using the methods of classical molecular physics. The characteristics of the motion of the C60 fullerene molecule were determined using the laws of classical mechanics, Euler's approach, and a step-by-step numerical method of a high order of accuracy. The influence of the action of a charged particle on the nature of the motion of a rotating fullerene was analyzed according to the results of the performed numerical experiments. [ABSTRACT FROM AUTHOR]

We present an approach to construct structure-preserving emulators for Hamiltonian flow maps and Poincaré maps based directly on orbit data. Intended applications are in moderate-dimensional systems, in particular, long-term tracing of fast charged particles in accelerators and magnetic plasma confinement configurations. The method is based on multi-output Gaussian process (GP) regression on scattered training data. To obtain long-term stability, the symplectic property is enforced via the choice of the matrix-valued covariance function. Based on earlier work on spline interpolation, we observe derivatives of the generating function of a canonical transformation. A product kernel produces an accurate implicit method, whereas a sum kernel results in a fast explicit method from this approach. Both are related to symplectic Euler methods in terms of numerical integration but fulfill a complementary purpose. The developed methods are first tested on the pendulum and the Hénon–Heiles system and results compared to spectral regression of the flow map with orthogonal polynomials. Chaotic behavior is studied on the standard map. Finally, the application to magnetic field line tracing in a perturbed tokamak configuration is demonstrated. As an additional feature, in the limit of small mapping times, the Hamiltonian function can be identified with a part of the generating function and thereby learned from observed time-series data of the system's evolution. For implicit GP methods, we demonstrate regression performance comparable to spectral bases and artificial neural networks for symplectic flow maps, applicability to Poincaré maps, and correct representation of chaotic diffusion as well as a substantial increase in performance for learning the Hamiltonian function compared to existing approaches. [ABSTRACT FROM AUTHOR]

In this article, we have explored the resonance behavior of a particle in the presence of a time dependent magnetic field (TDMF). The particle is bound in a harmonic potential well. Based on the Hamiltonian description of the system in terms of action and angle variables, we have derived the resonance condition for the applied TDMF along z-direction which is valid for arbitrary frequencies along x and y directions of the two dimensional harmonic oscillator. We have also derived resonance condition for the applied magnetic field which is lying in a plane. Finally, we have explored resonance condition for the isotropic magnetic field. To check the validity of the theoretical calculation, we have solved equations of motion numerically for the parameter sets which satisfy the derived resonance condition. The numerical experiment fully agrees with the theoretically derived resonance conditions. [ABSTRACT FROM AUTHOR]

We study the behavior of the non-ideal pion gas with the dynamically fixed number of particles, formed on an intermediate stage in ultra-relativistic heavy-ion collisions. The pion spectrum is calculated within the self-consistent Hartree approximation. General expressions are derived for cross-covariances of the number of various particle species in the pion gas of an arbitrary isospin composition. The behavior of the cross-variances is analyzed for the temperature approaching from above the maximal critical temperature of the Bose–Einstein condensation for the pion species a = ± , 0 , i.e. for T > max T cr a . It is shown that in the case of the system with equal averaged numbers of isospin species, the variance of the charge, Q = N + - N - , diverges at T → T cr = T cr a , whereas variances of the total particle number, N = N + + N - + N 0 , and of a relative abundance of charged and neutral pions, G = (N + + N -) / 2 - N 0 , remain finite in the critical point. Then, fluctuations are studied in the pion gas with small isospin imbalance 0 < | G | ≪ N and 0 < | Q | ≪ N and shifts of the effective masses, chemical potentials, and values of critical temperatures are calculated for various pion species, and the highest critical temperature, max T cr a is found, above which the pion system exists in the non-condensed phase. Various pion cross variances are calculated for T > max T cr a , which prove to be strongly dependent on the isospin composition of the system, whereas the variances of N and G are found to be independent on the isospin imbalance up to the term linear in G/N and Q/N. [ABSTRACT FROM AUTHOR]

Fundamentals of boron neutron capture therapy of malignant tumors are outlined, and the current status of the development of epithermal-neutron sources on the basis of charged-particle accelerators is surveyed. Attention is additionally given to a neutron source based on a charged-particle accelerator belonging to a new type—a tandem accelerator with vacuum insulation and a lithium neutron-producing target. [ABSTRACT FROM AUTHOR]

In both the International Commission on Radiological Protection (ICRP) and Medical Internal Radiation Dose (MIRD) schemata of internal dosimetry, the S-value is defined as the absorbed dose to a target organ per nuclear decay of the radionuclide in a source organ. Its computation requires data on the energies and yields of all radiation emissions from radionuclide decay, the mass of the target organ, and the value of the absorbed fraction—the fraction of particle energy emitted in the source organ that is deposited in the target organ. The specific absorbed fraction (SAF) is given as the ratio of the absorbed fraction and the target mass. Historically, in the early development of both schemata, computational simplifications were made to the absorbed fraction in considering both organ self-dose () and organ cross-dose (). In particular, the value of the absorbed fraction was set to unity for all 'non-penetrating' particle emissions (electrons and alpha particles) such that they contributed only to organ self-dose. As radiation transport codes for charged particles became more widely available, it became increasingly possible to abandon this distinction and to explicitly consider the transport of internally emitted electrons in a manner analogous to that for photons. In this present study, we report on an extensive series of electron SAFs computed in a revised series of the UF/NCI pediatric phantoms. A total of 28 electron energies—0–10 MeV—along a logarithmic energy grid are provided in electronic annexes, where 0 keV is associated with limiting values of the SAF. Electron SAFs were computed independently for collisional energy losses (SAFCEL) and radiation energy losses (SAFREL) to the target organ. A methodology was employed in which values of SAFREL were compiled by first assembling organ-specific and electron energy-specific bremsstrahlung x-ray spectra, and then using these x-ray spectra to re-weight a previously established monoenergetic database of photon SAFs for all phantoms and source–target combinations. Age-dependent trends in the electron SAF were demonstrated for the majority of the source–target organ pairs, and were consistent to values given for the ICRP adult phantoms. In selected cases, however, anticipated age-dependent trends were not seen, and were attributed to anatomical differences in relative organ positioning at specific phantom ages. Both the electron SAFs of this study, and the photon SAFs from our companion study, are presently being used by ICRP Committee 2 in its upcoming pediatric extension to ICRP Publication 133. [ABSTRACT FROM AUTHOR]

This review presents the author's view on modern trends in the development of charged particle accelerators for various applications, which is based on his own experience in this research field. The most promising, in the author's opinion, areas of application of resonance accelerators are shown, in which substantial progress has been made by using new technologies. The use of high-gradient structures, novel materials, new manufacturing technologies, cooling systems, and new principles of acceleration made it possible to achieve miniaturization, to increase cost efficiency, and to succeed in adjusting accelerator parameters (to achieve variability) for industrial, medical, and research purposes, as well as for applications in security systems and quantum computers. [ABSTRACT FROM AUTHOR]

Visibility graphs (VGs), horizontal visibility graphs (HVGs) and the sandbox algorithm (SB) are applied for multifractal characterization of complex network systems that are converted from time series measurements, are used to characterize the fluctuations in pseudorapidity densities of singly charged particles produced in 1 6 O–AgBr interactions at 60 A GeV. The work presents the analysis of ring-like and jet-like events in terms of multifractality characterization of 1 6 O–AgBr interactions at 60 A GeV. We systematically compared the experimental events of both ring- and jet-like events with Monte Carlo (MC) simulated events. The investigation reveals that the multifractal spectrum for the jet-like events and ring-like events is different and can be distinguished. The ring-like events have its parameters slightly higher than that of jet-like events. Further analysis shows that the strength of the nonstatistical fluctuations is larger for ring-like events than those of jet-like events. The SB method presented here appears to be more useful than the conventional methods used for multifractal characterization. [ABSTRACT FROM AUTHOR]

Proton–Proton (p p) collisions at the Large Hadron Collider (LHC) are simulated in order to study events with a high local density of charged particles produced in narrow pseudorapidty windows of Δ η = 0.1, 0.2, and 0.5. The p p collisions are generated at center of mass energies of s = 2. 3 6 , 7 , 8 , and 1 3 TeV, i.e., the energies at which the LHC has operated so far, using PYTHIA and HERWIG event generators. We have also studied the average of the maximum charged-particle density versus the event multiplicity for all events, using the different pseudorapidity windows. This study prepares for the multi-particle production background expected in a future search for anomalous high-density multiplicity fluctuations using the LHC data. [ABSTRACT FROM AUTHOR]

The spatial parallel diffusion coefficient (SPDC) is one of the important quantities describing energetic charged particle transport. There are three different definitions for the SPDC: the displacement variance definition , the Fick's law definition with , and the Taylor–Green–Kubo (TGK) formula definition. For a constant mean magnetic field, the three different definitions of the SPDC give the same result. However, for a focusing field, it is demonstrated that the results of the different definitions are not the same. In this paper, from the Fokker–Planck equation, we find that different methods, e.g., the general Fourier expansion and iteration method, can give different equations of the isotropic distribution function (EIDFs). But it is shown that one EIDF can be transformed into another by some derivative iterative operations (DIOs). If one definition of the SPDC is invariant for the DIOs, it is clear that the definition is also invariant for different EIDFs; therefore, it is an invariant quantity for the different derivation methods of the EIDF. For the focusing field, we suggest that the TGK definition is only an approximate formula, and the Fick's law definition is not invariant to some DIOs. However, at least for the special condition, in this paper we show that the definition is an invariant quantity to the DIOs. Therefore, for a spatially varying field, the displacement variance definition , rather than the Fick's law definition and TGK formula definition , is the most appropriate definition of the SPDCs. [ABSTRACT FROM AUTHOR]

In this work, the interactions of 7Li nuclei with emulsion at 3 A GeV/c were studied. Multiplicity of the charged secondary particles as well as the charge of the outgoing projectile fragments were measured, while correlations among them are discussed. The values of the total charge of the noninteracting projectile nucleons and the average number of interacting projectile nucleons are estimated. The dependence of the secondary particles on the number of heavily-ionized tracks is analyzed. The results show that interactions of 7Li nuclei with emulsion nuclei exhibit a number of regularities, which had been noted in experiments with lighter nuclei. The absorption of relativistic particles, while increasing the degree of target destruction, is observed. The average multiplicities of the secondary charged particles depend on the impact parameter, as their values increase, while decreasing the impact parameter. The number of secondary charged particles in the heavy-ion interactions depends on the degree of disintegration of the target nuclei. This dependence is not observed in the case of the interaction of hadron with emulsion. The experimental data of the interaction of 7Li are systematically compared with the other interactions at different energies. The results agree with the corresponding results at nearly the same energy. [ABSTRACT FROM AUTHOR]

We have studied the effect of time dependent magnetic field on the barrier crossing dynamics of a charged particle. An interplay of the magnetic field induced electric field and the applied field reveals several interesting features. For slowly oscillating field the barrier crossing rate increases remarkably particularly at large amplitude of the field. For appreciably large frequency a generically distinct phenomenon appears by virtue of parametric resonance manifested in multiple peaks appearing in the variation of the mean first passage time as a function of the amplitude. The parametric resonance is more robust against the variation of amplitude of the oscillating field compared to the case of variation of frequency. The barrier crossing time of a particle can be tuned para-metrically by appropriate choice of amplitude and frequency of the oscillating magnetic field. [ABSTRACT FROM AUTHOR]

Abstract— Diagnostics have been developed for measuring the efficiency of stripping a beam of negative ions in a gas stripping target of a tandem charged particle accelerator. The coefficient of ion-electron emission during the bombardment of copper by protons with an energy of 1 MeV was measured. A bending magnet with a horizontal nozzle was installed, which made it possible to place a Faraday cup and receive a stream of neutrals formed on it as a result of incomplete stripping of negative ions in the stripping target. Diagnostics of the efficiency of the gas stripping target were put into operation on the basis of measuring the current of electrons emitted from the surface of a Faraday cup during its bombardment by a directed stream of neutrals and the proton current by a non-contact current sensor. [ABSTRACT FROM AUTHOR]

Motivated by the recently introduced [Phys. Rev. A 94 , 042704 (2016)] and already investigated [J. Phys. B: At. Mol. Opt. Phys. 50 , 185201 (2017)] new approximate form for the stopping power in terms of scattering phase shifts, here we show analytically that within such a modeling of the observable an exact leading phase shift may contain that information which is completely enough to characterize the asymptotic charge-sign-independent Bethe term (∝ Z 1 2 ) and a charge-sign-dependent (Barkas) term (∝ Z 1 3 ) in the stopping force of a degenerate electron gas for fast projectiles with charge Z 1 . Our study is based on a spherical potential with velocity-dependent screening as in the above works. The next term in an asymptotic expansion, the Bloch term (∝ Z 1 4 ), measures the difference of the exact and first-order Born treatments with Coulomb potential. [ABSTRACT FROM AUTHOR]

Strong electromagnetic resonance in cavity resonators can lead to many configurations of resonant field enhancement. Some resonant modes lead to strongly enhanced electric fields, but there also exist modes in which the magnetic field enhancement dominates. The typical fluid model of gas breakdown and electromagnetic interaction does not account for magnetic fields, which can lead to significant differences between observed and numerically computed breakdown thresholds, as well as differences in post-breakdown plasma evolution. Starting from an expansion of the Boltzmann equation for charged particles, we develop an analytical model that captures how a strong oscillating magnetic field can affect plasma transport properties. Certain parameter regimes are shown to have resonance-like behavior of diffusion, drift, and energy deposition to electrons. We develop a model that incorporates the effects of both static and oscillating magnetic fields in terms of a local effective electric field model. The fluid model parameters are compared to electron swarm behavior in a particle computation with Monte–Carlo collisions. [ABSTRACT FROM AUTHOR]