Number Of Charged Particles Research Articles

Assessment of 14 MeV DT neutron generator emission with activation and particle track methods

The paper reports on measurements of neutron flux emitted from a 14 MeV DT neutron generator of NSD-35 type, which provides a controllable emission of a stabilized neutron flux, about 2.5 × 108 neutrons per second in 4π angle. The detection techniques that we used included the activation method and PADC track detector. During the experiment the detectors were placed in azimuthal plane, at various positions around the generator, and were irradiated for a chosen time interval. In order to record neutrons using the track detector, we used special converters that transformed the neutrons into charged particles which, in turn generated nuclear tracks in the detector material. Monte Carlo (MC) simulations allowed us to compute the number of charged particles emitted from the converter, which then could be registered by the used track detector. The MC calculations were also used for analysis and interpretation of the measurement results.

Nonrelativistic conformal field theories in the large charge sector

We study Schrödinger invariant field theories (nonrelativistic conformal field theories) in the large charge (particle number) sector. We do so by constructing the effective field theory (EFT) for a Goldstone boson of the associated U(1) symmetry in a harmonic potential. This EFT can be studied semi-classically in a large charge expansion. We calculate the dimensions of the lowest lying operators, as well as correlation functions of charged operators. We find universal behavior of three point function in large charge sector. We comment on potential applications to fermions at unitarity and critical anyon systems.

MPEXS-DNA, a new GPU-based Monte Carlo simulator for track structures and radiation chemistry at subcellular scale.

PurposeTrack structure simulation codes can accurately reproduce the stochastic nature of particle–matter interactions in order to evaluate quantitatively radiation damage in biological cells such as DNA strand breaks and base damage. Such simulations handle large numbers of secondary charged particles and molecular species created in the irradiated medium. Every particle and molecular species are tracked step‐by‐step using a Monte Carlo method to calculate energy loss patterns and spatial distributions of molecular species inside a cell nucleus with high spatial accuracy. The Geant4‐DNA extension of the Geant4 general‐purpose Monte Carlo simulation toolkit allows for such track structure simulations and can be run on CPUs. However, long execution times have been observed for the simulation of DNA damage in cells. We present in this work an improvement of the computing performance of such simulations using ultraparallel processing on a graphical processing unit (GPU).MethodsA new Monte Carlo simulator named MPEXS‐DNA, allowing high computing performance by using a GPU, has been developed for track structure and radiolysis simulations at the subcellular scale. MPEXS‐DNA physics and chemical processes are based on Geant4‐DNA processes available in Geant4 version 10.02 p03. We have reimplemented the Geant4‐DNA process codes of the physics stage (electromagnetic processes of charged particles) and the chemical stage (diffusion and chemical reactions for molecular species) for microdosimetry simulation by using the CUDA language. MPEXS‐DNA can calculate a distribution of energy loss in the irradiated medium caused by charged particles and also simulate production, diffusion, and chemical interactions of molecular species from water radiolysis to quantitatively assess initial damage to DNA. The validation of MPEXS‐DNA physics and chemical simulations was performed by comparing various types of distributions, namely the radial dose distributions for the physics stage, and the G‐value profiles for each chemical product and their linear energy transfer dependency for the chemical stage, to existing experimental data and simulation results obtained by other simulation codes, including PARTRAC.ResultsFor physics validation, radial dose distributions calculated by MPEXS‐DNA are consistent with experimental data and numerical simulations. For chemistry validation, MPEXS‐DNA can also reproduce G‐value profiles for each molecular species with the same tendency as existing experimental data. MPEXS‐DNA also agrees with simulations by PARTRAC reasonably well. However, we have confirmed that there are slight discrepancies in G‐value profiles calculated by MPEXS‐DNA for molecular species such as H2 and H2O2 when compared to experimental data and PARTRAC simulations. The differences in G‐value profiles between MPEXS‐DNA and PARTRAC are caused by the different chemical reactions considered. MPEXS‐DNA can drastically boost the computing performance of track structure and radiolysis simulations. By using NVIDIA's GPU devices adopting the Volta architecture, MPEXS‐DNA has achieved speedup factors up to 2900 against Geant4‐DNA simulations with a single CPU core.ConclusionThe MPEXS‐DNA Monte Carlo simulation achieves similar accuracy to Monte Carlo simulations performed using other codes such as Geant4‐DNA and PARTRAC, and its predictions are consistent with experimental data. Notably, MPEXS‐DNA allows calculations that are, at maximum, 2900 times faster than conventional simulations using a CPU.

Estimation of pion-emitting source in symmetric and asymmetric collisions using the UrQMD model

The femtoscopy technique allows one to measure spatial and temporal characteristics of the particle-emitting source produced in high-energy collisions. In non-central ultrarelativistic heavy-ion collisions the emission source can be tilted in the reaction plane. In the current analysis, the orientation of freeze-out distributions with respect to the first-order event plane in symmetric (Au+Au) and asymmetric (Cu+Au) collisions at $$\sqrt {{s_{NN}}} = 200$$ GeV was studied using the UrQMD model to extract information about the emission source tilt. The effect of the initial geometry on the femtoscopic radii of small systems was measured at the same number of charged particles and transverse momentum was studied in d+Au and 3He+Au collisions at $$\sqrt {{s_{NN}}} = 200$$ GeV. The implications of the results are discussed.

Study of themuon content of high-energy air showers with KASCADE-Grande

In this work, we report measurements on the muon content (Eth > 230 MeV) of extensive air showers (EAS) induced by cosmic rays with primary energy from 10 PeV up to 1 EeV performed with the KASCADE-Grande experiment. The measurements are confronted with SIBYLL 2.3. The results are focused on the dependence of the total muon number and the lateral density distribution of muons in EAS on the zenith angle and the total number of charged particles in the shower. We also present updated results of a detailed study of the attenuation length of shower muons, which reveal a deviation between the measured data and the predictions of the post-LHC hadronic interaction models SIBYLL 2.3, QGSJET-II-04 and EPOS-LHC.

Confinement and manipulation of electron plasmas in a multicell trap

Plasma dynamics and transport are studied experimentally in a multicell Penning-Malmberg trap. The goal is to develop methods for accumulation and long-term confinement of larger numbers of charged particles (e.g., positrons) than is presently possible. In this scheme, the particles constitute non-neutral plasmas which are confined separately in a parallel array of storage cells. Experiments are presented in which pure electron plasmas are transferred from a large-diameter “master cell” trapping region into four smaller, parallel “storage cells,” three of which are offset from the magnetic symmetry axis. The physics of the transfer process, as well as the confinement properties of plasmas in the storage cells, is discussed. We show that plasmas can be transferred into the storage cells and held there for up to a day or more using the rotating wall technique, provided that the plasma radius is sufficiently small compared to that of the cell wall. Experiments regarding the confinement of plasmas with kilovolt space charge are discussed. Recommendations are provided for future efforts with high-capacity multicell traps.

Control of Deuteron Ions to Escape from the Magnetic Mirror Bottle by a Perpendicular Supplemental Mirror

We have inquired into a means to decrease the number of charged particles escaping from a loss cone of a magnetic mirror reactor as many as possible. We previously reported the way of installing a supplemental magnetic mirror (which has a cyclotron heating space within) at the exit of a main magnetic bottle. The cyclotron heating space was set to increase a reflection-efficiency of the supplemental mirror. We could not suppress the loss of the escaping deuteron ions sufficiently even with a very long mirror and a very powerful electric field. Then, in this work we propose a new plan of installing another supplemental mirror besides the previous supplemental mirror. A new mirror is set perpendicularly to the center axis of the main bottle. By the addition of the perpendicular mirror, an efficiency of sending back of escaping deuteron ions is considerably theoretically improved. Also in the previous work, since we did not touch how to supply a high-frequency electric field to the cyclotron heating space, here we consider supplying it by an extraordinary-wave with a cyclotron frequency. It is mentioned that propagation of an extraordinary-wave with an electron cyclotron frequency depends on a magnetic field strength and density of escaping electrons.

Ultra high energy cosmic rays simulated with CONEX code

Today, many experiments around the world (Auger Observatory, Telescope Array, and soon Jem-Euso experiment...) are tracking ultra-high energy cosmic rays. They try to collect some exceptional data that would lift the veil on this type of cosmic rays , mainly to answer why does their energies exceed the GZK cutoff without pointing to astrophysical sources close to our galaxy. Furthermore, we do not really know neither the identity nor the acceleration processes that can provide them with such colossal energy. We have performed, using the CONEX program version 2r6.40 coupled to different hadronic interaction models (QGSJET01, EPOS LHC , SIBYLL 2.1 and QGSJETII-04) simulations focused on the slant depth Xmax of the maximum of the shower longitudinal profile and the charged particle number Nmax. Theses parameters and their fluctuations are very sensitive to the primary particle mass (identity) and energy. The obtained results are compared for proton and iron primaries at the energy range 1018-1021 eV.

Physics of laser plasma interaction and particle transport in the context of inertial confinement fusion

Lasers are unique tools for transporting extremely high powers over large distances, but transfer of such a power from photons to matter in small volumes is a very complicated problem. First of all, the interaction proceeds very far from equilibrium, as with photons having energy of a few electron-volts one would like to heat plasma to temperatures thousand times higher. Second, these processes are strongly nonlinear, as they correspond to transfer energies of a large number of photons to a much smaller number of charged particles in extremely small volumes and in very short time scales. Research in inertial confinement fusion (ICF) gave a strong push for studying all these processes in detail, and now, although many issues remain to be resolved, we have quite a good understanding of how they operate in ICF conditions and what limitations and advantages they offer.In this short review, I share my personal recollections of almost 50 years history of the physics of laser plasma interaction. Understanding of highly nonlinear microscopic processes allowed us to improve the hydrodynamic performance of ICF targets and to foresee future developments. The key point is that multiscale modeling allowed for the retainment of major elements of microscopic physics in macroscopic hydrodynamic codes and make them more accurate and predictive.

Systematics of azimuthal anisotropy harmonics in proton–nucleus collisions at the LHC from the Color Glass Condensate

Simple power counting arguments in the dilute-dense framework of the Color Glass Condensate (CGC) Effective Field Theory predict that even and odd azimuthal anisotropy harmonics of two-particle correlations in proton–nucleus collisions at the LHC will respectively satisfy v2n2{2}∝Nch0 and v2n+12{2}∝Nch, where Nch denotes the number of charged particles. We show that these expectations are borne out qualitatively, and even quantitatively, within systematic uncertainties, for v2 and v4 in comparisons with data from the ATLAS collaboration. We also observe that ATLAS data for the v3 azimuthal harmonic are in excellent agreement with our qualitative expectation; quantitative comparisons are numerically challenging at present. The lessons from this study fully complement those gained by the recent comparison of the CGC dilute-dense framework [1] to data from the PHENIX collaboration on small system collisions at RHIC.

To B or not to B: primordial magnetic fields from Weyl anomaly

The quantum effective action for the electromagnetic field in an expanding universe has an anomalous dependence on the scale factor of the metric arising from virtual charged particles in the loops. It has been argued that this Weyl anomaly of quantum electrodynamics sources cosmological magnetic fields in the early universe. We examine this long-standing claim by using the effective action beyond the weak gravitational field limit which has recently been determined. We introduce a general criteria for assessing the quantumness of field fluctuations, and show that the Weyl anomaly is not able to convert vacuum fluctuations of the gauge field into classical fluctuations. We conclude that there is no production of coherent magnetic fields in the universe from the Weyl anomaly of quantum electrodynamics, irrespective of the number of massless charged particles in the theory.

Fermi-Liquid Theory and Pomeranchuk Instabilities: Fundamentals and New Developments

This paper is a short review on the foundations and recent advances in the microscopic Fermi-liquid (FL) theory. We demonstrate that this theory is built on five identities, which follow from conservation of total charge (particle number), spin, and momentum in a translationally and $SU(2)$-invariant FL. These identities allows one to express the effective mass and quasiparticle residue in terms of an exact vertex function and also impose constraints on the "quasiparticle" and "incoherent" (or "low-energ" and "high-energy") contributions to the observable quantities. Such constraints forbid certain Pomeranchuk instabilities of a FL, e.g., towards phases with order parameters that coincide with charge and spin currents. We provide diagrammatic derivations of these constraints and of the general (Leggett) formula for the susceptibility in arbitrary angular momentum channel, and illustrate the general relations through simple examples treated in the perturbation theory.

Jet properties in PbPb and pp collisions at sqrt{s_{mathrm{N};mathrm{N}}}=5.02 TeV

Modifications of the properties of jets in PbPb collisions, relative to those in pp collisions, are studied at a nucleon-nucleon center-of-mass energy of sqrt{s_{mathrm{N};mathrm{N}}}=5.02 TeV via correlations of charged particles with the jet axis in relative pseudorapidity (Δη), relative azimuth (Δϕ), and relative angular distance from the jet axis varDelta mathrm{r}=sqrt{{left(varDelta eta right)}^2+{left(varDelta phi right)}^2} . This analysis uses data collected with the CMS detector at the LHC, corresponding to integrated luminosities of 404 μb−1 and 27.4 pb−1 for PbPb and pp collisions, respectively. Charged particle number densities, jet fragmentation functions, and jet shapes are presented as a function of PbPb collision centrality and charged-particle track transverse momentum, providing a differential description of jet modifications due to interactions with the quark-gluon plasma.

Electrostatic bending response of a charged helix.

We explore the electrostatic bending response of a chain of charged particles confined on a finite helical filament. We analyze how the energy difference ΔE between the bent and the unbent helical chain scales with the length of the helical segment and the radius of curvature and identify features that are not captured by the standard notion of the bending rigidity, normally used as a measure of bending tendency in the linear response regime. Using ΔE to characterize the bending response of the helical chain we identify two regimes with qualitatively different bending behaviors for the ground state configuration: the regime of small and the regime of large radius-to-pitch ratio, respectively. Within the former regime, ΔE changes smoothly with the variation of the system parameters. Of particular interest are its oscillations with the number of charged particles encountered for commensurate fillings which yield length-dependent oscillations in the preferred bending direction of the helical chain. We show that the origin of these oscillations is the nonuniformity of the charge distribution caused by the long-range character of the Coulomb interactions and the finite length of the helix. In the second regime of large values of the radius-to-pitch ratio, sudden changes in the ground state structure of the charges occur as the system parameters vary, leading to complex and discontinuous variations in the ground state bending response ΔE.

Influence of pulse front steepness on vacuum flashover characteristics

Studying flashover characteristics in vacuum environment is extremely significant for designing reliable insulation structures. The waveform of applied voltage excitations greatly affects the flashover process. In this study, the influence of nanosecond pulse front steepness on flashover process in vacuum is investigated. Firstly, flashover experiments with nanosecond pulses are conducted. Nanosecond pulses with different front steepness are generated and used to trigger flashovers on sample surface. The relationship between pulse front steepness and flashover voltage is studied. Meanwhile, a particle-in-cell with Monte Carlo collision (PIC-MCC) two-dimensional self-sustaining discharge model based on secondary electron emission avalanche (SEEA) scheme is established. The distribution of charged particles, electric field and their evolution during flashover process are presented. Furthermore, pulses with various rising steepness are applied to the model. The multiplication and propagation of charged particles in different pulse waveform conditions are studied. In all conditions, two stages during flashover process can be obviously distinguished based on charged particle number evolution which divides the overall flashover delay time into two parts. By analyzing the voltage development in these two time slots, the quasi-linear relationship between pulse front steepness and flashover voltage in nanosecond pulse flashover in vacuum is explained.

Measurement of long-range multiparticle azimuthal correlations with the subevent cumulant method in pp and p +Pb collisions with the ATLAS detector at the CERN Large Hadron Collider

A detailed study of multi-particle azimuthal correlations is presented using $pp$ data at $\sqrt{s}=5.02$ and 13 TeV, and $p$+Pb data at $\sqrt{s_{\rm{NN}}}=5.02$ TeV, recorded with the ATLAS detector at the LHC. The azimuthal correlations are probed using four-particle cumulants $c_{n}\{4\}$ and flow coefficients $v_n\{4\}=(-c_{n}\{4\})^{1/4}$ for $n=2$ and 3, with the goal of extracting long-range multi-particle azimuthal correlation signals and suppressing the short-range correlations. The values of $c_{n}\{4\}$ are obtained as a function of the average number of charged particles per event, $\left\langle N_{\rm{ch}} \right\rangle$, using the recently proposed two-subevent and three-subevent cumulant methods, and compared with results obtained with the standard cumulant method. The three-subevent method is found to be least sensitive to short-range correlations, which originate mostly from jets with a positive contribution to $c_{n}\{4\}$. The three-subevent method gives a negative $c_{2}\{4\}$, and therefore a well-defined $v_2\{4\}$, nearly independent of $\left\langle N_{\rm{ch}} \right\rangle$, which provides direct evidence that the long-range multi-particle azimuthal correlations persist to events with low multiplicity. Furthermore, $v_2\{4\}$ is found to be smaller than the $v_2\{2\}$ measured using the two-particle correlation method, as expected for long-range collective behavior. Finally, the measured values of $v_2\{4\}$ and $v_2\{2\}$ are used to estimate the number of sources relevant for the initial eccentricity in the collision geometry.

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.

Surface-wave-sustained plasma torch for water treatment

In this study the effects of water treatment by surface-wave-sustained plasma torch at 2.45 GHz are studied. Changes in two directions are obtained: (i) changes of the plasma characteristics during the interaction with the water; (ii) water physical and chemical characteristics modification as a result of the plasma treatment. In addition, deactivation of Gram positive and Gram negative bacteria in suspension are registered. A number of charged and excited particles from the plasma interact with the water. As a result the water chemical and physical characteristics such as the water conductivity, pH, H2O2 concentration are modified. It is observed that the effect depends on the treatment time, wave power, and volume of the treated liquid. At specific discharge conditions determined by the wave power, gas flow, discharge tube radius, thickness and permittivity, the surface-wave-sustained discharge (SWD) operating at atmospheric pressure in argon is strongly non-equilibrium with electron temperature Te much higher than the temperature of the heavy particles (gas temperature Tg). It has been observed that SWD argon plasma with Tg close to the room temperature is able to produce H2O2 in the water with high efficiency at short exposure times (less than 60 sec). The H2O2 decomposition is strongly dependant on the temperature thus the low operating gas temperature is crucial for the H2O2 production efficiency. After scaling up the device, the observed effects can be applied for the waste water treatment in different facilities. The innovation will be useful especially for the treatment of waters and materials for medical application.

Tests of the SIBYLL 2.3 high-energy hadronic interaction model using the KASCADE-Grande muon data

The KASCADE-Grande observatory was a ground-based air shower array dedicated to study the energy and composition of cosmic rays in the energy interval E = 1 PeV –1 EeV. The experiment consisted of different detector systems which allowed the simultaneous measurement of distinct components of air showers (EAS), such as the muon content. In this contribution, we study the total muon number and the lateral density distribution of muons in EAS detected by KASCADE-Grande as a function of the zenith angle and the total number of charged particles. The attenuation length of the muon content of EAS is also measured. The results are compared with the predictions of the SIBYLL 2.3 high-energy hadronic interaction model.

Screening in a multicomponent plasma by the example of a wet air plasma

A general theory of screening of a dust-particle charge in a multicomponent plasma is developed based on the asymptotic screening theory. In the asymptotic theory, the balance equations for the number of charged plasma particles in the diffusion-drift approximation supplemented with point sinks of plasma particles on a dust particle and the Poisson equation for the self-consistent electric field potential are solved by the linearization method using the three-dimensional Fourier transform. The coefficients of a secular or a characteristic polynomial, whose zeroes determine screening constants in a multicomponent plasma, were calculated by the Leverrier–Faddeev method, allowing one to find these coefficients for any number of initial balance equations for the number of charged plasma particles. By the example of a wet air plasma produced by an external gas-ionization source, the procedure is considered for constructing the truncated system of balance equations for main plasma ions and screening constants are determined. The influence of the number of main ions on screening constants is considered and the physical meaning of all screening constants is found.