Angular Distributions Of Charged Particles Research Articles

Vacuum breakdown in magnetic dipole wave by 10-PW class lasers.

The vacuum breakdown by 10-PW-class lasers is studied in the optimal configuration of laser beams in the form of an m-dipole wave, which maximizes the magnetic field. Using 3D PIC simulations we calculated the threshold of vacuum breakdown, which is about 10PW. We examined in detail the dynamics of particles and identified particle trajectories which contribute the most to vacuum breakdown in such highly inhomogeneous fields. We analyzed the dynamics of the electron-positron plasma distribution on the avalanche stage. It is shown that the forming plasma structures represent concentric toroidal layers and the interplay between particle ensembles from different spatial regions favors vacuum breakdown. Based on the angular distribution of charged particles and gamma photons a way to experimentally identify the process of vacuum breakdown is proposed.

Maximal kinetic energy and angular distribution analysis of spatial map imaging: Application to photoelectrons from a single quantum state of H2O.

Dynamical or spatial properties of charged species can be obtained using electrostatic lenses by velocity map imaging (VMI) or spatial map imaging (SMI), respectively. Here, we report an approach for extracting dynamical and spatial information from patterns in SMI images that map the initial coordinates, velocity vectors, and angular distributions of charged particles onto the detector, using the same apparatus as in VMI. Deciphering these patterns required analysis and modeling, involving both their predictions from convolved spatial and velocity distributions and fitting observed images to kinetic energies (KEs) and anisotropy parameters (βs). As the first demonstration of this capability of SMI, the ensuing photoelectrons resulting from (2 + 1) resonant ionization of water in a selected rotational state were chosen to provide a rigorous basis for comparison to VMI. Operation with low acceleration voltages led to a measured SMI pattern with a unique vertical intensity profile that could be least-squares fitted to yield KE and β, in good agreement with VMI measurement. Due to the potential for improved resolution and the extended KE range achievable by this new technique, we expect that it might augment VMI in applications that require the analysis of charged particles and particularly in processes with high KE release.

Measurement of jet structure and substructure in heavy ion collisions with ATLAS

Studies of jet structure in heavy-ion collisions can provide information about the mechanism of jet quenching in the hot and dense QCD medium created in these collisions and about its properties over a range of distance scales. These proceedings present the latest ATLAS measurement of the internal structure of jets to shed more light on the modification of the parton showering process in the presence of the medium. A measurement of the angular distribution of charged particles around the jet axis in Pb+Pb and pp collisions at a center-of-mass energy of 5.02 TeV is presented. Further, a measurement of how the suppression of large-radius jets depends on the internal jet structure characterized by the transverse momentum scale for the hardest splitting in the jet is shown.

Measurement of angular and momentum distributions of charged particles within and around jets in Pb+Pb and pp collisions at sNN=5.02 TeV with the ATLAS detector

Studies of the fragmentation of jets into charged particles in heavy-ion collisions can provide information about the mechanism of jet-quenching by the hot and dense QCD matter created in such collisions, the quark-gluon plasma. This paper presents a measurement of the angular distribution of charged particles around the jet axis in $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV Pb+Pb and $pp$ collisions, using the ATLAS detector at the LHC. The Pb+Pb and $pp$ data sets have integrated luminosities of 0.49 nb$^{-1}$ and 25 pb$^{-1}$, respectively. The measurement is performed for jets reconstructed with the anti-$k_{t}$ algorithm with radius parameter $R = 0.4$ and is extended to an angular distance of $r= 0.8$ from the jet axis. Results are presented as a function of Pb+Pb collision centrality and distance from the jet axis for charged particles with transverse momenta in the 1$-$63 GeV range, matched to jets with transverse momenta in the 126$-$316 GeV range and an absolute value of jet rapidity of less than 1.7. Modifications to the measured distributions are quantified by taking a ratio to the measurements in $pp$ collisions. Yields of charged particles with transverse momenta below 4 GeV are observed to be increasingly enhanced as a function of angular distance from the jet axis, reaching a maximum at $r=0.6$. Charged particles with transverse momenta above 4 GeV have an enhanced yield in Pb+Pb collisions in the jet core for angular distances up to $r = 0.05$ from the jet axis, with a suppression at larger distances.

Measurement of angular and momentum distributions of charged particles within and around jets in Pb+Pb and pp collisions at [formula omitted] with ATLAS at the LHC

Studies of the fragmentation of jets into charged particles in heavy-ion collisions can help in understanding the mechanism of jet quenching by the hot and dense QCD matter created in such collisions, the quark-gluon plasma. These proceedings present a measurement of the angular distribution of charged particles around the jet axis in sNN=5.02TeV Pb+Pb and pp collisions, done using the ATLAS detector at the LHC. The measurement is performed inside jets reconstructed with the anti-kt algorithm with radius parameter R=0.4, and is extended to regions outside the jet cone. Results are presented as a function of Pb+Pb collision centrality, and both jet and charged-particle transverse momenta.

Hardware-Software Complex for Measuring Energy and Angular Distributions of Charged Particles Produced in Nuclear Reactions

Hardware-Software Complex for Measuring Energy and Angular Distributions of Charged Particles Produced in Nuclear Reactions

Hardware-Software Complex for Measurement of Energy and Angular Distributions of Charged Particles Formed in Nuclear Reactions

A hardware-software complex for measurement of energy and angular distributions of charged particles formed in nuclear reactions is presented. Hardware and software structures of the complex, the basic set of the modular nuclear-physical apparatus of a multichannel detecting system on the basis of ΔE–E telescopes of silicon detectors, and the hardware of experimental data collection, storage, and processing are presented and described.

MCMC2 (version 1.1.2): A Monte Carlo code for multiply charged clusters

MCMC2 (version 1.1.2): A Monte Carlo code for multiply charged clusters

Correlations between jets and charged particles in PbPb and pp collisions at s N N = 2.76 $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV

The quark-gluon plasma is studied via medium-induced changes to correlations between jets and charged particles in PbPb collisions compared to pp reference data. This analysis uses data sets from PbPb and pp collisions with integrated luminosities of 166 inverse microbarns and 5.3 inverse picobarns, respectively, collected at sqrt(s[NN]) = 2.76 TeV. The angular distributions of charged particles are studied as a function of relative pseudorapidity (Delta eta) and relative azimuthal angle (Delta phi) with respect to reconstructed jet directions. Charged particles are correlated with all jets with transverse momentum (pt) above 120 GeV, and with the leading and subleading jets (the highest and second-highest in pt, respectively) in a selection of back-to-back dijet events. Modifications in PbPb data relative to pp reference data are characterized as a function of PbPb collision centrality and charged particle pt. A centrality-dependent excess of low-pt particles is present for all jets studied, and is most pronounced in the most central events. This excess of low-pt particles follows a Gaussian-like distribution around the jet axis, and extends to large relative angles of Delta eta approximately 1 and Delta phi approximately 1.

A modular end-station for atomic, molecular, and cluster science at the low density matter beamline of FERMI@Elettra

The low density matter end-station at the new seeded free electron laser FERMI@Elettra is a versatile instrument for the study of atoms, molecules and clusters by means of electron and ion spectroscopies. Beams of atoms, molecules and helium droplets as well as clusters of atoms, molecules and metals can be produced by three different pulsed valves. The atomic and molecular beams may be seeded, and the clusters and droplets may be pure, or doped with other atoms and molecules. The electrons and ions produced by the ionization and fragmentation of the samples by the intense light of FERMI can be analysed by the available spectrometers, to give mass spectra and energy as well as angular distributions of charged particles. The design of the detector allows simultaneous detection of electrons and ions using velocity map imaging and time-of-flight techniques respectively. The instruments have a high energy/mass resolution and large solid-angle collection efficiency. We describe the current status of the apparatus and illustrate the potential for future experiments.

Analytical derivation of higher-order terms of Molière’s series and accuracy of Molière’s angular distribution of fast charged particles

Molière’s series functions of higher orders describing angular distributions of charged particle under the multiple scattering process are solved by exactly evaluating Cauchy integral with poles within the contour of integration. The functions of Molière’s series giving higher-order terms are evaluated accurately by Poisson series expansion, both for spatial and projected angular distributions. Molière’s series for the integrated angular distributions are also derived. Accuracy of the Molière’s series expansion of higher orders is examined by comparing the reconstructed angular distributions with those derived exactly through the numerical Hankel transforms.

Details of 1π sr wide acceptance angle electrostatic lens for electron energy and two-dimensional angular distribution analysis combined with real space imaging

Abstract We propose a new 1π sr Wide Acceptance Angle Electrostatic Lens (WAAEL), which works as a photoemission electron microscope (PEEM), a highly sensitive display-type electron energy and two-dimensional angular distribution analyzer. It can display two-dimensional angular distributions of charged particles within the acceptance angle of ±60° that is much larger than the largest acceptance angle range so far and comparable to the display-type spherical mirror analyzer developed by Daimon et al. [1] . It has good focusing capabilities with 5-times magnification and 27(4) μm lateral-resolution. The relative energy resolution is typically from 2 to 5×10–3 depending on the diameter of energy aperture and the emission area on the sample. Although, the lateral resolution of the presented lens is far from those are available nowadays, but this is the first working model that can form images using charged particles collected from 1π sr wide acceptance angle. The realization of such lens system is one of the first possible steps towards reaching the field of imaging type atomic resolution electron microscopy Feynman et al. [2] . Here some preliminary results are shown.

New 1π sr acceptance angle display-type ellipsoidal mesh analyzer for electron energy and two-dimensional angular distribution as well as imaging analysis

We propose a Display-type Ellipsoidal Mesh Analyzer (DELMA) using a newly developed 1p sr wide acceptance angle electrostatic lens (WAAEL), energy aperture and some other electrostatic lenses [1–5] .I t can display two-dimensional angular distributions of charged particles within the acceptance angle of 7 601, which is much larger than the largest acceptance angle range so far and comparable to the displaytype spherical mirror analyzer (DIANA) developed by Daimon et al. [6,8–11]. It also has a focusing capability with 5 times magnification and � 30 mm lateral resolution. The relative energy resolution is typically from 2 to 5 � 10 � 3 depending on the emission area of the sample, as well as on the diameter of

The Silicon Cube detector

A new experimental device, the Silicon Cube detector, consisting of six double-sided silicon strip detectors placed in a compact geometry was developed at CENBG. Having a very good angular coverage and high granularity, it allows simultaneous measurements of energy and angular distributions of charged particles emitted from unbound nuclear states. In addition, large-volume Germanium detectors can be placed close to the collection point of the radioactive species to be studied. The setup is ideally suited for isotope separation on-line (ISOL)-type experiments to study multi-particle emitters and was tested during an experiment at the low-energy beam line of SPIRAL at GANIL.

Time-of-flight scintillation spectrometer of charged particles with a subnanosecond time resolution

A time-of-flight spectrometer based on a fast plastic scintillator was developed to study the spectral and angular distribution of charged particles emitted from laser-produced plasmas. The measured time resolution of the spectrometer was ∼0.3 ns, which made it possible to observe the fine structure in the spectrum of protons originated from the back surface of the target in experiments on the SOKOL-P laser facility.

Energy spectra and angular distributions of charged particles backscattered from solid targets

In this study, the EGSnrc (Electron Gamma Shower) Monte Carlo radiation transport code is used to simulate the energy spectra and the angular distributions of charged particles backscattered from solid targets. The study covers the energy range 10–70 keV, which is of interest to applied physics fields such as scanning electron microscopy, microprobe analysis and x-ray imaging. Simulation results are compared with experimental data from 11 different published experiments (1954–2002). Comparisons include electrons and positrons, low- and high-Z targets, normal and oblique incidence, different backscatter angles and backscatter planes, and backscatter from thin films. EGSnrc simulation results show excellent agreement with the majority of the published experimental data. Possible experimental and computational uncertainties explaining the few noted discrepancies are discussed. This study concludes that EGSnrc produces accurate backscatter data in the kilovoltage energy range. A documented EGSnrc user-code customized for backscatter calculations is available from the authors at http://www.physics.carleton.ca/clrp/backscatter.

Retrieving nuclear information from protons propagating through a thick target

The multiple scattering of high-energy particles in a thick target is formulated in an impact parameter representation. A formalism similar but not identical to that of Moliere is obtained. We show that calculations of particle beam broadening due to multiple Coulomb scattering alone can be given in closed form. The focus of this study is on determining whether the broadening of the Coulomb angular distribution prevents the retrieval of nuclear-interaction information from the measurement of the angular distributions of charged particles scattered from a thick target. For this purpose, we study multiple scattering with both the nuclear and Coulomb interactions included, and we do not make a small-angle expansion. Conditions for retrieving nuclear information from high-energy protons propagating through a block of material are obtained.

Approach for simultaneous measurement of two-dimensional angular distribution of charged particles. III. Fine focusing of wide-angle beams in multiple lens systems

This paper provides a way of focusing wide-angle charged-particle beams in multiple lens systems. In previous papers [H. Matsuda, Phys. Rev. E 71, 066503 (2005); 74, 036501 (2006)], it was shown that an ellipsoidal mesh, combined with electrostatic lenses, enables correction of spherical aberration over wide acceptance angles up to +/-60 degrees . In this paper, practical situations where ordinary electron lenses are arranged behind the wide-angle electrostatic lenses are taken into account using ray tracing calculation. For practical realization of the wide-angle lens systems, the acceptance angle is set to +/-50 degrees . We note that the output beams of the wide-angle electrostatic lenses have somewhat large divergence angles which cause unacceptable or non-negligible spherical aberration in additional lenses. A solution to this problem is presented showing that lens combinations to cancel spherical aberration are available, whereby wide-angle charged-particle beams can be finely focused with considerably reduced divergence angles less than +/-5 degrees .

Approach for simultaneous measurement of two-dimensional angular distribution of charged particles. II. Deceleration and focusing of wide-angle beams using a curved mesh lens

Recently, it was shown that using an ellipsoidal mesh in an einzel-type lens, spherical aberration can be corrected over a wide acceptance angle of up to 120 degrees. The present paper creates the possibility for beam analysis by achieving dramatic improvements in deceleration lens capabilities. This provides a scheme for simultaneous angular distribution measurement suitable for application to high-energy charged-particle beams up to around 10 keV. We consider the behavior of wide-angle charged-particle beams in electrostatic fields given by simple solutions of the Laplace equation, starting with a discussion on a spherically symmetric deceleration field. A beam focusing over a wide acceptance angle of 100 degrees is found in a special spherically symmetric field. However, in many cases of the spherically symmetric field, focusing of wide-angle beams is obstructed by the presence of spherical aberration. We show that the spherical aberration can be corrected by two kinds of deformation of the spherically symmetric field, a deformation of the field under a spherical boundary condition and an ellipsoidal deformation of the field. We study practical realization of such fields under the use of a few electrodes and a curved mesh (spherical or ellipsoidal mesh). Some variations of the arrangement of electrodes are considered, and simple designs of deceleration lenses with wide acceptance angles of up to 120 degrees are obtained. Here fine focusing of wide-angle beams can be achieved in a three-electrode deceleration lens with an ellipsoidal mesh.

On the theory and simulation of multiple coulomb scattering of heavy-charged particles

The Moliere theory of multiple Coulomb scattering is modified to take into account the difference between processes of scattering off atomic nuclei and electrons. A simple analytical expression for angular distribution of charged particles passing through a thick absorber is found. It does not assume any special form for a differential scattering cross section and has a wider range of applicability than a gaussian approximation. A well-known method to simulate multiple Coulomb scatterings is based on treating 'soft' and 'hard' collisions differently. An angular deflection in a large number of 'soft' collisions is sampled using the proposed distribution function, a small number of 'hard' collision are simulated directly. A boundary between 'hard' and 'soft' collisions is defined, providing a precise sampling of a scattering angle (1% level) and a small number of 'hard' collisions. A corresponding simulating module takes into account projectile and nucleus charged distributions and exact kinematics of a projectile-electron interaction.