Simultaneous Particles Research Articles

Multi-track event reconstruction to constrain the [formula omitted] background in Mu2e

Mu2e experiment will search for the neutrinoless, coherent conversion of μ−→e− in the field of an Al nucleus. One of the expected backgrounds is p̄’s annihilating in the stopping target to produce signal-like e−’s. Although not a dominant background, it has a large uncertainty and cannot be suppressed by the timing cuts used to reduce the prompt background. However, at Mu2e energies, pp̄ annihilation is the only source of events with multiple, simultaneous particles coming from the stopping target. We utilized this unique feature and developed a novel way to reconstruct multi-track events and estimate the p̄ background.

Space debris generation in GEO: Space materials testing and evaluation

The aim of this work is to evaluate what happens to the spacecraft materials beyond the spacecraft End of Life. A review of spacecraft external materials and effects of space environment is presented. This paper results from a continued study on spacecraft material degradation, and space debris formation in geostationary orbit (GEO). In this paper a 20-year GEO dose profile that combines simultaneous UV, particles irradiation and thermal cycling was applied to a set of external spacecraft materials. These materials comprised MLI assemblies, Velcros fixation and spacecraft painting. The evaluation of these external spacecraft materials, exposed to simulated space environment have confirmed the criticality of degradation of MLI, Velcros fixation and painting, with delamination mechanisms and particulate contamination. The synergy of space radiation (particles, UV) and thermal cycling ages the material and induces mechanical stress, causing creation of brittle surfaces, cracks and delamination. These phenomena cause serious damage to exposed surfaces, changing the surfaces thermo-optical properties, and may induce the generation of space debris. In particular, experimental results show the delamination of internal MLI layers and the severe degradation of the Velcros.

Achieving simultaneous Cu particles anchoring in meso-porous TiO2 nanofabrication for enhancing photo-catalytic CO2 reduction through rapid charge separation

A facile solvo-thermal approach was successfully employed to prepare titanium oxide (TiO2) nano-aggregates with simultaneous copper particles anchoring. The as-synthesized composite could convert CO2 into CH4 and CO products under simulated solar irradiation. The impact of copper loading amounts on the photo-reduction capability was evaluated. It was found proper amount of Cu loading could enhance the activity of CO2 photo-reduction. As a result, the optimal composite (TiO2-Cu-5%) consisting of TiO2 supported with 5% (mole ratio) Cu exhibits 2.2 times higher CH4 yield and 3 times higher CO yield compared with pure TiO2. Conduction band calculated from the band gap and valence X-ray photoelectron spectroscopy (XPS) indicated TiO2 nano-aggregates have suitable band edge alignment with respect to the CO2/CH4 and CO2/CO redox potential. Furthermore, with involving of Cu particles, an efficient separation of photo-generated charges was achieved on the basis of photocurrent response and photoluminescence spectra results, which contributed to the improved photo-catalytic performance. The present work suggested that the Cu-decorated TiO2 could serve as an efficient photo-catalyst for solar-driven CO2 photo-reduction.

Synthesis of manganese (IV) oxide at activated carbon on reduced graphene oxide sheets via laser irradiation technique for organic binder-free electrodes in flexible supercapacitors

We report a novel, green, scalable technique to synthesize binder-free, high-purity conductive composite comprising activated carbon (AC), manganese dioxide nanorods (MnO2), and reduced graphene oxide sheets (rGO) for flexible supercapacitors with outstanding electrochemical performance. UV pulsed laser irradiation of GO-based composite dispersion (AC/GO or MnO2@AC/GO) in ethanol aqueous medium was used to induce a photocatalytic reduction of GO and simultaneous anchor AC particles or AC loaded MnO2 nanorods (MnO2@AC) on the reduced GO sheets (rGO) at room temperature and atmospheric pressure. rGO sheets serve as a large surface area, conductive binder to enhance the ion adsorption, electrical conductivity, and mechanical flexibility of supercapacitor electrodes. This laser-induced photocatalytic reduction method was used to prepare two different rGO-based colloidal composites AC/rGO (CG) and MnO2@AC/rGO (MCG). The prepared rGO-based colloidal composites were used to fabricate symmetric supercapacitors (CG//CG and MCG//MCG) and asymmetric supercapacitors (MCG//CG) in which MCG is the positive electrode and CG is the negative one. All prepared rGO-based supercapacitors demonstrated significant improvement in their electrochemical performance compared with rGO-free AC based supercapacitors. The enhancement in the electrochemical properties of rGO-based supercapacitors could be attributed to the intrinsic characteristics of rGO, such as high surface area, excellent electrical conductivity, and super mechanical flexibility. Our approach is a one-step, scalable, cost-effective synthesis technique to produce all binder-free AC/rGO based composites for flexible energy-storage devices.

GPU‐accelerated simulation of polydisperse multiphase flows using dual‐quadrature‐based moment methods

AbstractPolydisperse multiphase flows can be simulated by coupling a population balance model to the multi‐fluid model. For the first time, this simulation is carried out using the dual‐quadrature method of generalized moments (DuQMoGeM) and its direct version to solve the population balance model. The main disadvantage of these methods is the high computational cost of the embedded cubature. Herein, this challenge was addressed by parallelization on graphics processing units, which resulted in a significant acceleration of the simulations, with speedups that can be larger than 1000. Numerical simulations considering simultaneous particles breakage and aggregation were conducted with direct DuQMoGeM‐FC and DQMoM‐FC, whose results were different due to the existence of quadrature error in the latter.

The role of surface coarsening and sintering during thermal decomposition of titanium hydride

Temperature programmed desorption - mass spectrometry was utilized to study the non-isothermal hydrogen desorption from as-received and pre-oxidized TiH2 powder samples. Above the temperature of 750 °C, hydrogen desorption from the thermally decomposed as-received powder is kinetically delayed compared to that from the pre-oxidized samples. The scanning electron microscopy observations suggest that the delay stems from simultaneous surface coarsening and particles sintering that occur predominantly in the as-received powder at lower temperatures. It is also suggested that the difference in morphology evolution of the as-received and pre-oxidized powders originates from the dependence of Ti diffusion on the concentration of oxygen dissolved in Ti, since the oxide layer itself was found to dissociate at lower temperatures (∼500 °C).

Statistical algorithms for particle trajectography

The various algorithms used to extrapolate particle trajectories from measurements are often very time-consuming with computational complexities which are typically quadratic. In this article, we propose a new algorithm called GEM with a lower complexity and reasonable performance on linear tracks. It is an extension of the EM algorithm used to fit Gaussian mixtures. It works in arbitrary dimension and with an arbitrary number of simultaneous particles. In a second part, we extend it to circular tracks (for charged particles) and even a mix of linear and circular tracks. This algorithm is implemented in an open-source library called “libgem” and two applications are proposed, based on data-sets from two kinds of particle trackers.

Mechanical Property of Hydrogels Regulated by Different Ratios of Latex Particles and Hydrophobic Segments

AbstractThe introduction of latex particles into hydrogels has been proven to be an effective strategy for enhancing the mechanical strength. For latex particles toughened hydrogels, however, the effect of crosslinking ways from latex particles and hydrophobic segments on the mechanical property has not been clearly explored. In this investigation, different ratios of latex particles and hydrophobic segments were introduced into hydrogels and the crosslinking ways included latex particles filling, hydrophobic segment aggregation induced by latex particles, simultaneous latex particles and polymeric micelles. The mechanical property was measured via stretching, loading‐unloading process, compression and rheology. Subsequently, an energy dissipation model was established and the theoretical results were proved to be consistent with the experimental tests. As a result, it was envisioned that the theoretical model could predicted mechanical predictability for a new generation of latex particles hydrogels.

Copper nano-particles for antibacterial properties of wrinkle resistant cotton fabric

In this research cotton fabrics were treated with different concentrations of maleic acid (MA), as cross-linking agent, and sodium hypophosphite (NaH2PO2) as the catalyst, with constant concentration of copper nano particles by two methods: Separately and simultaneously. Laundering test was done due to the standard test method for determination of durability of the treatment. Some physical properties such as crease recovery angle and weight gain were examined. The maleic acid treated cotton fabrics were dyed with methylene blue dye. Reflective spectrophotometer was used to determine methylene blue dye absorption. FTIR/ATR analysis was done for investigation of chemical structure, and atomic absorption spectroscopy was used for determining of copper ions contents. The antibacterial properties were investigated by using AATCC-100 standard test method. The results showed that the crease recovery angle, weight and methylene blue dye absorption were increased by increasing the concentration of maleic acid. By comparing the results of separate and simultaneous copper nano particles treatment, in simultaneous method, antimicrobial properties, copper ion absorption and weight gain reduced and washing fastness was increased. Whereas by Separate method, antimicrobial properties, copper absorption and weight gain were increased.

The knee in the cosmic ray energy spectrum from the simultaneous EAS charged particles and muon density spectra

In this work we examine with the help of Monte Carlo simulation whether a consistent primary energy spectrum of cosmic rays emerges from both the experimentally observed total charged particles and muon size spectra of cosmic ray extensive air showers considering primary composition may or may not change beyond the knee of the energy spectrum. It is found that EAS-TOP observations consistently infer a knee in the primary energy spectrum provided the primary is pure unchanging iron whereas no consistent primary spectrum emerges from simultaneous use of the KASCADE observed total charged particle and muon spectra. However, it is also found that when primary composition changes across the knee the estimation of spectral index of total charged particle spectrum is quite tricky, depends on the choice of selection of points near the knee in the size spectrum.

Preliminary study for the detection of neutrons in heavy-ion collisions with charged particle detectors

At Laboratori Nazionali del Sud (LNS) the CHIMERA 4π multidetector has been designed and setup to detect charged particles emitted in heavy ion collisions at intermediate energies. Properties and performances of CHIMERA have been widely demonstrated by published results obtained in the performed experiments. Moreover, in recent years, a new charged particle detector (ChPD) for correlation studies (FARCOS) has been designed, and recently a first prototype has been coupled to CHIMERA, in order to test performances in view of correlation measurements in coincidence with 4π detectors. Simultaneous neutrons and charged particles detection in heavy ion collisions represents an important experimental progress for future experiments to be performed with both stable and exotic nuclei. In order to investigate about this possibility, simple Monte Carlo simulations have been performed. Preliminary simulations have been carried out by means of MCNPX transport code to evaluate the perturbation effects, including cross-talk and time response, induced in CHIMERA and/or FARCOS Si-CsI(Tl) telescopes on (typical 20MeV) neutron signals coming from a typical reaction in heavy ion collisions at the Fermi energy. Moreover, first data analysis results of the INKIISSY experiment indicates sizable probability to detect neutrons by properly shadowing CHIMERA Si-CsI(Tl) telescopes. Analysis is still in progress.

Propagation dynamics and optical trapping of a radial Airy array beam

Analytical propagation expression of a radial Airy array beam in coherent and incoherent combination passing through paraxial ABCD system is derived, and used to investigate the effect of combination scheme, array orientation and initial phase of Airy beamlet on propagation dynamics of the resulting beam in free space, where optical spot array and vortex array with different shapes are also found, respectively. And then taking four-beamlet Airy array beam in same array orientation as an example, square optical spot array obtained in focal field can be used for simultaneous trapping multiple Rayleigh particles with relative refractive index larger than 1. The transverse gradient forces serving as restore forces tend to push particles at different initial positions to their individual optical spot center. The analysis of trapping stability indicates that larger input peak intensity of Airy beamlet and smaller particle size are benefit to trapping particle owing to many deeper potential wells. Vortex array produced by coherent combined Airy array beam in this paper is expected to be useful for simultaneous trapping microparticles with relative refractive index smaller than 1.

Converting Poorly Soluble Materials into Stable Aqueous Nanocolloids

Aqueous nanocolloids of poorly soluble materials were produced via sonicated layer-by-layer (LbL) encapsulation with polycation / polyanion shells. Synergy of simultaneous breaking powder particles with ultrasonication and coating them with polycations allowed for the production of 150-200 nm diameter polyelectrolyte coated nanoparticles with sufficient surface electrical potential for colloidal stability. This technique increases water dispersibility of low soluble materials ranging from anticancer drugs to anticorrosion agents, dyes and inorganic salts.

The RPC current time structure. Fast current peak measurement in the ATLAS RPC system

We have developed an analog RPC read out based on the observation of the signal produced in the high voltage circuit by many simultaneous particles crossing the same gas gap. The proposed method allows to measure particle densities by far much larger that those accessible to the standard digital read out. We applied this method to study with the ATLAS RPC system the beam “splash” events produced by LHC at the beginning of its activity.

Simultaneous magnetic particles washing and concentration in a microfluidic channel

Purification of magnetic microparticles was demonstrated, with a purification efficiency of (72±14) % at a flow rate of 3 μl/min, in a microfluidic chip using a rotational magnetic system under continuous flow conditions. The rotation of a periodically arranged magnetic assembly close to a fluidic channel carrying magnetic particles suspension allows the trapping and releasing of particles in periodical manner, leaving other particles to be discarded in the waste. Each trapping and releasing event resembles one washing cycle in a conventional biological assay.

Fully kinetic simulation of coupled plasma and neutral particles in scrape-off layer plasmas of fusion devices

Fluid descriptions of plasmas, which are usually applied to a collisional plasma, can only be justified for very small Coulomb Knudsen numbers. However, the scrape-off layer (SOL) plasmas of experimental magnetic confinement fusion devices tend to have operational regimes characterized by a Coulomb Knudsen number around 0.1. In interesting detached regimes of an SOL plasma in a tokamak, when the plasma detaches from the limiters or divertors, this number may increase along with the local plasma gradients. Plasma gradients are also known to increase (and thus drive non-local effects) in inertial confinement fusion. Neutrals, which are being produced owing to plasma recombination at the plasma–divertor interface, may be in a mixed collisional regime as well. Thus simultaneous kinetic treatments of plasma and neutral particles with self-consistent evaluation of boundary conditions at the material walls are required. We present a physical model and a numerical scheme, and discuss results of purely kinetic simulations of plasmas and neutrals for actual conditions in the Alcator C-Mod and Tokamak-de-Varennes experimental tokamaks. Results for both steady-state and transient regimes of SOL plasma flow are presented. Our approach, unlike particle-in-cell and Monte Carlo methods, is free from statistical noise.

Monte carlo simulation of soot aggregation with simultaneous surface growth-why primary particles appear spherical

Soot aggregation with simultaneous surface growth was modeled using a dynamic Monte Carlo method. Simulations were performed in the environment of a 10-bar laminar premixed flame of ethylene. The Monte Carlo algorithm begins in the particle inception zone and constructs soot particles via ensemble-averaged collisions between small spheres and deposition of gaseous species on the sphere surfaces. Simulations were conducted using three scenarios. Scenario 1 forces all spheres to grow at a uniform rate, whereas scenario 2 only permits them to grow once they have collided and stuck to each other. Results from 1 and 2 were compared to a reference, labeled scenario 0, which simulates aggregation in the absence of surface growth. The simulations demonstrate that aggregation with sufficiently small spherical particles in the presence of surface growth leads to a spheroidal shape. The results show that the spheroidal shape of particles is attributed to rapid surface growth and intense particle nucleation. In addition, particle shape may also be affected by rearrangement of the internal structure of colliding aromatic clusters.

A new type of multiparticle imaging detector

The foil-induced dissociation of molecular ions can provide a direct image of the stereochemical structures of small molecules. Such experiments require high-resolution measurements of the relative momenta of all dissociation fragments. In order to improve and extend previous studies of this type to a larger variety of molecules and clusters, we have developed a new type of low-pressure multiwire proportional counter. The novel feature of this large-area (25×50 cm2 ) multiparticle detector is that all the signals are recorded from a single two-level printed circuit board which serves as the anode. This segmented anode consists of three families of nonintersecting ‘‘wires’’ which are interwoven on the rear surface of the board. By redundantly determining positions and arrival times, the new segmented anode multiparticle detector provides good time resolution (100–200 ps) and high spatial resolution (0.2 mm) for detecting as many as six simultaneous particles.

Reduction of the ionization loss distribution width of several simultaneous relativistic particles traversing a scintillation counter

A Poisson distribution of number of electrons at the input stages of a photomultiplier has been folded into the Landau-Symon distribution of ionization losses in a plastic scintillator and a distribution of the smallest value out of n detectors was derived analytically for m simultaneous particles. A group of four identical scintillation counters was constructed and the smallest of the four output pulses was used for selective triggering of the bubble chamber flash with the greater precision engendered by the considerably reduced distribution width.

High energy particle identification using multilayer proportional counters

An optimised system of proportional counters consisting of 128 layers (32 channels each, 190 × 60 cm 2 detection area) is being developed to work in connection with the Big European Bubble Chamber at SPS energies. It will be capable of identification of simultaneous particles up to 70 GeV/ c by ionization measurements in the region of the relativistic rise. Preliminary tests with a reduced version of 32 layers have been made with pions, kaons and protons at 16 GeV/ c, the results of which are presented.