Particle Incident Angle Research Articles

Thin n-in-p planar pixel sensors and active edge sensors for the ATLAS upgrade at HL-LHC

Silicon pixel modules employing n-in-p planar sensors with an active thickness of 200 μm, produced at CiS, and 100-200 μm thin active/slim edge sensor devices, produced at VTT in Finland have been interconnected to ATLAS FE-I3 and FE-I4 read-out chips. The thin sensors are designed for high energy physics collider experiments to ensure radiation hardness at high fluences. Moreover, the active edge technology of the VTT production maximizes the sensitive region of the assembly, allowing for a reduced overlap of the modules in the pixel layer close to the beam pipe. The CiS production includes also four chip sensors according to the module geometry planned for the outer layers of the upgraded ATLAS pixel detector to be operated at the HL-LHC. The modules have been characterized using radioactive sources in the laboratory and with high precision measurements at beam tests to investigate the hit efficiency and charge collection properties at different bias voltages and particle incidence angles. The performance of the different sensor thicknesses and edge designs are compared before and after irradiation up to a fluence of 1.4 × 1016 neq/cm2.

Numerical investigation of particle saltation in the bed-load regime

This paper numerically investigates particle saltation in a turbulent channel flow having a rough bed consisting of 2–3 layers of densely packed spheres. In this study, we combined three the state-of-the-art technologies, i.e., the direct numerical simulation of turbulent flow, the combined finite-discrete element modelling of the deformation, movement and collision of the particles, and the immersed boundary method for the fluid-solid interaction. Here we verify our code by comparing the flow and particle statistical features with the published data and then present the hydrodynamic forces acting on a particle together with the particle coordinates and velocities, during a typical saltation. We found strong correlation between the abruptly decreasing particle stream-wise velocity and the increasing vertical velocity at collision, which indicates that the continuous saltation of large grain-size particles is controlled by collision parameters such as particle incident angle, local rough bed packing arrangement, and particle density, etc. This physical process is different from that of particle entrainment in which turbulence coherence structures play an important role. Probability distribution functions of several important saltation parameters and the relationships between them are presented. The results show that the saltating particles hitting the windward side of the bed particles are more likely to bounce off the rough bed than those hitting the leeside. Based on the above findings, saltation mechanisms of large grain-size particles in turbulent channel flow are presented.

Saltation of particles in turbulent channel flow.

This paper numerically investigates particle saltation in a turbulent channel flow having a rough bed consisting of two to three layers of densely packed spheres. The Shields function is 0.065 which is just above the sediment entrainment threshold to give a bed-load regime. The applied methodology is a combination of three technologies, i.e., the direct numerical simulation of turbulent flow; the combined finite-discrete element modeling of the deformation, movement, and collision of the particles; and the immersed boundary method for the fluid-solid interaction. It is shown that the presence of entrained particles significantly modifies the flow profiles of velocity, turbulent intensities, and shear stresses in the vicinity of a rough bed. The quasi-streamwise-aligned streaky structures are not observed in the near-wall region and the particles scatter on the rough bed owing to their large size. However, in the outer flow region, the turbulent coherent structures recover due to the weakening rough-bed effects and particle interferences. First- and second-order statistical features of particle translational and angular velocities, together with sediment concentration and volumetric flux density profiles, are presented. Several key parameters of the particle saltation trajectory are calculated and agree closely with published experimental data. Time histories of the hydrodynamic forces exerted upon a typical saltating particle, together with those of the particle's coordinates and velocities, are presented. A strong correlation is shown between the abruptly decreasing streamwise velocity and increasing vertical velocity at collision which indicates that the continuous saltation of large-grain-size particles is controlled by collision parameters such as particle incident angle, local bed packing arrangement, and particle density, etc.

Residual stress induced by cold spray coating of magnesium AZ31B extrusion

Aluminum particles were successfully sprayed on wrought magnesium AZ31B extrusion using the cold spray technology. Cold spray high impact velocity of particles colliding with the substrate induced beneficial compressive residual stresses. Magnitude of the residual stress at the surface and its distribution through the thickness were measured using X-ray diffraction. With particle spraying velocity of 400m/s, the residual stress was measured to be −25MPa at the surface. The process of collision and development of residual stress was then modeled using LS-DYNA software to study the effect of the cold spray process parameters on the residual stress profile. Various models were employed to simulate the impact of the single and multiple particles. An asymmetric material model that considers the strain rate effect was employed to model AZ31B different behavior in tension and compression. Results of simulations for impact of multiple particles were compared with the results of XRD measurements on the substrate surface and through the depth of the substrate. After the validation of the models, a parametric study was performed on the impact of a single particle to find the optimum cold spray particle velocity, size, shape, incident angle, and friction parameters. Parameters leading to the optimum residual stress profile are introduced herein.

Ion beam sputtering of Ag – Angular and energetic distributions of sputtered and scattered particles

Ion beam sputter deposition (IBD) provides intrinsic features which influence the properties of the growing film, because ion properties and geometrical process conditions generate different energy and spatial distribution of the sputtered and scattered particles. A vacuum deposition chamber is set up to measure the energy and spatial distribution of secondary particles produced by ion beam sputtering of different target materials under variation of geometrical parameters (incidence angle of primary ions and emission angle of secondary particles) and of primary ion beam parameters (ion species and energies).A representative set of Ag thin films is deposited arranged on a substrate holder equatorial to the Ag target in steps of 10° and characterized concerning their film thickness by profilometry to determine the angular distribution of the sputtered particles. The film thickness distributions show a tilted, cosine-like shape and a shifting of the maximum position depending on the primary particle energy and incidence angle of the primary ions.The energy distributions of sputtered and scattered ions and of sputtered neutrals are measured with an energy-selective mass spectrometer. The average energy of the sputtered ions increases with increasing emission angle and also increases with increasing incidence angle of the primary ions. In contrast, the average energy of the sputtered ions is nearly unaffected by the primary particle energy and particle species. The energy distribution of the scattered Ar ions reveals high energetic maxima which shift with increasing emission angle to higher energies. These maxima are not observed for Xe bombardment. The total energies of sputtered and scattered ions show significant differences between the two bombarding species. The maximum of the energy distribution of sputtered Ag neutrals is used to conclude on the surface binding energy of Ag (2.72eV).All experimental data are compared with Monte Carlo simulations done with the well-known TRIM.SP.

Electron scattering by a crystal layer

We consider the one-particle discrete Schrodinger operator H with a periodic potential perturbed by a function ɛW that is periodic in two variables and exponentially decreasing in the third variable. Here, ɛ is a small parameter. We study the scattering problem for H near the point of extremum with respect to the third quasimomentum coordinate for a certain eigenvalue of the Schrodinger operator with a periodic potential in the cell, in other words, for the small perpendicular component of the angle of particle incidence on the potential barrier ɛW. We obtain simple formulas for the transmission and reflection probabilities.

RETRACTED: The influence of sand diameter and wind velocity on sand particle lift-off and incident angles in the windblown sand flux

The problem of impact entrainment is one of the central issues in understanding the process of saltation. In this paper, through improving the experimental scheme of Particle Image Velocimetry (PIV) and data processing methods using wind tunnel data, the measurement of sand particle lift-off and incident angles near the sand bed was achieved. Based on experimental data, we analyze the probability distribution of sand particle lift-off and incident angles and the influence of wind velocity and sand diameter on the probability distribution, as well as the relation between incident angle and lift-off angle. The results demonstrate that wind velocity and sand diameter have no obvious influence on the distribution shape of sand particle lift-off and incident angles. However, wind velocity will influence the decay constant and amplitude of the probability distribution. (c) 2013 Elsevier B.V. All rights reserved.

Development of the theory of diffraction radiation from surfaces with finite conductivity

A solution of the problem on diffraction radiation arising at inclined passage of a point-like charged particle near the thin rectangular screen of finite sizes, finite conductivity, and frequency dispersion is found. The problem on diffraction radiation arising at inclined passage of a charge through a rectangular slit in a conductive screen is solved. For zero slit width, the results obtained completely coincide with the corresponding results of the theory of transition radiation at arbitrary values of the dielectric permittivity and angle of particle incidence on the screen surface. In addition to the diffraction mechanism, expressions obtained for the radiation intensity describe the Cherenkov radiation mechanism.

Nuclear track detector characterization for alpha-particle spectroscopy

Solid State Nuclear Track Detectors (SSNTDs), CR-39™ type, are usually adopted in many applications in which it could be necessary to select tracks according to the incident alpha-particle energy; so several authors have argued that track parameters such as the major/minor axis being the most often reported, can be used to determine the alpha-particle’s energy. However, the use of these parameters only do an univocal result, for example the same axis length can be obtained for different combinations of incident angles and energies. We report on a track analysis performed by a semiautomatic system that classifies tracks according to two parameters, diameter length and mean grey level. This kind of analysis can give information about the track depth, that increases monotonically with the incident energy and angle of the alpha particle. Combining the information on the two parameters it is possible to determine univocally the incident alpha-particle energy values. In order to characterize CR-39 detectors according to the physical track parameters, detectors were irradiated, inside a vacuum chamber, by alpha particles at thirteen energy values, obtained by different mylar layers in front of a 241 Am source. After the exposure the detectors were chemically etched to enlarge the tracks and then analyzed by means of a semiautomatic system, consisting on an optical microscope equipped with a CCD camera connected to a personal computer for image storage. A suitable routine analyzed the track parameters: diameter and mean grey level, allowing us to differentiate tracks according to the incident alpha-particle energy and then to individuate the discrimination factors for radon alpha tracks, when nuclear track detectors are applied in radon surveys. ► CR-39. ► Geometric and optical parameter. ► α spectrometry. ► Calibration.

First calibration of a Cherenkov beam loss sensor at ALICE using SiPM

The need for real-time monitoring of beam losses, including evaluation of their intensity and localization of their exact position, together with the possibility to overcome the limitations due to the reduced space for the diagnostics, makes exploitation of the Cherenkov effect in optical fibres, one of the most suitable candidates for beam loss monitoring.In this article, we report on the first tests of an optical fibre beam loss monitor based on large numerical aperture pure silica fibres and silicon photomultipliers. The tests were carried out at the ALICE accelerator research and development facility, Daresbury Laboratories, UK.In contrast to the results already published where the fibres are longitudinally placed with respect to the accelerator beam path and the losses are multidirectional charged particle showers, for the first time a dedicated set-up with an incident accelerator beam impinging directly on the optical fibre was used for optimizing the collection efficiency of the Cherenkov effect as a function of the incident angle by changing the fibre direction. For this purpose large core fibres were used together with the latest generation silicon detector instead of the standard photomultiplier tubes commonly used for Cherenkov beam loss monitoring.The experiments described in this contribution aim to demonstrate the suitability of the optical fibre sensor for loss monitoring, to optimize the Collection Efficiency (CE) of the Cherenkov photons inside the fibre as a function of the particle incident angle, to calibrate the sensor and calculate its sensitivity, and to understand the limits of temporal resolution of losses from different bunches in the accelerator.

A new type of Time-Of-Propagation (TOP) Cherenkov detector for particle identification

A new type of particle identification (PID) detector based on measurements of 1-D Time-Of-Propagation (TOP) and 1-D space information is described. Geant4 toolkit is used to simulate the propagation of Cherenkov photon in thin quartz bar radiator. Contributions to the timing uncertainty are discussed. The π/K separability (S0) is defined and its dependence on the particle momentum, incident angle and propagation length are studied, respectively.

Design and simulations for the detector based on DSSSD

The present paper describes the design and simulation results of a position-sensitive charged particle detector based on the Double Sided Silicon Strip Detector (DSSSD). Also, the characteristics of the DSSSD and its testing result were are discussed. With the application of the DSSSD, the position-sensitive charged particle detector can not only give particle flux and energy spectra information and identify different types of charged particles, but also measure the location and angle of incident particles. As the detector can make multiparameter measurements of charged particles, it is widely used in space detection and exploration missions, such as charged particle detection related to earthquakes, space environment monitoring and solar activity inspection.

3D silicon pixel sensors: Recent test beam results

The 3D silicon sensors aimed for the ATLAS pixel detector upgrade have been tested with a high energy pion beam at the CERN SPS in 2009. Two types of sensor layouts were tested: full-3D assemblies fabricated in Stanford, where the electrodes penetrate the entire silicon wafer thickness, and modified-3D assemblies fabricated at FBK-irst with partially overlapping electrodes. In both cases three read-out electrodes are ganged together to form pixels of dimension 50 × 400 μ m 2 . Data on the pulse height distribution, tracking efficiency and resolution were collected for various particle incident angles, with and without a 1.6 T magnetic field. Data from a planar sensor of the type presently used in the ATLAS detector were used at the same time to give comparison.

Design and construction of a new chamber for measuring the thickness of alpha-particle sources

The thickness of charged-particle emitting sources can be determined by varying the incidence angle of particles using silicon semiconductor detectors. The differences in energy between the peaks for an alpha emission measured with different incident angles are due to the energy loss of alpha particles in the source. These shifts can thus be used to estimate the source thickness. A new detection chamber has been constructed for this purpose. Its advantage is the registration of the alpha particles emitted from a given source using up to three different detectors simultaneously. Monte Carlo simulation was used to help to determine the best measurement conditions and interpret the results.

Digital Image Analysis of Etch Pit Formation in CR-39 Track Detector

An in-situ observation system was developed to record time-lapse images of etch pits formed on the surface of a solid-state nuclear track detector (SSNTD), CR-39. The CR-39 track detector was irradiated with alpha and Li particles produced by a neutron capture reaction, 10B(n,α)7Li. The time-lapse images of the etched surface of the detector were carefully observed to elucidate the etch pit formation process. Pit-evolution images were constructed by digital image processing of the data of the time-lapse images. In addition, a finite element model of SSNTD was used to simulate the etch pit formation. Pit-evolution image analysis and computational simulation were performed to reveal the etch pit formation obtained via the incidence angle of energetic particles on a CR-39.

A New Numerical Approach to Evaluate Variation of Electric Field Strength at the End of Particle Trajectory in Nuclear Track Detectors

A geometrical model for an electrochemical etching (ECE) track in a dielectric detector is defined and a primary programme is written to generate the track. The generated track is transformed to an M × N matrix of primary voltages. Using a numerical method, the matrix of final voltages is computed, and using another numerical approach, the electric field strengths in the elements of detector volume are computed. The final field strength at the end of particle trajectory is obtained. The results of our numerical computation show that there are exact correlations between the field strength at the end of particle trajectory and the parameters of track under ECE. It is found that although two traditional models of Mason and Smythe in dielectrics can be partly applied for short and long tracks, none of them are able to explain the behaviour of field strength in a 'general case'. Furthermore, we find that there is an expressive relationship between the field strength and the incidence angle of impacted particle, while the mentioned traditional models are not able to explain this effect.

Analytical scanning and transmission electron microscopy of laboratory impacts on Stardust aluminum foils: Interpreting impact crater morphology and the composition of impact residues

Abstract— The known encounter velocity (6.1 kms−1) and particle incidence angle (perpendicular) between the Stardust spacecraft and the dust emanating from the nucleus of comet Wild‐2 fall within a range that allows simulation in laboratory light‐gas gun (LGG) experiments designed to validate analytical methods for the interpretation of dust impacts on the aluminum foil components of the Stardust collector. Buckshot of a wide size, shape, and density range of mineral, glass, polymer, and metal grains, have been fired to impact perpendicularly on samples of Stardust Al 1100 foil, tightly wrapped onto aluminum alloy plate as an analogue of foil on the spacecraft collector. We have not yet been able to produce laboratory impacts by projectiles with weak and porous aggregate structure, as may occur in some cometary dust grains. In this report we present information on crater gross morphology and its dependence on particle size and density, the pre‐existing major‐ and trace‐element composition of the foil, geometrical issues for energy dispersive X‐ray analysis of the impact residues in scanning electron microscopes, and the modification of dust chemical composition during creation of impact craters as revealed by analytical transmission electron microscopy. Together, these observations help to underpin the interpretation of size, density, and composition for particles impacted on the Stardust aluminum foils.

Investigation of processing parameters for pulsed closed field unbalanced magnetron sputtered titanium carbide thin films

Titanium carbide is a well established wear resistant coating owing to its excellent tribological properties including high hardness and elastic modulus, good wear resistance, low coefficient of friction against steel and high temperature stability. Recent advances in sputtering technology have resulted in improvements in the properties and performance of wear resistant coatings. Closed field unbalanced magnetron sputtering and pulsed magnetron sputtering have greatly improved the structure and properties of titanium carbide films by increasing ion bombardment at the substrate. However, film quality is highly dependent on the placement of the substrate relative to the sputtering targets. Titanium carbide films were deposited using a cosputtering configuration from one graphite target and one titanium target. At short substrate to target distances films exhibited an open, porous structure with low hardness and a high coefficient of friction. As the substrate to target distance was increased, along with the angle of incident particles, improvements were seen in both the microstructure and tribological properties.

Effect of different incidence angles on bonding performance in cold spraying

The deformation behaviour of spray particles impacting upon a substrate under the oblique impact condition in cold spraying was investigated using finite element analysis(FEA) method. The effect of incidence angle of particle on the deformation of particle and substrate was examined. It is found that the contact area between the deformed particle and substrate decreases and the crater depth in the substrate reduces with increasing the tilting angle at the same impact velocity. The normal component of impact velocity takes an important role in the impacting process and formation of bonding.

Theoretical prediction of liftoff angular velocity distributions of sand particles in windblown sand flux

The liftoff angular velocities, including the rebound ones and the ejected ones, of sand particles in a windblown sand flux have a significant influence on the saltation trajectories and the transport flux and so on. However, they are not easy to determine actually both in field and in a wind tunnel, especially when the sand particles are small and the wind speed is low. A stochastic particle‐bed collision model is developed in this paper to calculate the liftoff angular velocities. Having taken the incident velocity and angle of an incident particle, the impact angle between the incident and the impacted particles in the sand bed and its creep velocity as well as the contact angle between the impacted particle and other particles in the bed as random variables in the collision model, the probability distributions of the liftoff angular velocities for different particle diameters and wind speeds are gained and agree well to the experimental results. The rebound probability distribution function looks like Gumbel distribution with a cusp in the peak, and the ejected one looks like the normal one. The effect of the wind speed and the particle diameter on the probability density functions is discussed in detail.