Variational iteration method and projection method solution of the spatially distributed population balance equation

In this work, two major hydrodynamic parameters, the holdup of the dispersed phase and the Sauter diameter, are considered. This is done for describing the hydrodynamics of interacting liquid–liquid dispersions using different particle breakage, coalescence and growth models in a particle population balance model. Based on the semi-analytical solution method of the population balance, namely, the variational iteration method (VIM), different process cases have been performed, and it is possible to find the exact solution or a closed approximate solution of a problem. For the simultaneous growth and coalescence terms comparisons between the present method and projection method which include discontinuous Galerkin and collocation techniques are made, respectively. The VIM technique overcomes the difficulties of discretization of the variables, introduces an efficient algorithm that improves the standard discretization method and is able to handle quite successful these process of population balance equations. The results are encouraging and the new method has proven to be suitable to predict holdup and Sauter diameter profiles

Euclid H2RG detectors: Impact of crosshatch patterns on photometric and centroid errors

International audienceIn the framework of the ESA’s Science programme, the Euclid mission has the objective to map the geometry of the Dark Universe. For the Near Infrared Spectrometer and Photometer instrument (NISP), the state-of-the-art HAWAII-2RG detectors will be used, in association with the SIDECAR ASIC readout electronics. A dedicated test bench has been designed, developed and validated at ESTEC to perform tests on these detectors. This test bench is equipped with a spot projector system as well as a set of LEDs allowing to project the Euclid like beam and perform persistence measurements. The detector under test shows crosshatch patterns that may correspond to sub-pixel variations in Quantum Efficiency or charge redistribution. The goal of the tests was to evaluate the impact of crosshatches patterns on the Euclid photometric performance and centroid calculation after flat fielding correction. The second part of the publication discusses different persistence mitigation tests using the LEDs test set up

Comparison of persistence in spot versus flat field illumination and single pixel response on a Euclid HAWAII-2RG at ESTEC

International audienceEuclid is an ESA mission to map the geometry of the dark Universe with a planned launch date in 2020. Euclid is optimised for two primary cosmological probes, weak gravitational lensing and galaxy clustering. They are implemented through two science instruments on-board Euclid, a visible imager (VIS) and a near-infrared spectro-photometer (NISP), which are being developed and built by the Euclid Consortium instrument development teams. The NISP instrument contains a large focal plane assembly of 16 Teledyne HgCdTe HAWAII-2RG detectors with 2.3μm cut-off wavelength and SIDECAR readout electronics. While most Euclid NISP detector system on-ground tests involve flat-field illumination, some performance tests require point-like sources to be projected onto the detector. For this purpose a dedicated test bench has been developed by ESA at ESTEC including a spot projector capable of generating a Euclid-like PSF. This paper describes the test setup and results from two characterisation tests involving the spot projector. One performance parameter to be addressed by Euclid is image (charge) persistence resulting from previous exposures in the science acquisition sequence. To correlate results from standard on-ground persistence tests from flat-field illumination to realistic scenes, the persistence effect from spot illumination has been evaluated and compared to the flat-field. Another important aspect is the photometric impact of intra-pixel response variations. Preliminary results of this measurement on a single pixel are presented

Description and performance of track and primary-vertex reconstruction with the CMS tracker

A description is provided of the software algorithms developed for the CMS tracker both for reconstructing charged-particle trajectories in proton-proton interactions and for using the resulting tracks to estimate the positions of the LHC luminous region and individual primary-interaction vertices. Despite the very hostile environment at the LHC, the performance obtained with these algorithms is found to be excellent. For tbar t events under typical 2011 pileup conditions, the average track-reconstruction efficiency for promptly-produced charged particles with transverse momenta of p(T) > 0.9GeV is 94% for pseudorapidities of |η| < 0.9 and 85% for 0.9 < |η| < 2.5. The inefficiency is caused mainly by hadrons that undergo nuclear interactions in the tracker material. For isolated muons, the corresponding efficiencies are essentially 100%. For isolated muons of p(T) = 100GeV emitted at |η| < 1.4, the resolutions are approximately 2.8% in p(T), and respectively, 10μm and 30μm in the transverse and longitudinal impact parameters. The position resolution achieved for reconstructed primary vertices that correspond to interesting pp collisions is 10–12μm in each of the three spatial dimensions. The tracking and vertexing software is fast and flexible, and easily adaptable to other functions, such as fast tracking for the trigger, or dedicated tracking for electrons that takes into account bremsstrahlung

Precision measurement of the structure of the CMS inner tracking system using nuclear interactions

The structure of the CMS inner tracking system has been studied using nuclear interactions of hadrons striking its material. Data from proton-proton collisions at a center-of-mass energy of 13 TeV recorded in 2015 at the LHC are used to reconstruct millions of secondary vertices from these nuclear interactions. Precise positions of the beam pipe and the inner tracking system elements, such as the pixel detector support tube, and barrel pixel detector inner shield and support rails, are determined using these vertices. These measurements are important for detector simulations, detector upgrades, and to identify any changes in the positions of inactive elements