572,376 research outputs found
Charge-Collection Efficiency in Back-Illuminated Charge-Coupled Devices
Low-noise fully depleted charge-coupled devices have been identified as a unique tool for dark-matter searches, low-energy neutrino physics, and x-ray detection. The charge-collection efficiency (CCE) for these detectors is a critical performance parameter for current and future experiments. We present a technique to characterize the CCE in back-illuminated CCDs based on soft x rays. This technique is used to study two different detector designs. The results demonstrate the importance of the backside processing for the detection of charge packages near threshold, showing that a recombination layer of a few microns significantly distorts the low-energy spectrum. The studies demonstrate that the region of partial charge collection can be reduced to a thickness of less than 1μm with adequate backside processing.Fil: Fernández Moroni, Guillermo. Fermi National Accelerator Laboratory; Estados UnidosFil: Andersson, Kevin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina. Fermi National Accelerator Laboratory; Estados UnidosFil: Botti, Ana Martina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Estrada, Juan. Fermi National Accelerator Laboratory; Estados UnidosFil: Rodrigues Ferreira Maltez, Dario Pablo. Fermi National Accelerator Laboratory; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Tiffenberg, Javier Sebastian. Fermi National Accelerator Laboratory; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Recent results on GaAs detectors - 137
The present understanding of the charge collection in GaAs detectors with
respect to the materials used and its processing are discussed. The radiation
induced degradation of the charge collection efficiency and the leakage current
of the detectors are summarised. The status of strip and pixel detectors for
the ATLAS experiment are reported along with the latest results from GaAs X-ray
detectors for non-high energy physics applications.Comment: 7 pages. 4 postscript figures + 1 postscript preprint logo + 1 LaTeX
file + 1 style file. Also available at
http://ppewww.ph.gla.ac.uk/preprints/97/05
Scavenging of aerosol particles by large water drops 2. The effect of electrical forces
The effect of electrical forces on the collection efficiency of millimeter-sized water drops collecting micron-sized aerosol particles has been investigated in a laboratory experiment. The observations show higher collection efficiencies for drops of 3.6- to 4.8-mm diameters than reported in some of the earlier studies for smaller drops. The limited and sparse data obtained in our experiments show that the collection efficiency of a drop is higher when it is charged or interacts with the aerosol in the presence of an electric field. The collection efficiency shows a maximum when the drop charge of either polarity is in the range of 10−12 to 10−11 C. The data show that the drop surface charge density required for this maximum decreases with the increase in drop size but is independent of the particle size. However, the peak value of collection efficiency is higher for larger particles. Moreover, the total charge on the drop required for this maximum remains almost constant at about 2–3×10−12C. The collection efficiency increases with the increase in the electric field, and the effect of the electric field is stronger for larger drops. In high fields, the drop collection efficiency shows a maximum for particles of diameter between 3.5 and 5 μm. The change in collection efficiency for the same change in particle size is larger for higher electric fields. Distortion of large drops and the consequent charge accumulation on the rim of the drop has been proposed to explain the results. The decrease in collection efficiency for large values of drop charge and electric field support the drop-to-particle charge transfer during their interaction
Modeling the Charge Collection Efficiency in the Li-diffused Inactive Layer of a P-type Point-Contact Germanium Detector
A model of the Li-diffused inactive layer in P-type high purity germanium
detectors is built to describe the transportation of charge carriers and
calculate the charge collection efficiency therein. The model is applied to
calculate charge collection efficiency of a P-type point-contact germanium
detector used in rare event physics experiments and validated in another P-type
semi-planar germanium detector. The calculated charge collection efficiency
curves are well consistent with measurements for both detectors. Effects of the
Li doping processes on the charge collection efficiency are discussed based on
the model. This model can be easily extended to other P-type germanium
detectors, for instance, the P-type broad-energy Ge detector, and the P-type
inverted-coaxial point-contact detector.Comment: 13 pages, 7 figure
Theoretical evaluation of MTF and charge collection efficiency in CCD and CMOS image sensor
Classical models used to calculate the Modulation Transfer function (MTF) of a solid-state image sensor generally
use a sinusoidal type of illumination. The approach, described in this paper, consists in considering a point-source illumination to built a theoretical three dimensional model of the diffusion and the collection of photo-carriers created within the image sensor array. Fourier transform formalism is used for this type of illumination. Solutions allow to evaluate the spatial repartition of the charge density collected in the space charge region, i.e. to get the Pixel Response Function (PRF) formulation. PRF enables to calculate analytically both MTF and crosstalk at every needed wavelengths. The model can take into account a uniformly doped substrate and an epitaxial layer grown on a highly doped substrate. The built-in electric field induced by the EPI/Substrate doping gradient is also taken into account. For these configurations, MTF, charge collection efficiency and crosstalk proportion are calculated. The study is established in the case of photodiode pixel but it can be easily extended to pinned photodiode pixels and photogate pixels
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