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تسجيل مستخدم جديدBeam Test of Gamma-ray Large Area Space Telescope Components
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A beam test of GLAST (Gamma-ray Large Area Space Telescope) components was performed at the Stanford Linear Accelerator Center in October, 1997. These beam test components were simp
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(Abridged) The Large Area Telescope (Fermi/LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from below 20
MeV to more than 300 GeV. This paper describes the LAT, its pre-flight expected performance, and summarizes the key science objectives that will be addressed. On-orbit performance will be presented in detail in a subsequent paper. The LAT is a pair-conversion telescope with a precision tracker and calorimeter, each consisting of a 4x4 array of 16 modules, a segmented anticoincidence detector that covers the tracker array, and a programmable trigger and data acquisition system. Each tracker module has a vertical stack of 18 x,y tracking planes, including two layers (x and y) of single-sided silicon strip detectors and high-Z converter material (tungsten) per tray. Every calorimeter module has 96 CsI(Tl) crystals, arranged in an 8 layer hodoscopic configuration with a total depth of 8.6 radiation lengths. The aspect ratio of the tracker (height/width) is 0.4 allowing a large field-of-view (2.4 sr). Data obtained with the LAT are intended to (i) permit rapid notification of high-energy gamma-ray bursts (GRBs) and transients and facilitate monitoring of variable sources, (ii) yield an extensive catalog of several thousand high-energy sources obtained from an all-sky survey, (iii) measure spectra from 20 MeV to more than 50 GeV for several hundred sources, (iv) localize point sources to 0.3 - 2 arc minutes, (v) map and obtain spectra of extended sources such as SNRs, molecular clouds, and nearby galaxies, (vi) measure the diffuse isotropic gamma-ray background up to TeV energies, and (vii) explore the discovery space for dark matter.
At the core of the AGILE scientific instrument, designed to operate on a satellite, there is the Gamma Ray Imaging Detector (GRID) consisting of a Silicon Tracker (ST), a Cesium Iodide Mini-Calorimeter and an Anti-Coincidence system of plastic scinti
llator bars. The ST needs an on-ground calibration with a $gamma$-ray beam to validate the simulation used to calculate the energy response function and the effective area versus the energy and the direction of the $gamma$ rays. A tagged $gamma$-ray beam line was designed at the Beam Test Facility (BTF) of the INFN Laboratori Nazionali of Frascati (LNF), based on an electron beam generating $gamma$ rays through bremsstrahlung in a position-sensitive target. The $gamma$-ray energy is deduced by difference with the post-bremsstrahlung electron energy cite{prest}-cite{hasan}. The electron energy is measured by a spectrometer consisting of a dipole magnet and an array of position sensitive silicon strip detectors, the Photon Tagging System (PTS). The use of the combined BTF-PTS system as tagged photon beam requires understanding the efficiency of $gamma$-ray tagging, the probability of fake tagging, the energy resolution and the relation of the PTS hit position versus the $gamma$-ray energy. This paper describes this study comparing data taken during the AGILE calibration occurred in 2005 with simulation.
The High Energy cosmic-Radiation Detector (HERD) facility is planned to go onboard Chinas Space Station, planned to be operational starting in around 2025 for about 10 years. The main scientific objectives of HERD are the search for signals of dark m
atter annihilation products, precise cosmic electron/positron spectrum and measurements of anisotropy up to 10 TeV, precise cosmic ray spectrum and composition measurements up to the knee energy (1 PeV), and high energy $gamma$-ray monitoring and survey. HERD consists of a 3D cubic crystals calorimeter (CALO) surrounded by microstrip silicon trackers (STKs) and scintillating fiber trackers (FIT) and by a Plastic Scintillator Detector (PSD) for $gamma$-ray veto and ion charge measurement. A PSD prototype consisting of a scintillator tile readout by two arrays of SiPMs on opposite sides has been tested with proton and C ion beam at the CNAO (Centro Nazionale Adroterapia Oncologica) in Pavia, (Italy). Preliminary results on charge resolution are presented.
In the unification scheme, radio quasars and FR II radio galaxies come from the same parent population, but viewed at different angles. Based on the Comptonization models for the gamma-ray emission from active galactic nuclei (AGNs), we estimate the
number of radio quasars and FR II radio galaxies to be detected by the Gamma-Ray Large Area Space Telescope (GLAST) using the luminosity function (LF) of their parent population derived from the flat-spectrum radio quasar (FSRQ) LF. We find that ~1200 radio quasars will be detected by GLAST, if the soft seed photons for Comptonization come from the regions outside the jets. We also consider the synchrotron self-Comptonization (SSC) model, and find it unlikely to be responsible for gamma-ray emission from radio quasars. We find that no FR II radio galaxies will be detected by GLAST. Our results show that most radio AGNs to be detected by GLAST will be FSRQs (~99 % for the external Comptonization model, EC model), while the remainder (~1 %) will be steep-spectrum radio quasars (SSRQs). This implies that FSRQs will still be good candidates for identifying gamma-ray AGNs even for the GLAST sources. The contribution of all radio quasars and FR II radio galaxies to the extragalactic gamma-ray background (EGRB) is calculated, which accounts for ~30 % of the EGRB.
Cosmic-ray background fluxes were modeled based on existing measurements and theories and are presented here. The model, originally developed for the Gamma-ray Large Area Space Telescope (GLAST) Balloon Experiment, covers the entire solid angle (${rm
4pi sr}$), the sensitive energy range of the instrument (${rm sim 10 MeV to 100 GeV}$) and abundant components (proton, alpha, $e^{-}$, $e^{+}$, $mu^{-}$, $mu^{+}$ and gamma). It is expressed in analytic functions in which modulations due to the solar activity and the Earth geomagnetism are parameterized. Although the model is intended to be used primarily for the GLAST Balloon Experiment, model functions in low-Earth orbit are also presented and can be used for other high energy astrophysical missions. The model has been validated via comparison with the data of the GLAST Balloon Experiment.
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