SuperAGILE: The hard X-ray imager for the AGILE space mission Feroci, M.; Costa, E.; Soffitta, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2007, Letnik:
581, Številka:
3
Journal Article
Recenzirano
SuperAGILE is a coded mask experiment based on silicon microstrip detectors. It operates in the 15–45
keV nominal energy range, providing crossed one-dimensional images of the X-ray sky with an ...on-axis angular resolution of 6
arcmin, over a field of view in excess of 1
sr. It was designed as the hard X-ray monitor of the AGILE space mission, a small satellite of the Italian Space Agency devoted to image the gamma-ray sky in the 30
MeV–50
GeV energy band. The AGILE mission was launched in a low-earth orbit on 23rd April 2007. In this paper we describe the SuperAGILE experiment, its construction and test processes, and its performance before flight, based on the on-ground test and calibrations.
Low energy polarization sensitivity of the Gas Pixel Detector Muleri, F.; Soffitta, P.; Baldini, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2008, 2008-1-00, Letnik:
584, Številka:
1
Journal Article
Recenzirano
An X-ray photoelectric polarimeter based on the Gas Pixel Detector has been proposed to be included in many upcoming space missions to fill the gap of about 30 years from the first (and to date only) ...positive measurement of polarized X-ray emission from an astrophysical source. The estimated sensitivity of the current prototype peaks at an energy of about 3
keV, but the lack of readily available polarized sources in this energy range has prevented the measurement of detector polarimetric performances.
In this paper we present the measurement of the Gas Pixel Detector polarimetric sensitivity at energies of a few keV and the new, light, compact and transportable polarized source that was devised and built to this aim. Polarized photons are produced, from unpolarized radiation generated with an X-ray tube, by means of Bragg diffraction at nearly
45
∘
. The diffraction angle is constrained with two orthogonal capillary plates, which allow good collimation with limited size thanks to the
10
μ
m
diameter holes. Polarized photons at energy as low as a few keV can be produced with a proper choice of diffracting crystal, while the maximum energy is limited by the X-ray tube voltage, since all the orders defined by the crystal lattice spacing are diffracted. The best trade-off between reasonable fluxes and high degree of polarization can be achieved selecting the degree of collimation provided by capillary plates.
The employment of mosaic graphite and flat aluminum crystals allow the production of nearly completely polarized photons at 2.6, 3.7, and 5.2
keV from the diffraction of unpolarized continuum or line emission. The measured modulation factor of the Gas Pixel Detector at these energies is in good agreement with the estimates derived from a Monte Carlo software, which was up to now employed for driving the development of the instrument and for estimating its low energy sensitivity. In this paper we present the excellent polarimetric performance of the Gas Pixel Detector at energies where the peak sensitivity is expected. These measurements not only support our previous claims of high sensitivity but confirm the feasibility of astrophysical X-ray photoelectric polarimetry.
We report on the measurements of the total charge changing fragmentation cross-sections in high-energy nucleus–nucleus collisions using Fe, Si and Pb incident ions. Several stacks of CR39 nuclear ...track detectors with different target combinations were exposed at normal incidence to high-energy accelerator beams to integrated densities of about 2000
ions/cm
2. The nuclear track detector foils were chemically etched, and ion tracks were measured using an automatic image analyzer system. The cross-section determination is based on the charge identification of beam ions and their fragments and on the reconstruction of their path through the stacks.
The AGILE Mission Barbiellini, G.; Argan, A.; Boffelli, F. ...
Astronomy & astrophysics,
08/2009, Letnik:
502, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Context. AGILE is an Italian Space Agency mission dedicated to observing the gamma-ray Universe. The AGILE's very innovative instrumentation for the first time combines a gamma-ray imager (sensitive ...in the energy range 30 MeV–50 GeV), a hard X-ray imager (sensitive in the range 18–60 keV), a calorimeter (sensitive in the range 350 keV–100 MeV), and an anticoincidence system. AGILE was successfully launched on 2007 April 23 from the Indian base of Sriharikota and was inserted in an equatorial orbit with very low particle background. Aims. AGILE provides crucial data for the study of active galactic nuclei, gamma-ray bursts, pulsars, unidentified gamma-ray sources, galactic compact objects, supernova remnants, TeV sources, and fundamental physics by microsecond timing. Methods. An optimal sky angular positioning (reaching 0.1 degrees in gamma-rays and 1–2 arcmin in hard X-rays) and very large fields of view (2.5 sr and 1 sr, respectively) are obtained by the use of Silicon detectors integrated in a very compact instrument. Results. AGILE surveyed the gamma-ray sky and detected many Galactic and extragalactic sources during the first months of observations. Particular emphasis is given to multifrequency observation programs of extragalactic and galactic objects. Conclusions. AGILE is a successful high-energy gamma-ray mission that reached its nominal scientific performance. The AGILE Cycle-1 pointing program started on 2007 December 1, and is open to the international community through a Guest Observer Program.
We present the calibration of the Makrofol–DE nuclear track detector (NTD) using Pb-ions of 158
GeV/amu. Improvements in the post-etched surfaces, reduction in the surface background of the ...Makrofol–DE NTDs and high-contrast tracks were achieved with the appropriate addition of ethyl alcohol in KOH aqueous solutions. The calibration of Makrofol–DE has shown for the first time all the peaks arising due to nuclear fragments with
Z
⩾
52
. The measurement of the cone heights shows well-separated individual peaks for
Z
/
β
=
59
–
82
and 83 (charge pickup).
SLIM is a large area experiment (440
m
2
) installed at the Chacaltaya cosmic ray laboratory since 2001, and about 100
m
2
at Koksil, Himalaya, since 2003. It is devoted to the search for ...intermediate mass magnetic monopoles (10
7
–10
13
GeV/
c
2
) and nuclearites in the cosmic radiation using stacks of CR-39 and Makrofol nuclear track detectors. In four years of operation it will reach a sensitivity to a flux of about 10
-
15
cm
-
2
s
-
1
sr
-
1
. We present the results of the calibration of CR-39 and Makrofol and the analysis of a first sample of the exposed detector.
Aims. We present a variability study of a sample of bright γ-ray(30 Mev−50 Gev) sources. This sample is an extension of the first AGILE catalogue of γ-ray sources (1AGL), obtained using the complete ...set of AGILE observations in pointing mode performed during a 2.3 year period from July 9, 2007 until October 30, 2009. Methods. The dataset of AGILE pointed observations covers a long time interval and its γ-ray data archive is useful for monitoring studies of medium-to-high brightness γ-ray sources. In the analysis reported here, we used data obtained with an improved event filter that covers a wider field of view, on a much larger (about 27.5 months) dataset, integrating data on observation block time scales, which mostly range from a few days to thirty days. Results. The data processing resulted in a better characterized source list than 1AGL was, and includes 54 sources, 7 of which are new high galactic latitude (|BII| ≥ 5) sources, 8 are new sources on the galactic plane, and 20 sources from the previous catalogue with revised positions. Eight 1AGL sources (2 high-latitude and 6 on the galactic plane) were not detected in the final processing either because of low OB exposure and/or due to their position in complex galactic regions. We report the results in a catalogue of all the detections obtained in each single OB, including the variability results for each of these sources. In particular, we found that 12 sources out of 42 or 11 out of 53 are variable, depending on the variability index used, where 42 and 53 are the number of sources for which these indices could be calculated. Seven of the 11 variable sources are blazars, the others are Crab pulsar+nebula, LS I +61°303, Cyg X-3, and 1AGLR J2021+4030.
Aims. We report the γ-ray activity from the intermediate BL Lac S5 0716+714 during observations acquired by the AGILE satellite in September and October 2007. These detections of activity were ...contemporaneous with a period of intense optical activity, which was monitored by GASP–WEBT. This simultaneous optical and γ-ray coverage allows us to study in detail the light curves, time lags, γ-ray photon spectrum, and Spectral Energy Distributions (SEDs) during different states of activity. Methods. AGILE observed the source with its two co-aligned imagers, the Gamma-Ray Imaging Detector (GRID) and the hard X-ray imager (Super-AGILE), which are sensitive to the 30 MeV–50 GeV and 18–60 keV energy ranges, respectively. Observations were completed in two different periods, the first between 2007 September 4–23, and the second between 2007 October 24–November 1. Results. Over the period 2007 September 7–12, AGILE detected γ-ray emission from the source at a significance level of 9.6-σ with an average flux (E > 100 MeV) of (97 ± 15) $\times$ 10-8 photons cm-2 s-1, which increased by a factor of at least four within three days. No emission was detected by Super-AGILE for the energy range 18–60 keV to a 3-σ upper limit of 10 mCrab in 335 ks. In October 2007, AGILE repointed toward S5 0716+714 following an intense optical flare, measuring an average flux of (47 ± 11) $\times$ 10-8 photons cm-2 s-1 at a significance level of 6.0-σ. Conclusions. The γ-ray flux of S5 0716+714 detected by AGILE is the highest ever detected for this blazar and one of the most intense γ-ray fluxes detected from a BL Lac object. The SED of mid-September appears to be consistent with the synchrotron self-Compton (SSC) emission model, but only by including two SSC components of different variabilities.
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