arXiv subjects

G. Pareschi

Publications and source records attributed to G. Pareschi.

At least 55 records · Page 3Linked to original sources

arXiv2015

A magnetic diverter for charged particle background rejection in the SIMBOL-X telescope

Minimization of charged particle background in X-ray telescopes is a well known issue. Charged particles (chiefly protons and electrons) naturally present in the cosmic environment constitute an important background source when they collide with the X-ray detector. Even worse, a serious degradation of spectroscopic performances of the X-ray detector was observed in Chandra and Newton-XMM, caused by soft protons with kinetic energies ranging between 100 keV and some MeV being collected by the grazing-incidence mirrors and funneled to the detector. For a focusing telescope like SIMBOL-X, the exposure of the soft X-ray detector to the proton flux can increase significantly the instrumental background, with a consequent loss of sensitivity. In the worst case, it can also seriously compromise the detector duration. A well-known countermeasure that can be adopted is the implementation of a properly-designed magnetic diverter, that should prevent high-energy particles from reaching the focal plane instruments of SIMBOL-X. Although Newton-XMM and Swift-XRT are equipped with magnetic diverters for electrons, the magnetic fields used are insufficient to effectively act on protons. In this paper, we simulate the behavior of a magnetic diverter for SIMBOL-X, consisting of commercially-available permanent magnets. The effects of SIMBOL-X optics is simulated through GEANT4 libraries, whereas the effect of the intense required magnetic fields is simulated along with specifically-written numerical codes in IDL.

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arXiv2015

Development of mirrors made of chemically tempered glass foils for future X-ray telescopes

Thin slumped glass foils are considered good candidates for the realization of future X-ray telescopes with large effective area and high spatial resolution. However, the hot slumping process affects the glass strength, and this can be an issue during the launch of the satellite because of the high kinematical and static loads occurring during that phase. In the present work we have investigated the possible use of Gorilla glass (produced by Corning), a chemical tempered glass that, thanks to its strength characteristics, would be ideal. The un-tempered glass foils were curved by means of an innovative hot slumping technique and subsequently chemically tempered. In this paper we show that the chemical tempering process applied to Gorilla glass foils does not affect the surface micro-roughness of the mirrors. On the other end, the stress introduced by the tempering process causes a reduction in the amplitude of the longitudinal profile errors with a lateral size close to the mirror length. The effect of the overall shape changes in the final resolution performance of the glass mirrors was studied by simulating the glass foils integration with our innovative approach based on glass reinforcing ribs. The preliminary tests performed so far suggest that this approach has the potential to be applied to the X-ray telescopes of the next generation.

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arXiv2014

Evaluation of the surface strength of glass plates shaped by hot slumping process

The Hot Slumping Technology is under development by several research groups in the world for the realization of grazing-incidence segmented mirrors for X-ray astronomy, based on thin glass plates shaped over a mould at temperatures above the transformation point. The performed thermal cycle and related operations might have effects on the strength characteristics of the glass, with consequences on the structural design of the elemental optical modules and consecutively on the entire X-ray optic for large astronomical missions like IXO and ATHENA. The mechanical strength of glass plates after they underwent the slumping process was tested through destructive double-ring tests in the context of a study performed by the Astronomical Observatory of Brera with the collaboration of Stazione Sperimentale del Vetro and BCV Progetti. The entire study has been realized on more than 200 D263 Schott borosilicate glass specimens of dimension 100 mm x 100 mm and thickness 0.4 mm, either flat or bent at a Radius of Curvature of 1000 mm through the particular pressure assisted hot slumping process developed by INAF-OAB. The collected experimental data have been compared to non-linear FEM analyses and treated with Weibull statistic to assess the current IXO glass X-ray telescope design, in terms of survival probability, when subject to static and acoustic loads characteristic of the launch phase. The paper describes the activities performed and presents the obtained results.

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arXiv2014

The INAF ASTRI Project in the framework of CTA

The ASTRI project aims to develop, in the framework of the Cherenkov Telescope Array, an end-to-end prototype of the small-size telescope, devoted to the investigation of the energy range ~ 1-100 TeV. The proposed design is characterized by two challenging but innovative technological solutions which will be adopted for the first time on a Cherenkov telescope: a dual-mirror Schwarzschild-Couder configuration and a modular, light and compact camera based on Silicon photo-multipliers. Here we describe the prototype design, the expected performance and the possibility to realize a mini array composed by a few such telescopes, which shall be placed at the final CTA Southern Site.

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arXiv2014

The imaging properties of the Gas Pixel Detector as a focal plane polarimeter

X-rays are particularly suited to probe the physics of extreme objects. However, despite the enormous improvements of X-ray Astronomy in imaging, spectroscopy and timing, polarimetry remains largely unexplored. We propose the photoelectric polarimeter Gas Pixel Detector (GPD) as an instrument candidate to fill the gap of more than thirty years of lack of measurements. The GPD, in the focus of a telescope, will increase the sensitivity of orders of magnitude. Moreover, since it can measure the energy, the position, the arrival time and the polarization angle of every single photon, allows to perform polarimetry of subsets of data singled out from the spectrum, the light curve or the image of source. The GPD has an intrinsic very fine imaging capability and in this work we report on the calibration campaign carried out in 2012 at the PANTER X-ray test facility of the Max-Planck-Institut für extraterrestrische Physik of Garching (Germany) in which, for the first time, we coupled it to a JET-X optics module with a focal length of 3.5 m and an angular resolution of 18 arcsec at 4.5 keV. This configuration was proposed in 2012 aboard the X-ray Imaging Polarimetry Explorer (XIPE) in response to the ESA call for a small mission. We derived the imaging and polarimetric performance for extended sources like Pulsar Wind Nebulae and Supernova Remnants as case studies for the XIPE configuration, discussing also possible improvements by coupling the detector with advanced optics, having finer angular resolution and larger effective area, to study with more details extended objects.

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arXiv2013

Athena+: The first Deep Universe X-ray Observatory

The Advanced Telescope for High-energy Astrophysics (Athena+) is being proposed to ESA as the L2 mission (for a launch in 2028) and is specifically designed to answer two of the most pressing questions for astrophysics in the forthcoming decade: How did ordinary matter assemble into the large scale structures we see today? and how do black holes grow and shape the Universe? For addressing these two issues, Athena+ will provide transformational capabilities in terms of angular resolution, effective area, spectral resolution, grasp, that will make it the most powerful X-ray observatory ever flown. Such an observatory, when opened to the astronomical community, will be used for virtually all classes of astrophysical objects, from high-z gamma-ray bursts to the closest planets in our solar neighborhood. In this paper, we briefly review the core science objectives of Athena+, present the science requirements and the foreseen implementation of the mission, and illustrate its transformational capabilities compared to existing facilities.

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arXiv2013

Status of the technologies for the production of the Cherenkov Telescope Array (CTA) mirrors

The Cherenkov Telescope Array (CTA) is the next generation very high-energy gamma-ray observatory, with at least 10 times higher sensitivity than current instruments. CTA will comprise several tens of Imaging Atmospheric Cherenkov Telescopes (IACTs) operated in array-mode and divided into three size classes: large, medium and small telescopes. The total reflective surface could be up to 10,000 m2 requiring unprecedented technological efforts. The properties of the reflector directly influence the telescope performance and thus constitute a fundamental ingredient to improve and maintain the sensitivity. The R&D status of lightweight, reliable and cost-effective mirror facets for the CTA telescope reflectors for the different classes of telescopes is reviewed in this paper.

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arXiv2013

The ASTRI Mini-Array Software System

ASTRI ("Astrofisica con Specchi a Tecnologia Replicante Italiana") is a Flagship Project financed by the Italian Ministry of Education, University and Research, and led by INAF, the Italian National Institute of Astrophysics. Main goals of the ASTRI project are the realization of an end-to-end prototype of a Small Size Telescope (SST) for the Cherenkov Telescope Array (CTA) in a dual-mirror configuration (SST-2M) and, subsequently, of a mini-array composed of a few SST-2M telescopes to be placed at the final CTA Southern Site. Here we present the main features of the Mini-Array Software System (MASS) that has a central role in the success of the ASTRI Project and will also serve as a prototype for the CTA software system. The MASS will provide a set of tools to prepare an observing proposal, to perform the observations specified therein (monitoring and controlling all the hardware components of each telescope), to analyze the acquired data online and to store/retrieve all the data products to/from the archive.}

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arXiv2013

The ASTRI Mini-Array Science Case

ASTRI is a Flagship Project financed by the Italian Ministry of Education, University and Research, and led by INAF, the Italian National Institute of Astrophysics. Within this framework, INAF is currently developing an end-to-end prototype of a Small Size Telescope in a dual-mirror configuration (SST-2M) for the Cherenkov Telescope Array (CTA), scheduled to start data acquisition in 2014. Although the ASTRI SST-2M prototype is mainly a technological demonstrator, it will perform scientific observations of the Crab Nebula, Mrk 421 and Mrk 501 at E>1 TeV. A remarkable improvement in terms of performance could come from the operation, in 2016, of a SST-2M mini-array, composed of a few SST-2M telescopes to be placed at final CTA Southern Site. The SST mini-array will be able to study in great detail relatively bright sources (a few x 10E-12 erg/cm2/s at 10 TeV) with angular resolution of a few arcmin and energy resolution of about 10-15%. Thanks to the stereo approach, it will be possible to verify the wide field of view (FoV) performance through the detections of very high-energy showers with core located at a distance up to 500 m, to compare the mini-array performance with the Monte Carlo expectations by means of deep observations of selected targets, and to perform the first CTA science at the beginning of the mini-array operations. Prominent sources such as extreme blazars, nearby well-known BL Lac objects and radio-galaxies, galactic pulsar wind nebulae, supernovae remnants, micro-quasars, and the Galactic Center can be observed in a previously unexplored energy range, in order to investigate the electron acceleration and cooling, relativistic and non relativistic shocks, the search for cosmic-ray (CR) Pevatrons, the study of the CR propagation, and the impact of the extragalactic background light on the spectra of the sources.

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arXiv2013

The dual-mirror Small Size Telescope for the Cherenkov Telescope Array

In this paper, the development of the dual mirror Small Size Telescopes (SST) for the Cherenkov Telescope Array (CTA) is reviewed. Up to 70 SST, with a primary mirror diameter of 4 m, will be produced and installed at the CTA southern site. These will allow investigation of the gamma-ray sky at the highest energies accessible to CTA, in the range from about 1 TeV to 300 TeV. The telescope presented in this contribution is characterized by two major innovations: the use of a dual mirror Schwarzschild-Couder configuration and of an innovative camera using as sensors either multi-anode photomultipliers (MAPM) or silicon photomultipliers (SiPM). The reduced plate-scale of the telescope, achieved with the dual-mirror optics, allows the camera to be compact (40 cm in diameter), and low-cost. The camera, which has about 2000 pixels of size 6x6 mm^2, covers a field of view of 10°. The dual mirror telescopes and their cameras are being developed by three consortia, ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana, Italy/INAF), GATE (Gamma-ray Telescope Elements, France/Paris Observ.) and CHEC (Compact High Energy Camera, universities in UK, US and Japan) which are merging their efforts in order to finalize an end-to-end design that will be constructed for CTA. A number of prototype structures and cameras are being developed in order to investigate various alternative designs. In this contribution, these designs are presented, along with the technological solutions under study.

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arXiv2013

Expected performance of the ASTRI-SST-2M telescope prototype

ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) is an Italian flagship project pursued by INAF (Istituto Nazionale di Astrofisica) strictly linked to the development of the Cherenkov Telescope Array, CTA. Primary goal of the ASTRI program is the design and production of an end-to-end prototype of a Small Size Telescope for the CTA sub-array devoted to the highest gamma-ray energy region. The prototype, named ASTRI SST-2M, will be tested on field in Italy during 2014. This telescope will be the first Cherenkov telescope adopting the double reflection layout in a Schwarzschild-Couder configuration with a tessellated primary mirror and a monolithic secondary mirror. The collected light will be focused on a compact and light-weight camera based on silicon photo-multipliers covering a 9.6 deg full field of view. Detailed Monte Carlo simulations have been performed to estimate the performance of the planned telescope. The results regarding its energy threshold, sensitivity and angular resolution are shown and discussed.

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arXiv2013

Mirror Development for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) is a planned observatory for very-high energy gamma-ray astronomy. It will consist of several tens of telescopes of different sizes, with a total mirror area of up to 10,000 square meters. Most mirrors of current installations are either polished glass mirrors or diamond-turned aluminium mirrors, both labour intensive technologies. For CTA, several new technologies for a fast and cost-efficient production of light-weight and reliable mirror substrates have been developed and industrial pre-production has started for most of them. In addition, new or improved aluminium-based and dielectric surface coatings have been developed to increase the reflectance over the lifetime of the mirrors compared to those of current Cherenkov telescope instruments.

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arXiv2013

Towards the ASTRI mini-array

The Cherenkov Telescope Array (CTA) will consist of an array of three types of telescopes covering a wide energy range, from tens of GeV up to more than 100 TeV. The high energy section (> 3 TeV) will be covered by the Small Size Telescopes (SST). ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) is a flagship project of the Italian Ministry of Research and Education led by INAF, aiming at the design and construction of a prototype of the Dual Mirror SST. In a second phase the ASTRI project foresees the installation of the first elements of the SST array at the CTA southern site, a mini-array of 5-7 telescopes. The optimization of the layout of this mini-array embedded in the SST array of the CTA Observatory has been the object of an intense simulation effort. In this work we present the expected mini-array performance in terms of energy threshold, angular and energy resolution and sensitivity.

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arXiv2013

The ASTRI Project: a mini-array of dual-mirror small Cherenkov telescopes for CTA

ASTRI is a flagship project of the Italian Ministry of Education, University and Research, which aims to develop an end-to-end prototype of the CTA small-size telescope. The proposed design is characterized by a dual-mirror Schwarzschild-Couder configuration and a camera based on Silicon photo-multipliers, two challenging but innovative technological solutions which will be adopted for the first time on a Cherenkov telescope. Here we describe the current status of the project, the expected performance and the possibility to realize a mini-array composed by a few small-size telescopes, which shall be placed at the final CTA Southern Site.

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arXiv2013

The ASTRI Project: prototype status and future plans for a Cherenkov dual-mirror small-telescope array

ASTRI ("Astrofisica con Specchi a Tecnologia Replicante Italiana") is a flagship project of the Italian Ministry of Education, University and Research. Within this framework, INAF is currently developing a wide field of view (9.6 degrees in diameter) end-to-end prototype of the CTA small-size telescope (SST), devoted to the investigation of the energy range from a fraction of TeV up to tens of TeVs, and scheduled to start data acquisition in 2014. For the first time, a dual-mirror Schwarzschild-Couder optical design will be adopted on a Cherenkov telescope, in order to obtain a compact optical configuration. A second challenging, but innovative technical solution consists of a modular focal surface camera based on Silicon photo-multipliers with a logical pixel size of 6.2mm x 6.2mm. Here we describe the current status of the project, the expected performance, and its possible evolution in terms of an SST mini-array. This CTA-SST precursor, composed of a few SSTs and developed in collaboration with CTA international partners, could not only peruse the technological solutions adopted by ASTRI, but also address a few scientific test cases that are discussed in detail.

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arXiv2010

The New Hard X-ray Mission

The Italian New Hard X-ray Mission (NHXM) has been designed to provide a real breakthrough on a number of hot astrophysical issues that includes: black holes census, the physics of accretion, the particle acceleration mechanisms, the effects of radiative transfer in highly magnetized plasmas and strong gravitational fields. NHXM is an evolution of the HEXIT-Sat concept and it combines fine imaging capability up to 80 keV, today available only at E<10 keV, with sensitive photoelectric imaging polarimetry. It consists of four identical mirrors, with a 10 m focal length, achieved after launch by means of a deployable structure. Three of the four telescopes will have at their focus identical spectral-imaging cameras, while X-ray imaging polarimetric cameras will be placed at the focus of the fourth. In order to ensure a low and stable background, NHXM will be placed in a low Earth equatorial orbit. In this paper we provide an overall description of this mission that is currently in phase B.

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arXiv2010

A wide field X-ray telescope for astronomical survey purposes: from theory to practice

X-ray mirrors are usually built in the Wolter I (paraboloid-hyperboloid) configuration. This design exhibits no spherical aberration on-axis but suffers from field curvature, coma and astigmatism, therefore the angular resolution degrades rapidly with increasing off-axis angles. Different mirror designs exist in which the primary and secondary mirror profiles are expanded as a power series in order to increase the angular resolution at large off-axis positions, at the expanses of the on-axis performances. Here we present the design and global trade off study of an X-ray mirror systems based on polynomial optics in view of the Wide Field X-ray Telescope (WFXT) mission. WFXT aims at performing an extended cosmological survey in the soft X-ray band with unprecedented flux sensitivity. To achieve these goals the angular resolution required for the mission is very demanding ~5 arcsec mean resolution across a 1-deg field of view. In addition an effective area of 5-9000 cm^2 at 1 keV is needed.

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arXiv2010

The Soft X-ray Imager on board EXIST

The Soft X-ray Imager (SXI) is one of the three instruments on board EXIST, a multi-wavelength observatory in charge of performing a global survey of the sky in hard X-rays searching for Super-massive Black Holes (Grindlay & Natalucci, these Proceedings). One of the primary objectives of EXIST is also to study with unprecedented sensitivity the most unknown high energy sources in the Universe, like high redshift GRBs, which will be pointed promptly by the Spacecraft by autonomous trigger based on hard X-ray localization on board. The presence of a soft X-ray telescope with an effective area of about 950cm2 in the energy band 0.2-3 keV and extended response up to 10 keV will allow to make broadband studies from 0.1 to 600 keV. In particular, investigations of the spectra components and states of AGNs and monitoring of variability of sources, study of the prompt and afterglow emission of GRBs since the early phases, which will help to constrain the emission models and finally, help the identification of sources in the EXIST hard X-ray survey and the characterization of the transient events detected. SXI will also perform surveys: a scanning survey with sky coverage 2pi and a limiting flux of 5x10^(-14) cgs plus other serendipitous.

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