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E. Caroli, R.M.C. da Silva,
J.B. Stephen,
A. Pisa,
N. Auricchio,
S. del Sordo,
A. Donati,
F. Schiavone,
G. Landini,
V. Honkimaki,
F. Frontera
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ABSTRACT: A new generation of high sensitivity telescopes based on the use of Laue lenses coupled with high efficiency solid state focal plane detectors has been identified as a possibility for hard X and soft gamma ray astronomy. For this kind of space mission, polarimetry is recognized as a very important observational parameter and therefore this capability should be included as one of the primary scientific requirements. In this framework our group has realized an experiment to demonstrate that the combination of a Laue Lens, built using Cu mosaic crystals, with a CZT pixel detector is capable of measuring the polarization of hard X ray sources contemporaneously with spectroscopy and imaging. This experiment was performed at the beginning of March 2008 using the ID15B beam line at ESRF (Grenoble). The instrument was based on a pixel CZT detector (5 mm thick array with 11times11 pixels of 2.5times2.5 mm<sup>2</sup>) with a sensitive area of 3times3 cm<sup>2</sup> in conjunction with a mosaic Cu crystal (15times15 mm<sup>2</sup>, 4 mm thick) used in the Laue diffraction configuration. During the tests the Cu crystal was rotated so as to simulate a Laue lens ring, and the detector was moved in order to have the diffracted beam always impinging on the same pixel. The ID15B beamline allowed us to test the response of this system to almost 100% linearly polarized photons at ~90, 270, and 350 keV. In this paper, we describe the experimental setup and we report on the first results, with particular emphasis on the evaluation of possible systematic effects introduced in the detected polarization of the impinging photons by the Laue diffraction process.
IEEE Transactions on Nuclear Science 09/2009; · 1.45 Impact Factor
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ABSTRACT: In astrophysics, hard X- and soft gamma-ray polarimetry has had limited development. To date, no dedicated polarimeters have ever been launched into space. However, previous Monte Carlo simulations and prototype experimental studies have been carried out by the authors in order to evaluate the polarimetric performance of pixelised CZT matrices. We have applied this Monte Carlo code to the case of a CZT pixel instrument proposed as a Gamma-ray burst monitor (GRBM) for an X-ray payload on board the International Space Station (ISS): the LOBSTER experiment, which has already successfully passed the ESA Phase A study for a future flight in 2009. Herein we present the results of the study of the 4 detection units that compose the GRBM detector. Each of these units is a 24times12 matrix of CZT elementary crystals and the pixels have a cross section of 8times8 mm<sup>2</sup>, giving an active area of about 184 cm<sup>2</sup> for each unit. The detector thickness is nominally 3 mm, with a maximum of 5 mm should this thickness be crucial to exploit the GRBM as a polarimeter. The 4 detection units have a rectangular FOV of 55degtimes 35deg FWHM and their axes are misaligned with each other by 45deg in the direction perpendicular to the ISS motion and 10deg along the ISS direction of motion. The GRBM will operate in the energy range between 3 keV and 300 keV. The energy dependent polarimetric Q factor and detection efficiencies are presented and the expected minimum detectable polarization for gamma ray bursts is discussed
IEEE Transactions on Nuclear Science 03/2006; · 1.45 Impact Factor
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ABSTRACT: A gas proportional scintillation counter having as photosensor a dual-cathode microstrip plate covered with a CsI film is described. This dual-cathode new technique has the advantage of increasing the VUV sensitive area of the microstrip plate. A detailed description of the technique is presented together with a discussion of the performance. The results obtained for a xenon filled gas proportional scintillation counter show an improvement of the energy resolution for 5.9 keV X-rays from 12.5%, for a single cathode device, to 11.1% for the dual-cathode device.
Nuclear Science Symposium Conference Record, 2005 IEEE; 11/2005
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ABSTRACT: The study of solar X-ray emissions can be very useful to predict and prevent the undesirable consequences of charged particles generated by solar flares on Earth, since charged particles take about 20 to 40 hours to reach Earth, while X-rays that are simultaneously emitted by the same solar flares only take about 8 minutes. Herein, we present a large area window (20 cm<sup>2</sup>) and high-pressure (up to 5 atm) hybrid gas proportional scintillation counter/microstrip gas chamber (GPSC/MSGC) for a satellite borne experiment to study solar flare X-ray emissions in the energy range between 20 keV and 80 keV. Xenon filled GPSC/MSGCs are low production cost and low power consumption detectors that provide large detection areas, room temperature operation and optimal energy resolution for solar X-ray observations. Therefore, the performances of a laboratory prototype designed to study solar X-rays was analysed. Namely the energy resolution as a function of the Xe pressure (1 atm to 5 atm), since for energies above 60 keV the gas pressure is a critical parameter to detection efficiency. The results obtained for the energy resolution dependence with the gas pressure (about 6.5% up to 4 atm) will be presented and discussed.
Nuclear Science Symposium Conference Record, 2005 IEEE; 11/2005
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ABSTRACT: Up to date there have been very few developments in the field of polarimetry in hard X- and soft γ-ray astronomy, even if this measurement can give unique information about the geometry and the processes responsible of high energy emission from cosmic sources. We have recently proposed an instrument devoted to polarimetric measurements in this energy range known as the Coded Imager and Polarimeter for High Energy Radiation (CIPHER), a telescope which uses a detection plane optimized for the detection of Compton scattered events. In order to study the response of this polarimeter concept to linearly polarized radiation in the 100 keV to 1 MeV energy range, we have prepared an experiment (POLCA: POLarimetry with CdTe Arrays) based on CdTe detector prototypes of 4×4 pixels. The use of a beamline at the European Synchrotron Radiation Facility (ERSF) allowed us to study the Compton double-event efficiency and distribution, for beams of nearly 100% linearly polarized radiation in the energy range from 100 keV to 400 keV. We have obtained polarimetric modulation factors higher than 0.4 with double-event efficiencies higher than 20%. The photon beam energy and detector thickness dependencies will be discussed, comparing these experimental results with those calculated using Monte Carlo simulations.
IEEE Transactions on Nuclear Science 11/2004; · 1.45 Impact Factor
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ABSTRACT: Polarimetry in astronomy for the hard X- and soft γ-ray energy range has not been developed much to date. Indeed no dedicated polarimeters have ever been launched either in space or as a balloon-borne experiment. We propose a polarimetry project for hard X-ray and soft gamma-ray astrophysics known as the Coded Imager and Polarimeter for High Energy Radiation (CIPHER) telescope. The novel design of this telescope, using a matrix of thick CdTe microspectrometers as the detection plane, will allow this type of measurement to be performed for the first time by a dedicated instrument. In order to compare the results already obtained from simulations with experiment, we have constructed a prototype detector of 4×4 pixels, to study the response of this concept of polarimeter to linearly polarized radiation in the 100 keV to 1 MeV energy range. The use of a beamline at the European Synchrotron Radiation Facility (ERSF) allowed us to study double event efficiency and distribution, for beams of nearly 100% linearly polarized radiation in the energy range from 100 keV to 1 MeV. Polarimetric Q factors higher than 0.4 for relative efficiencies higher than 20% were observed. The photon beam energy and detector thickness dependencies will be discussed, comparing these experimental results with those calculated by Monte Carlo simulations.
IEEE Transactions on Nuclear Science 09/2003; · 1.45 Impact Factor
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[show abstract]
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ABSTRACT: Polarimetry in astronomy for the hard X- and soft γ-ray energy range has not been developed much to date, indeed no dedicated polarimeters have ever been launched either in space or as a balloon-borne experiment. We propose a polarimetry project for hard X-ray and soft gamma ray astrophysics known as the Coded Imager and Polarimeter for High Energy Radiation (CIPHER) telescope. The novel design of this telescope, using a matrix of thick CdTe micro-spectrometers as the detection plane will allow this type of measurement to be performed for the first time by a dedicated instrument. In order to compare the results already obtained from simulations with experiment, we have constructed a prototype detector of 4×4 pixels, to study the response of this concept of polarimeter to linearly polarised radiation in the 100 keV to 1 MeV energy range. The use of a beamline at the European Synchrotron Radiation Facility; (ERSF) allowed us to study double event efficiency and distribution, for beams of nearly 100% linearly polarised radiation in the energy range from 100 keV to 1 MeV. Polarimetric Q factors higher than 0.4 for relative efficiencies higher than 20% were observed. The photon beam energy and detector thickness dependencies will be discussed, comparing these experimental results with those calculated by Monte Carlo simulations.
Nuclear Science Symposium Conference Record, 2002 IEEE; 12/2002
