G. Loffredo

Laue lens development for hard X-rays (>60 keV)

Results of reflectivity measurements of mosaic crystal samples of Cu (111) are reported. These tests were performed in the context of a feasibility study of a hard X-ray focusing telescope for space astronomy based on mosaic crystals in transmission configuration (Laue lens). The Laue lens assumed has the shape of a sphere segment with radius R equal to 2 times the focal length f of the lens and is made of flat mosaic crystal tiles properly positioned in the lens. The goal is to develop lenses for astrophysical applications with broad energy passband from 60 to 600 keV. The samples were grown and worked for this project at the Institute Laue-Langevin (ILL) in Grenoble, France, while the reflectivity tests were performed at the X-ray facility of the Physics Department of the University of Ferrara

X-ray facility for the ground calibration of the X-ray monitor JEM-X on board INTEGRAL

We describe the X-ray facility developed for the calibration of the X-ray monitor JEM-X on board the INTEGRAL satellite. The apparatus allowed the scanning of the detector geometric area with a pencil beam of desired energy over the major part of the passband of the instrument. The monochromatic radiation is obtained with the use of a double crystal monochromator at fixed exit. We discuss the facility performance.

Development status of a Laue lens project for gamma-ray astronomy

We report the status of the HAXTEL project, devoted to perform a design study and the development of a Laue lens prototype. After a summary of the major results of the design study, the approach adopted to develop a Demonstration Model of a Laue lens is discussed, the set up described, and some results presented.

Development status of a Laue lens for high-energy x rays (>60 keV)

A Laue lens for focusing X-ray photons with energies above 60 keV for astrophysical applications is being developed. The lens is based on mosaic crystals of Cu (111) produced at the Institute Laue-Langevin. A feasibility study has allowed to establish lens geometry and crystal properties required. The test of the crystals has provided very satisfactory results. We are now developing a Demonstration Model (DM) of the lens in order to establish the best assembling technique of the crystals. We will discuss the status of the project and its prospects.

New results on focusing of gamma-rays with Laue lenses

We report on new results on the development activity of broad band Laue lenses for hard X-/gamma-ray astronomy (70/100-600 keV). After the development of a first prototype, whose performance was presented at the SPIE conference on Astronomical Telescopes held last year in Marseille (Frontera et al. 2008), we have improved the lens assembling technology. We present the the development status of the new lens prototype that is on the way to be assembled.

Gamma-ray lens development status for a European Gamma-Ray Imager

A breakthrough in the sensitivity level of the hard X-/gamma-ray telescopes, which today are based on detectors that view the sky through (or not) coded masks, is expected when focusing optics will be available also in this energy range. Focusing techniques are now in an advanced stage of development. To date the most efficient technique to focus hard X-rays with energies above 100 keV appears to be the Bragg diffraction from crystals in transmission configuration (Laue lenses). Crystals with mosaic structure appear to be the most suitable to build a Laue lens with a broad passband, even though other alternative structures are being investigated. The goal of our project is the development of a broad band focusing telescope based on gamma-ray lenses for the study of the continuum emission of celestial sources from 60 keV up to >600 keV. We will report details of our project, its development status and results of our assessment study of a lens configuration for the European Gamma Ray Imager (GRI) mission now under study for the ESA plan Cosmic Vision 2015-2025.

Feasibility study of a Laue lens for hard x rays for space astronomy

We report on the feasibility study of a Laue lens for hard X-rays (> 60 keV) based on mosaic crystals, for astrophysical applications. In particular we discuss the scientific motivations, its functioning principle, the procedure followed to select the suitable crystal materials, the criteria adopted to establish crystal dimensions and their distribution on the lens in order to obtain the best lens focusing capabilities, and the criteria for optimizing the lens effective area in a given passband. We also discuss the effects of misalignments of the crystal tiles due to unavoidable mechanical errors in assembling the lens. A software was developed to face all these topics and to evaluate the expected lens performance.

JEM-X: the x-ray monitor on INTEGRAL

The INTEGRAL X-ray monitor, JEM-X, (together with the two gamma ray instruments, SPI and IBIS) provides simultaneous imaging with arcminute angular resolution in the 3-35 keV band. The good angular resolution and low energy response of JEM-X plays an important role in the detection and identification of gamma ray sources as well as in the analysis and scientific interpretation of the combined X-ray and gamma ray data. JEM-X is a coded aperture X-ray telescope consisting of two identical detectors. Each detector has a sensitive area of 500 cm2, and views the sky through its own coded aperture mask. The coded masks are located 3.4 m above the detector windows. The detector field of view is constrained by X-ray collimators (6.6° FOV, FWHM).