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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 development status of the new lens prototype that is on the way to be assembled.
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We report on the first results obtained from our development project of focusing gamma-rays ($>$60 keV) by using Laue lenses. The first lens prototype model has been assembled and tested. We describe the technique adopted and the lens focusing capabilities at about 100 keV.
We present the results obtained with the new Laue lens prototype built in the LARIX facility in the Physics Department of University of Ferrara. Following the results of the first prototype presented at the SPIE conference in Marseille, and also thanks to the methods adopted for improving the prototype (SPIE conference in San Diego, Ferrari et al. 2009) here we present the results of the new prototype with improved performances in terms of point spread function (PSF) and spectral response.
Thick diffractive optical elements offer a promising way to achieve focusing or imaging at a resolution approaching 1 nm for X-ray wavelengths shorter than about 0.1 nm. Efficient focusing requires that these are fabricated with structures that vary in period and orientation so that rays obey Braggs law over the entire lens aperture and give rise to constructive interference at the focus. Here the analysis method of ray-tracing of thick diffractive optical elements is applied to such lenses to optimise their designs and to investigate their operating and manufacturing tolerances. Expressions are provided of the fourth-order series expansions of the wavefront aberrations and transmissions of both axi-symmetric lenses and pairs of crossed lenses that each focuses in only one dimension like a cylindrical lens. We find that aplanatic zone-plate designs, whereby aberrations are corrected over a large field of view, can be achieved by axi-symmetric lenses but not the crossed lenses. We investigate the performance of 1 nm-resolution lenses with focal lengths of about 1 mm and show their fields of view are mainly limited by the acceptance angle of Bragg diffraction, and that aberrations can limit the performance of lenses with longer focal lengths. We apply the ray-tracing formalism for a tolerancing analysis of imperfect lenses and examine some strategies for the correction of their aberrations.
Carpet is an air-shower array at Baksan, Russia, equipped with a large-area muon detector, which makes it possible to separate primary photons from hadrons. We report first results of the search for primary photons with energies E>100 TeV. The experiments ongoing upgrade and future sensitivity are also discussed.
The Fermi Large Area Telescope (LAT) is a powerful pulsar detector, as demonstrated by the over one hundred objects in its second catalog of pulsars. Pass 8 is a new reconstruction and event selection strategy developed by the Fermi-LAT collaboration. Due to the increased acceptance at low energy, Pass 8 improves the pulsation detection sensitivity. Ten new pulsars rise above the 5 sigma threshold and are presented in this work, as well as one previously seen with the former Pass 7 reconstruction. More than 60$%$ of the known pulsars with spin-down power ($dot{E}$) greater than $10^{36}$ erg/s show pulsations in gamma-rays, as seen with the Fermi Large Area Telescope. Many non-detections of these energetic pulsars are thought to be a consequence of a high background level, or a large distance leading to a flux below the sensitivity limit of the instrument. The gamma-ray beams of the others probably miss the Earth. The new Pass 8 data now allows the detection of gamma ray pulsations from three of these high spin-down pulsars, PSRs J1828$-$1101, J1831$-$0952 and J1837$-$0604, as well as three others with $dot{E}$ $ge 10^{35}$ erg/s. We report on their properties and we discuss the reasons for their detection with Pass 8.
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