Papers by Valerio Bellucci
We propose a technique to fabricate self-standing curved crystals for high-efficiency concentrati... more We propose a technique to fabricate self-standing curved crystals for high-efficiency concentration of hard X-ray photons by a Laue lens. This technique relies on superficial grooves on a mono- crystal by a diamond saw. Extension of the method to materials with higher atomic number, e.g., Ge, has been undertaken to provide high-efficiency diffraction up to 800 keV. With respect to other proposed techniques, the method of indentations is cheap, simple and reproducible, being based on mass production tools. It is possible to use curved crystal in two different geometries. Employing the ``geometry one'', it is possible to exploit the curvature directly imparted to the crystal to achieve high-efficiency diffraction. Grooved Si crystals were characterized in this geometry at ESRF and efficiently diffracted up to 500 keV, peaking 95% at 150 keV. The ``geometry two'' consists in exploiting the so-called quasi-mosaicity to obtain high-resolution focusing of X-rays. As a result of primary curvature imparted to the crystal, a secondary curvature (Quasi-Mosaic curvature) occurs. We demonstrated that a combination of primary and quasi-mosaic curvatures allows high-efficiency diffraction and high-resolution focusing of diffracted photons. Quasi-Mosaic crystals would increases the signal-to-noise ratio of about one orders of magnitude with respect to mosaic crystals and no mosaic defocusing would occur.
Optics for EUV, X-Ray, and Gamma-Ray Astronomy V, 2011
Quasi-mosaicity is an effect of secondary bending within a crystal driven by crystalline anisotro... more Quasi-mosaicity is an effect of secondary bending within a crystal driven by crystalline anisotropy. This effect can be used to fabricate a series of curved crystals for the realization of a Laue lens. We highlight that crystals bent by quasi-mosaic effect envisage very high resolution focusing with respect to mosaic crystals. Under same conditions for energy passband and flux of incident photons, a Laue lens based on quasi-mosaic crystals would increase the signal-to-noise ratio by more than one order of magnitude as for the same lens with mosaic crystals. A proposal for the realization of a self-standing quasi-mosaic crystal is given. Here permanent bending of a crystal is achieved as a result of superficial indentations. Downloaded From: https://proceedings.spiedigitallibrary.org/ on 03/13/2014 Terms of Use: https://spiedl.org/terms Proc. of SPIE Vol. 8147 81471G-2 Downloaded From: https://proceedings.spiedigitallibrary.org/ on 03/13/2014 Terms of Use: https://spiedl.org/terms Proc. of SPIE Vol. 8147 81471G-7 Downloaded From: https://proceedings.spiedigitallibrary.org/ on 03/13/2014 Terms of Use: https://spiedl.org/terms
Optics for EUV, X-Ray, and Gamma-Ray Astronomy V, 2011
We present an experimental study on the method of surface grooving for bending crystals for the r... more We present an experimental study on the method of surface grooving for bending crystals for the realization of a hard x-ray Laue lens. Bent Si and Ge crystalline plates were analyzed by x-ray diffraction of their (111) planes at the European Synchrotron Radiation Facility. Crystals diffracted photons from 150 to 700 keV with efficiency peaking 95% at 150 keV for Si. Measured rocking curves of the samples showed flat-topped profiles with their FWHM equal to the crystal bending, i.e., the method of surface grooving proved to evenly bend the crystals, their energy passband being very well controlled. Surface grooving technique has been found to offer both high reproducibility and easy control of diffraction properties of the crystals. Besides, this method is cheap, simple and compatible with mass production, making it a reliable technique for fabrication of a Laue lens, where serial production of crystals should be envisaged. A Laue lens made of crystals bent by surface grooves can lead to significant detection improvement in astrophysical applications. Downloaded From: https://proceedings.spiedigitallibrary.org/ on 03/13/2014 Terms of Use: https://spiedl.org/terms Proc. of SPIE Vol. 8147 81471E-2 Downloaded From: https://proceedings.spiedigitallibrary.org/ on 03/13/2014 Terms of Use: https://spiedl.org/terms
Applied Physics Letters, 2015
Journal of Applied Crystallography, 2015
The European Physical Journal C, 2014
The usage of a crystalline undulator (CU) has been identified as a promising solution for generat... more The usage of a crystalline undulator (CU) has been identified as a promising solution for generating powerful and monochromatic γ -rays. A CU was fabricated at Sensors and Semiconductors Lab (SSL) through the grooving method, i.e., by the manufacturing of a series of periodical grooves on the major surfaces of a crystal. The CU was extensively characterized both morphologically via optical interferometry at SSL and structurally via X-ray diffraction at ESRF. Then, it was finally tested for channeling with a 400 GeV/c proton beam at CERN. The experimental results were compared to Monte Carlo simulations. Evidence of planar channeling in the CU was firmly observed. Finally, the emission spectrum of the positron beam interacting with the CU was simulated for possible usage in currently existing facilities.
Experimental Astronomy, 2014
Crystals with curved diffracting planes have been investigated as highefficiency optical componen... more Crystals with curved diffracting planes have been investigated as highefficiency optical components for the realization of a Laue lens for satellite-borne experiments in astrophysics. Curved crystals implementing the quasi-mosaic effect, namely an effect of crystalline anisotropy, are able to focus an X-ray beam to a size far smaller than that of the diffracting element, in turn increasing the focusing power of a Laue lens. This work provides first results about the feasibility of a self-standing stack composed of quasi-mosaic crystals. Stacking of crystalline lamellae is a solution to overcome the thickness limitation in existing self-standing quasi-mosaic crystals. Ten thin silicon crystalline lamellae were stacked, and then the planes affected by the quasi-mosaic effect were tested by polychromatic X-ray diffraction. The multicrystal behaved as one diffracting element, yielding a broad and smooth diffraction profile. The effective realization of a quasi-mosaic multicrystal opens up the prospective of building a Laue lens with a large integrated reflectivity, which leads to a high sensitivity, a necessary condition for the observation of celestial X-ray sources via a Laue lens.
Journal of Applied Crystallography, 2015
A code to calculate the anisotropic elastic properties in a silicon or germanium crystal is intro... more A code to calculate the anisotropic elastic properties in a silicon or germanium crystal is introduced. The program, named AniCryDe, allows the user to select the crystallographic configuration of interest. For the selected crystallographic orientation, AniCryDe calculates several key mechanical parameters, such as Young's modulus, Poisson's ratio and the shear modulus. Furthermore, the program displays both the compliance and the stiffness tensors concerning the crystallographic orientation of interest. The code enables the user to set several parameters through a user-friendly control stage. As a result, the user obtains the complete displacement field of a deformed crystal and the curvature of any crystallographic plane. Manufacturing wafer defects such as miscut and misflat angle are also taken into account.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2015
a b s t r a c t X-and c-ray detection is currently a hot topic for a wide scientific community, s... more a b s t r a c t X-and c-ray detection is currently a hot topic for a wide scientific community, spanning from astrophysics to nuclear medicine. However, lack of optics capable of focusing photons of energies in the energy range 0.1-1 MeV leaves the photon detection to a direct-view approach, resulting in a limited efficiency and resolution. The main scope of the INFN-LOGOS project is the development of technologies that enable manufacturing highly performing optical elements to be employed in the realization of hard X-ray lenses. Such lenses, typically named Laue lenses, consist of an ensemble of crystals disposed in concentric rings in order to diffract the incident radiation towards the focus of the lens, where a detector is placed. In particular, the INFN-LOGOS project aims at the realization of intrinsically bent silicon and germanium crystals exploiting the quasi-mosaic effect for focusing hard X-rays. Crystal manufacturing relies on a proper revisitation of techniques typically employed in silicon micromachining, such as thin film deposition and patterning or ion implantation.
ABSTRACT Crystals with curved diffraction planes (CDPC) are an emerging technology in X-ray optic... more ABSTRACT Crystals with curved diffraction planes (CDPC) are an emerging technology in X-ray optics. CDPC allow manipulating the trajectories of high-energy photons with efficiency near the unity in a broad energy range. An elective application of CDPC is the construction of hard X-ray lenses. Up to now, the impossibility to focalize hard X-rays left the observation of the sky in this energy range to direct-view instruments, featuring low sensitivity and resolution. In fact, only the spectra of few and strongest sources is known above 70 keV. Mosaic crystals have already been implemented for the construction of focusing optics, but they show low reproducibility in the fabrication, and diffraction efficiency is physically limited to 50% at most. The theory of diffraction in curved crystals was developed in the past half century in the frame of the dynamical theory of diffraction, with particular contribution by C. Malgrange If the curvature is quite strong, is possible to find a simple expression to quantitatively determine the fraction of diffracted photons. To date, it exists no analytical theory that quantitatively calculates the diffraction efficiency for crystals of low curvature. Indeed, the applications of CDPC sometimes requires a curvature radius in this range. For this reason, we developed a model, which is able to produce realistic previsions of the diffraction efficiency of a thick crystal in Laue geometry for any curvature radius. The model agrees with the results of the dynamical theory when this latter is applicable. It also leads to the same results of the flat crystal case when the curvature radius is very large, and gives a realistic and quantitative description of diffraction efficiency when these two cases are not applicable.
Journal of Applied Crystallography, 2015
The grooving technique was employed for manufacturing a self-standing curved Ge crystal. The crys... more The grooving technique was employed for manufacturing a self-standing curved Ge crystal. The crystal focuses hard X-rays with high efficiency by diffraction in Laue geometry through asymmetric bent planes. The sample was tested at the Institut Laue-Langevin (Grenoble, France), undergoing two types of characterization. A monochromatic and low-divergence -ray beam was used to test the curvature of asymmetric planes, showing a diffraction performance better than for any mosaic crystal under equal conditions. Then, the focusing capability of the crystal was probed through a polychromatic and fine-focus hard X-ray beam. Asymmetric (220) planes were chosen for analysis because of the impossibility of obtaining a curvature along this family of planes via any symmetric configuration in focusing crystals. A method for calculating the curvatures induced in any family of lattice planes is also presented.
Experimental Astronomy, 2014
311) curved planes can be exploited for efficiently focus hard Xrays. With this purpose, a self-s... more 311) curved planes can be exploited for efficiently focus hard Xrays. With this purpose, a self-standing bent crystal was manufactured at the Sensor and Semiconductor Laboratory of Ferrara (Italy). The crystal was designed as an optical component for a X-ray concentrator such as a Laue lens. The curvature of (311) planes was obtained through the quasi-mosaic effect. The diffraction efficiency of the sample was tested at the Institut Laue Langevin of Grenoble (France) by using a collimated monochromatic X-ray beam. This was the first prove of the diffraction properties of (311) quasimosaic planes. Diffraction efficiency resulted 35% with a 182 keV X-ray beam, in agreement with the theoretical expectation. It corresponded to a reflectivity of 33%. While the chosen orientation is not the most performing lying of planes, it can be used, in addition to smaller-index planes, in order to raise the total effective area of a Laue lens. To quantify it, a Laue lens based on quasi-mosaic silicon and germanium crystals, exploiting (111), (422) and (311) diffracting planes, was achieved and simulated with the LaueGen code.
Journal of Applied Crystallography, 2015
A Laue lens is an ensemble of crystals capable of focusing, through diffraction in transmission g... more A Laue lens is an ensemble of crystals capable of focusing, through diffraction in transmission geometry, a fraction of the photons emitted by an X-or -ray source onto a small area of a detector. The present study facilitates a thorough understanding of the effect of each system parameter on the efficiency, the resolution and the field of view of the lens. In this way, the structure and the size of the crystals can be set to achieve a compact lens capable of providing a highresolution image of the radioactivity distribution lying inside a restricted region of a patient's body. As an application, a Laue lens optimized at 140.5 keV, theline emitted by 99m Tc, has been designed. The lens is composed of ten rings of Ge crystals with curved diffracting planes and focuses the photons onto a detector 50 cm apart from the source with 1.16 Â 10 À5 efficiency and 0.2 mm resolution. The combination of these two important figures of merit makes the proposed device better performing than pinhole single photon emission computed tomography, which is the technique employed for top-resolution images in nuclear medicine. Finally, the imaging capability of the designed lens has been tested through simulations performed with a custom-made Monte Carlo code. research papers J. Appl. Cryst. (2015). 48, 125-137 Gianfranco Paternò et al. A Laue lens for nuclear medicine 127 research papers J. Appl. Cryst. (2015). 48, 125-137 Gianfranco Paternò et al. A Laue lens for nuclear medicine 133
Optics for EUV, X-Ray, and Gamma-Ray Astronomy VI, 2013
We will describe the LAUE project, supported by the Italian Space Agency, whose aim is to demonst... more We will describe the LAUE project, supported by the Italian Space Agency, whose aim is to demonstrate the capability to build a focusing optics in the hard X-/soft gamma-ray domain (80-600 keV). To show the lens feasibility, the assembling of a Laue lens petal prototype with 20 m focal length is ongoing. Indeed, a feasibility study, within the LAUE project, has demonstrated that a Laue lens made of petals is feasible. Our goal is a lens in the 80-600 keV energy band. In addition to a detailed description of the new LARIX facility, in which the lens is being assembled, we will report the results of the project obtained so far.
Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray, 2012
ABSTRACT A stacking of plate-like curved crystals is proposed as an optical element for realizati... more ABSTRACT A stacking of plate-like curved crystals is proposed as an optical element for realization of a highly efficient Laue lens in astrophysics. Si mono-crystal plates have been bent by surface grooving and positioned one over the other to form a stack. Reciprocal alignment of the curved diffracting planes in the stack has been investigated by hard x-ray diffractometry using a polychromatic and divergent beam. The stack exhibited a single and well-defined focal spot under x-ray diffraction, highlighting that the plates are sufficiently aligned to behave as they were a single crystal. The curvature of the plates in the stack is self-standing and can be highly controlled by adjusting the experimental parameters of grooving. Thanks to the stacking, it would be possible to realize optical elements with arbitrarily large size. This achievement opens up important implications toward the realization of satellite-borne experiments in astrophysics or instruments for nuclear medicine with superior resolution. Surface grooving is easy, cheap, highly reproducible and has been established for Si and Ge, highlighting very high diffraction efficiency over a broad range of energies up to 700 keV, peaking 95% at 150 keV for Si.
Optics for EUV, X-Ray, and Gamma-Ray Astronomy VI, 2013
ABSTRACT Quasi-mosaicity is a mechanical property driven by anisotropy in diamond-like structure ... more ABSTRACT Quasi-mosaicity is a mechanical property driven by anisotropy in diamond-like structure crystals such as Si and Ge. QM crystals were recently proposed as optical components of a Laue lens for focusing hard X-rays (with energy larger than 70 keV). In contrast to a Laue lens based on conventional crystals (e.g. mosaic crystals), usage of QM crystals allows focusing the incident beam in a spot smaller than the dimension of the diffracting crystal. Focusing of photons in a small spot would allow an unprecedented resolution and sensitivity, together with a wide-passband response. In astrophysics, a Laue lens implementing QM crystals should allow observations of cosmic phenomena producing X-ray emissions with high sensitivity. As another, a Laue lens would be useful for imaging in nuclear medicine, leading to a lower radioactive dose imparted to the patient because of no need for tomography scanning. Quasi-mosaicity was also used for bending Si crystals in order to steer high-energy particles via coherent effects in crystals, viz. planar channeling and volume reflection. Channeled or reflected light particles are also useful as sources of gamma ray beams with intense flux, which can be either monochromatic or polychromatic.
Optics for EUV, X-Ray, and Gamma-Ray Astronomy VI, 2013
Experimental Astronomy, 2014
We report the results obtained from the characterisation of bent Silicon, Germanium and Gallium A... more We report the results obtained from the characterisation of bent Silicon, Germanium and Gallium Arsenide crystals, which are being used for focusing photons in the 90-300 keV energy range, in the framework of the LAUE project. Such crystals represent the best choice for building Laue lenses thanks to their high reflectivity and to the narrow Point Spread Function (PSF) they can provide. The test aims to select the best material, to optimize the thickness and to estimate the curvature radius of the crystal tiles that will be used for building a 20 m focal length Laue lens petal.
Uploads
Papers by Valerio Bellucci