Ilaria Neri

Proposal for a Laue lens with quasi-mosaic crystalline tiles

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. It is highlighted that crystals bent by the quasi-mosaic effect allow very high resolution focusing with respect to mosaic crystals. Under the same conditions for energy passband, crystal size and flux of incident photons, a Laue lens based on quasi-mosaic crystals would increase the signal-to-noise ratio by about an order of magnitude compared to the same lens with mosaic crystals. Moreover, no mosaic defocusing occurs for quasi-mosaic crystals.

Self-standing quasi-mosaic crystals for focusing hard X-rays

A quasi mosaic bent crystal for high-resolution diffraction of X and γ rays has been realized. A net curvature was imprinted to the crystal thanks to a series of superficial grooves to keep the curvature without external devices. The crystal highlights very high diffraction efficiency due to quasi mosaic curvature. Quasi mosaic crystals of this kind are proposed for the realization of a high-resolution focusing Laue lens for hard X-rays.

Ordered stacking of crystals with adjustable curvatures for hard X- and γ-ray broadband focusing

A stack of plate-like curved crystals is proposed as an optical element for X- and γ-ray focusing. Si mono-crystal plates have been bent by surface grooving and positioned one over the other to form a stack. The relative alignment of the curved diffracting planes in the stack has been tested by hard X-ray diffractometry using a polychromatic and divergent beam. The stack exhibited a single and well defined spot under X-ray diffraction, highlighting that the plates are sufficiently aligned to behave as a single crystal. The curvature of the plates in the stack can be precisely set by tightly controlling the experimental parameters of grooving. Once set, the curvature is self-standing, i.e. it is maintained without any need for an external bender. Thanks to the stacking, it would be possible to realize optical elements with arbitrarily large size. This achievement has important implications for the realization of satellite-borne experiments in astrophysics and instruments for nuclear medicine with superior resolution.

Quasi-mosaic crystals for high-resolution focusing of hard x-rays through a Laue lens

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.

NaNet-10: A 10GbE network interface card for the GPU-based low-level trigger of the NA62 RICH detector

A GPU-based low level (L0) trigger is currently integrated in the experimental setup of the RICH detector of the NA62 experiment to assess the feasibility of building more refined physics-related trigger primitives and thus improve the trigger discriminating power. To ensure the real-time operation of the system, a dedicated data transport mechanism has been implemented: an FPGA-based Network Interface Card (NaNet-10) receives data from detectors and forwards them with low, predictable latency to the memory of the GPU performing the trigger algorithms. Results of the ring-shaped hit patterns reconstruction will be reported and discussed.

Calculation of diffraction efficiency for curved crystals with arbitrary curvature radius

A model is proposed to calculate the diffraction efficiency of X-rays in Laue geometry for curved crystals with an arbitrary value of the curvature radius. The model generalizes the results based on the dynamical theory of diffraction, which are valid only for crystals with a radius of curvature lower than the critical curvature. The model is proposed for any kind of crystal, and its efficiency tends to one-half in the limit of a thick flat crystal. On the basis of this model, it was possible to reconsider the results of recently observed diffraction efficiency for curved crystals. Finally, the model sets an upper limit for diffraction efficiency of low-curvature curved crystals, this latter being useful in applications such as the construction of a hard X-ray Laue lens.

Fabrication of quasi-mosaic Ge crystals for the LAUE project

A series of quasi-mosaic curved crystals has been fabricated for the Laue project to build up a prototype of a Laue lens. Curvature has been imparted to the samples thanks to the grooving method, which makes it possible to realize self-standing curved plates. Samples are 10 × 30 × 2 mm3 Ge crystals characterized by two curvatures of different crystallographic planes. The primary curvature allows the focalization of the diffracted X-rays on a focal spot smaller than the crystal dimension. The secondary curvature, i.e. quasi-mosaic curvature, amplifies the diffraction efficiency by more than one order of magnitude with respect to an equivalent crystal without quasi-mosaic curvature.

Bent crystals by surface grooving method for high-efficiency concentration of hard x-ray photons by a Laue lens

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.

Quasi-mosaicity as a tool for focusing hard x-rays

Quasi-mosaicity can be used to fabricate self-standing curved crystals with two curvatures of different crystalline planes. Indeed, a primary curvature imparted to a crystal results in quasi-mosaic curvature of a different plane direction. We show that, since the size of the focal spot of the photons diffracted by a crystal can be controlled by the quasi-mosaic curvature, quasi-mosaic crystals allow focusing with very high resolution. A Laue lens, exploiting quasi-mosaic effect, has been simulated and main results are shown. Self-standing quasi-mosaic crystals can be fabricated through several techniques, such as film deposition or surface grooving method.

Level Zero Trigger processor for the ultra rare kaon decay experiment—NA62

In the NA62 experiment at CERN-SPS the communication between detectors and the Lowest Level (L0) trigger processor is performed via Ethernet packets, using the UDP protocol. The L0 Trigger Processor handles the signals from sub-detectors that take part to the trigger generation. In order to choose the best solution for its realization, two different approaches have been implemented. The first approach is fully based on a FPGA device while the second one joins an off-the-shelf PC to the FPGA. The performance of the two systems will be discussed and compared.The main purpose of the NA62 experiment is to measure the branching ratio of the (ultra) rare decay