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Reflection is a natural phenomenon that occurs when light passes the interface between materials with different refractive index. In many applications, such as solar cells or photodetectors, reflection is an unwanted loss process. Many ways to reduce reflection from a substrate have been investigated so far, including dielectric interference coatings, surface texturing, adiabatic index matching and scattering from plasmonic nanoparticles. Here we present an entirely new concept that suppresses the reflection of light from a silicon surface over a broad spectral range. A two-dimensional periodic array of subwavelength silicon nanocylinders designed to possess strongly substrate-coupled Mie resonances yields almost zero total reflectance over the entire spectral range from the ultraviolet to the near-infrared. This new antireflection concept relies on the strong forward scattering that occurs when a scattering structure is placed in close proximity to a high-index substrate with a high optical density of states. Minimising reflection from the interface between materials is an important goal for optical devices such as solar cells or photodetectors. Spinelli et al . show almost total loss of reflection over a broad spectral range from a silicon surface using periodic arrays of sub-wavelength silicon nanocylinders.

Pulsars are rapidly spinning, highly magnetized neutron stars, created in the gravitational collapse of massive stars. We report the detection of pulsed giga–electron volt gamma rays from the young pulsar PSR J0540–6919 in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. This is the first gamma-ray pulsar detected in another galaxy. It has the most luminous pulsed gamma-ray emission yet observed, exceeding the Crab pulsar's by a factor of 20. PSR J0540–6919 presents an extreme test case for understanding the structure and evolution of neutron star magnetospheres.

Gamma-ray spectroscopy and gamma-ray imaging are two complementary techniques used for the localization and the identification of radioactive sources containing gamma-ray emitting radioisotopes. The radioactivity monitoring is focused on the detection of both artificial and environmental radioactive sources like Naturally Occurring Radioactive Materials (NORM). This kind of contamination becomes dangerous when the detection of the unwanted substances exhibits a concentration significantly above the environmental radioactive background radiation levels. For this purpose, we have developed, tested and shown a High Efficiency fast-Response GAmma (HERGA) detector useful for the identification of radionuclides and for gamma-ray imaging. A first version of the gamma detector prototype was composed of 16 CsI(Tl) scintillating crystals of 3x3x10 cm3 size, arranged in 4x4 matrix coupled with standard Photomultiplier tubes (PMTs). An image reconstruction of a radioactive gamma emitter source is possible using the coded mask technique, in which a 7x7 mask, made of Plastic and Tungsten tiles, is placed in front of the detector and a pattern recognition algorithm based on classical statistical methods (Kolmogorov Smirnov) is used to reconstruct the source position. The measurements carried out showed a point spread function (PSF) of a few mrad for pointlike sources. The Minimum Detectable Activity (MDA) was also determined in the case of pointlike radioactive sources. In this contribution we will present an update of the HERGA detector prototype in which Silicon Photomultipliers (SiPMs) are used in place of the PMTs. SiPMs provide similar or even better performance compared to the standard PMT sand provide benefits in terms of lower power consumption and reduced cost and compactness. The advantages of the SiPM technology are also characterized by the robustness of the photosensor that makes the new prototype compact, portable, ideal for in-situ and real-time. We will show a comparison between the results obtained with the newest SiPM read-out technology with respect to those obtained with the PMT one, in terms of energy and spatial resolution. The imaging performance is also in phase of testing in order to localize extended radioactive sources such as for example NORM samples or to detect inaccessible or hidden nuclear waste.

In order to prevent seismic damage on building heritage built before Seismic Standards, constructions require to be assess to verify the structural response in the case of multi-level intensity seismic actions. This problem especially concerns those buildings with a social function as schools, hospitals, etc., or with historical and architectural value as that designed by important builders of the past. This is the case of the bar-restaurant building of \"Bellariva\" Sport Centre, designed and built in Florence by the World-famous Italian engineer Pier Luigi Nervi in the Sixty years. Its structure is characterized by reinforced concrete frames and hosts the locker rooms of the swimming pool and a bar on the first floor, a restaurant on the second, where a long crack was observed. The presence of a large balcony with heavy perimeter planters near the cracked zone motivated the execution of on-site tests finalized to determine the steel bars connecting the restaurant floor to the balcony. A Ground Penetrating Radar survey was performed in order to determine the internal structure of the floor, dimensions and disposition of steel bars, and to gather information about the connections between perimeter beams and balcony at the level of the restaurant. The experimental campaign allowed to refine a computational Finite Element Model that was utilized for the performance analysis of the structure in the current state. The paper presents the main results of a preliminary seismic analysis carried out on the structure, on the basis of which some retrofit intervention are suggested.

Naturally occurring radioactive materials (NORM) and technologically enhanced naturally occurring radioactive materials (TENORM) consists of materials enriched with radioactive elements, found in the environment, with concentrations over the ambient natural radioactivity average, such as industrial wastes and extraction byproducts. We designed a camera for gamma-ray imaging and radionuclide identification based on the coded mask technique. The camera proposed is a compact, lightweight instrument, ideal for real-time analysis, with a low power consumption, suitable for industrial process and ambient monitoring. We built a prototype consisting in 16 CsI(Tl) scintillators coupled to photo-multiplier tubes (PMTs) with a digital readout. We used a 7 × 7 mask composed by transparent and opaque tiles to encode radioactive gamma-rays sources image and use a reconstruction algorithm for decoding. The system was first tested using free gamma-ray radioactive sources placed at a fixed distance from the mask and than, the same sources, was placed inside an industrial nuclear waste drum to test shielding and detection limit. We will also show the results with a NORM igneous rock sample and we will try to identify the radioactive sources after a estimation of the count rate over the background, the test was carried out in lead chamber to shield the natural laboratory background. The performance of the prototype camera in terms of energy and spatial resolution with respect the detection time will be shown.

Studying of hadron production in forward direction at the LHC energy has a great interest both for understanding of the fundamental QCD processes and also in applied areas such as the description of ultra-high energy cosmic particle interactions. The energies of secondary hadrons in such studies almost reach the maximum energy available at the LHC of ~6 TeV, which corresponds to a Lorentz γ-factor up to 104 and above. The only effective technique able to identify particles in this range is based on the transition radiation detectors (TRD). Prototypes of such kind of detector were built and tested at the CERN SPS accelerator. Some experimental results obtained in these tests are briefly presented here and compared with Monte Carlo (MC) simulations. MC model demonstrates a good agreement with the experiment. On this basis a concept of a full-scale TRD optimized for the hadron identification in the TeV energy region is proposed. Different particle identification techniques were considered and examined. The expected detector performance to reconstruct secondary hadrons produced in forward direction at the LHC is presented.

New developments of pixel detectors based on GaAs sensors offer effective registration of the transition radiation (TR) X-rays and perform simultaneous measurements of their energies and emission angles. This unique feature opens new possibilities for particle identification on the basis of maximum available information about generated TR photons. Results of studies of TR energy-angular distributions using a 500 |j.m thick GaAs sensor attached to a Timepix3 chip are presented. Measurements, analysis techniques and a comparison with Monte Carlo (MC) simulations are described and discussed.

Many modern and future accelerator and cosmic ray experiments require identification of particles with Lorentz γ-factor up to 104 and above. The only technique which reaches this range of Lorentz factors is based on the transition radiation detectors (TRD). This paper describes the development of a TRD based on straw proportional tubes. A prototype of such kind of detector was built and tested at the CERN SPS accelerator. Monte Carlo simulation model of the detector which matches well the experimental data was developed. This program was used for the simulation of a full-scale TRD for hadron identification at TeV energy scale.

We plan to develop an advanced Transition Radiation Detector (TRD) for hadron identification in the TeV momentum range, based on the simultaneous measurement of the energies and of the emission angles of the Transition Radiation (TR) X-rays with respect to the radiating particles. To study the feasibility of this project, we have carried out a beam test campaign at the CERN SPS facility with 20 GeV/c electrons and muons up to 300 GeV/c. To detect the TR X-rays and the radiating particles, we used a 300 μm thick double-sided silicon strip detector, with a strip readout pitch of 50 μm. A 2 m long helium pipe was placed between the radiators and the detector, in order to ensure adequate separation between the TR X-rays and the radiating particle on the detector plane and to limit the X-ray absorption before the detector. We measured the double-differential (in energy and angle) spectra of the TR emitted by several radiators. The results are in good agreement with the predictions obtained from the TR theory.

In recent years, developments of gaseous detectors based on a combination of electron multiplication gap in the gas and pixel readout chips as a part of the anode plane (GasPixel detectors) reached a level where they can offer unique opportunities for particle detection. Transition radiation (TR) detectors based on this technology can be one of the possible applications. In this work, measurements of energy spectra and angular distributions of transition radiation photons produced by particles with different gamma factors made with a GridPix detector prototype are presented. The observed results are compared with theoretical predictions.