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Photoluminescence of nitrogen-vacancy and silicon-vacancy color centers in phosphorus-doped diamond at room and higher temperatures
No full textPhosphorus-doped diamond is relevant for applications in sensing,optoelectronics and quantum photonics, since the unique optical properties of color centers in diamond can be combined with the n-type conductivity attained by the
inclusion of phosphorus. Here, we investigate the photoluminescence signal of the nitrogen-vacancy and silicon-vacancy color centers in phosphorus-doped diamond as a function of temperature starting from ambient conditions up to about 100◦ Celsius, focusing on the zero-phonon line (ZPL). We find that the wavelength and width
of the ZPL of the two color centers exhibit a comparable dependence on temperature, despite the strong difference in the photoluminescence spectra. Moreover, the temperature sensitivity of the ZPL of the silicon-vacancy center is not significantly affected by phosphorus-doping, as we infer by comparison with silicon-vacancy centers in optical-grade single-crystal diamond
Measurement of multipole phases in optics and electron microscopy by means of conformal transformations
No full textConformal mappings have been recently rediscovered as a practical solution to measure physical quantities in an efficient manner by implementing a unitary transformation on structured wavefields. For instance, one of the most
known is the log-pol mapping, enabling the measurement of orbital angular momentum of optical and electron vortices. We report our latest research on a new family of conformal mappings, the circular-sector transformations, applied to wavefunctions endowed with multipole phases, showing disruptive applications in optics and matter-waves physics, in particular electron microscopy. The results suggest an innovative and promising method to measure astigmatisms and electric/magnetic dipoles in a fast and direct way
Quantitative material characterization based on the spectral decomposition of X-ray tomographic images
No full textA single-energy CT provides a map of gray levels simply related to X-rays linear attenuation coefficients, which could be very similar for different materials at a given energy. Images acquired at multiple energies allows for a quantitative description of an object. In this work, phantom images were acquired using synchrotron radiation CT at precisely defined energies. A successful attempt was made to differentiate the phantom materials with respect to their decomposition into basis materials
On the use of Laser-Induced Fluorescence for biological agent detection
No full textThe uncontrolled spread of biological agents, such as bacteria and viruses, could be hazardous for human health. Despite the interest in detecting their presence, the common methods are usually impracticable, since the diagnosis methods are time-consuming, could be invasive or require a lot of consumables which make the cost unsustainable. A good candidate to perform biological agent
detection is the Laser-Induced Fluorescence (LIF) spectroscopy since the emitted spectra are characteristic of the chemical composition of the agent. For this study,
some tests with this technique on some biological agents have been performed and the classification and detection performances have been evaluate
Segmented hyperpure germanium detector
No full textThe segmentation process of high purity germanium detectors
(HPGe) is here described. A photolithography technique is used to obtain a segmented gamma detector. The photolithography is applied on a planar square detector where the junction/contact region is covered with a gold thin film. Small segmented detectors are characterized to verify the quality of the photolithography process. Optical and scanning microscopy measures (SEM) are used to analyse the quality of the segmentation and to improve the photolithography process parameters. Finally, the leakage current of the diode and the passivation resistance between
electrodes are studied and discusse
“And nothing else exists to constitute the Universe”: Augusto Righi and the ultimate physical reality at the dawn of the 20th Century
No full textOn 12 April 1907, the well-known physicist Augusto Righi gave a lecture-demonstration for the opening of the Institute of Physics of the University of Bologna and engaged the audience with the notion of “electrical constitution of matter”. The paper reconstructs Righi’s explanation and shows how the subject stimulated interesting philosophical debates at the dawn of the Centur
Researcher for one day: An Astrophysics Masterclass
No full textIn the last years the importance in providing the students, and people in general, with a more realistic view on the scientific research world is becoming more and more evident. In this framework many initiatives are beeing carried out to
put students closer to scientists. The Astrophysics Masterclass, held in our Department, is an example of such activities, consisting in a one-day outreach event during
which high school students experience the research methods in the astrophysics field. In this paper we describe this activity, which allows the participants to work on real
research data in a real research cente
Presentation and development of a Physics experiment devised for didactic learning: The Lambert-Beer-Bouguer law
No full textThe Lambert-Beer-Bouguer law refers to the decay of the intensity of a radiation travelling through a dissipative medium. Due to the simple phenomenology and to the easiness of the realization of an experimental apparatus for its verification and measure, such law represents, from a didactic point of view, a powerful tool to illustrate the basic features of the exponential decay behaviour to undergraduate students. This paper describes how such purpose can be reached by employing simple equipment and very accessible formalism
Clusters morphology by Zernike polynomials
No full textThe study of the morphology of multiwavelength images of galaxy clusters is largely used to infer their dynamical state. We presented a novel approach of morphological analysis based on modelling clusters images with Zernike polynomials (ZPs). We used mock maps of the thermal component of the Sunyaev-Zel’dovich (tSZ) effect generated for synthetic clusters in THE THREE HUNDRED project, in the redshift range 0 ≤ z ≤ 1.03. Each tSZ map was modelled with several ZPs, in order to recover morphological features that could be related to different dynamical
states. We concluded that morphological differences can be quantified by defining an indicator that includes the contribution of the different ZPs to the fit of the tSZ
maps. The feasibility of this new method is prone to the angular resolution of the maps. Our results were also correlated with common morphological parameters and
dynamical state indicators applied on the same clusters sample
High resolution geophysical surveys to characterise Norba archaeological site (Norma, Central Italy)
Get PDFThe site of Norba is located in the Latium Region, about 90 km S of Rome, Italy. The city is one of the best example of urban town planning, with a regular layout dating back to antiquity. Over the years, many studies and archaeological excavations have brought to light important remains of several buildings, which are still very well preserved. To enhance the knowledge of the unexcavated portions of the archaeological site and to locate the position of the unknown and hypothesized buried structures, extensive geophysical surveys employing the Ground Penetrating Radar (GPR) and Gradiometric methods were planned and conducted between 2017 and 2018. For the measurements, a GPR system SIR3000 (GSSI), equipped with a 400 MHz bistatic antenna with constant offset, was used to survey 27 different sectors close to few excavated areas. Taking into account the environmental conditions of the site and the nature of the buried structures, some areas were surveyed with a spacing interval between parallel profiles of 0.25 m while other areas were investigated with a spatial interval between closed parallel profiles of 0.50 m. Furthermore, fluxgate differential magnetic (Gradiometric) surveys were carried out using the geoscan FM256 in two areas, overlapping the GPR areas. In order to have a better understanding of the subsurface, methods of qualitative and quantitative integration of the results have been employed: maps overlays and RGB color composites (graphical integration), binary data analysis and cluster analysis (discrete data integration), and data sum, data product and principal component analysis (continuous data integration). The results obtained from the geophysical surveys were interpreted together with the archaeologists to define the meaning of the structures identified and to enhance the knowledge of the ancient town's layout and mapping