Measurement of the effect of Non Ionising Energy Losses on the leakage current of Silicon Drift Detector prototypes for the LOFT satellite

The silicon drift detectors are at the basis of the instrumentation aboard the Large Observatory For x-ray Timing (LOFT) satellite mission, which underwent a three year assessment phase within the "Cosmic Vision 2015 - 2025" long-term science plan of the European Space Agency. Silicon detectors are especially sensitive to the displacement damage, produced by the non ionising energy losses of charged and neutral particles, leading to an increase of the device leakage current and thus worsening the spectral resolution. During the LOFT assessment phase, we irradiated two silicon drift detectors with a proton beam at the Proton Irradiation Facility in the accelerator of the Paul Scherrer Institute and we measured the increase in leakage current. In this paper we report the results of the irradiation and we discuss the impact of the radiation damage on the LOFT scientific performance.Comment: 21 pages, 7 figures, 2 tables. Accepted for publication by Journal of Instrumentation (JINST

Simulations of the X-ray imaging capabilities of the Silicon Drift Detectors (SDD) for the LOFT Wide Field Monitor

The Large Observatory For X-ray Timing (LOFT), selected by ESA as one of the four Cosmic Vision M3 candidate missions to undergo an assessment phase, will revolutionize the study of compact objects in our galaxy and of the brightest supermassive black holes in active galactic nuclei. The Large Area Detector (LAD), carrying an unprecedented effective area of 10 m^2, is complemented by a coded-mask Wide Field Monitor, in charge of monitoring a large fraction of the sky potentially accessible to the LAD, to provide the history and context for the sources observed by LAD and to trigger its observations on their most interesting and extreme states. In this paper we present detailed simulations of the imaging capabilities of the Silicon Drift Detectors developed for the LOFT Wide Field Monitor detection plane. The simulations explore a large parameter space for both the detector design and the environmental conditions, allowing us to optimize the detector characteristics and demonstrating the X-ray imaging performance of the large-area SDDs in the 2-50 keV energy band.Comment: Proceedings of SPIE, Vol. 8443, Paper No. 8443-210, 201

Humeral greater tuberosity osteolysis as a complication of intraosseous calcification migration: Natural history depicted by imaging

Migration of calcification within the bone leading to greater tuberosity osteolysis is a peculiar complication of the calcifying tendinitis of the rotator cuff. The case of a 38-year-old woman complaining of right shoulder pain, which had been going on for one year, is hereby described. The evolution of the infraspinatus tendon calcifying tendinitis leading to osteolysis of the greater tuberosity of the humerus is depicted by imaging and, particularly, by the MR and CT features changing over time. In this paper we focus on the importance of both MR and CT exams in the diagnostic process of the different phases of the disease. The correlation between clinical symptoms and imaging features is also helpful for imaging interpretation: the most painful phase corresponds to the migration of the calcification, whereas pain tends to decrease when the osteolysis develops. Awareness of the existence of this condition may prevent unnecessary invasive procedures. (www.actabiomedica.it)

The X-Gamma Imaging Spectrometer (XGIS) onboard THESEUS

A compact and modular X and gamma-ray imaging spectrometer (XGIS) has been designed as one of the instruments foreseen on-board the THESEUS mission proposed in response to the ESA M5 call. The experiment envisages the use of CsI scintillator bars read out at both ends by single-cell 25 mm 2 Silicon Drift Detectors. Events absorbed in the Silicon layer (lower energy X rays) and events absorbed in the scintillator crystal (higher energy X rays and Gamma-rays) are discriminated using the on-board electronics. A coded mask provides imaging capabilities at low energies, thus allowing a compact and sensitive instrument in a wide energy band (~2 keV up to ~20 MeV). The instrument design, expected performance and the characterization performed on a series of laboratory prototypes are discussed.Comment: To be published in the Proceedings of the THESEUS Workshop 2017 (http://www.isdc.unige.ch/theseus/workshop2017.html), Journal of the Italian Astronomical Society (Mem.SAIt), Editors L. Amati, E. Bozzo, M. Della Valle, D. Gotz, P. O'Brien. Details on the THESEUS mission concept can be found in the white paper Amati et al. 2017 (arXiv:171004638) and Stratta et al. 2017 (arXiv:1712.08153

GAME: Grb and All-sky Monitor Experiment

We describe the GRB and All-sky Monitor Experiment (GAME) mission submitted by a large international collaboration (Italy, Germany, Czech Repubblic, Slovenia, Brazil) in response to the 2012 ESA call for a small mission opportunity for a launch in 2017 and presently under further investigation for subsequent opportunities. The general scientific objective is to perform measurements of key importance for GRB science and to provide the wide astrophysical community of an advanced X-ray all-sky monitoring system. The proposed payload was based on silicon drift detectors (~1-50 keV), CdZnTe (CZT) detectors (~15-200 keV) and crystal scintillators in phoswich (NaI/CsI) configuration (~20 keV-20 MeV), three well established technologies, for a total weight of ~250 kg and a required power of ~240 W. Such instrumentation allows a unique, unprecedented and very powerful combination of large field of view (3-4 sr), a broad energy energy band extending from ~1 keV up to ~20 MeV, an energy resolution as good as ~300 eV in the 1-30 keV energy range, a source location accuracy of ~1 arcmin. The mission profile included a launch (e.g., by Vega) into a low Earth orbit, a baseline sky scanning mode plus pointed observations of regions of particular interest, data transmission to ground via X-band (4.8 Gb/orbit, Alcantara and Malindi ground stations), and prompt transmission of GRB / transient triggers.Comment: 13 pages, 8 figures, published in International Journal of Modern Physics

252. Prediction of subject-specific SAR distribution in MSK MR exam at 7 T

Purpose we predict SAR during MRI exam using a 7 T 1H 298 MHz eight-channel degenerate birdcage coil1 combining SAR simulations with subject-specific measured (RF) maps. Materials and Methods We simulated the coil1 in CST MW Suite, loaded by a model of human knee (Fig. 1, top). was calculated in an axial slice crossing the patella. The maximum local SAR for an Axial “Zero” Time-of-Echo (ZTE) sequence “SILENT”2 was calculated. We acquired maps of an adult (female) knee with a Bloch-Siegert sequence on 7 axial slices, centered on the same slice of the simulation, on a GE MR950 7T human system. For each slice a coefficient C, proportional to avg, was used to scale the SAR simulated3. Results Fig. 1 shows: bottom left, simulated magnitude; bottom center, local SAR for an input of 1 W per channel; bottom right, simulated magnitude for a FA = 90° (length = 3.2 ms) sinc-pulse in the slice previously chosen. Fig. 2 shows the subject-specific measured for a FA = 90° sinc-pulse. The predicted SAR obtained with scaled maps are 0.50 W/kg (global) and 3.68 W/kg (maximum). Conclusions we obtained a good agreement between simulated and measured in vivo maps, and we were able to calculate the distribution of SAR exposure, a safety MRI parameter not available in current exams, where only global SAR is provided, combining simulations and subject-specific measurements. Limits on global and local SAR (20 W/kg) were met for this sequence [1], [2], [3]

Development and tests of a new prototype detector for the XAFS beamline at Elettra Synchrotron in Trieste

The XAFS beamline at Elettra Synchrotron in Trieste combines X-ray absorption spectroscopy and X-ray diffraction to provide chemically specific structural information of materials. It operates in the energy range 2.4-27 keV by using a silicon double reflection Bragg monochromator. The fluorescence measurement is performed in place of the absorption spectroscopy when the sample transparency is too low for transmission measurements or the element to study is too diluted in the sample. We report on the development and on the preliminary tests of a new prototype detector based on Silicon Drift Detectors technology and the SIRIO ultra low noise front-end ASIC. The new system will be able to reduce drastically the time needed to perform fluorescence measurements, while keeping a short dead time and maintaining an adequate energy resolution to perform spectroscopy. The custom-made silicon sensor and the electronics are designed specifically for the beamline requirements.Comment: Proceeding of the 6YRM 12th-14th Oct 2015 - L'Aquila (Italy). Accepted for publication on Journal of Physics: Conference Serie

Accelerator experiments with soft protons and hyper-velocity dust particles: application to ongoing projects of future X-ray missions

We report on our activities, currently in progress, aimed at performing accelerator experiments with soft protons and hyper-velocity dust particles. They include tests of different types of X-ray detectors and related components (such as filters) and measurements of scattering of soft protons and hyper-velocity dust particles off X-ray mirror shells. These activities have been identified as a goal in the context of a number of ongoing space projects in order to assess the risk posed by environmental radiation and dust and qualify the adopted instrumentation with respect to possible damage or performance degradation. In this paper we focus on tests for the Silicon Drift Detectors (SDDs) used aboard the LOFT space mission. We use the Van de Graaff accelerators at the University of T\"ubingen and at the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg, for soft proton and hyper-velocity dust tests respectively. We present the experimental set-up adopted to perform the tests, status of the activities and some very preliminary results achieved at present time.Comment: Proceedings of SPIE, Vol. 8443, Paper No. 8443-24, 201

The GAPS Experiment to Search for Dark Matter using Low-energy Antimatter

The GAPS experiment is designed to carry out a sensitive dark matter search by measuring low-energy cosmic ray antideuterons and antiprotons. GAPS will provide a new avenue to access a wide range of dark matter models and masses that is complementary to direct detection techniques, collider experiments and other indirect detection techniques. Well-motivated theories beyond the Standard Model contain viable dark matter candidates which could lead to a detectable signal of antideuterons resulting from the annihilation or decay of dark matter particles. The dark matter contribution to the antideuteron flux is believed to be especially large at low energies (E < 1 GeV), where the predicted flux from conventional astrophysical sources (i.e. from secondary interactions of cosmic rays) is very low. The GAPS low-energy antiproton search will provide stringent constraints on less than 10 GeV dark matter, will provide the best limits on primordial black hole evaporation on Galactic length scales, and will explore new discovery space in cosmic ray physics. Unlike other antimatter search experiments such as BESS and AMS that use magnetic spectrometers, GAPS detects antideuterons and antiprotons using an exotic atom technique. This technique, and its unique event topology, will give GAPS a nearly background-free detection capability that is critical in a rare-event search. GAPS is designed to carry out its science program using long-duration balloon flights in Antarctica. A prototype instrument was successfully flown from Taiki, Japan in 2012. GAPS has now been approved by NASA to proceed towards the full science instrument, with the possibility of a first long-duration balloon flight in late 2020. Here we motivate low-energy cosmic ray antimatter searches and discuss the current status of the GAPS experiment and the design of the payload.Comment: 8 pags, 3 figures, Proc. 35th International Cosmic Ray Conference (ICRC 2017), Busan, Kore

Two years of flight of the Pamela experiment: results and perspectives

PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range (protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antinuclei with a precision of the order of $10^{-8}$). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, $15^{th}$ 2006 in a $350\times 600 km$ orbit with an inclination of 70 degrees. In this work we describe the scientific objectives and the performance of PAMELA in its first two years of operation. Data on protons of trapped, secondary and galactic nature - as well as measurements of the December $13^{th}$ 2006 Solar Particle Event - are also provided.Comment: To appear on J. Phys. Soc. Jpn. as part of the proceedings of the International Workshop on Advances in Cosmic Ray Science March, 17-19, 2008 Waseda University, Shinjuku, Tokyo, Japa