The X-HPD: Conceptual Study of a Large Spherical Hybrid Photodetector

We present the results of a conceptual study demonstrating the feasibility of a large spherical hybrid photodetector with central anode. A prototype tube with 208 mm diameter and an anode in form of a metallic cube has been fabricated. In the final version of the so-called X-HPD concept the anode will be a scintillator cube with plated faces and a small photodetector to read out the bottom. The bialkali photocathode covers three quarters of the sphere surface. Combined use of this cathode in transmissive and reflective mode leads to effective quantum efficiency values exceeding those obtained in conventional hemispherical PMT designs. Further features of the concept are a photoelectron collection efficiency approaching 100% and a photon amplification in the scintillator crystal leading to a distinct single photoelectron signal. Using a custom built electron accelerator based on a CsI transmissive photocathode, LSO and YAP block crystals in geometries adapted to the anode of an X-HPD have been tested with single photoelectrons in the 10-30 keV energy range. The scintillation light was read out with a conventional PMT or a Si-PM. More than 30 photoelectrons per incident electron could be detected with the PMT

The X-HPD: Development of a large spherical hybrid photodetector

The X-HPD concept is a modern implementation of the Dumand and Lake Baikal approach to large area photon detectors, primarily aimed at water based Cherenkov detectors. Our prototype detector consists of an almost spherical vacuum tube of 8-inch diameter with a semi-transparent bialkali photocathode and a LYSO scintillation crystal mounted in the centre of the tube. The scintillation light produced after the impact of a photoelectron which was accelerated to about 20-30 keV energy is detected by a small standard PMT. In addition to the attractive characteristics already established with its historic predecessors, namely high gain, large collection efficiency and immunity to the earth magnetic field, the X-HPD concept leads to very high effective Q.E. values, an extended viewing angle and marginal transit time spread.We present recent results obtained with a prototype tube built at CERN and a second full tube under preparation in collaboration with the company Photonis

The X-HPD -Conceptual Study of a Large Spherical Hybrid Photodetector

Abstract We present the results of a conceptual study demonstrating the feasibility of a large spherical hybrid photodetector with central anode. A prototype tube with 208 mm diameter and an anode in form of a metallic cube has been fabricated. In the final version of the so-called X-HPD concept the anode will be a scintillator cube with plated faces and a small photodetector to read out the bottom. The bialkali photocathode covers three quarters of the sphere surface. Combined use of this cathode in transmissive and reflective mode leads to effective quantum efficiency values exceeding those obtained in conventional hemispherical PMT designs. Further features of the concept are a photoelectron collection efficiency approaching 100% and a photon amplification in the scintillator crystal leading to a distinct single photoelectron signal. Using a custom built electron accelerator based on a CsI transmissive photocathode, LSO and YAP block crystals in geometries adapted to the anode of an X-HPD have been tested with single photoelectrons in the 10-30 keV energy range. The scintillation light was read out with a conventional PMT or a Si-PM. More than 30 photoelectrons per incident electron could be detected with the PMT

Impact of radon and thoron levels on technosphere objects in the total urban environment

Thoron and radon exhalation from earth's crust is the most important source of atmospheric radioactive gases, along with its daughter products present in the soil is one of the major contributors to the external gamma dose in the atmosphere, since its distribution in the earth's crust is important for controlling the production of 220Rn and 222Rn. In this study trace amount of 232Th, 238U permeate almost all soils and rocks, in part due to the influence of buildings from which radioactive gas can emanate over geological time scales. Results obtained from this study indicate that the region has background radioactivity levels within the natural limits and a detailed discussion of the results is presented in the work

A low budget detector for high energy cosmic ray experiments

Contemporary projects such as AUGER in Argentina or HESS in Namibia are rather expensive experiments. We have constructed a simple detector arrangernent based on the water Cherenkov technique to be used for the detection of high-energy particles in cosmic ray experiments either as stand-alone experiment or as addition to other set-ups. A first prototype has been taken into successful operation. The construction of this detector is the starting point for extended studies in future cosmic ray experiments. The detector can be expanded by adding more and more modules at a very low price

Clinical and echocardiographic predictors of embolism in infective endocarditis: systematic review and meta-analysis

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Supercontinuum-based Fourier transform infrared spectromicroscopy

International audienceFourier-transform infrared (FTIR) spectromicroscopy combines the spatial resolution of optical microscopy with the spectral selectivity of vibrational spectroscopy. Synchrotron sources can provide diffraction-limited beams in the infrared, and therefore synchrotron-based FTIR spectromicroscopy is nowadays an indispensable tool for biology and materials science studies where high spatial resolution is required. However, the increasing need for accurate and highly spatially resolved characterization is calling for alternative laboratory-based sources to complement synchrotron radiation. To date, the low brightness of thermal emitters or high temporal coherence and narrow bandwidth or tunability of laser sources have hindered the progress of bench-top FTIR spectromicroscopy. Here, we demonstrate that fiber-based supercontinuum sources in the mid-infrared enable fast spectral mapping of localized material properties with close to diffraction-limited resolution (3  μm×3  μm) and pave the way to table-top, on-demand, fast, and highly spatially resolved studies. We illustrate these capabilities by imaging thin sections of human liver samples and compare the results and performance with those obtained using a synchrotron source

Determinants of left atrial volume index in patients with aortic stenosis: A multicentre pilot study [Facteurs déterminants du volume indexé de l'oreillette gauche chez les patients porteurs d'un rétrécissement aortique: étude pilote multicentrique]

International audienceBackground Left atrial (LA) enlargement is frequent in patients with aortic stenosis (AS), yet its determinants and prognostic implications are poorly understood. Aims To identify the echocardiographic variables associated with increased LA volume index (LAVI), and test the prognostic value of LAVI in AS. Methods We prospectively included 715 patients with AS in sinus rhythm at enrolment. Echocardiography was performed at baseline. Median follow-up was 22.0 (9–34) months. Patients were divided into two groups according to the best cut-off for event prediction during follow-up (45 mL/m2). Results Compared with LAVI andlt; 45 mL/m2, patients with LAVI ≥ 45 mL/m2 had a lower stroke volume, cardiac output and left ventricular (LV) ejection fraction, greater LV volumes and mass and higher filling pressures. By linear regression, LAVI was best correlated with E wave mitral velocity (r = 0.34), E/A ratio (r = 0.34), E/e’ ratio (r = 0.28), indexed LV mass (r = 0.29), systolic pulmonary artery pressure (r = 0.34) and LV longitudinal strain (r = –0.28). Multivariable analysis confirmed the independent association of LAVI with age (P andlt; 0.001), indexed aortic valve area (P = 0.04), indexed LV mass (P andlt; 0.001), LV ejection fraction (P = 0.007), LV end-diastolic volume (P = 0.001), E/A ratio (P andlt; 0.001) and E/e’ ratio (P andlt; 0.001). LAVI ≥ 45 mL/m2 was independently predictive of the combined endpoint of cardiovascular death or hospitalization for heart failure (adjusted hazard ratio 1.69, 95% confidence interval 1.04–2.73). Conclusion LA enlargement is correlated with AS severity, but also with variables reflecting LV systolic and diastolic dysfunction. Further studies are needed to investigate the outcome implication of LA enlargement in patients with AS. © 2017 Elsevier Masson SA