Basic Considerations on the Overlap Detectors of the ATLAS ALFA system

We discuss the motivation and possible implementation of Overlap Detectors for the relative alignment of the two halves of the ATLAS Roman Pot detectors. We propose a system design and a set of prototype detectors for a proof of principle in a test beam experiment

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

Stable Branched Electron Flow

The pattern of branched electron flow revealed by scanning gate microscopy shows the distribution of ballistic electron trajectories. The details of the pattern are determined by the correlated potential of remote dopants with an amplitude far below the Fermi energy. We find that the pattern persists even if the electron density is significantly reduced such that the change in Fermi energy exceeds the background potential amplitude. The branch pattern is robust against changes in charge carrier density, but not against changes in the background potential caused by additional illumination of the sample.Comment: Accepted for publication in New Journal of Physic

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

Design, Construction and Metrology of the Overlap Detectors for the ALFA system

The Overlap Detectors of the ALFA syste

Detecting Determinacy in Prolog Programs: 22nd International Conference, ICLP 2006, Seattle, WA, USA, August 17-20, 2006. Proceedings

In program development it is useful to know that a call to a Prolog program will not inadvertently leave a choice-point on the stack. Determinacy inference has been proposed for solving this problem yet the analysis was found to be wanting in that it could not infer determinacy conditions for programs that contained cuts or applied certain tests to select a clause. This paper shows how to remedy these serious deficiencies. It also addresses the problem of identifying those predicates which can be rewritten in a more deterministic fashion. To this end, a radically new form of determinacy inference is introduced, which is founded on ideas in ccp, that is capable of reasoning about the way bindings imposed by a rightmost goal can make a leftmost goal deterministic

Определение оператора поворота вектора в квадриплексном пространстве

Рассмотрен один метод определения оператора поворота вектора в квадриплексном пространстве до совмещения с направлением, заданным другим вектором. Метод базируется на изоморфизме квадриплексных и бикомплексных чисел.Розглянуто один метод визначення оператора повороту вектора в квадриплексному просторі до суміщення з напрямком, який задано іншим вектором. Метод базується на ізоморфізмові квадриплексних та бікомплексних чисел.A method of determination of an operator of vector rotational displacement in quadruplex space before overlapping with a direction given by other vectors is considered. The method is founded on the isomorphism of quadruplex and bicomplex numbers

Effect of inorganic fillers on the light transmission through traditional or flowable resin-matrix composites for restorative dentistry

Objectives: The aim of this in vitro study was to evaluate the light transmission through five different resin-matrix composites regarding the inorganic filler content. Methods: Resin-matrix composite disc-shaped specimens were prepared on glass molds. Three traditional resin-matrix composites contained inorganic fillers at 74, 80, and 89 wt. % while two flowable composites revealed 60 and 62.5 wt. % inorganic fillers. Light transmission through the resin-matrix composites was assessed using a spectrophotometer with an integrated monochromator before and after light curing for 10, 20, or 40s. Elastic modulus and nanohardness were evaluated through nanoindentation’s tests, while Vicker’s hardness was measured by micro-hardness assessment. Chemical analyses were performed by FTIR and EDS, while microstructural analysis was conducted by optical microscopy and scanning electron microscopy. Data were evaluated using two-way ANOVA and Tukey’s test (p < 0.05). Results: After polymerization, optical transmittance increased for all specimens above 650-nm wavelength irradiation since higher light exposure time leads to increased light transmittance. At 20- or 40-s irradiation, similar light transmittance was recorded for resin composites with 60, 62, 74, or 78–80 wt. % inorganic fillers. The lowest light transmittance was recorded for a resin-matrix composite reinforced with 89 wt. % inorganic fillers. Thus, the size of inorganic fillers ranged from nano- up to micro-scale dimensions and the high content of micro-scale inorganic particles can change the light pathway and decrease the light transmittance through the materials. At 850-nm wavelength, the average ratio between polymerized and non-polymerized specimens increased by 1.6 times for the resin composite with 89 wt. % fillers, while the composites with 60 wt. % fillers revealed an increased ratio by 3.5 times higher than that recorded at 600-nm wavelength. High mean values of elastic modulus, nano-hardness, and micro-hardness were recorded for the resin-matrix composites with the highest inorganic content. Conclusions: A high content of inorganic fillers at 89 wt.% decreased the light transmission through resin-matrix composites. However, certain types of fillers do not interfere on the light transmission, maintaining an optimal polymerization and the physical properties of the resin-matrix composites. Clinical significance: The type and content of inorganic fillers in the chemical composition of resin-matrix composites do affect their polymerization mode. As a consequence, the clinical performance of resin-matrix composites can be compromised, leading to variable physical properties and degradation. Graphical Abstract: [Figure not available: see fulltext.].info:eu-repo/semantics/publishedVersio

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