H.E.S.S.––the high energy stereoscopic system––is a new system of large imaging atmospheric Cherenkov telescopes, with about 100 m
2 mirror area for each of four telescopes, and photomultiplier ...cameras with a large field of view (5°) and small pixels (0.16°). The dish and reflector are designed to provide good imaging properties over the full field of view, combined with mechanical stability. The paper describes the design criteria and specifications of the system, and the individual components––dish, mirrors, and Winston cones––as well as their characteristics. The optical performance of the telescope as a whole is the subject of a companion paper.
Mirror facets of the high energy stereoscopic system imaging atmospheric Cherenkov telescopes are aligned using stars imaged onto the closed lid of the photomultiplier camera, viewed by a CCD camera. ...The alignment procedure works reliably and includes the automatic analysis of CCD images and control of the facet alignment actuators. On-axis, 80% of the reflected light is contained in a circle of less than 1 mrad diameter. The spot widens with increasing angle to the telescope axis. In accordance with simulations, the spot size has roughly doubled at an angle of 1.4° from the axis. The expected variation of spot size with elevation due to deformations of the support structure is visible, but is completely non-critical over the usual working range. Overall, the optical quality of the telescope exceeds the specifications.
The H1 forward proton spectrometer at HERA van Esch, P.; Kapichine, M.; Morozov, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2000, Letnik:
446, Številka:
3
Journal Article
Recenzirano
The forward proton spectrometer is part of the H1 detector at the HERA collider. Protons with energies above 500
GeV and polar angles below 1
mrad can be detected by this spectrometer. The main ...detector components are scintillating fiber detectors read out by position-sensitive photo-multipliers. These detectors are housed in the so-called Roman Pots which allow them to be moved close to the circulating proton beam. Four Roman Pot stations are located at distances between 60 and 90
m from the interaction point.
One of the main goals of the HERA-B experiment at DESY in Hamburg, Germany, is to study the properties of B-mesons with the emphasis on CP violation. B-mesons are produced in hadronic interactions of ...a 920-GeV proton beam with an internal wire target. An effective bunch crossing rate of about 8.5 MHz leads to about 200 charged tracks per event. Therefore, a highly selective and efficient trigger system providing high suppression of background events is required. The HERA-B trigger system consists of four levels. A rate reduction factor of 200 is aimed at by the first-level trigger (FLT). The muon pretrigger system, as a part of the FLT, is a modular system consisting of about 100 large-size VME modules of three different types: the pretrigger link board (PLB), the pretrigger coincidence unit (PCU), and the pretrigger message generator (PMG). The data rate processed by the pretrigger system is about 19.5 GByte/s. The PLBs process digitized hit information in eight independent electronic channels in parallel. Every electronic channel handles 32 bits of hit information received from the front-end driver buffer system. Optical links operating at 800 Mb/s transmit the data after serialization to PCUs, which calculate coincidences using complex programmable logic devices. The PMGs transform this coincidence information into messages for the FLT processors. The concept and design as well as results of the muon pretrigger running at HERA-B are presented.
This paper describes the muon pretrigger system of the HERA-B experiment. The muon pretrigger is designed to detect track candidates for muons in order to generate seeds for the first level trigger ...(FLT) search algorithm. Muons provide the cleanest event signature in the large amount of hadronic background. In order to achieve the required precision the muon pretrigger system has to cope with an interaction rate of about 40 MHz at the HERA bunch crossing rate of 10.4 MHz. This results in a total input data rate of about 10 Gbyte/s. A total rate reduction by a factor of 200 is aimed at by the complete FLT, including the pretrigger systems (electromagnetic calorimeter, muon and high-p/sub T/), within at most 12 /spl mu/s.
The HERA-B high-p/sub T/ trigger Popov, V.; Riege, H.; Schutt, J. ...
IEEE transactions on nuclear science,
2001-Aug., 2001-8-00, Letnik:
48, Številka:
4
Journal Article
Recenzirano
The high-p/sub T/ trigger to select tracks with high transverse momenta has been developed. The concept, design criteria, and system components are described. A dedicated data processing (pretrigger ...logic) system has been developed to select and process in real time pretrigger signals out of 3/spl times/10/sup 12/ combinations per second. The operational performance of the data-processing system and other components of the trigger system are presented.
The high-p)T) trigger to select tracks with high transverse momenta has been developed. The concept, design criteria, and system components are described. A dedicated data processing (pretrigger ...logic) system has been developed to select and process in real time pretrigger signals out of 3x10(12) combinations per second. The operational performance of the data-processing system and other components of the trigger system are presented
The high-p sub(T) trigger to select tracks with high transverse momenta has been developed. The concept, design criteria, and system components are described. A dedicated data processing (pretrigger ...logic) system has been developed to select and process in real time pretrigger signals out of 310 super(12) combinations per second. The operational performance of the data-processing system and other components of the trigger system are presented
Summary This systematic literature review has shown that patients experiencing hip fracture after low-impact trauma are at considerable excess risk for death compared with nonhip fracture/community ...control populations. The increased mortality risk may persist for several years thereafter, highlighting the need for interventions to reduce this risk. Patients experiencing hip fracture after low-impact trauma are at considerable risk for subsequent osteoporotic fractures and premature death. We conducted a systematic review of the literature to identify all studies that reported unadjusted and excess mortality rates for hip fracture. Although a lack of consistent study design precluded any formal meta-analysis or pooled analysis of the data, we have shown that hip fracture is associated with excess mortality (over and above mortality rates in nonhip fracture/community control populations) during the first year after fracture ranging from 8.4% to 36%. In the identified studies, individuals experienced an increased relative risk for mortality following hip fracture that was at least double that for the age-matched control population, became less pronounced with advancing age, was higher among men than women regardless of age, was highest in the days and weeks following the index fracture, and remained elevated for months and perhaps even years following the index fracture. These observations show that patients are at increased risk for premature death for many years after a fragility-related hip fracture and highlight the need to identify those patients who are candidates for interventions to reduce their risk.
PDF
