142 research outputs found
Structural studies of argon-sputtered amorphous carbon films by means of extended x-ray-absorption fine structure
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Fast pixelated quantum-well-based sensor for multi-wavelength photon detection
No full textIn order to cover a wide range of experimental applications, the opportunity to use InGaAs/InAlAs quantum well (QW) devices as fast pixelated photon detectors has been investigated. QW structures are planar objects in which electrons are confined in one dimension. Devices with several combinations of barrier and well materials can be fabricated by using compound semiconductors; in the case of InGaAs/InAlAs QWs this allows to tune the energy band gap down to 0.6 eV. Thanks to their direct, low-energy gap such devices operated at room temperature may be used as detectors for photon energies ranging from visible to hard X-ray. Internal charge amplification mechanism can be applied for very low signal levels, while the high carrier mobility allows the design of very fast photon detectors with sub-nanosecond response times. QW devices grown with molecular beam epitaxy have been pixelated by using standard photolithographic techniques. In order to fit commercially available readout chips, a pixelated sensor with pixel size of 172 × 172 μm2 is currently under development. A small-scale version of the pixelated QW sensor has been preliminarily tested with synchrotron radiation, conventional X-rays and UV laser light. The reported results indicate that these devices show fair charge sharing in the clearances between the pixels and feature very short response times to 100-fs-wide laser pulse
Fast, multi-band photon detectors based on quantum well devices for beam-monitoring in new generation light sources
No full textIn order to monitor the photon-beam position for both diagnostics and calibration purposes, we have investigated the possibility to use InGaAs/InAlAs
Quantum Well (QW) devices as position-sensitive photon detectors for Free-Electron Laser (FEL) or Synchrotron Radiation (SR).
Owing to their direct, low-energy band gap and high electron mobility, such QW devices may be used also at Room Temperature (RT) as fast multi-band sensors for photons ranging from visible light to hard X-rays. Moreover, internal charge-amplification mechanism can be applied for very low signal levels, while the high carrier mobility allows the design of very fast photon detectors with sub-nanosecond response times. Segmented QW sensors have been preliminary tested with 100-fs-wide 400 nm laser pulses and X-ray SR. The reported results indicate that these devices respond with 100 ps rise-times to such ultra-fast laser pulses. Besides, linear scan on the back-pixelated device has shown that these detectors are sensitive to the position of each ultrashort beam bunch
Cultural landscape – active protection by valuation
No full textOchrona krajobrazu kulturowego miast, których społeczność stanowi społeczeństwo informacyjne powinna być rozpatrywana w sposób odmienny niż miało to miejsce jeszcze kilkanaście lat temu. Priorytetowym zadaniem stało się uświadamianie społeczeństwu wartości tego krajobrazu przez udostępnianie informacji na ten temat przy zastosowaniu nowoczesnych metod komunikacji. Dla opinii publicznej łatwiej zrozumiałe jest przełożenie wartości krajobrazu kulturowego na czynniki wymierne np. finansowe, niż dyskusje teoretyczne. W tym celu zastosowano metodę prof. Bogdanowskiego jako podstawę do opracowania teorii systemu komputerowego łączącego w sobie elementy planowania i administracji krajobrazem z danymi socjologicznymi i finansowymi. Metoda JARK-WAK umożliwia pracę w różnych skalach miasta i skorelowaniu jednostek różnych poziomów planowania w jeden system. Może on stanowić narzędzie programowego zarządzania i ochrony krajobrazów kulturowych.Protection of the cultural landscapes of cities where the community is information society should be considered in a different way than it was several years ago. The priority task is to raise public awareness of this landscape by providing information using modern communication methods. More effective communication tool than the problem discussions about the value of the cultural landscape is to indicate on the basis of financial data that it actually is. For this purpose, the method of prof. Bogdanowski was chosen as the platform for computer program development. Program made on basis of JARK-WAK analisys could combine elements of the planning and administration of the landscape with sociological and financial data. This method could work in different scales of the city and correlate units of different levels of planning in a single system. It can be a tool for program management and protection of cultural landscapes
Fast Synchrotron and FEL Beam Monitors Based on Single Crystal Diamond Detectors and InGaAs/InAlAs Quantum-Well Devices
No full textSimultaneous photon-beam position and intensity monitoring is becoming of increasing importance for new-generation synchrotron-radiation (SR) sources and free-electron lasers (FEL). Thus, novel concepts of beam diagnostics are required in order to keep such beams under control.
From this perspective diamond is a promising material for the production of semitransparent in situ photon-beam monitors which can withstand the high dose rates occurring in such radiation facilities. Here, we report on the development of freestanding, single-crystal chemical-vapor-deposited diamond detectors with segmented electrodes.
Due to their direct, low-energy band gap, InGaAs quantum-well (QW) devices operated at room temperature may be used as fast detectors for photons ranging from visible to X-ray. These features are valuable in low-energy and time-resolved FEL applications. In particular, a novel segmented InGaAs/InAlAs device has been developed and will be discussed.
Dedicated measurements carried out on both these devices at the Elettra Synchrotron show their capability to monitor the position and the intensity of the photon beam with bunch-by-bunch temporal performances. Furthermore, preliminary tests have been performed on diamond detectors at the Fermi FEL, extracting quantitative intensity and position information for 100-fs-wide FEL pulses with a photon energy of 28.8 eV
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