Search results for "Array"
showing 10 items of 1264 documents
Observation of high energy atmospheric neutrinos with the Antarctic muon and neutrino detector array
2002
The Antarctic Muon and Neutrino Detector Array (AMANDA) began collecting data with ten strings in 1997. Results from the first year of operation are presented. Neutrinos coming through the Earth from the Northern Hemisphere are identified by secondary muons moving upward through the array. Cosmic rays in the atmosphere generate a background of downward moving muons, which are about 10^6 times more abundant than the upward moving muons. Over 130 days of exposure, we observed a total of about 300 neutrino events. In the same period, a background of 1.05*10^9 cosmic ray muon events was recorded. The observed neutrino flux is consistent with atmospheric neutrino predictions. Monte Carlo simulat…
Spatial coherence properties of a multiple aperture system an analysis based on the Walsh functions
1997
Analysis of the spatial coherence of the light transmitted by an optical device composed of a periodical array of identical apertures is developed by employing an approach based on the properties of the binary Walsh functions. The successive interactions between each aperture, and the mutual intensity characterizing the coherence state of the transmitted light, can be adequately explained through the behaviour of the Walsh-Hadamard spectrum associated with the intensity distribution resulting from the far-field propagated light at the output of the aperture array.
Wisps in the Galactic center: Near-infrared triggered observations of the radio source Sgr A* at 43 GHz
2016
Context. The compact radio and near-infrared (NIR) source Sagittarius A* (Sgr A*) associated with the supermassive black hole in the Galactic center was observed at 7 mm in the context of a NIR triggered global Very Long Baseline Array (VLBA) campaign. Aims. Sgr A* shows variable flux densities ranging from radio through X-rays. These variations sometimes appear in spontaneous outbursts that are referred to as flares. Multi-frequency observations of Sgr A* provide access to easily observable parameters that can test the currently accepted models that try to explain these intensity outbursts. Methods. On May 16-18, 2012 Sgr A* has been observed with the VLBA at 7 mm (43 GHz) for 6 hours each…
Variable delay line for phased-array antenna based on a chirped fiber grating
2000
We present a theoretical and experimental analysis of the performance of phased-array antennas steered by a single chirped fiber grating. Two approaches consisting of conventional and single-sideband (SSB) modulation techniques of the optical signal are presented in order to compare their performance and suitability for beamforming applications in microwave antennas. By using a 40-cm-long chirped grating, we measure the phase and amplitude response and calculate the corresponding radiation patterns to demonstrate wide-band operation and continuous spatial scanning properties of both configurations. SSB modulation Is presented as a real alternative to the first one offering broader operation…
Electrical control of a laterally ordered InAs/InP quantum dash array
2009
5 páginas, 5 figuras.
Effect of the electromagnetic environment on arrays of small normal metal tunnel junctions: Numerical and experimental investigation
2000
We present results of a set of experiments to investigate the effect of dissipative external electromagnetic environment on tunneling in linear arrays of junctions in the weak tunneling regime. The influence of this resistance decreases as the number of junctions in the chain increases and ultimately becomes negligible. Further, there is a value of external impedance, typically \~5 k$\Omega$, at which the half-width of the zero-voltage dip in the conductance curve shows a maximum. Some new analytical formulae, based on the phase-correlation theory, along with numerical results will be presented.
VLBI imaging of M81* at 43GHz
2011
The nearby spiral galaxy M81 harbors in its core a Low-Luminosity AGN (LLAGN), and appears closely related to the more distant and powerful AGNs seen in quasars and radio galaxies. The intrinsic size of this object is unknown due to scattering, and it has shown a core-jet morphology with weak extended emission rotating with wavelength. The proximity of M\,81 (D=3.63 Mpc) allows a detailed investigation of its nucleus to be made. The nucleus is four orders of magnitude more luminous than the Galactic centre, and is therefore considered a link between SgrA* and the more powerful nuclei of radio galaxies and quasars. Our main goal was to determine the size of M81* at a shorter wavelength thus …
A 16 channel high resolution (<11 ps RMS) Time-to-Digital Converter in a Field Programmable Gate Array
2012
A 16-channel Time-to-Digital Converter (TDC) was implemented in a general purpose Field-Programmable Gate Array (FPGA). The fine time calculations are achieved by using the dedicated carry-chain lines. The coarse counter defines the coarse time stamp. In order to overcome the negative effects of temperature and power supply dependency bin-by-bin calibration is applied. The time interval measurements are done using 2 channels. The time resolution of channels are calculated for 1 clock cycle and a minimum of 10.3 ps RMS on two channels, yielding 7.3 ps RMS (10.3 ps/√2) on a single channel is achieved.
Optimal filtering algorithm implementation in FPGAs for the ATLAS TileCal Read-Out drivers
2011
TileCal is the hadronic calorimeter of the ATLAS experiment in the LHC (CERN). Its Read-Out Drivers (RODs) process, in real time, the digitized information coming from the front-end electronics and send it to the Read-Out System. Data processing in the ROD boards is performed in Processing Unit Mezzanine Cards that use commercial DSPs to run the Optimal Filtering (OF) algorithms.
Level Scheme of 102In first observed
2019
Neutron deficient nuclei close to 100Sn have been investigated in-beam by particle and γ -ray spectroscopic methods using the NORDBALL detector array following the bombartment of a 54Fe target with a beam of 270 MeV 58Ni. Protons and α particles were identified with a 4 π ΔE -type Si-multidetector and neutrons with a 1π liquid-scintillator-detectorassembly placed in the forward derection. Excited states of 102 In were identified for the first time. The level scheme constructed from γ - γ -particle-coincidence and γ angular correlations is discussed and compared to the structure of neighboring nuclei in the framework of the nuclear shell model.