619 research outputs found
Search for ultra-high energy photons with the Pierre Auger Observatory
No full textThe Pierre Auger Observatory has an unprecedented sensitivity to photons at energies above 10^18 eV.
Particularly the combination of ground array and fluorescence detection techniques offers a unique power to discriminate the primary particles based on different observables. Implications of photon searches extend from astrophysics to fundamental and particle physics. Current results and future prospects are reported
Renewal of DNA in Purkinje cell nuclei of the mouse cerebellum. A 9 months follow-up autoradiographic study.
No full textUse of star tracks to determine photocathode anisotropy of PMTs and absolute pointing of the Pierre Auger fluorescence detector telescopes
No full textThe fluorescence detector (FD) of the Southern Pierre Auger Observatory consists of four groups of six telescopes, concentrated in four different buildings at the periphery of the 3000 km^2 observatory site. Each telescope consists of a 3.5x3.5 m^2 mirror of 3.4-m radius, an aperture of 2.2 m diameter covered by a UV filter, a corrector ring in its periphery, and an array of PMTs, disposed as a matrix of 20 columns by 22 rows in its focal surface. The pointing accuracy should be verified regularly during the whole life of the experiment, estimated to be about 20 years.
Recording background-light tracks left by stars gives important information for this scope. In addition, the response along known
tracks of many PMTs can be mapped by averaging the signals left by the same star in different nights. During the engineering array phase of the experiment, all PMTs have been equipped with the optically-coupled current-mirror, a novel optoelectronic system
developed to perform a highly sensitive measurement of the dc or slowly varying component of the anode current, despite the
fact that the PMT is biased with cathode grounded. We proved that the FD telescopes are extremely sensitive, even to 5.4 visual
magnitude stars that could be clearly recorded despite the fact that a UV filter was present at the telescope aperture
Tracking stars with the fluorescence detector of the Pierre Auger observatory
No full textRecording tracks of stars traversing the field of view of the Auger's fluorescence detector (FD) is a powerful tool to
monitor various FD parameters. Regular control of these tracks would allow checking the telescope's stability during
the whole life of the experiment, estimated to be about 20 years. The prototypes used during the engineering array phase
have been equipped with a novel optoelectronic system that measured the DC anode current. Dim stars were clearly
recorded. We report the results of a reconstruction performed to determine the pointing of a telescope as well as
comparisons of a PMT's response to shower and star signals
Galvanically isolated and linear transmission of analog current-signals using the optically coupled current–mirror architecture
No full textWe describe a novel circuit architecture, the optically coupled current-mirror (OCCM), that allows linear transmission of analog current signals over optical fibers. The OCCM ensures Galvanic isolation between the detector where the current-signals flow, and ground. A remarkable difference compared to other methods used so far for the analog transmission of signals via optical means, is that the input stage of the OCCM, the only one that remains at the detector side, is passive; therefore, it does not require to be powered. This is the most distinctive feature of the OCCM, which opens new opportunities for the realization of multichannel analog links for particle physics experiments and other applications requiring Galvanic isolation and linear transmission with a dynamic range of at least two orders of magnitude. In addition, operation at LAr or LXe temperatures improves the loop-gain by a factor 2: The signal bandwidth, at present about 5 MHz; is expected to increase by at least the same factor by optimizing the gain-bandwidth product of the open-loop amplifier
Search for primary photons and neutrinos in the ultra-high energy cosmic rays with the Pierre Auger Observatory
No full textAlong with primary protons and nuclei most of the scenarios of the origin of cosmic rays predict fluxes of photons and neutrinos at the highest energies. Thanks to the huge collection area and the hybrid design, combining ground array and fluorescence detection techniques, the Pierre Auger Observatory is a unique tool to search for primary photons and neutrinos in ultra-high energy cosmic rays. Implications of these searches extend from astrophysics to fundamental and particle physics. Current results and future perspectives are reported
Ultrastructural cytochemistry of cis-dichlorodiammineplatinum II-induced apoptosis in immatura rat cerebellum.
No full textPremitotic DNA synthesis in the brain of the adult frog (Rana esculenta L.): An autoradiographic 3H-thymidine study
No full textInfluence of cis-dichlorodiammineplatinum on the structure of the immature rat cerebellum
No full textIntranuclear differences in the response of Purkinje cell DNA of the rat cerebellum to bleomycin. A microphotometric and autoradiographic study.
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