9,948 research outputs found
Primary proton spectrum between 200 TeV and 1000 TeV observed with the Tibet burst detector and air shower array
Since 1996, a hybrid experiment consisting of the emulsion chamber and burst
detector array and the Tibet-II air-shower array has been operated at
Yangbajing (4300 m above sea level, 606 g/cm^2) in Tibet. This experiment can
detect air-shower cores, called as burst events, accompanied by air showers in
excess of about 100 TeV. We observed about 4300 burst events accompanied by air
showers during 690 days of operation and selected 820 proton-induced events
with its primary energy above 200 TeV using a neural network method. Using this
data set, we obtained the energy spectrum of primary protons in the energy
range from 200 to 1000 TeV. The differential energy spectrum obtained in this
energy region can be fitted by a power law with the index of -2.97 0.06,
which is steeper than that obtained by direct measurements at lower energies.
We also obtained the energy spectrum of helium nuclei at particle energies
around 1000 TeV.Comment: 25 pages, 22 figures, Accepted for publication in Phys. Rev.
A Monte Carlo simulation of the Sudbury Neutrino Observatory proportional counters
The third phase of the Sudbury Neutrino Observatory (SNO) experiment added an
array of 3He proportional counters to the detector. The purpose of this Neutral
Current Detection (NCD) array was to observe neutrons resulting from
neutral-current solar neutrino-deuteron interactions. We have developed a
detailed simulation of the current pulses from the NCD array proportional
counters, from the primary neutron capture on 3He through the NCD array
signal-processing electronics. This NCD array Monte Carlo simulation was used
to model the alpha-decay background in SNO's third-phase 8B solar-neutrino
measurement.Comment: 38 pages; submitted to the New Journal of Physic
Air Shower Measurements with the LOPES Radio Antenna Array
LOPES is set up at the location of the KASCADE-Grande extensive air shower
experiment in Karlsruhe, Germany and aims to measure and investigate radio
pulses from Extensive Air Showers. Since radio waves suffer very little
attenuation, radio measurements allow the detection of very distant or highly
inclined showers. These waves can be recorded day and night, and provide a
bolometric measure of the leptonic shower component. LOPES is designed as a
digital radio interferometer using high bandwidths and fast data processing and
profits from the reconstructed air shower observables of KASCADE-Grande. The
LOPES antennas are absolutely amplitude calibrated allowing to reconstruct the
electric field strength which can be compared with predictions from detailed
Monte Carlo simulations. We report about the analysis of correlations present
in the radio signals measured by the LOPES 30 antenna array. Additionally,
LOPES operates antennas of a different type (LOPES-STAR) which are optimized
for an application at the Pierre Auger Observatory. Status, recent results of
the data analysis and further perspectives of LOPES and the possible large
scale application of this new detection technique are discussed.Comment: 8 pages, 10 figures, Contribution to the Arena 2008 conference, Rome,
June 200
OAM multiple transmission using uniform circular arrays: numerical modeling and experimental verification with two digital television signals
In this work we present the outcomes of a radio-frequency OAM transmission
between two antenna arrays performed in a real-world context. The analysis is
supplemented by deep simulative investigations able to provide both a
preliminary overview of the experimental scenario and a posteriori validation
of the achieved results. As a first step, the far-field OAM communication link
is tested at various frequencies and the corresponding link budget is studied
by means of an angular scan generated by the rotation of the receiving system.
Then, on the same site, two digital television signals encoded as OAM modes
(=1 and =-1) are simultaneously transmitted at a common frequency
of 198.5 MHz with good mode insulation.Comment: 16 pages, 14 figure
The Panchromatic High-Resolution Spectroscopic Survey of Local Group Star Clusters - I. General Data Reduction Procedures for the VLT/X-shooter UVB and VIS arm
Our dataset contains spectroscopic observations of 29 globular clusters in
the Magellanic Clouds and the Milky Way performed with VLT/X-shooter. Here we
present detailed data reduction procedures for the VLT/X-shooter UVB and VIS
arm. These are not restricted to our particular dataset, but are generally
applicable to different kinds of X-shooter data without major limitation on the
astronomical object of interest. ESO's X-shooter pipeline (v1.5.0) performs
well and reliably for the wavelength calibration and the associated
rectification procedure, yet we find several weaknesses in the reduction
cascade that are addressed with additional calibration steps, such as bad pixel
interpolation, flat fielding, and slit illumination corrections. Furthermore,
the instrumental PSF is analytically modeled and used to reconstruct flux
losses at slit transit and for optimally extracting point sources. Regular
observations of spectrophotometric standard stars allow us to detect
instrumental variability, which needs to be understood if a reliable absolute
flux calibration is desired. A cascade of additional custom calibration steps
is presented that allows for an absolute flux calibration uncertainty of less
than ten percent under virtually every observational setup provided that the
signal-to-noise ratio is sufficiently high. The optimal extraction increases
the signal-to-noise ratio typically by a factor of 1.5, while simultaneously
correcting for resulting flux losses. The wavelength calibration is found to be
accurate to an uncertainty level of approximately 0.02 Angstrom. We find that
most of the X-shooter systematics can be reliably modeled and corrected for.
This offers the possibility of comparing observations on different nights and
with different telescope pointings and instrumental setups, thereby
facilitating a robust statistical analysis of large datasets.Comment: 22 pages, 18 figures, Accepted for publication in Astronomy &
Astrophysics; V2 contains a minor change in the abstract. We note that we did
not test X-shooter pipeline versions 2.0 or later. V3 contains an updated
referenc
Single Event Effects in the Pixel readout chip for BTeV
In future experiments the readout electronics for pixel detectors is required
to be resistant to a very high radiation level. In this paper we report on
irradiation tests performed on several preFPIX2 prototype pixel readout chips
for the BTeV experiment exposed to a 200 MeV proton beam. The prototype chips
have been implemented in commercial 0.25 um CMOS processes following radiation
tolerant design rules. The results show that this ASIC design tolerates a large
total radiation dose, and that radiation induced Single Event Effects occur at
a manageable level.Comment: 15 pages, 6 Postscript figure
High-speed surface profilometry based on an adaptive microscope with axial chromatic encoding
An adaptive microscope with axial chromatic encoding is designed and developed, namely the AdaScope. With the ability to confocally address any locations within the measurement volume, the AdaScope provides the hardware foundation for a cascade measurement strategy to be developed, dramatically accelerating the speed of 3D confocal microscopy
The spectrum features of UHECRs below and surrounding GZK
The energy spectrum of UHECRs is discussed on the basis of the Yakutsk array
database analysis. In the region E=0.1 to 30 EeV the showers are detected under
trigger-500, while at energies above 30 EeV the whole acceptance area for
trigger-1000 is used in order to utilize all the data available in the region
of GZK cutoff.Comment: Invited talk at CRIS2004: GZK and surroundings, Catania, Italy,
31.05.04. To appear in Nucl. Phys. B Proc. Supp
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