90 research outputs found
Proton and Helium Spectra from the CREAM-III Flight
Primary cosmic-ray elemental spectra have been measured with the
balloon-borne Cosmic Ray Energetics And Mass (CREAM) experiment since 2004. The
third CREAM payload (CREAM-III) flew for 29 days during the 2007-2008 Antarctic
season. Energies of incident particles above 1 TeV are measured with a
calorimeter. Individual elements are clearly separated with a charge resolution
of ~0.12 e (in charge units) and ~0.14 e for protons and helium nuclei,
respectively, using two layers of silicon charge detectors. The measured proton
and helium energy spectra at the top of the atmosphere are harder than other
existing measurements at a few tens of GeV. The relative abundance of protons
to helium nuclei is 9.53+-0.03 for the range of 1 TeV/n to 63 TeV/n. The ratio
is considerably smaller than other measurements at a few tens of GeV/n. The
spectra become softer above ~20 TeV. However, our statistical uncertainties are
large at these energies and more data are needed
Measurement of the cosmic-ray antiproton spectrum in the range 0.12 to 0.4 GeV with BESS-Polar II
The energy spectra of cosmic-ray antiprotons and protons near solar minimum were precisely measured with BESS-Polar II (Balloon-borne Experiment with a Superconducting Spectrometer) during a long-duration flight over Antarctica in December 2007 and January 2008. The upper-TOF (UTOF) and lower-TOF (LTOF) scintillator hodoscopes measure the charge and velocity of incident particles. A thin plastic scintillator middle-TOF (MTOF) hodoscope is installed on the lower surface of the magnet bore to measure low-energy particles that cannot reach the LTOF. The MTOF further lowers the threshold energy to about 120 MeV for antiproton or proton measurements. We report absolute spectra of the cosmic-ray antiproton in the range 0.12 to 0.4 GeV and the antiproton/proton ratio calculated with UTOF-MTOF trigger events. These new results are independent of the UTOF-LTOF triggered antiproton spectrum published in 2012 and proton spectrum published in 2016
MEASUREMENTS OF COSMIC-RAY PROTON AND HELIUM SPECTRA FROM THE BESS-POLAR LONG-DURATION BALLOON FLIGHTS OVER ANTARCTICA
The BESS-Polar Collaboration measured the energy spectra of cosmic-ray protons and helium during two long-duration balloon flights over Antarctica in 2004 December and 2007 December at substantially different levels of solar modulation. Proton and helium spectra probe the origin and propagation history of cosmic rays in the galaxy, and are essential to calculations of the expected spectra of cosmic-ray antiprotons, positrons, and electrons from interactions of primary cosmic-ray nuclei with the interstellar gas, and to calculations of atmospheric muons and neutrinos. We report absolute spectra at the top of the atmosphere for cosmic-ray protons in the kinetic energy range 0.2–160 GeV and helium nuclei in the range 0.15–80 GeV/nucleon. The corresponding magnetic-rigidity ranges are 0.6–160 GV for protons and 1.1–160 GV for helium. These spectra are compared to measurements from previous BESS flights and from ATIC-2, PAMELA, and AMS-02. We also report the ratio of the proton and helium fluxes from 1.1 to 160 GV and compare this to the ratios from PAMELA and AMS-02
Time Variations of Cosmic-Ray Helium Isotopes with BESS-Polar I
The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) is configured with a solenoidal superconducting magnet and a suite of precision particle detectors, including time-of-flight hodoscopes based on plastic scintillators, a silica-aerogel Cherenkov detector, and a high resolution tracking system with a central jet-type drift chamber. The charges of incident particles are determined from energy losses in the scintillators. Their magnetic rigidities (momentum/charge) are measured by reconstructing each particle trajectory in the magnetic field, and their velocities are obtained by using the time-of-flight system. Together, these measurements can accurately identify helium isotopes among the incoming cosmic-ray helium nuclei up to energies in the GeV per nucleon region. The BESS-Polar I instrument flew for 8.5 days over Antarctica from December 13th to December 21st, 2004. Its long-duration flight and large geometric acceptance allow the time variations of isotopic fluxes to be studied for the first time. The time variations of helium isotope fluxes are presented here for rigidities from 1.2 to 2.5 GV and results are compared to previously reported proton data and neutron monitor data
Acoustic and optical variations during rapid downward motion episodes in the deep north-western Mediterranean Sea
An Acoustic Doppler Current Profiler (ADCP) was moored at the deep-sea site
of the ANTARES neutrino telescope near Toulon, France, thus providing a unique
opportunity to compare high-resolution acoustic and optical observations
between 70 and 170 m above the sea bed at 2475 m. The ADCP measured downward
vertical currents of magnitudes up to 0.03 m s-1 in late winter and early
spring 2006. In the same period, observations were made of enhanced levels of
acoustic reflection, interpreted as suspended particles including zooplankton,
by a factor of about 10 and of horizontal currents reaching 0.35 m s-1. These
observations coincided with high light levels detected by the telescope,
interpreted as increased bioluminescence. During winter 2006 deep dense-water
formation occurred in the Ligurian subbasin, thus providing a possible
explanation for these observations. However, the 10-20 days quasi-periodic
episodes of high levels of acoustic reflection, light and large vertical
currents continuing into the summer are not direct evidence of this process. It
is hypothesized that the main process allowing for suspended material to be
moved vertically later in the year is local advection, linked with topographic
boundary current instabilities along the rim of the 'Northern Current'.Comment: 30 pages, 7 figure
Status and Recent Results of the Acoustic Neutrino Detection Test System AMADEUS
The AMADEUS system is an integral part of the ANTARES neutrino telescope in
the Mediterranean Sea. The project aims at the investigation of techniques for
acoustic neutrino detection in the deep sea. Installed at a depth of more than
2000m, the acoustic sensors of AMADEUS are based on piezo-ceramics elements for
the broad-band recording of signals with frequencies ranging up to 125kHz.
AMADEUS was completed in May 2008 and comprises six "acoustic clusters", each
one holding six acoustic sensors that are arranged at distances of roughly 1m
from each other. The clusters are installed with inter-spacings ranging from
15m to 340m. Acoustic data are continuously acquired and processed at a
computer cluster where online filter algorithms are applied to select a
high-purity sample of neutrino-like signals. 1.6 TB of data were recorded in
2008 and 3.2 TB in 2009. In order to assess the background of neutrino-like
signals in the deep sea, the characteristics of ambient noise and transient
signals have been investigated. In this article, the AMADEUS system will be
described and recent results will be presented.Comment: 7 pages, 8 figures. Proceedings of ARENA 2010, the 4th International
Workshop on Acoustic and Radio EeV Neutrino Detection Activitie
Time calibration of the ANTARES neutrino telescope
The ANTARES deep-sea neutrino telescope comprises a three-dimensional array of photomultipliers to detect the Cherenkov light induced by upgoing relativistic charged particles originating from neutrino interactions in the vicinity of the detector. The large scattering length of light in the deep sea facilitates an angular resolution of a few tenths of a degree for neutrino energies exceeding 10 TeV. In order to achieve this optimal performance, the time calibration procedures should ensure a relative time calibration between the photomultipliers at the level of similar to 1 ns. The methods developed to attain this level of precision are described
Performance of the front-end electronics of the ANTARES neutrino telescope
ANTARES is a high-energy neutrino telescope installed in the Mediterranean
Sea at a depth of 2475 m. It consists of a three-dimensional array of optical
modules, each containing a large photomultiplier tube. A total of 2700
front-end ASICs named Analogue Ring Samplers (ARS) process the phototube
signals, measure their arrival time, amplitude and shape as well as perform
monitoring and calibration tasks. The ARS chip processes the analogue signals
from the optical modules and converts information into digital data. All the
information is transmitted to shore through further multiplexing electronics
and an optical link. This paper describes the performance of the ARS chip;
results from the functionality and characterization tests in the laboratory are
summarized and the long-term performance in the apparatus is illustrated.Comment: 20 pages, 22 figures, published in Nuclear Instruments and Methods
Search for a diffuse flux of high-energy with the ANTARES neutrino telescope
A search for a diffuse flux of astrophysical muon neutrinos, using data
collected by the ANTARES neutrino telescope is presented. A
sr sky was monitored for a total of 334 days of equivalent live time. The
searched signal corresponds to an excess of events, produced by astrophysical
sources, over the expected atmospheric neutrino background. The observed number
of events is found compatible with the background expectation. Assuming an
flux spectrum, a 90% c.l. upper limit on the diffuse flux of
E^2\Phi_{90%} = 5.3 \times 10^{-8} \ \mathrm{GeV\ cm^{-2}\ s^{-1}\ sr^{-1}}
in the energy range 20 TeV - 2.5 PeV is obtained. Other signal models with
different energy spectra are also tested and some rejected.Comment: 14 pages, 6 figure
Precision Measurement of the Boron to Carbon Flux Ratio in Cosmic Rays from 1.9 GV to 2.6 TV with the Alpha Magnetic Spectrometer on the International Space Station
Knowledge of the rigidity dependence of the boron to carbon flux ratio (B/C) is important in understanding the propagation of cosmic rays. The precise measurement of the B/C ratio from 1.9 GV to 2.6 TV, based on 2.3 million boron and 8.3 million carbon nuclei collected by AMS during the first 5 years of operation, is presented. The detailed variation with rigidity of the B/C spectral index is reported for the first time. The B/C ratio does not show any significant structures in contrast to many cosmic ray models that require such structures at high rigidities. Remarkably, above 65 GV, the B/C ratio is well described by a single power law R[superscript Δ] with index Δ=-0.333±0.014(fit)±0.005(syst), in good agreement with the Kolmogorov theory of turbulence which predicts Δ=-1/3 asymptotically.National Science Foundation (U.S.) (Grants 1455202 and 1551980)Wyle Research (Firm) (Grant 2014/T72497)United States. National Aeronautics and Space Administration (NASA Earth and Space Science Fellowship Grant HELIO15F-0005
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