90 research outputs found
CaloCube: a novel calorimeter for high-energy cosmic rays in space
In order to extend the direct observation of high-energy cosmic rays up to
the PeV region, highly performing calorimeters with large geometrical
acceptance and high energy resolution are required. Within the constraint of
the total mass of the apparatus, crucial for a space mission, the calorimeters
must be optimized with respect to their geometrical acceptance, granularity and
absorption depth. CaloCube is a homogeneous calorimeter with cubic geometry, to
maximise the acceptance being sensitive to particles from every direction in
space; granularity is obtained by relying on small cubic scintillating crystals
as active elements. Different scintillating materials have been studied. The
crystal sizes and spacing among them have been optimized with respect to the
energy resolution. A prototype, based on CsI(Tl) cubic crystals, has been
constructed and tested with particle beams. Some results of tests with
different beams at CERN are presented.Comment: Seven pages, seven pictures. Proceedings of INSTR17 Novosibirs
Search for GeV Gamma-ray Counterparts of Gravitational Wave Events by CALET
We present results on searches for gamma-ray counterparts of the LIGO/Virgo
gravitational-wave events using CALorimetric Electron Telescope ({\sl CALET})
observations. The main instrument of {\sl CALET}, CALorimeter (CAL), observes
gamma-rays from GeV up to 10 TeV with a field of view of nearly 2 sr.
In addition, the {\sl CALET} gamma-ray burst monitor (CGBM) views 3 sr
and sr of the sky in the 7 keV -- 1 MeV and the 40 keV -- 20 MeV
bands, respectively, by using two different crystal scintillators. The {\sl
CALET} observations on the International Space Station started in October 2015,
and here we report analyses of events associated with the following
gravitational wave events: GW151226, GW170104, GW170608, GW170814 and GW170817.
Although only upper limits on gamma-ray emission are obtained, they correspond
to a luminosity of erg s in the GeV energy band
depending on the distance and the assumed time duration of each event, which is
approximately the order of luminosity of typical short gamma-ray bursts. This
implies there will be a favorable opportunity to detect high-energy gamma-ray
emission in further observations if additional gravitational wave events with
favorable geometry will occur within our field-of-view. We also show the
sensitivity of {\sl CALET} for gamma-ray transient events which is the order of
~erg\,cm\,s for an observation of 100~s duration.Comment: 12 pages, 8 figures, 1 table. Accepted for publication in
Astrophysical Journa
CaloCube: an innovative homogeneous calorimeter for the next-generation space experiments
The direct measurement of the cosmic-ray spectrum, up to the knee region, is one of the instrumental challenges for next generation space experiments. The main issue for these measurements is a steeply falling spectrum with increasing energy, so the physics performance of the space calorimeters are primarily determined by their geometrical acceptance and energy resolution. CaloCube is a three-year R&D project, approved and financed by INFN in 2014, aiming to optimize the design of a space-born calorimeter. The peculiarity of the design of CaloCube is its capability of detecting particles coming from any direction, and not only those on its upper surface. To ensure that the quality of the measurement does not depend on the arrival direction of the particles, the calorimeter will be designed as homogeneous and isotropic as possible. In addition, to achieve a high discrimination power for hadrons and nuclei with respect to electrons, the sensitive elements of the calorimeter need to have a fine 3-D sampling capability. In order to optimize the detector performances with respect to the total mass of the apparatus, which is the most important constraint for a space launch, a comparative study of different scintillating materials has been performed using detailed Monte Carlo simulation based on the FLUKA package. In parallel to simulation studies, a prototype consisting in 14 layers of 3 x 3 CsI(Tl) crystals per layer has been assembled and tested with particle beams. An overview of the obtained results during the first two years of the project will be presented and the future of the detector will be discussed too
CALOCUBE: An approach to high-granularity and homogenous calorimetry for space based detectors
Future space experiments dedicated to the observation of high-energy gamma and cosmic rays will increasingly rely on a highly performing calorimetry apparatus, and their physics performance will be primarily determined by the geometrical dimensions and the energy resolution of the calorimeter deployed. Thus it is extremely important to optimize its geometrical acceptance, the granularity, and its absorption depth for the measurement of the particle energy with respect to the total mass of the apparatus which is the most important constraint for a space launch. The proposed design tries to satisfy these criteria while staying within a total mass budget of about 1.6 tons. Calocube is a homogeneous calorimeter instrumented with Cesium iodide (CsI) crystals, whose geometry is cubic and isotropic, so as to detect particles arriving from every direction in space, thus maximizing the acceptance; granularity is obtained by filling the cubic volume with small cubic CsI crystals. The total radiation length in any direction is more than adequate for optimal electromagnetic particle identification and energy measurement, whilst the interaction length is at least sufficient to allow a precise reconstruction of hadronic showers. Optimal values for the size of the crystals and spacing among them have been studied. The design forms the basis of a three-year R&D activity which has been approved and financed by INFN. An overall description of the system, as well as results from preliminary tests on particle beams will be described
Predicting needlestick and sharps injuries in nursing students: Development of the SNNIP scale
Aim: To develop an instrument to investigate knowledge and predictive factors of needlestick and sharps injuries (NSIs) in nursing students during clinical placements. Design: Instrument development and cross-sectional study for psychometric testing. Methods: A self-administered instrument including demographic data, injury epidemiology and predictive factors of NSIs was developed between October 2018–January 2019. Content validity was assessed by a panel of experts. The instrument's factor structure and discriminant validity were explored using principal components analysis. The STROBE guidelines were followed. Results: Evidence of content validity was found (S-CVI 0.75; I-CVI 0.50–1.00). A three-factor structure was shown by exploratory factor analysis. Of the 238 participants, 39% had been injured at least once, of which 67.3% in the second year. Higher perceptions of “personal exposure” (4.06, SD 3.78) were reported by third-year students. Higher scores for “perceived benefits” of preventive behaviours (13.6, SD 1.46) were reported by second-year students
Direct Measurement of the Nickel Spectrum in Cosmic Rays in the Energy Range from 8.8 GeV/n to 240 GeV/n with CALET on the International Space Station
The relative abundance of cosmic ray nickel nuclei with respect to iron is by
far larger than for all other trans-iron elements, therefore it provides a
favorable opportunity for a low background measurement of its spectrum. Since
nickel, as well as iron, is one of the most stable nuclei, the nickel energy
spectrum and its relative abundance with respect to iron provide important
information to estimate the abundances at the cosmic ray source and to model
the Galactic propagation of heavy nuclei. However, only a few direct
measurements of cosmic-ray nickel at energy larger than 3 GeV/n are
available at present in the literature and they are affected by strong
limitations in both energy reach and statistics. In this paper we present a
measurement of the differential energy spectrum of nickel in the energy range
from 8.8 to 240 GeV/n, carried out with unprecedented precision by the
Calorimetric Electron Telescope (CALET) in operation on the International Space
Station since 2015. The CALET instrument can identify individual nuclear
species via a measurement of their electric charge with a dynamic range
extending far beyond iron (up to atomic number = 40). The particle's
energy is measured by a homogeneous calorimeter (1.2 proton interaction
lengths, 27 radiation lengths) preceded by a thin imaging section (3 radiation
lengths) providing tracking and energy sampling. This paper follows our
previous measurement of the iron spectrum [O. Adriani et al., Phys. Rev. Lett.
126, 241101 (2021).], and it extends our investigation on the energy dependence
of the spectral index of heavy elements. It reports the analysis of nickel data
collected from November 2015 to May 2021 and a detailed assessment of the
systematic uncertainties. In the region from 20 to 240 GeV our present
data are compatible within the errors with a single power law with spectral
index .Comment: main text: 8 pages, 4 figures; supplemental material: 8 pages, 9
figures, 1 table. arXiv admin note: text overlap with arXiv:2106.0803
Cosmic-Ray Boron Flux Measured from 8.4 GeV/n to 3.8 TeV/n with the Calorimetric Electron Telescope on the International Space Station
We present the measurement of the energy dependence of the boron flux in cosmic rays and its ratio to the carbon flux in an energy interval from 8.4 GeV/n to 3.8 TeV/n based on the data collected by the Calorimetric Electron Telescope (CALET) during ∼6.4 yr of operation on the International Space Station. An update of the energy spectrum of carbon is also presented with an increase in statistics over our previous measurement. The observed boron flux shows a spectral hardening at the same transition energy E0∼200 GeV/n of the C spectrum, though B and C fluxes have different energy dependences. The spectral index of the B spectrum is found to be γ=-3.047±0.024 in the interval 25<200 GeV/n. The B spectrum hardens by ΔγB=0.25±0.12, while the best fit value for the spectral variation of C is ΔγC=0.19±0.03. The B/C flux ratio is compatible with a hardening of 0.09±0.05, though a single power-law energy dependence cannot be ruled out given the current statistical uncertainties. A break in the B/C ratio energy dependence would support the recent AMS-02 observations that secondary cosmic rays exhibit a stronger hardening than primary ones. We also perform a fit to the B/C ratio with a leaky-box model of the cosmic-ray propagation in the Galaxy in order to probe a possible residual value λ0 of the mean escape path length λ at high energy. We find that our B/C data are compatible with a nonzero value of λ0, which can be interpreted as the column density of matter that cosmic rays cross within the acceleration region. © 2022 authors. Published by the American Physical Society
Observation of Spectral Structures in the Flux of Cosmic-Ray Protons from 50 GeV to 60 TeV with the Calorimetric Electron Telescope on the International Space Station
A precise measurement of the cosmic-ray proton spectrum with the Calorimetric Electron Telescope (CALET) is presented in the energy interval from 50 GeV to 60 TeV, and the observation of a softening of the spectrum above 10 TeV is reported. The analysis is based on the data collected during ∼6.2 years of smooth operations aboard the International Space Station and covers a broader energy range with respect to the previous proton flux measurement by CALET, with an increase of the available statistics by a factor of ∼2.2. Above a few hundred GeV we confirm our previous observation of a progressive spectral hardening with a higher significance (more than 20 sigma). In the multi-TeV region we observe a second spectral feature with a softening around 10 TeV and a spectral index change from -2.6 to -2.9 consistently, within the errors, with the shape of the spectrum reported by DAMPE. We apply a simultaneous fit of the proton differential spectrum which well reproduces the gradual change of the spectral index encompassing the lower energy power-law regime and the two spectral features observed at higher energies
Direct Measurement of the Spectral Structure of Cosmic-Ray Electrons+Positrons in the TeV Region with CALET on the International Space Station
Detailed measurements of the spectral structure of cosmic-ray electrons and
positrons from 10.6 GeV to 7.5 TeV are presented from over 7 years of
observations with the CALorimetric Electron Telescope (CALET) on the
International Space Station. Because of the excellent energy resolution (a few
percent above 10 GeV) and the outstanding e/p separation (10), CALET
provides optimal performance for a detailed search of structures in the energy
spectrum. The analysis uses data up to the end of 2022, and the statistics of
observed electron candidates has increased more than 3 times since the last
publication in 2018. By adopting an updated boosted decision tree analysis, a
sufficient proton rejection power up to 7.5 TeV is achieved, with a residual
proton contamination less than 10%. The observed energy spectrum becomes
gradually harder in the lower energy region from around 30 GeV, consistently
with AMS-02, but from 300 to 600 GeV it is considerably softer than the spectra
measured by DAMPE and Fermi-LAT. At high energies, the spectrum presents a
sharp break around 1 TeV, with a spectral index change from -3.15 to -3.91, and
a broken power law fitting the data in the energy range from 30 GeV to 4.8 TeV
better than a single power law with 6.9 sigma significance, which is compatible
with the DAMPE results. The break is consistent with the expected effects of
radiation loss during the propagation from distant sources (except the highest
energy bin). We have fitted the spectrum with a model consistent with the
positron flux measured by AMS-02 below 1 TeV and interpreted the electron +
positron spectrum with possible contributions from pulsars and nearby sources.
Above 4.8 TeV, a possible contribution from known nearby supernova remnants,
including Vela, is addressed by an event-by-event analysis providing a higher
proton-rejection power than a purely statistical analysis.Comment: main text: 7 pages, 4 figures; supplemental material: 10 pages, 8
figures, 1 tabl
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