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. This 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.
Abstract
The Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM) experiment successfully recorded data for 539 days from 2017 August to 2019 February. We report the energy ...spectrum of cosmic-ray protons from the ISS-CREAM experiment at energies from 1.60 × 10
3
to 6.55 × 10
5
GeV. The measured spectrum deviates from a single power law. A smoothly broken power-law fit to the data, including statistical and systematic uncertainties, shows the spectral index change at 9.0 × 10
3
GeV from 2.57 ± 0.03 to 2.82 ± 0.02 with a significance of greater than 3
σ
. This bump-like structure is consistent with a spectral softening recently reported by the balloon-borne CREAM, DAMPE, and NUCLEON, but ISS-CREAM extends measurements to higher energies.
The ISS-CREAM instrument is the modified version of the Cosmic Ray Energetics And Mass (CREAM) experiment, which was flown on balloons multiple times over Antarctica and later installed on the ...International Space Station (ISS). Its primary objective is to measure the energy spectra of individual cosmic-ray elements for the charge range of Z = 1 to Z = 26, in the energy range of ∼ 1012 to ∼ 1015 eV. The instrument comprises a tungsten/scintillator calorimeter and a pixelated silicon charge detector as primary detectors to determine the energy and charge of cosmic rays. Additionally, it includes top and bottom scintillator counting detectors and a boronated scintillator detector to differentiate between electrons and hadrons for multi-TeV electron measurements. The ISS-CREAM instrument was installed on the ISS in August 2017 and operated until February 2019. This paper provides an overview of the instrument, focusing on its detectors, trigger systems, common electronics, and power systems. The paper highlights the modifications made to these components to optimize their performance for ISS operations.
The boronated scintillator detector of the ISS-CREAM experiment Amare, Y.; Anderson, T.; Angelaszek, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2019, Letnik:
943
Journal Article
Recenzirano
Odprti dostop
The Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM) instrument is a next-generation experiment for the direct detection and study of cosmic-ray nuclei and electrons. ...With a long exposure in low Earth orbit, the experiment will determine the particle fluxes and spectral details of cosmic-ray nuclei from hydrogen to iron, over an energy range of about 1012 eV to >1015 eV, and of cosmic-ray electrons over an energy range of about 5 ×1010 eV to >1013 eV. The instrument was deployed to the ISS in August 2017 on the SpaceX CRS-12 mission. We review the design, implementation and performance of one of the ISS-CREAM detector systems: a boron loaded scintillation detector used in discriminating electron-induced events from the much more abundant cosmic-ray nuclei.
The Cosmic Ray Energetics And Mass (CREAM) instrument is configured with a suite of particle detectors to measure TeV cosmic-ray elemental spectra from protons to iron nuclei over a wide energy ...range. The goal is to extend direct measurements of cosmic-ray composition to the highest energies practical, and thereby have enough overlap with ground based indirect measurements to answer questions on cosmic-ray origin, acceleration and propagation. The balloon-borne CREAM was flown successfully for about 161days in six flights over Antarctica to measure elemental spectra of Z=1–26 nuclei over the energy range 1010 to >1014eV. Transforming the balloon instrument into ISS-CREAM involves identification and replacement of components that would be at risk in the International Space Station (ISS) environment, in addition to assessing safety and mission assurance concerns. The transformation process includes rigorous testing of components to reduce risks and increase survivability on the launch vehicle and operations on the ISS without negatively impacting the heritage of the successful CREAM design. The project status, including results from the ongoing analysis of existing data and, particularly, plans to increase the exposure factor by another order of magnitude utilizing the International Space Station are presented.
Coalescence of liquid drops by surface tension Menchaca-Rocha, A; Martínez-Dávalos, A; Núñez, R ...
Physical review. E, Statistical, nonlinear, and soft matter physics,
04/2001, Letnik:
63, Številka:
4 Pt 2
Journal Article
Recenzirano
The merging of two mercury drops at very low kinetic energy is observed using fast, digital, and analog imaging techniques. Sequences showing the time evolution of the overall-surface shape as well ...as an amplified view of the contact region are shown. Qualitative and quantitative comparisons with computations of the Navier-Stokes equation with a free surface are made. In the model, the surface is tracked by a marker-chain method.
An extensive experimental survey of the features of the disassembly of a small quasiprojectile system with A{approx}36, produced in the reactions of 47 MeV/nucleon {sup 40}Ar + {sup 27}Al, {sup ...48}Ti, and {sup 58}Ni, has been carried out. Nuclei in the excitation energy range of 1-9 MeV/nucleon have been investigated employing a new method to reconstruct the quasiprojectile source. At an excitation energy {approx}5.6 MeV/nucleon many observables indicate the presence of maximal fluctuations in the deexcitation processes. These include the normalized second moments of the Campi plot and normalized variances of the distributions of order parameters such as the atomic number of the heaviest fragment Z{sub max} and the total kinetic energy. The evolution of the correlation of the atomic number of the heaviest fragment with that of the second heaviest fragment and a bimodality test are also consistent with a transition in the same excitation energy region. The related phase separation parameter, S{sub p}, shows a significant change of slope at the same excitation energy. In the same region a {delta}-scaling analysis for of the heaviest fragments exhibits a transition to {delta} = 1 scaling, which is predicted to characterize a disordered phase. The fragment topological structure shows that the rank-sorted fragments obey Zipf's law at the point of largest fluctuations, providing another indication of a liquid gas phase transition. The Fisher droplet model critical exponent {tau} {approx} 2.3 obtained from the charge distribution at the same excitation energy is close to the critical exponent of the liquid gas phase transition universality class. The caloric curve for this system shows a monotonic increase of temperature with excitation energy and no apparent plateau. The temperature at the point of maximal fluctuations is 8.3{+-}0.5 MeV. Taking this temperature as the critical temperature and employing the caloric curve information we have extracted the critical exponents {beta},{gamma}, and {sigma} from the data. Their values are also consistent with the values of the universality class of the liquid gas phase transition. Taken together, this body of evidence strongly suggests a phase change in an equilibrated mesoscopic system at, or extremely close to, the critical point.
Optimizing urban traffic control using a rational agent Ibarra-Martínez, Salvador; Castán-Rocha, José A; Laria-Menchaca, Julio
Frontiers of information technology & electronic engineering,
12/2014, Letnik:
15, Številka:
12
Journal Article
Recenzirano
This paper is devoted to developing and evaluating a set of technologies with the objective of designing a methodology for the implementation of sophisticated traffic lights by means of rational ...agents. These devices would be capable of optimizing the behavior of a junction with multiple traffic signals, reaching a higher level of autonomy without losing reliability, accuracy, or efficiency in the offered services. In particular, each rational agent in a traffic signal will be able to analyze the requirements and constraints of the road, in order to know its level of demand. With such information, the rational agent will adapt its light cycles with the view of accomplishing more fluid traffic patterns and minimizing the pollutant environmental emissions produced by vehicles while they are stopped at a red light, through using a case-based reasoning (CBR) adaptation. This paper also integrates a microscopic simulator developed to run a set of tests in order to compare the presented methodology with traditional traffic control methods. Two study cases are shown to demonstrate the efficiency of the introduced approach, increasing vehicular mobility and reducing harmful activity for the environment. For instance, in the first scenario, taking into account the studied traffic volumes, our approach increases mobility by 23% and reduces emissions by 35%. When the roads are managed by sophisticated traffic lights, a better level of service and considerable environmental benefits are achieved, demonstrating the utility of the presented approach.
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