Isotopes In Galactic Cosmic Rays Research Articles

Antiproton identification below threshold with the AMS-02 RICH detector**Supported by China Scholarship Council (CSC) under Grant No.201306380027.

The Alpha Magnetic Spectrometer (AMS-02), which is installed on the International Space Station (ISS), has been collecting data successfully since May 2011. The main goals of AMS-02 are the search for cosmic anti-matter, dark matter and the precise measurement of the relative abundance of elements and isotopes in galactic cosmic rays. In order to identify particle properties, AMS-02 includes several specialized sub-detectors. Among these, the AMS-02 Ring Imaging Cherenkov detector (RICH) is designed to provide a very precise measurement of the velocity and electric charge of particles. We describe a method to reject the dominant electron background in antiproton identification with the use of the AMS-02 RICH detector as a veto for rigidities below 3 GV. A ray tracing integration method is used to maximize the statistics of p̄ with the lowest possible e− background, providing 4 times rejection power gain for e− background with respect to only 3% of p̄ signal efficiency loss. By using the collected cosmic-ray data, e− contamination can be well suppressed within 3% with β ≈ 1, while keeping 76% efficiency for p̄ below the threshold.

OB Associations, Wolf–Rayet Stars, and the Origin of Galactic Cosmic Rays

We have measured the isotopic abundances of neon and a number of other species in the galactic cosmic rays (GCRs) using the Cosmic Ray Isotope Spectrometer (CRIS) aboard the ACE spacecraft. Our data are compared to recent results from two-component (Wolf–Rayet material plus solar-like mixtures) Wolf–Rayet (WR) models. The three largest deviations of galactic cosmic ray isotope ratios from solar-system ratios predicted by these models, 12C/16O, 22Ne/20Ne, and 58Fe/56Fe, are very close to those observed. All of the isotopic ratios that we have measured are consistent with a GCR source consisting of ∼20% of WR material mixed with ∼80% material with solar-system composition. Since WR stars are evolutionary products of OB stars, and most OB stars exist in OB associations that form superbubbles, the good agreement of our data with WR models suggests that OB associations within superbubbles are the likely source of at least a substantial fraction of GCRs. In previous work it has been shown that the primary 59Ni (which decays only by electron-capture) in GCRs has decayed, indicating a time interval between nucleosynthesis and acceleration of >105 y. It has been suggested that in the OB association environment, ejecta from supernovae might be accelerated by the high velocity WR winds on a time scale that is short compared to the half-life of 59Ni. Thus the 59Ni might not have time to decay and this would cast doubt upon the OB association origin of cosmic rays. In this paper we suggest a scenario that should allow much of the 59Ni to decay in the OB association environment and conclude that the hypothesis of the OB association origin of cosmic rays appears to be viable.

High performance particle detection system for trans iron isotopes in galactic cosmic rays

The isotope identification with the solid-state track detector (SSTD) newly developed for the observation of heavy cosmic ray particles was performed using 56Fe and 55Fe ions with 460 MeV/nucleon. Mass resolution for iron isotope was thus improved to ∼ 0.20 amu in rms. The high speed automatic system of microscope analyzer was also developed to scan and analyze tracks formed by heavy ions in SSTD. The combination of isotope telescope consisting of SSTD with the high speed scanning system enables us to realize a large-scaled observation for trans-iron galactic cosmic rays (GCRs).

Observations of the Li, Be, and B isotopes and constraints on cosmic-ray propagation

The abundance of Li, Be, and B isotopes in galactic cosmic rays (GCRs) between E = 50 and 200 MeV/nucleon has been observed by the Cosmic Ray Isotope Spectrometer (CRIS) on NASA’s ACE mission since 1997 with high statistical accuracy. Precise observations of Li, Be, and B can be used to constrain GCR propagation models. We find that a diffusive reacceleration model with parameters that best match CRIS results (e.g., B/C, Li/C, etc.) are also consistent with other GCR observations. A ∼15–20% overproduction of Li and Be in the model predictions is attributed to uncertainties in the production cross-section data. The latter becomes a significant limitation to the study of rare GCR species that are generated predominantly via spallation.

What are the Limits for Ace Galactic Cosmic-Ray Isotope Studies?

The CRIS experiment on ACE, with its excellent charge and mass resolution and a geometrical factor ∼10× that of any previous experiment, holds the promise of rewriting the book on galactic cosmic-ray abundance studies. Translating these measurements into precise cosmic-ray source abundances and using these measurements to determine more accurately the propagation history of cosmic rays is a different matter, however. In many important cases these studies will be limited by the accuracy of the nuclear cross- sections that determine how the cosmic-ray composition is modified as it traverses the interstellar matter. In this paper we will discuss these cross-sections and how well they are known as a function of the energy and the charge and mass of the cosmic-ray nuclei. This will then be used to discuss what new limits can be expected on several contemporary problems of interest in cosmic rays from the CRIS measurements.

Measurements of hydrogen and helium isotopes in Galactic cosmic rays from 1978 through 1984

view Abstract Citations (29) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Measurements of Hydrogen and Helium Isotopes in Galactic Cosmic Rays from 1978 through 1984 Kroeger, R. Abstract The propagation of light cosmic rays is examined using measurements of the relative abundances of the isotopes H-1, H-2 and He-3 and He-4 made with the ISEE 3 instrumentation. It is believed that cosmic ray particles experience spallation in traveling through the interstellar medium, thereby producing the isotopes examined in the present study. The isotopic ratios are therefore expected to yield data on outward migrating particles, which lose energy while moving toward extragalactic space, i.e., the 'leaky box approximation'. The energy ranges covered are 26-138 MeV/nucleon for H-1 and He-4, 24-89 MeV/nucleon for H-2 and 43-146 MeV/nucleon for He-3. Solar activity ranged from minimum to maximum over the observational period. Details of the experimental strategies, instrumentation features and calibration techniques employed with the particle detectors are provided. Histograms were geneated of the energies attributable to each particle track and mass ratios of the various isotopes were calculated over the measured energy ranges. Account was taken of errors introduced by solar modulation, and an escape path length of 5.6-7.8 g/sq cm was estimated for particle propagation through the Galaxy. The projected path length agrees with previous estimates based on data from heavier cosmic ray nuclei. Publication: The Astrophysical Journal Pub Date: April 1986 DOI: 10.1086/164130 Bibcode: 1986ApJ...303..816K Keywords: Galactic Cosmic Rays; Helium Isotopes; Hydrogen Isotopes; Abundance; Calibrating; Energy Spectra; Instrument Errors; Time Dependence; Space Radiation; COSMIC RAYS: ABUNDANCES full text sources ADS |

Isotopes in Galactic Cosmic Rays

The data on isotopic ratios of elements in Galactic Cosmic Rays (GCR) is steadily improving and has recently reached the point where some information can be extracted, which has bearing on the problem of the origin of the cosmic rays. By and large, these data have generally confirmed the similarity between solar-type matter and GCR source, when spallation effects and selective acceleration are taken into account. The silicon and iron isotopic ratios, for instance, are consistent with meteoritic ratios. For iron, this is particularly important since two or perhaps even three different nucleosynthesis mechanisms are required to account for the species 54Fe, 56Fe, 58Fe. For carbon, nitrogen and oxygen the problem is that the spallation corrections are large compared to the solar system ratios but nevertheless the present upper limits are not in contradiction with the solar system ratios.

The abundances of light isotopes in galactic cosmic rays and the interstellar gas density

The fluxes of the light isotopes in the galactic cosmic rays are calculated in the energy range from 10 MeV to 5 GeV. The mean amount of matter traversed is taken to increase with decreasing energy, and various forms of the source spectrum are assumed. It is shown that it is possible to reconcile all observed abundance ratios including the low /sup 10/Be abundance found by Garcia-Munoz et al. with an interstellar gas density of 1 atom cm/sup -1/. However, a low value for the adiabatic deceleration in the solor cavity must be assumed. Comparing isotopes of the light elements does not give a unique solution for the deceleration, and it seems to be more profitable to use the isotopes of H and He for this purpose.