T. Hams

Measurement of the cosmic-ray low-energy antiproton spectrum with the first BESS-Polar Antarctic flight

Abstract The BESS-Polar spectrometer had its first successful balloon flight over Antarctica in December 2004. During the 8.5-day long-duration flight, almost 0.9 billion events were recorded and 1,520 antiprotons were detected in the energy range 0.1–4.2 GeV. In this Letter, we report the antiproton spectrum obtained, discuss the origin of cosmic-ray antiprotons, and use antiproton data to probe the effect of charge-sign-dependent drift in the solar modulation.

Measurement of the cosmic-ray antiproton spectrum at solar minimum with a long-duration balloon flight over Antarctica

The energy spectrum of cosmic-ray antiprotons (ps) from 0.17 to 3.5 GeV has been measured using 7886 ps detected by BESS-Polar II during a long-duration flight over Antarctica near solar minimum in December 2007 and January 2008. This shows good consistency with secondary p calculations. Cosmologically primary ps have been investigated by comparing measured and calculated p spectra. BESS-Polar II data show no evidence of primary ps from the evaporation of primordial black holes.

Measurement of the Abundance of Radioactive Be-10 and Other Light Isotopes in Cosmic Radiation Up to 2 GeV /Nucleon with the Balloon-Borne Instrument Isomax

The Isotope Magnet Experiment (ISOMAX), a balloon-borne superconducting magnet spectrometer, was designed to measure the isotopic composition of the light isotopes (3 ≤ Z ≤ 8) of cosmic radiation up to 4 GeV nucleon^(-1) with a mass resolution of better than 0.25 amu by using the velocity versus rigidity technique. To achieve this stringent mass resolution, ISOMAX was composed of three major detector systems: a magnetic rigidity spectrometer with a precision drift chamber tracker in conjunction with a three-layer time-of-flight system, and two silica-aerogel Cerenkov counters for velocity determination. A special emphasis of the ISOMAX program was the accurate measurement of radioactive ^(10)Be with respect to its stable neighbor isotope ^9Be, which provides important constraints on the age of cosmic rays in the Galaxy. ISOMAX had its first balloon flight on 1998 August 4–5 from Lynn Lake, Manitoba, Canada. Thirteen hours of data were recorded during this flight at a residual atmosphere of less than 5 g cm^(-2). The isotopic ratio at the top of the atmosphere for 10Be/9Be was measured to be 0:195 ± 0:036 (statistical) ± 0:039 (systematic) between 0.26 and 1.03 GeV nucleon^(-1) and 0:317 ± 0:109 (statistical) ± 0:042 (systematic) between 1.13 and 2.03 GeV nucleon^(-1). This is the first measurement of its kind above 1 GeV nucleon^(-1). ISOMAX results tend to be higher than predictions from current propagation models. In addition to the beryllium results, we report the isotopic ratios of neighboring lithium and boron in the energy range of the time-of-flight system (up to ~1 GeV nucleon^(-1)). The lithium and boron ratios agree well with existing data and model predictions at similar energies.

Search for Antihelium with the BESS-Polar Spectrometer

In two long-duration balloon flights over Antarctica, the Balloon-borne Experiment with a Superconducting Spectrometer (BESS) collaboration has searched for antihelium in the cosmic radiation with the highest sensitivity reported. BESS-Polar I flew in 2004, observing for 8.5 days. BESS-Polar II flew in 2007-2008, observing for 24.5 days. No antihelium candidate was found in BESS-Polar I data among 8.4×10(6) |Z|=2 nuclei from 1.0 to 20 GV or in BESS-Polar II data among 4.0×10(7) |Z|=2 nuclei from 1.0 to 14 GV. Assuming antihelium to have the same spectral shape as helium, a 95% confidence upper limit to the possible abundance of antihelium relative to helium of 6.9×10(-8)} was determined combining all BESS data, including the two BESS-Polar flights. With no assumed antihelium spectrum and a weighted average of the lowest antihelium efficiencies for each flight, an upper limit of 1.0×10(-7) from 1.6 to 14 GV was determined for the combined BESS-Polar data. Under both antihelium spectral assumptions, these are the lowest limits obtained to date.

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 December 2004 and December 2007, 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 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 GV to 160 GV and compare to ratios from PAMELA and AMS-02.

Design and Performance of the X-ray Polarimeter X-Calibur

X-ray polarimetry promises to give qualitatively new information about high-energy astrophysical sources, such as binary black hole systems, micro-quasars, active galactic nuclei, neutron stars, and gamma-ray bursts. We designed, built and tested a X-ray polarimeter, X-Calibur, to be used in the focal plane of the balloon-borne InFOCuS grazing incidence X-ray telescope. X-Calibur combines a low-Z scatterer with a CZT detector assembly to measure the polarization of 20-80keV X-rays making use of the fact that polarized photons scatter preferentially perpendicular to the electric field orientation. X-Calibur achieves a high detection efficiency of ~80%. The X-Calibur detector assembly is completed, tested, and fully calibrated. The response to a polarized X-ray beam was measured successfully at the Cornell High Energy Synchrotron Source. This paper describes the design, calibration and performance of the X-Calibur polarimeter. In principle, a similar space-borne scattering polarimeter could operate over the broader 2-100keV energy band.

CALET UPPER LIMITS on X-RAY and GAMMA-RAY COUNTERPARTS of GW151226

We present upper limits in the hard X-ray and gamma-ray bands at the time of the LIGO gravitational-wave event GW 151226 derived from the CALorimetric Electron Telescope (CALET) observation. The main instrument of CALET, CALorimeter (CAL), observes gamma-rays from ~1 GeV up to 10 TeV with a field of view of ~2 sr. The CALET gamma-ray burst monitor (CGBM) views ~3 sr and ~2pi sr of the sky in the 7 keV - 1 MeV and the 40 keV - 20 MeV bands, respectively, by using two different scintillator-based instruments. The CGBM covered 32.5% and 49.1% of the GW 151226 sky localization probability in the 7 keV - 1 MeV and 40 keV - 20 MeV bands respectively. We place a 90% upper limit of 2 x 10^{-7} erg cm-2 s-1 in the 1 - 100 GeV band where CAL reaches 15% of the integrated LIGO probability (~1.1 sr). The CGBM 7 sigma upper limits are 1.0 x 10^{-6} erg cm-2 s-1 (7-500 keV) and 1.8 x 10^{-6} erg cm-2 s-1 (50-1000 keV) for one second exposure. Those upper limits correspond to the luminosity of 3-5 x 10^{49} erg s-1 which is significantly lower than typical short GRBs.

THE SuperTIGER Instrument: Measurement of Elemental Abundances of Ultra-Heavy Galactic Cosmic Rays

The SuperTIGER (Super Trans-Iron Galactic Element Recorder) instrument was developed to measure the abundances of galactic cosmic-ray elements from _(10)Ne to _(40)Zr with individual element resolution and the high statistics needed to test models of cosmic-ray origins. SuperTIGER also makes exploratory measurements of the abundances of elements with 40 29 and ∼60 with Z >49. Here, we describe the instrument, the methods of charge identification employed, the SuperTIGER balloon flight, and the instrument performance.

Galactic Cosmic Ray Origins and OB Associations: Evidence from SuperTIGER Observations of Elements

We report abundances of elements from

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