Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session S13: Intermediate Energy Cosmic RaysFocus
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Sponsoring Units: DAP Chair: Jason Link, NASA Room: 250F |
Monday, April 18, 2016 1:30PM - 2:06PM |
S13.00001: Current and Future Measurements of Ultra-Heavy Galactic Cosmic Rays. Invited Speaker: Jason Link There is strong evidence from recent experiments that suggest a source of galactic cosmic rays is in superbubble regions and that particles here are accelerated through the shocks from supernova explosions. Through further study of ultra-heavy cosmic-rays, those particles with a Z \textgreater 26, we can verify and explore the particle source and acceleration process of cosmic-rays. Measuring these particles is a challenge due to their low flux and high interaction cross section, requiring extremely large detectors flown on balloons and in space. In this talk we will discuss how past and recent ultra-heavy cosmic ray measurements have shaped our understanding of the cosmic-ray source and acceleration process and what we hope to learn from future measurements. We will present results on the abundances of ultra-heavy cosmic rays in the charge range 26 $\le $ Z $\le $ 40 from the SuperTIGER Antarctic balloon flight and compare these with previous results from ACE-CRIS and TIGER. We will also review the current status of active missions to measure ultra-heavy cosmic rays and discuss future possibilities. [Preview Abstract] |
Monday, April 18, 2016 2:06PM - 2:18PM |
S13.00002: Observation of $^6$$^0$Fe in the Galactic Cosmic Rays M.H. Israel, W.R. Binns, E.R. Christian, A.C. Cummings, G.A. deNolfo, K.A. Lave, R.A. Leske, R.A. Mewaldt, E.C. Stone, T.T. vonRosenvinge, M.E. Wiedenbeck The Cosmic Ray Isotope Spectrometer (CRIS) on the ACE spacecraft has been measuring the isotopic composition of Galactic Cosmic Rays (GCRs) since August 1997. Using selected data from the past seventeen years, we have a set of 2.95 x 10$^5$ $^5$$^6$Fe nuclei in the energy interval ~240 to ~470 MeV/nucleon with excellent mass resolution characterized by $\sigma$ = 0.24 amu. In this data set we have detected fifteen well resolved $^6$$^0$Fe nuclei. $^6$$^0$Fe is $\beta$$^-$ unstable with a half-life of 2.6 million years. The detection of these radioactive nuclei permits us to set an upper limit of a few million years on the time between nucleosynthesis of these nuclei and their acceleration to cosmic-ray energies. A lower limit of ~10$^5$ years was established by the CRIS observation that the electron-capture isotope $^5$$^9$Ni is essentially absent in the GCRs. These two limits bracket the nucleosynthesis-to-acceleration time to a range that is consistent with the emerging evidence that the bulk of GCRs are accelerated in associations of massive stars (OB associations). [Preview Abstract] |
Monday, April 18, 2016 2:18PM - 2:30PM |
S13.00003: Abundances of Ultra-Heavy Galactic Cosmic Rays from the SuperTIGER Instrument Ryan Murphy The SuperTIGER (Trans-Iron Galactic Element Recorder) experiment was launched on a long-duration balloon flight from Williams Field, Antarctica, on December 8, 2012. The instrument measured the relative elemental abundances of Galactic cosmic rays (GCR) in the charge ($Z$) range $Z>$10 with excellent charge resolution, displaying well resolved individual element peaks for 10$\leq Z \leq$40. During its record-breaking 55-day flight, SuperTIGER collected $\sim$4.73 $\times10^6$ Iron nuclei, $\sim$8 times as many as detected by its predecessor, TIGER, with charge resolution at iron of $<$ 0.18 cu. SuperTIGER measures charge ($Z$) and energy (E) using a combination of three scintillator and two Cherenkov detectors, and employs a scintillating fiber hodoscope for event trajectory determination. The data include more than 600 events in the charge range 30$< Z \leq$40. SuperTIGER is the first experiment to resolve elemental abundances in this charge range with single-element resolution and high statistics. The SuperTIGER measured abundances are generally consistent with previous experimental results from TIGER and ACE-CRIS, with improved statistical precision. Our results confirm the earlier results from TIGER, supporting a model of cosmic-ray origin in OB associations. [Preview Abstract] |
Monday, April 18, 2016 2:30PM - 2:42PM |
S13.00004: Recovery of the SuperTIGER Instrument and Preparations for the Flight of SuperTIGER-2 N.E. Walsh On December 8, 2012, the SuperTIGER (Trans-Iron Galactic Element Recorder) instrument began its long-duration balloon flight from Williams Field, Antarctica. Flying for a record-breaking 55 days at a mean altitude of 125,000 feet, the instrument successfully measured the relative elemental abundances of Galactic cosmic ray nuclei having charge (Z) greater than Z=10, showing very well resolved individual element peaks up to Z=40. The instrument measures particle charge and energy through the combined use of two Cherenkov detectors and three scintillation detectors, and determines particle trajectory with a scintillating fiber hodoscope. After cutdown and two years on the ice, SuperTIGER was successfully recovered in January, 2015. Its detectors and hodoscopes are being tested and refurbished, and are expected to be used again for a second flight, SuperTIGER-2. The second flight is aimed at improving SuperTIGER's already excellent charge resolution as well as at accumulating more data to be combined with that of SuperTIGER for improved statistics. In November 2015, a test of the scintillator saturation effect was performed at CERN using a beam of interacted Pb nuclei to help create more accurate charge reconstruction models that will help resolve elements in the range Z=41 to Z=60. [Preview Abstract] |
Monday, April 18, 2016 2:42PM - 2:54PM |
S13.00005: Measurement of Relative Abundances of Ultra-Heavy Cosmic Rays with CALET on the ISS Brian Rauch The CALorimetric Electron Telescope (CALET) is a Japanese-Italian-US astroparticle observatory that was launched from the Tanegashima Space Center on the H-IIB Launch Vehicle No.5 (H-IIB F5) aboard the KOUNOTORI5 (HTV5 cargo transfer vehicle) to the International Space Station (ISS) on August 19, 2015. The HTV5 arrived at the ISS on August 24, and CALET was installed on port 9 of the Japanese Experiment Module ``Kibo'' Exposed Facility (JEM-EF), where CALET underwent the planned turn on and checkout procedures. CALET has completed its commissioning phase and its main calorimeter (CAL) is observing the highest energy cosmic electrons from 1 GeV to 20 TeV, along with cosmic ray nuclei through iron up to 1,000 TeV and gamma-rays above 10 GeV. In a five-year mission CALET will also have the exposure to measure the relative abundances of the ultra-heavy (UH) cosmic rays with $\sim$4$\times$ the statistics of the TIGER instrument for the full CAL acceptance. Rigidity cutoffs based on the earth's geomagnetic field in the 51.6$^{\circ}$ inclination ISS orbit can provide an energy independent UH measurement with expanded acceptance with $\sim$10$\times$ the TIGER statistics. An overview of the anticipated performance and preliminary CALET UH analysis data will be presented. [Preview Abstract] |
Monday, April 18, 2016 2:54PM - 3:06PM |
S13.00006: The All Particle Cosmic-Ray Energy Spectrum Measured with HAWC Zigfried Hampel-Arias We present results of a measurement of the all-particle cosmic-ray energy spectrum above 10 TeV with the High-Altitude Water Cherenkov (HAWC) Observatory. HAWC is a ground based air shower array deployed on the slopes of Volc\'{a}n Sierra Negra in the state of Puebla, M\'{e}xico. It comprises 300 large light-tight water tanks covering an area of 20,000 square meters. Each tank is instrumented with four photomultipliers to detect particles from extensive air showers produced by gamma rays and cosmic rays upon entering the Earth's atmosphere. HAWC is optimized for the detection of gamma-ray induced air showers, yet the background flux of hadronic air showers is four orders of magnitude greater, allowing for a detailed study of the cosmic-ray flux in the TeV energy range. The primary cosmic-ray energy is determined with a maximum likelihood approach using the particle density as a function of distance to the shower core. Introducing quality cuts to isolate events with shower cores landing on the array, the reconstructed energy distribution is unfolded iteratively. We will report on the energy resolution of the technique and the results of the unfolding. [Preview Abstract] |
Monday, April 18, 2016 3:06PM - 3:18PM |
S13.00007: Measurement of cosmic-ray induced high energy muons with the HAWC observatory Ahron Barber High energy muons/muon bundles (E$_{muon}$ $>$ 1 TeV) can be created in primary interactions of ultra-high energy (UHE) cosmic rays with the Earth's atmosphere. The number and lateral distribution of high energy muons is related to the mass and energy of the primary cosmic ray, as well as specific details of the hadronic interaction between the primary cosmic ray and the atmospheric target nucleus. The HAWC observatory, located at 4100 m asl on the northern slope of Sierra Negra, Mexico, can detect near-horizontal trajectory (elevation 0-15 degrees) high energy muons as they traverse through individual water Cherenkov detectors. The extended size of HAWC (150 m x 150 m) allows detection of several thousand near-horizontal cosmic-ray generated high energy (E $>$ 3 TeV) muons every year. In this talk, I will describe the prospects for using the HAWC observatory to explore UHE cosmic ray properties through measurements of near-horizontal muon bundles. [Preview Abstract] |
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