[Show abstract][Hide abstract] ABSTRACT: The cosmic ray elemental abundances of Zn, Ga, and Ge provide important tests of the emerging model of the OB-association origin of galactic cosmic rays. These ultra-heavy (Z>29) nuclei are very rare and require an instrument with a large geometrical factor exposed over a long period of time. We have measured these abundances using the CRIS instrument, which has a large geometrical factor of about 250 cm2sr, on the NASA-ACE spacecraft. Over the 11+ years since launch in 1997 we have collected ˜400 nuclei with Z>29 at energies of ˜150 to 600 MeV/nucleon. These measured abundances relative to Nickel will be presented and compared with those expected if OB associations are the source of most galactic cosmic rays. Additionally, our measurements will be compared with results from the TIGER and HEAO-3 experiments.
[Show abstract][Hide abstract] ABSTRACT: In a recent paper Heinz and Sunyaev suggest that relativistic jets observed in microquasars might result in narrow features in the energy spectra of heavy cosmic rays with ≈1 to ≈10 GeV/nuc. They further argue that such features might be observable if there has been one or more microquasars nearby within the last few million years. We report preliminary results of a search for evidence of such features using data from a 32-day balloon flight of the Trans-Iron Galactic Element Recorder (TIGER). Although this flight took place near solar maximum, calculations of the broadening effects of solar modulation indicate that a narrow feature of sufficient intensity should still be observable. An energy spectrum for iron with high statistical significance has been derived from ≈100,000 Fe events in the energy range from about 2.5 to 10 GeV/nuc. Although our preliminary results do not reveal any obvious features, we will discuss the possibility of observing such features with TIGER and other instruments.
Advances in Space Research 01/2006; 37(10-37):1955-1959. DOI:10.1016/j.asr.2005.10.037 · 1.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Isotope Magnet Experiment (ISOMAX) a balloon-borne superconducting magnet spectrometer was designed to measure the isotopic composition of the light isotopes (3 less than or equal to Z less than or equal to 8) of the cosmic radiation up to 4 GeV nucleon (exp -1) with a mass resolution of better than 0.25 amu by using the velocity vs. rigidity technique. To achieve this stringent mass resolution ISOMAX was comprised 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 Cherenkov counters for the velocity determination. A special emphasis of the ISOMAX program was the accurate measurement of radioactive Be-10 with respect to its stable neighbor isotope Be-9, which provides important constraints on the age of cosmic rays in the Galaxy. ISOMAX had its first balloon flight on August 4-5, 1998, from Lynn Lake, Manitoba, Canada. Thirteen hours of data were recorded during this flight at a residual atmosphere of less than 5 g per square centimeter. The isotopic ratio at the top of the atmosphere for Be-10/Be-9 was measured to be 0.195 plus or minus 0.036 (statistical) plus or minus 0.039 (systematic) between 0.26 - 1.03GeV nucleon (exp -1) and 0.317 plus or minus 0.109 (statistical) plus or minus 0.042 (systematic) between 1.13 - 2.03GeV nucleon(exp -1). This is the first measurement of its kind above 1 GeV nucleon (exp -1). ISOMAX results tend to be higher than predictions from current propagation models.
[Show abstract][Hide abstract] ABSTRACT: We present new results on the elemental abundances of galactic cosmic rays with atomic number, Z, greater than 30, and comparison of these observations with abundances expected from galactic propagation of various suggested models of the cosmic-ray source. We combine preliminary results from the 2003-04 flight of the Trans-Iron Galactic Element Recorder (TIGER) cosmic-ray detector with previously reported results from the 2001-02 flight. This instrument flew over Antarctica for nearly 32 days at a mean atmospheric depth of 5.2 mb in December 2001 - January 2002. At the time of submission of this abstract, January 8, 2004, TIGER was again in the air over Antarctica having completed 22 days of an expected 30day flight at a mean atmospheric depth of about 4 nb, Data from the first flight demonstrated excellent resolution of individual elements, and we expect similar resolution from the second flight.
[Show abstract][Hide abstract] ABSTRACT: The Trans-Iron Galactic Element Recorder (TIGER) has been flown in 2001 and 2003 for a combined total float time of ˜ 50 aboard long-duration balloon flights launched from Antarctica and has made the most precise measurements to date for the elements Zn (Z=30), Ga (Z=31), Ge (Z=32), and Se (Z=34). To collect sufficient particles to make precise measurements for all elements up through molybdenum (Z=42), and to improve our current measurements, it will be necessary to develop and fly an instrument with substantially larger collecting power than the current TIGER instrument. We have defined an instrument with an effective collecting power that is greater than 6 times that of the current TIGER instrument, and when flown near solar minimum will result in a factor of ˜ 9 times more particles collected than for TIGER which was flown near solar maximum. This will enable us to place strong constraints on models of cosmic ray origin. Measurement of the energy spectra in the several GeV/nucleon range will also enable us to search for a narrow-line energy spectral component that may be present in the 3-10 GeV/nucleon range for heavy nuclei if one or more micro-quasars have been active in the solar neighborhood within the past few million years. This work was supported by NASA Grants at Washington U., Caltech, and GSFC.
[Show abstract][Hide abstract] ABSTRACT: We report on galactic cosmic ray elemental abundance measurements made with the Trans-Iron Galactic Element Recorder (TIGER) for elements with charge (Z) between 20 and 40 during an Antarctic LDB flight this past year. TIGER flew for 31.8 days from McMurdo Base, Antarctica, circling the south pole twice and setting a new record for LDB flight duration. The TIGER instrument had sufficient resolution to measure the elemental abundances for even and odd-Z elements in the Z=30s charge range and will provide for the first time a measurement of the odd-Z elements in this range. These odd-Z elements are important because they provide information as to which elemental property, FIP or volatility, gives order to the GCR source abundances. We shall report on the results of these measurements and discuss their implications for the source of the material being injected into the GCR accelerator.
[Show abstract][Hide abstract] ABSTRACT: TIGER is a cosmic-ray detector consisting of several scintillator and
Cherenkov light boxes and a scintillating fiber hodoscope. It will be
able to measure the elemental abundances of GCRs with 26 ≤ Z ≤ 40
and energies above 300 MeV/nucleon. TIGER will measure the individual
abundances of the odd-Z elements between Z=30 and Z=40 for the first
time. These odd-Z nuclei are important for distinguishing between the
effects of first-ionization potential and volitilty in the injection
process, for models of nucleosynthesis and constraining models of
cosmic-ray propagation at short pathlengths. We will discuss some of the
scientific questions we hope to be able to address with the TIGER
[Show abstract][Hide abstract] ABSTRACT: We present a new measurement of air shower muons made during atmospheric ascent of the High Energy Antimatter Telescope balloon experiment. The muon charge ratio μ+/μ- is presented as a function of atmospheric depth in the momentum interval 0.3–0.9 GeV/c. The differential μ- momentum spectra are presented between 0.3 and ∼50 GeV/c at atmospheric depths between 13 and 960 g/cm2. We compare our measurements with other recent data and with Monte Carlo calculations of the same type as those used in predicting atmospheric neutrino fluxes. We find that our measured μ- fluxes are smaller than the predictions by as much as 70% at shallow atmospheric depths, by ∼20% at the depth of shower maximum, and are in good agreement with the predictions at greater depths. We explore the consequences of this on the question of atmospheric neutrino production.
Physical Review D 06/2000; 62(3). DOI:10.1103/PhysRevD.62.032001 · 4.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Charge (Z) Identification Module (ZIM) for ACCESS has as its primary
objective the measurement of the cosmic-ray abundance of every
individual element in the interval 10<=Z<=83 with cleanly resolved
individual element resolution and with sufficient collection power to
give excellent statistical significance. This instrument will, for the
first time, determine the full element-by-element composition of cosmic
rays, throughout the heavy two-thirds of the periodic table, providing
definitive tests of theories of sites and mechanisms of cosmic-ray
acceleration. We expect that detectors with this UH configuration will
serve as the Charge Module for the full ACCESS instrument. In this paper
we describe the science objectives of ZIM and the measurements that can
be achieved with this instrument.
[Show abstract][Hide abstract] ABSTRACT: Super-TIGER (Super Trans-Iron Galac- tic Element Recorder) is a new long-duration balloon-borne instrument designed to test and clarify an emerging model of cosmic-ray origins and models for atomic processes by which nuclei are selected for acceleration. A sensitive test of the origin of cosmic rays is the measurement of ultra heavy elemental abundances (Z ‚ 30). Super-TIGER is a large-area (5 m2) instrument designed to measure the abundances of elements in the interval 30 • Z• 42 with individual-element resolution and high statistical precision, and make exploratory measure- ments through Z=60. It will also measure with high statistical accuracy the energy spectra of the more abundant elements in the interval 14 • Z • 30 at energies 0.8 • E• 10 GeV/nucleon. These spectra will give a sensitive test of the hypothesis that micro- quasars or other sources could superpose spectral features on the otherwise smooth energy spectra previously measured with less statistical accuracy. Super-TIGER builds on the heritage of the smaller TIGER, which produced the first well-resolved mea- surements of elemental abundances of the elements 31Ga, 32Ge, and 34Se. We present the Super-TIGER design, schedule, and progress to date, and discuss the relevance of UH measurements to cosmic-ray origins.
[Show abstract][Hide abstract] ABSTRACT: In a one-day balloon flight of the Trans-Iron Galactic Element Recorder (TIGER) in 1997, the instrument achieved excellent charge resolution for elements near the Fe peak, permitting a new measurement of the element ratio Co/Ni. The best fit to the data, extrapolated to the top of the atmosphere, gives an upper limit for this ratio of 0.093±0.037 over the energy interval 0.8 to 4.3 GeV/nucleon; because a Co peak is not seen in the data, this result is given as an upper limit. Comparing this upper limit with calculations by Webber & Gupta suggests that at the source of these cosmic rays a substantial amount of the electron-capture isotope 59Ni survived. This conclusion is in conflict with the clear evidence from ACE/CRIS below 0.5 GeV/nucleon that there is negligible 59Ni surviving at the source. Possible explanations for this apparent discrepancy are discussed.
[Show abstract][Hide abstract] ABSTRACT: The Charge (Z) Identification Module (ZIM) for ACCESS has as its primary objective the measurement of the cosmic-ray abundance of every individual element in the interval 10