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著者人数: 71名, Accepted: 2004-04-14, 資料番号: SA1003385000

著者人数: 15名, Accepted: 2011-04-18, 資料番号: SA1003044000

The Trans-Iron Galactic Element Recorder (TIGER) was launched in December 2001 and 2003 from McMurdo, Antarctica and was designed to observe elements ranging from over an extended energy range. Observations of radioactive isotopes produced during explosive nucleosynthesis such as Ni that decay only through electron capture provide important constraints on the delay between nucleosynthesis and the acceleration of galactic cosmic rays (GCRs). The isotopes of Co and Ni at low energies, in particular, the observations of the Ni and Co from the Cosmic Ray Isotope Spectrometer (CRIS) on the Advanced Composition Explorer, indicate a significant time delay (7.6 10 yr) between GCR nucleosynthesis and acceleration. While TIGER is not able to resolve isotopes, observations of the elemental abundances of Co and Ni at high energies further constrain models for the acceleration and propagation of GCRs. The 2001 2003 flights of TIGER lasted a total of 50 days and collected sufficient statistics to study the Co/Ni elemental ratio over a wide range in energies. We present the elemental ratio of Co/Ni in galactic cosmic rays between 0.8-5.0 GeV/nucleon and compare these results with previous measurements and models for cosmic-ray propagation.

著者人数: 72名, 資料番号: SA1003390000

Observations of Ultra-Heavy galactic cosmic rays (GCR) help to distinguish the possible origins of GCRs. The Trans-Iron Galactic Element Recorder (TIGER) measures the charge (Z) and energy of GCRs using a combination of scintillation counters, Cherenkov counters, and a scintillating fiber hodoscope. TIGER has accumulated data on two successful flights from McMurdo, Antarctica: the first launched in December of 2001 with a total flight duration of 31.8 days and the second in December of 2003 with a total flight duration of 18 days. We present a preliminary analysis of the combined data from both flights for Ultra-Heavy GCRs.

The Trans-Iron Galactic Element.Recorder (TIGER) instrument was launched in December 2001 from McMurdo, Antarctica. TIGER is a cosmic-ray telescope that uses four scintillation counters, two Cherenkov detectors and a scintillating fiber hodoscope to determine the charge (Z) and energy of a particle. During the 31.8 day flight it measured ~100 ultra-heavy galactic cosmic-ray (GCR) events with Z > 30 and demonstrated charge resolution sufficient to resolve the individual elemental abundances in this region. The abundances of the Ultra-Heavy GCRs in this range can be used to distinguish between GCR source models. We present our measurements and discuss the implications for the GCR source.

The Trans-Iron Galactic Element Recorder (TIGER) was launched on December 21, 2001 and flew for about 32 days on a long-duration balloon mission from McMurdo Base in Antarctica. On December 26, 2001 at about 5:30 UT, a ground-level solar particle event (M7.6 flare) was observed by a number of neutron monitors. The SIS instrument aboard the ACE spacecraft measured the elemental composition and particle energy spectra up to ∼150MeV/nuc. While not designed to operate under such conditions, TIGER data for the same period show interesting variations in the count rate and composition of the measured particles that may be related to the detection of heavy Solar particles (Si to Fe) in the ∼GeV/nuc range. We discuss the TIGER observations in relation to other available data from this event.

The HNX mission is composed of the ENTICE and ECCO experiments. The experimental goal of ENTICE is to measure with high precision the elemental abundances of all nuclei with 10≤Z≤82. This will enable us to determine if the injection mechanism for the cosmic ray accelerator is controlled by FIP or Volatility and to study the mix of nucleosynthetic processes that contribute to the galactic cosmic ray source. The ENTICE experiment utilizes the dE/dx-C method of charge determination and consists of silicon dE/dx detectors, Cherenkov detectors with two different refractive indices, and a fiber hodoscope. We will describe the instrument and its performance based on beam tests of a prototype instrument.

The ECCO instrument is one of two instruments which comprise the HNX mission. The principal goal of ECCO (the Extremely-heavy Cosmic-ray Composition Observer) is to measure the age of galactic cosmic ray nuclei using the actinides (Th, U, Pu, Cm) as clocks. As a bonus, ECCO will search with unprecedented sensitivity for longlived elements in the superheavy island of stability. ECCO is an enormous array (23 m2 ) of BP-1 glass track-etch detectors, and is based on the successful flight heritage of the Trek detector which was deployed externally on Mir. We present a description of the instrument, estimates of expected performance, and recent calibrations which demonstrate that the actinides can be resolved from each other with good charge resolution.

The primary scientific objectives of HNX, which was recently selected by NASA for a Small Explorer (SMEX) Mission Concept Study, are to measure the age of the galactic cosmic rays (GCR) since nucleosynthesis, determine the injection mechanism for the GCR accelerator (Volatility or FIP), and study the mix of nucleosynthetic processes that contribute to the source of GCRs. The experimental goal of HNX is to measure the elemental abundances of all individual stable nuclei from neon through the actinides and possibly beyond. HNX is composed of two instruments: ECCO, which measures elemental abundances of nuclei with Z≥72, and ENTICE, which measures elemental abundances of nuclei with 10≤Z≤82. We describe the mission and the science that can be addressed by HNX. 1. Introduction The Heavy Nuclei eXplorer (HNX) mission that is currently being studied as a possible Small Explorer Mission (SMEX) has the primary objective of determining the origin of the galactic cosmic rays. The abundance patterns of the elements and isotopes in the GCRs provide the key because they are the fingerprints of GCR origin. HNX will, for the first time, measure with high precision the abundance of every individual element in the periodic table from neon through the actinides (thorium, uranium, plutonium, curium, and perhaps beyond). The HNX spacecraft will carry two high-precision instruments, the Extremely-heavy Cosmic-ray Composition Observer (ECCO) and the ENergetic Trans-Iron Composition Experiment (ENTICE), which cover overlapping ranges of the periodic table (Figure 1).

The Trans-Iron Galactic Element Recorder (TIGER) for the Ultra-Long Duration Balloon project Demo2000 (TD2K) is designed to measure the abundances of all elements in the Galactic Cosmic Rays (GCRs) with 26 ≤ Z ≤ 40 and energies above 300 MeV/nucleon. TD2K's flight is expected to approach 100 days in length. Launch will be from New Zealand in 2001. TD2K will have sufficiently good resolution to measure the individual abundances of the odd-Z elements between Z=26 and Z=40 for the first time. Measurements of odd-Z nuclei are important for distinguishing between the effects of first ionization potential and volatility in the injection process for ultraheavy GCRs, for models of nucleosynthesis, and constraining models of cosmic-ray propagation at short pathlengths. TD2K uses a combination of Cherenkov and scintillation counters to determine the atomic number and energy of incident cosmic rays, and a coded cintillating-fiber hodoscope for trajectory corrections. TD2K is an improved version of the TIGER instrument flown in 1997, results from which are reported at this conference (Sposato et al., 1999). We will present the status of the TD2K instrument and of the ULDB program as it affects the Demo 2000 flight.

TIGER is a balloon-borne cosmic-ray experiment designed to measure the elemental abundances of Galactic Cosmic Rays (GCRs) in the charge range 26

We report the results of an accelerator calibration of detectors planned for use in the ZIM experiment for ACCESS. The experiment utilizes silicon detectors to measure dE/dx, and aerogel and acrylic Cherenkov counters for velocity measurements. For a 79Au beam with energy 10.6 GeV/nucleon, we obtain resolution in charge for the silicon, acrylic Cherenkov, and aerogel Cherenkov of 0.20, 0.22, and 0.45 cu respectively.

The geomagnetically trapped a...r10malous cosmic rays have been monitored continuously by instrumentation on the SAMPEX satellite since its launch in mid-1992. With the approach of solar mimmum the intensity has been increasing along with that of the interplanetary anomalous cosmic ray source. We compare the time variations of the two components using data from the MAST instrument: describe improved measurements of the spatiaJ distribution of the trapped component, and discuss implications for the trapping and lifetime of the trapped component.

Ionic charge states of anomalous cosmic ray nitrogen, oxygen, and neon with kinetic energies above 15 MeV /nucleon have been measured using the geomagnetic field as a rigidity filter. Data from the MAST instrument on the polar-orbiting SAMPEX satellite taken during the period from 1992 to 1996 show that all three elements are predominantly multiply charged at high energies, confirming the earlier result for oxygen alone based on a smaller data set. Energy spectra of the singly charged and multiply charged components of each element are compared with model predictions.

Our previous studies showed that the fragmentation cross sections of gold nuclei interacting in hydrogen have large variations between the values measured at 0.9 and 10.6 GeV/n, which has very significant implications on calculations of the propagation of the heaviest UH cosmic ray nuclei, such as Pb and Pt We have now completed a series of runs at the Brookhaven AGS using beams of gold nuclei of intermediate energy. The data from these runs will allow us to establish the excitation functions for these cross sections in a wide range of targets and hence model propagation more accurately than hitherto. In addition we will be able to study the energy dependence of nuclear charge pickup, electromagnetic dissociation and fission. Beams of gold nuclei with seven energies between 4.0 and 0.9 Ge V /n were studied interacting in targets ranging in mass from hydrogen to lead. We will present data on the cross sections derived from several of these beams and discuss some of the implications.

With the addition of krypton and silver projectiles we have extended our previous studies of the fragmentation of heavy relativistic nuclei in targets ranging in mass from hydrogen to lead. These projectiles were studied at a number of discrete energies between 450 and 1500A MeV. The total and partial charge-changing cross sections were determined for each energy, target, and projectile, and the values compared with previous predictions. A new parametrization of the dependence of the total charge-changing cross sections on the target and projectile is introduced, based on nuclear charge radii derived from electron scattering. We have also parametrized the energy dependence of the total cross sections over the range of energies studied. New parameters were found for a previous representation of the partial charge-changing cross sections in hydrogen and a new parametrization has been introduced for the nonhydrogen targets. The evidence that limiting fragmentation has been attained for these relatively light projectile nuclei at Bevalac energies is shown to be inconclusive, and further measurements at higher energies will be needed to address this question.

We have measured the charge-changing cross sections of 10.6 GeV/nucleon ^(197)Au nuclei interacting in targets of CH_2 (polyethylene), C, Al, Cu, Sn, and Pb. Cross sections for H are calculated from those measured in C and CH_2. The total charge-changing cross sections are higher than those measured at energies of ≤1 GeV/nucleon. The measured cross sections for the heavier targets are somewhat larger than those predicted by a model based on data taken at lower energies with lighter targets. Partial charge-changing cross sections for the production of fragments from the incident Au projectiles were measured for charge changes (ΔZ) from ΔZ=+1_(,80)Hg, down to approximately ΔZ=-29_(,50)Sn. In comparison to lower energy measurements, these partial cross sections are found to be smaller for small ΔZ and larger or the same for large ΔZ. The H partial cross sections are found to follow a power law in ΔZ similar to that for heavier targets, instead of the exponential form observed at lower energies. Factorization is found to hold for all partial cross sections with ΔZ greater than two. In the heavier targets, the cross sections for one and two proton removal have significant contributions from electromagnetic dissociation. The electromagnetic dissociation contribution to the total cross section is derived and found to be relatively small, but with a strong dependence on the charge of the target nuclei of the form Z_T^(1.75±0.01).

We have measured the charge-changing cross sections of 10.6 GeV/nucleon ^(197)Au nuclei interacting in targets of CH2 (polyethylene), C, Al, Cu, Sn, and Pb. Cross sections for H are calculated from those measured in C and CH_2. The total charge-changing cross sections are higher than those measured at energies of ≤1 GeV/nucleon. The measured cross sections for the heavier targets are somewhat larger than those predicted by a model based on data taken at lower energies with lighter targets. Partial charge-changing cross sections for the production of fragments from the incident Au projectiles were measured for charge changes (ΔZ) from ΔZ=+1, _(80)Hg, down to approximately ΔZ=-29, _(50)Sn. In comparison to lower energy measurements, these partial cross sections are found to be smaller for small ΔZ and larger or the same for large ΔZ. The H partial cross sections are found to follow a power law in ΔZ similar to that for heavier targets, instead of the exponential form observed at lower energies. Factorization is found to hold for all partial cross sections with ΔZ greater than two. In the heavier targets, the cross sections for one and two proton removal have significant contributions from electromagnetic dissociation. The electromagnetic dissociation contribution to the total cross section is derived and found to be relatively small, but with a strong dependence on the charge of the target nuclei of the form Z__T^(1.75±0.01).

We have used data from the SAMPEX. Ulysses, Voyager 1 (Vl), Voyager 2 (V2), and Pioneer 10 (PIO) spacecraft to determine the radial and latitudinal gradients of anomalous cosmic ray oxygen at 10 MeV/nuc during 1994 days 209 - 313. These five spacecraft cover radial distances from 1 AU (SAMPEX) to 61 AU (PIO) and latitudes to 80° S (Ulysses) and 33° N (Vl). We find that the radial gradient is a decreasing function of radial distance, -r^(-n) , with n = 0.7 ± 0.7. The large-scale radial gradient between the inner and outer heliosphere is much smaller than it was during the last solar minimum period in ~1987. The latitudinal gradient is small and positive, 2.1 ± 0.6 %/deg, as opposed to the large and negative latitudinal gradients found during 1987, but similar to the small positive latitudinal gradient reported in a similar study for 1993 and also similar to that measured during 1976 for anomalous cosmic ray helium. These observations confirm that effects of curvature and gradient drift in the large scale magnetic field of the Sun are important for establishing the three-dimensional intensity distributions of these particles in the heliosphere during periods of solar minimum conditions.

New measurements of the anomalous cosmic ray (ACR) isotopic composition are presented, using data from the Mass Spectrometer Telescope (MAST) on SAMPEX. At high invariant latitudes or in interplanetary space, ACR isotopic composition measurements require correction for contamination from galactic cosmic rays (GCRs); however, at lower latitudes singly-charged ACRs can penetrate the Earth's magnetic field while fully stripped GCRs of similar energies are excluded, allowing us to study a pure ACR sample. Preliminary values for ACRs obtained using this geomagnetic filter approach are: ^(15)N /N < 0.032, ^(18)0/^(16)0 < 0.0057, and ^(22)Ne = ^(20)Ne = 0.087(+0.137, -0.026). We compare our values with those found by previous investigators and with those measured in other samples of solar and galactic material.

We use instrumentation on SAMPEX and the Earth's field as a magnetic rigidity filter in a new "double spectrometer" approach to measure the composition and energy spectra of anomalous cosmic rays. We obtain a "pure" sample of anomalous cosmic ray C, N, 0, and Ne, with no significant evidence for other species. The energy spectrum of anomalous oxygen extends to -100 MeV/nuc, which has implications for models of the acceleration of these nuclei.

The mean charge states of abundant heavy ions with ~15 - 70 MeV/n in the two large solar energetic particle (SEP) events of 1992 October 30 and November 2 have been determined using measurements of invariant latitude of the geomagnetic cutoffs as a function of time, particle energy, and element from the Mass Spectrometer Telescope (MAST) on SAMPEX. The deduced charge state values are in good agreement with the mean values measured directly in previous SEP events at much lower energies of ~1 MeV/n, with inferred equilibrium source temperatures of typically 2 x 10^6 K, which provides additional evidence that SEPs in gradual-type events are accelerated coronal material.

We summarize additions to our data base of charge-changing cross sections for relativistic ultraheavy nuclei interacting in targets ranging from H to Pb. We have improved parametric fits to those cross sections as functions of energy and of projectile, target, and fragment charge. At high energies, we have determined cross sections for Au projectiles at 10.6 GeV /nucleon in targets of H, CH_2, C, Al, Cu, Sn, and Pb. Compared with cross sections at 1 GeV /n, fragment production is substantially changed, especially for the H target. These changes have important implications for calculations of interstellar propagation of ultraheavy nuclei. At lower energies, we have added Kr and Ag to our list of projectiles. Analysis of these data has led to a better understanding of the systematics of these cross sections, hence more physically meaningful parameterizations for fragmentation at high energies and for charge pickup.