Session B09: Observations of Galactic Cosmic Rays

Live

SuperTIGER (Super Trans-Iron Galactic Element Recorder) is a large-area instrument designed to make a precision measurement of the elemental composition of the ultra-heavy galactic cosmic rays (UHGCR) with atomic number Z $\geq$ 30. After a record-breaking 55 day SuperTIGER-1 long-duration flight in the 2012/2013 Antarctic season, a second flight was planned for the 2017/2018 season. However, unfavorable weather conditions throughout the season prevented a launch despite 16 attempts, and the instrument ended up overwintering in the Long Duration Balloon (LDB) assembly building near McMurdo Station. In the 2018/2019 season, the balloon was launched on December 20, 2018, but it couldn’t reach float altitude and the flight was terminated after 6 hours. The instrument was recovered in the same season, reassembled and tested prior to shipping north, the mechanical damage from landing was repaired, and the payload was integrated and sent back to Antarctica. Finally in the 2019/2020 season the balloon was launched on the first attempt, reached float altitude successfully, and started observing cosmic-ray events on December 16, 2019. We provide an overview of the SuperTIGER-2 flight and report on its preliminary results.   

Live

On December 8, 2012 the SuperTIGER (Trans-Iron Galactic Element Recorder) instrument was launched from Williams Field, Antarctica on a long-duration balloon flight that lasted 55 days and maintained a mean altitude of 125,000 feet. SuperTIGER measured the relative abundances of Galactic cosmic-ray (GCR) nuclei with high statistical precision and well resolved individual element peaks from $_{10}$Ne to $_{40}$Zr. SuperTIGER also made exploratory measurements of the relative abundances up to $_{56}$Ba. The SuperTIGER data analysis reported in Murphy et al. 2016 was performed before the Antarctic recovery effort in 2015 and only included data transmitted during line-of-site periods and via telemetry. The current analysis includes additional data saved to on-board solid-state drives that were retrieved during recovery. Although the statistics are low for elements heavier than $_{40}$Zr, we show relative abundances of charges Z=41-56 with individual element resolution. The relative abundances of elements $_{40}$Zr through $_{60}$Nd are of particular interest because they are likely formed by both supernova explosions and binary neutron star mergers. A well resolved measurement of this charge range can constrain the contributions to the GCR composition from both these possible sources.   

Live

The Cosmic Ray Isotope Spectrometer (CRIS) instrument on the NASA Advanced Composition Explorer (ACE) satellite was launched in August, 1997, and has collected data over this $\sim$22 year period of time. The large geometrical factor of the instrument, combined with the very long exposure time, has enabled us to measure the cosmic ray isotopic abundances of $_{31}$Ga, $_{32}$Ge, $_{33}$As, and $_{34}$Se for the first time, and to greatly improve earlier published measurements for $_{29}$Cu and $_{30}$Zn. We have collected a total of more than 1100 nuclei with Z=30 or greater, with energies in the range of $\sim$150 to 600 MeV/nucleon. In this paper we report preliminary isotopic cosmic-ray composition measurements and compare the observed isotopic fractions with those in the solar system.   

Live

The Calorimetric Electron Telescope (CALET) was launched to the International Space Station in August 2015 and has continuously taken data since shortly thereafter. Recent results include measurement of the spectra of cosmic-ray electrons$+$positrons to 4.8 TeV and protons to 10 TeV, with ongoing analyses of nuclear spectra, ratios, and ultra-heavy abundances. The calorimeter is sensitive to gamma rays from 1 GeV to beyond 1 TeV, and the corresponding instrument response functions have been determined through simulations and comparison with flight data. We present CALET observations of gamma-ray emission from the quiescent Sun over the period November 2015 -- October 2019. Previous observations with the Fermi Large Area Telescope (LAT) indicate a hard spectrum in excess of predictions. Recent results with LAT extend this measurement to higher energies, revealing emission beyond 100 GeV, and indicate an increase in the flux at solar minimum and the presence of a ``dip'' feature in the spectrum at energies of 30 -- 50 GeV. In this work, we demonstrate general consistency with the hard, intense spectrum detected by the LAT at energies up to tens of GeV. Furthermore, we investigate the presence of the time dependence of the flux and the unexpected spectral feature.   

Live

The CALorimetric Electron Telescope (CALET) is a high-energy astroparticle physics experiment on the International Space Station (ISS) developed and operated by Japan in collaboration with researchers in Italy and the US. In extended observations the main calorimeter (CAL) can measure the cosmic-ray electron+positron spectrum up to 20 TeV, gamma rays up to 10 TeV, and nuclei from $_{1}$H to $_{40}$Zn up to 1,000 TeV. The CAL is comprised of a two-layer scintillator paddle charge detector, a scintillating fiber imaging calorimeter with 3 radiation lengths (RL) of tungsten plates, and a 27 RL deep lead tungstate total absorption calorimeter. There is also the CALET Gamma-ray Burst Monitor (CGBM) subsystem with two hard X-ray monitors (HXM) sensitive to 7-1000 keV photons and a soft gamma-ray monitor (SGM) sensitive to 100 keV-20 MeV photons utilizing two LaBr3 (Ce) and one BGO scintillators, respectively. Major CALET results to date include measurements of the electron+positron energy spectrum to $\sim$5 TeV, the spectra of protons and other nuclei, and gamma-ray observations including LIGO/Virgo counterpart searches. CALET began science operations in mid-October 2015 and is now approved to continue through March 2021 with the possibility that operations may be extended further.   

On Demand

SuperTIGER (Trans-Iron Galactic Element Recorder) is a large-area balloon-borne instrument built to measure the galactic cosmic-ray (GCR) abundances of elements from Z=10 (Ne) through Z=56 (Ba) at energies from 0.8 to $\sim$10 GeV/nuc. SuperTIGER flew over Antarctica for a record-breaking 55 days, from December 8, 2012 to February 1, 2013. We will report updated calculations of galactic cosmic ray spectra for abundant elements between Ne and Zn from the SuperTIGER flight data. The energy spectra calculations will incorporate refinements to the energy calibrations for the acrylic and aerogel Cherenkov detectors in the instrument, as well as new corrections for interactions derived from a new GEANT4 simulation of the instrument. Heinz and Sunyaev (2002) suggested that microquasar jets like those observed in GRS 1915+105 and GRO J1655-40 may be observable as near-monoenergetic peaks in heavy ion spectra from 3 to 10 GeV/nuc. We will compare SuperTIGER spectra with ACE/CRIS and HEAO-3 spectra and with model GCR spectra solar modulated for the time period of the flight, to search for peaks that may arise from microquasar jets. Finally, we may report on early spectrum results of SuperTIGER-2, which launched over Antarctica on December 15, 2019 and flew into January 2020.   

On Demand

The Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM) experiment is designed for measurements of energy spectra and elemental composition of cosmic rays. It was launched and installed on the International Space Station (ISS) in August 2017. The ISS-CREAM instrument can measure protons to iron nuclei in the energy range of TeV – PeV. For the elemental identification of cosmic rays, we use the silicon charge detector (SCD) placed at the top of the ISS-CREAM payload. The four-layer SCD consists of 10,752 silicon pixels, and active area in each layer is 78.2 x 73.6 cm${^2}$. Each pixel is 1.37 x 1.57 x 0.05 cm${^3}$ in size. Our preliminary analysis shows good performance of the SCD throughout the flight with charge resolutions of 0.1 – 0.3e for protons to iron nuclei. The multilayer configuration provides redundant charge measurements and reduces risks associated with operation in space environment. The energy measurements are made with the calorimeter with carbon target, which provides the tracks of incident cosmic rays. We will report preliminary spectra and elemental composition of the high energy cosmic rays using the data accumulated on the ISS. In this study, we tried to Machine learning for separating the backscattering and incident particles.   

On Demand

The Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM) experiment is designed to study high-energy cosmic rays on the ISS. The ISS-CREAM instrument was launched on 14th of August 2017 aboard the SpaceX-12 Dragon spacecraft. The silicon charge detector provides measurement of cosmic-ray charges with resolutions of 0.1-0.3 e. The calorimeter (CAL) provides measurement of the incident cosmic-ray energies using shower energy deposited. The Top and Bottom Counting Detectors (TCD/BCD) are used to separate electrons from protons using the different shower shapes between hadronic and electromagnetic showers. Since the TCD/BCD, two arrays of 20 $\times$ 20 photodiodes on a plastic scintillator, are placed above and below the CAL., the TCD/BCD can measure the longitudinal and lateral profiles of the showers. In this study, a machine learning technique is used with TCD/BCD for the separation of electrons from protons. Protons with a power-law E$^{-2.7}$ and electrons with energies from 300 GeV to 10 TeV, generated from Geant3 Monte Carlo (MC) simulations, are used for training data. The MC data were smeared with noise from pedestal data to represent the instrument effects. We will present preliminary results on the study of cosmic-ray electron-proton separations.   

On Demand

The Calorimetric Electron Telescope, CALET, onboard the International Space Station has been collecting scientific data since October 2015. CALET is performing a precise measurement of the cosmic ray electron spectrum in the TeV region as well as measuring nuclear spectra from protons to iron in the range from a few tens of GeV to the PeV scale. These allow for the investigation of the details of their acceleration and propagation mechanisms in the Galaxy. The features of the CALET instrument include excellent charge resolution of 0.18$e$ for carbon and 0.30$e$ for iron based on the segmented scintillator paddles and scintillating fibers and energy resolution of 30 - 40 \% for hadrons provided by its 30X$_o$ thick calorimeter. The details about the analysis procedure of nuclei measurements, comparison with our Monte Carlo simulations and preliminary results of the energy spectra for nuclei up to 100 TeV with four years of operations will be presented.