Yosui Akaike

The CALorimetric Electron Telescope (CALET) for high-energy astroparticle physics on the International Space Station

The CALorimetric Electron Telescope (CALET) is a space experiment, currently under development by Japan in collaboration with Italy and the United States, which will measure the flux of cosmic-ray electrons (and positrons) up to 20 TeV energy, of gamma rays up to 10 TeV, of nuclei with Z from 1 to 40 up to 1 PeV energy, and will detect gamma-ray bursts in the 7 keV to 20 MeV energy range during a 5 year mission. These measurements are essential to investigate possible nearby astrophysical sources of high energy electrons, study the details of galactic particle propagation and search for dark matter signatures. The main detector of CALET, the Calorimeter, consists of a module to identify the particle charge, followed by a thin imaging calorimeter (3 radiation lengths) with tungsten plates interleaving scintillating fibre planes, and a thick energy measuring calorimeter (27 radiation lengths) composed of lead tungstate logs. The Calorimeter has the depth, imaging capabilities and energy resolution necessary for excellent separation between hadrons, electrons and gamma rays. The instrument is currently being prepared for launch (expected in 2015) to the International Space Station ISS, for installation on the Japanese Experiment Module - Exposure Facility (JEM-EF).

Relativistic electron precipitation at International Space Station: Space weather monitoring by Calorimetric Electron Telescope

The charge detector (CHD) of the Calorimetric Electron Telescope (CALET) on board the International Space Station (ISS) has a huge geometric factor for detecting MeV electrons and is sensitive to relativistic electron precipitation (REP) events. During the first 4 months, CALET CHD observed REP events mainly at the dusk to midnight sector near the plasmapause, where the trapped radiation belt electrons can be efficiently scattered by electromagnetic ion cyclotron (EMIC) waves. Here we show that interesting 5–20 s periodicity regularly exists during the REP events at ISS, which is useful to diagnose the wave-particle interactions associated with the nonlinear wave growth of EMIC-triggered emissions.

Expected CALET telescope performance from monte carlo simulations

The CALorimetric Electron Telescope, CALET, is a versatile detector for exploring the high energy universe, planned to be placed on the Japanese Experiment Module Facility of the International Space Station, ISS. CALET is designed to perform direct measurements of electrons from 1 GeV to 20 TeV, gamma-rays from 10 GeV to 10 TeV, and protons and nuclei from several 10 GeV to 1000 TeV. The main detector consists of a Charge Detector (CHD), an Imaging Calorimeter (IMC), and a Total Absorption Calorimeter (TASC). The total thickness of the calorimeter is 30 X0 for electromagnetic particles or 1.3 λ for protons. We have been carrying out Monte Carlo simulations with EPICS to study the CALET performance. With its imaging and deep calorimeter, CALET provides excellent proton rejection, ∼ 10, and a high energy resolution, ∼2%, over 100 GeV for electromagnetic particles, which make possible the observation of electrons and gamma-rays into the TeV region. In this paper, we will present the expected performance in observing the different particle species, including the geometric factor, the trigger efficiency, the energy resolution and the particle identification power.

Balloon Borne Experiment with CALET Prototype

We carried out a balloon observation of cosmic rays with a prototype of the CALET (bCALET-1) at the Sanriku Balloon Center of the Japan Aerospace Exploration Agency. The main purpose of the experiment was verification of the CALET. The detector consists of 1024 scintillating fibers for precise imaging and 24 BGO scintillator for total absorption of showers. The observation was carried at an altitude between 35 and 37 km for about 3.5 hours. We measured electrons in the energy region between 1 to 10 GeV. The prototype system was verified in the balloon environment. We have obtained the electron flux which is useful to investigate solar modulation. In combination with the flux between 10 to 100 GeV measured by BETS, rigidity cutoff effect was clearly observed. These results showed good agreement with that of our Monte-Carlo simulation and demonstrated the detection capability of the CALET in the enegy region below 10 GeV. Now we are planning a series of balloon experiments with larger-scale detectors and lo...

Performance of the CALET prototype: CERN beam test

We are developing the CALET mission to observe high energy cosmic rays at the Japanese Experiment Module/Exposed Facility (JEM/EF) on the International Space Station. The instrument will be flown in 2013, and will be used for 5 years. The primary scientific purpose of CALET is to search for nearby cosmic ray sources and dark matter. We carried out an accelerator beam test with high energy particles with the CALET prototype at the CERN-SPS. The purpose of this test was to assess the detector performance as well as to study the accuracy of the Monte Carlo simulation method. The prototype detector consists of an imaging calorimeter with 256 scintillating fibers and a total absorption calorimeter consisting of 16 PWO logs. The longitudinal structure is similar with the CALET instrument. We used positron and proton beams in the energy region from 6 to 200 GeV, and from 30 to 150 GeV, respectively. Comparing the experimental data with the simulation results, we have measured the energy deposition in each component, the energy resolution, the lateral shower spread and the e/p separation capability.

The event trigger system for CALET

The CALorimetric Electron Telescope, CALET, is a mission to study high energy phenomena in the universe by observing high energy cosmic rays (electrons, gamma rays, and nuclei) on the International Space Station. The instrument consists of a segmented plastic scintillator charge-measuring module, an imaging calorimeter consisting of 8 scintillating fiber planes interleaved with tungsten plates of 3 radiation length, and a total absorption calorimeter consisting of orthogonal PWO logs of 27 radiation length. It is necessary to eliminate the background events, mostly low energy protons that prevent efficient observation of high energy cosmic rays. Therefore, CALET has an on-board trigger system to select events which are 1) high energy showers, 2) low energy showers and 3) non-interacting protons or heavy nuclei. These triggers are generated by a combination of the signals from the charge detector, the imaging calorimeter, and the top layer of PWO in the total absorption calorimeter. A CERN-SPS beam test of the CALET prototype detector was carried out by using muons, electrons, and hadrons. We introduce the CALET trigger system and present its performance verified during the beam test.

The balloon-bone CALET prototype detector (bCALET)

The CALET payload will be installed in the Japanese Experiment Module Exposed Facility (JEM-EF) of the International Space Station (ISS). We developed a balloon-borne payload to evaluate the performance of CALET by carrying out precursor flights for the electron and gamma-ray observations. The first flight of bCALET-1 (balloon-borne CALET prototype) was carried out in 2006, and the enhanced version, bCALET-2, was successfully flown in August 2009. The bCALET-2 is composed of IMaging Calorimeter (IMC) and Total AbSorption Calorimeter (TASC). The IMC has an area of 256 mm × 256 mm, and is consisted of 8 layers of scintillating fiber belts with a total 3.6 radiation lengths of tungsten plates interleaved within the fiber planes for imaging the pre-shower development. TASC is consisted of crossed BGO logs (25 mm × 25 mm × 300 mm in each) with a total of 13.4 radiation lengths depth, for measuring the total energy deposit of incoming shower particles. The geometry factor is nearly 320 cm 2 sr over 10 GeV. We succeeded the observation of the electron energy spectrum in 1 GeV ∼ several 10 GeV electron and the atmospheric gamma-rays in 1G eV∼ a few 10 GeV, which are consistent with previous observations by BETS. The results are compared with simulations for confirming the detector performance.

The CALET CHD for determination of nuclear charge

Calorimetric Electron Telescope (CALET) will be a high energy cosmic ray observatory on the Japanese Experimental Module – Exposed Facility of the International Space Station. In addition to electrons and gamma-rays, CALET has an excellent detection capability of cosmic ray nuclei. In order to determine the atomic number of measured nuclei, the CHarge Detector (CHD) is placed on the top of the calorimeter. The CALET-CHD consists of two orthogonal layers of plastic scintillator charge-measuring modules. Each layer is segmented into 14 scintillator paddles (45 cm×3.2 cm×1 cm) for the reduction of back scattering effects. We evaluated the charge resolution of the plastic scintillators with heavy ion accelerators. In this presentation, we will report the design of the CALET-CHD and its nuclei identification capability as inferred from heavy ion beam tests.

Expected performance of CALET by Monte carlo simulation

The CALET (CALorimetric Electron Telescope) is a detector planned to be on board the JEM-EF (Exposed Facility of Japanese Experiment Module) of the International Space Station to investigate high energy universe by observing high energy gamma-rays, electrons and hadronic cosmic rays. The main part of CALET is composed of an IMaging Calorimeter (IMC), a Total AbSorption Calorimeter (TASC), SIlicon Array (SIA) and Anti-Coincidence Detector (ACD). Monte Carlo simulation has been carried out to obtain basic performance of CALET on orbit.