PoS(ICRC2015)581 http://pos.sissa.it/ Department of Physics, Waseda University & for the CALET collaboration ∗ [email protected] Speaker. The CALorimetric Electron Telescopeby (CALET) Japan space in experiment, collaboration which withmission Italy has to and been be the installed developed United on the States,mission International is Space a include Station high-energy (ISS). investigating astroparticle The physics primary possibledetails goals nearby of of the galactic sources CALET particle of propagationyear mission, and high extendable searching to energy five for years, electrons, dark theelectrons CALET matter studying experiment (including signatures. will positrons) measure the the to During flux 20 a ofto cosmic-ray TeV, two- gamma-rays several to 100 10 TeV. The TeVthe instrument and cosmic-ray consists nuclei charge with of identification Z=1 (CHD), two a toimaging layers 3 40 calorimeter of radiation up segmented (IMC) length thick plastic and tungsten-scintillating scintillatorsCALET a fiber has for 27 sufficient radiation depth, length imagingclear capabilities thick separation and lead-tungstate between excellent calorimeter hadrons energy and (TASC). resolutionThe electrons to instrument and is allow between currently for being charged a prepared particles(H-II for and Transfer launch gamma on Vehicle rays. August 5) 16, and(JEM-EF) 2015 to installed the on ISS with the HTV-5 Japanese Experiment Module- Exposed Facility ∗ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. c

The 34th International Cosmic Ray30 Conference, July- 6 August, 2015 The Hague, The Netherlands (JP) E-mail: Shoji Torii Research Institute for Science and Engineering The CALorimetric Electron Telescope (CALET):Energy High Astroparticle Physics Observatory onInternational the Space Station PoS(ICRC2015)581 2 Shoji Torii shows CALET attach 1 CALET instrument package showing the
Figure 2: main calorimeter composed of CHD, IMC(see and §2 TASC for the details), and CGBM subsystems. " 2

! A C Japanese Experiment Module-Exposed The unique feature of CALET is its thick, fully active calorimeter that allows measurements The primary science goal of CALET is to perform high-precision measurement of the electron CALorimetric Electron Telescope (CALET) is a Japan-led international mission funded by well into the TeVupper calorimeter energy to region accurately identify with thehave starting excellent excellent point separation energy of between electromagnetic hadrons resolution, showers. and electronsrays. CALET coupled and will These between with features charged are particles a essential and to fine gamma electrons search and imaging for possible search nearby for astrophysical dark sourcesthe of matter TeV high region. signatures energy in The bothacceleration hadronic the in data supernova electron provide remnants and another or gamma-ray channel other spectra through sources up which will to be the investigated. details of Equipped with particle a charge Figure 1: Facility and CALET attached2015). at the #9 port (as of . The instrumentray pallet monitor includes (HXM) a and Gamma-ray aattitude Burst determination, soft a Monitor Mission gamma-ray Data (CGBM), monitor Controller composed (MDC) (SGM),and to handle of an manage the the Advanced a individual accumulated Sky detector hard data, systems Camera as X- (ASC) well as for the CALET instrument itself. spectrum from 1 GeV toour 20 local TeV to region observe of discrete the sources Galaxy.from of Thanks a high few to GeV energy its up particle observations to of accelerationmission the cosmic-ray in TeV will electrons and nuclei and address from gamma-rays a many fewthe outstanding 10 GeV origin questions up of to of the High-Energythe cosmic several 100 Astroparticle existence TeV, the rays Physics, CALET of (CRs), such nearbywith as the CR a mechanism sources dedicated and of gamma-ray burst dark CR detector matter. acceleration and solar and It modulation. will galactic also Figure propagation, monitor gamma ray transients the Japanese Space Agency (JAXA),was the designed Italian Space and Agencycollaborators (ASI) built in and Italy in NASA. and The the Japan,on instrument United August States. with 16, The hardware 2015 instrument byon is contribution the a currently Japanese from being Japanese Experiment prepared Module-Exposed carrier, Italy Facility for H-II(ISS) (JEM-EF) launch Transfer on and for Vehicle the a (HTV), International assistance two-year Space and Station mission, from roboticallyand extendable gamma-rays. installed to five years, collecting new data on high-energy cosmic CALET 1. Introduction point #9 on the JEM-EF. A schematic overview of the CALET instrument is presented in Fig. PoS(ICRC2015)581 , 2 Z Z ]. with a 1 3 Shoji Torii 45 degrees ∼ =40 [ Z ], giving a charge 3 in the Fe region. e direction and capped by an Y 0.30-0.35 and ' X ), preceded by a particle identification ] and CERN-SPS [ I 2 λ ) for B to e 3 40. Charge identification capabilities of CHD have been ∼ =1 Z 10 mm(H). This segmented configuration has been optimized to × ) and 1.3 proton interaction lengths ( 0 32 mm(W) sr and the total weight is 613 kg. × 2 A schematic side view of the main calorimeter. An example of a simulation event for a 1 TeV The IMC will image the early shower profile with a fine granularity by using 1 mm square cross The main instrument of the mission is the calorimeter, shown in detail in Fig. The CHD has been designed to measure the charge of incoming particles via the 1200 cm ' section scintillating fibers (SciFi) individually readanode out by Hamamatsu Multi-Anode R7600-M64). Photomultiplier Tubes (64- Theeach imaging separated pre-shower by consists of 2 7 layers layers of of SciFi tungsten plates belts arranged in the resolution ranging from 0.15 electron charge units ( of the incoming cosmicfrom rays, proton CALET to will iron and perform will long-exposure detect observations trans-iron of elements with cosmic2. a nuclei dynamic The range CALET up Instrument to and its performance system. The energy measurement relies onIMaging two Calorimeter kinds of (IMC), calorimeters: followed aidentify the fine by individual granulated chemical pre-shower a elements in Total theat cosmic-ray AbSorption the flux, top a Calorimeter Charge of Detector the (TASC). (CHD)is instrument. is In placed The order effective geometrical to factor for CALET for high-energy electrons dependence of the specificplaced ionization loss above in the double IMC.450 layered, segmented, Each mm(L) plastic layer scintillatorreduce consists array multi-hits of on 14 eachare plastic paddle scintillator orthogonally caused by paddles, arrangedscintillation backscattering with to light particles. is dimensions determine collected The and thefront-end read two out electronics incident layers by have of a position photomultiplier been paddles dynamic of tube designed (PMT). range cosmic-rays. to The for CHD provide and charges incident related The in particle generated identification over a large Figure 3: electron is over-written to illustrate the shower development in the calorimeter. identifier module, placed at the top of the apparatus and capable to identify the atomic number, measured by exposing it on an ion beam at GSI facility [ CALET simulated shower profile produced byfrom a the 1TeV zenith. electron, which CALET hasradiation is a lengths an field (X all-calorimetric of instrument, view with of a total thickness equivalent to 30 PoS(ICRC2015)581 20 × Shoji Torii 19 mm (W) × ]. and the last 2 layers 5 ]. Another necessary [ 4 0 5 10 MIPs, which is the energy 6 ∼ , which is better than that of ◦ 500, while the electron rejection 0.16 ∼ ∼ ]. and the total thickness corresponds to 7 2 ]. 6 [ 2 % above 100 GeV [ 4 ≤ 326 mm 4 × 448 mm (W). The total thickness of the IMC is equivalent × in normal incidence. Each PWO log at the top layer is readout by the I λ SciFi layer pair. Each SciFi belt is assembled with 448 fibers and the dimensions sampling. The IMC fine granularity allows to : (i) reconstruct the incident particle , while the angular resolution for electrons is ◦ 0 and 1.2 Y , 0 X 0.24 . The first 5 tungsten-SciFi layers sample the shower every 0.2 X ∼ 0 Charged particles and gamma rays with energy larger than 10 GeV will be triggered above In the region above 10 GeV, electrons and gamma rays are separated by the IMC, as gamma It has become increasingly clear in recent years that major changes in, and the evolution of, The main scientific objective of CALET is the measurement of the electron spectrum over The homogeneous calorimeter is designed to measure the total energy of the incident particle power (for gamma-ray observations) is better than 10 a 15 MIP threshold fromthreshold the from sum the of signal theGeV of and signals the 10 GeV from top will the be layer observed lastThe in only trigger two for the rate a IMC above TASC. limited SciFi 10 exposure Electrons by belts GeV in reducing is and the the estimated IMC a energy trigger around 55 thresold. 13 range MIP Hz between [ 1 rays have nomeasurements tracks of the in CHD can the berejection used IMC, power to reject except (for photons. electron for At energies observations) backscattered less is than particles. 1 expected TeV, a to gamma-ray be Furthermore, the charge our own and otherexplosions, galaxies Black are Hole accretion, intrinsically Active linkedthe Galactic acceleration to Nuclei of (AGN) high jets, charged energy etc. particles,particles phenomena fuels - often the - and to galactic cosmic that e.g. extreme radiation, these energies. while involve the Supernova The interactions of release the of energetic particles these produce high energy 3. CALET Science Goals requirement is to efficiently identifyof CR high-energy protons. electrons among Particle identification theelectron information detection overwhelming from efficiency background above both 80 IMC % and and TASC a is proton used rejection to power achieve an PMT to generate aPhotoDiode trigger signal. (Dual APD/PD) Hybrid are packagesthe used of eleven layers. to silicon The Avalanche detect PhotoDiode readoutwith photons and front Charge from Sensitive end silicon Amplifier all system (CSA) of of andsystem each pulse the provides pair shaping remaining a amplifier of with dynamic the PWO dual range APD/PDbar bars gain. sensors covering signal Such in is 6 spanning a from configured orders readout 0.5 of MIPs magnitudes (Minimum and Ionizing allows Particles) to to 10 measure in each the range from 1response from GeV GeV to up 20features to as TeV. the For expected TeV region this in andMonte case purpose, an Carlo of TASC excellent simulations the is resolution presence and toincident required of CERN-SPS electrons resolve to nearby and beam possible have CR gamma spectral test sources rays a data, with or linear TASC resolution dark energy can matter. measure According the to energy of the CALET additional mm (H) . Layersprovide are a 3D alternately reconstruction arrangedYZ of with view. the the showers. The logs total Sixabout oriented area layers 27 along image of X orthogonal the the XZ directions TASC is view to 326 and the other six the deposit expected from a proton-induced 1000 TeV shower. of the SciFi layers areto 448 3 mm X (L) and discriminate the electromagnetic from hadronicconsists showers. of TASC 16 is lead composed tungstate of (PWO) 12 logs. layers, Each each log has dimensions of 326 mm (L) provide 1.0 X trajectory; (ii) determine the startingbackscattered point particles. of the Above shower; severalrays (iii) tens is separate of the GeV, incident the particlesgamma-rays. expected from angular resolution for gamma- PoS(ICRC2015)581 . 4
Shoji Torii shows the $ % # 4 ! "

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! & ], Fig. 8 5 10 % in the electron arrival directions is expected for Vela as also presented in Fig. ∼ Expected observation by CALET with measured and expected data compared with calculations years and less than 1 kpc far from the Solar System. Since the number of such nearby For a given choice of assumed model parameters as calculated by [ Electrons provide a singularly sensitive probe of nearby high-energy cosmic accelerators. It is generally accepted that CRs are accelerated in shock waves of supernova remnants 5 10 Figure 4: as described in text. Theright figure the at energy the dependence bottom of right the presents amplitude the of expected anisotropy anisotropy. from Vela and at the top simulated electron spectrum (dotted line)mission and compared the to anticipated data aanisotropy points compilation from of a previous five year electronThe CALET measurements. investigation of Moreover, possible aobservation significant of spectral a features possible inof anisotropy CALET. the in the electron direction (and of positron) the spectrum Vela SNR and are the one of the main goals Unlike the hadronic componenttheir of energy CRs, in the proportion electrons, toscattering. their during squared their∼ energy diffusion Thus by in TeV synchrotron the radiation electrons Galaxy, and lose observedSNRs inverse Compton is at limited Earth (e.g.:energy likely Vela, Monogem spectrum originated and around Cygnus insignificant Loop 1 anisotropy sources remnants in TeV and younger the could few electronresolution than others), arrival and exhibit directions capability the to is spectral electron discriminate expected. electronspossible features from Thanks hadrons, spectral to and, CALET structures its will by be excellent at able detectingexperimental energy to evidence very very investigate of high-energy the high electrons presence and energies, of possibly a a nearby provide CR the source. first (SNRs), which are thethe CR only flux. galactic candidatesprovided Evidence known by that electron with particle synchrotron sufficient accelerationevidence and to energy for gamma multi-TeV output particle ray energy acceleration to emission is inparticles sustain measurements. escape taking SNR the is place source Although region. clear, in the CALET therenearby SNR, is photon is uniquely SNR is able sources no to via address direct very this evidence question high that by energy investigating the electrons. accelerated 3.1 Search for nearby sources of high-energy electrons CALET X ray and gammaCALET will radiation provide through another synchrotron, importantenergy electrons, window inverse hadrons, on Compton, diffuse the gamma and rays High up pion Energy to Universe decay the by highest processes. observing energies observed high in space. PoS(ICRC2015)581 Shoji Torii 900 TeV, the ∼ 20 TeV/n. It will ∼ . 6 , up to a few TeV. δ Expected B/C ratio by CALET comparing is a key parameter in the description of the CR 6 ] for proton and helium spectra. δ Figure 6: with present data, whichpower index, is capable of defining the 10 . On the other hand, experiments in space are free from δ , where δ ) and measure the energy spectra of the most abundant heavy − 5 E ] and AMS-02 [ 9 Expected p and He spectrum by Besides studying the CR sources and diffusion, CALET will also conduct a sensitive search CALET will be able to identify CR nuclei with individual element resolution and measure Additional information on the CR propagation might be obtained by directly measuring, A direct measurement of the high-energy spectra of individual cosmic-ray nuclei up to the PeV 3.3 Indirect dark matter search Figure 5: this limitation. Taking advantage ofCALET its mission long will exposure provide, in as space wellmeasurements and as and the AMS-02, extend absence new them data of above to 1TeV/n, atmosphere, as improve the the illustrated accuracy in of Fig. the present CALET five-year observationpresent comparing data. with their energies in thedata range taking from on a the few ISS, tens it of is GeV expectedprimary to to nuclei extend C, several O, the hundreds Ne, proton Mg, of energy Si TeV. and In spectrum Fe up five with sufficient years to statistical of precision up to besides proton andBoron/Carbon helium - can energy discriminate, spectra, viaThis its the energy observable dependence, is secondary-to-primary among less different fluxabundances prone propagation of models. ratios, to CR systematic most secondary-to-primary errors elements notably following than (like a B/C absolute power or flux sub-Fe/Fe) law measurements. are in known The energy to relative decrease, scale provide important complementary information toPossible the charge-dependent one high-energy derived from spectral electron cutoffs,or observations. spectral hypothesized hardening to due explain to thespace experiment non-linear CR with acceleration long "knee" enough mechanisms, , exposure could toto extend only unprecedented the energies. be direct measurement investigated of by CR nuclei a spectra CALET 3.2 Measurements of primary and secondary nuclei He spectrum up to 400 TeV/n (Fig. diffusion in the Galaxy athighest high energies. energies Unfortunately, with the Long availablelarge measurements, Duration pushed systematic Balloon to errors experiments, the suffer ataltitude. from several statistical TeV/n, limitations This due and setsratios to obtainable the an with residual effective measurements atmospheric limitexperimental on overburden constraint to balloons on at the and the balloon has value highest of not energy allowed points so of far to the place secondary-to-primary a stringent also investigate precisely possible spectral featuresas or observed by deviations from PAMELA a [ pure power-law spectrum, PoS(ICRC2015)581 , ], 7 11 Shoji Torii . 8 ]. CALET has a potential 15 2 % over 100 GeV), it is an ideal ∼ CALET flight model assembled on the HTV 7 Figure 8: palette. ], has fueled an intense debate whether this observation is related 13 ] and AMS-02 [ 12 CALET flight model viewed from ]. Should CALET results not be compatible with the assumed single pulsar case in the 14 [ Since CALET has an outstanding energy resolution ( The final review for the CALET flight model production has successfully been done after The prominent increase of the positron fraction over 10 GeV, reported by PAMELA [ − e + 
to detect the distinctive featuresenergy spectrum from in dark the matter TeV region annihilation/decay while in it the cannot electron separate the anddetector sign positron to of observe charge. monochromatic gammaof rays GeV up from to dark several matter tens annihilations of from TeV. several tens Figure 7: the calorimeter side. the functional and environmental teststo (EMC, the Acoustic, assembling Thermal of vacuum, eachcarried muon component out: runs, (CHD, etc.), (i) IMC Prior UV andPD laser TASC), with irradiation ground to dual tests each for gainusing PWO calibrations ( pulses log were i.e: to simulated get by APD-high,of a actual each APD-low, correlation trigger component. PD-high, data signals. between The PD-low). APD payload (iii) assembled and (ii) Muon in Trigger the runs function JEM-EF including standard test thermal-vacuum package by test presented in Fig. 4. Current status of the CALET mission 4.1 Status of the CALET flight model was transferred in the beginning of(TNSC), April, and 2015 was to mounted the on launch the site HTV at exposed the facility Tanegashima pallet Space as Center shown in Fig. TeV region, it may hint atit Dark Matter completely, partially for contributing to example, the in positron excess the or form even causing of decaying Dark Matter [ to dark matter orhadron it rejection is power the result andquestion. of long On an the exposure assumption astrophysical in thatwill effect. the space, be positron With CALET able excess its is to willcurrent excellent caused set experimental shed energy by data, significantly a resolution, new especially single more light fore nearby stringent Lightest on pulsar, CALET Kaluza-Klein limits this partices on open with Dark annihilation Matter to only annihilation compared to CALET for signatures of darkgamma-ray matter candidates (10 in GeV both -by the 10 electron the TeV) plus spectra. available positron experimental SurvivingMassive (1 findings Particles dark GeV (WIMPs) and matter - . current candidates 20 theoretical (i.e. TeV) and work) not include yet Weakly excluded Interacting Fermi-LAT [ PoS(ICRC2015)581 Shoji Torii 8 ]. The off-line data analysis is performed by the international CALET , Nucl. Instrum. Meth. A, 659 (2011) 477. . 7 , Phys. Rev. Lett. 108, 011103 (2012). . , Ap.J. 601 (2004) 340. . et al , Phys. Rev. Lett. 114, 17113 (2015). , Science 332 (2011) 69. , Nature 458 (2009) 607. . , Phys. Rev. Lett. 113, 121101 (2013). . . et al . et al , Advances in Space Research, 55 (2015) 2500. . , Phys. Lett. B741 (2015) 134. . et al et al et al et al et al et al H. Motz for the CALETM. collaboration, Ibe Proc. of the 34th ICRC, this conference (2015). Y. Akaike for the CALET collaboration,M.Mori Proc. for of the the CALET 32nd collaboration, ICRCY.Asaoka Proc. for (Beijing) of the Vol.6 the 346 CALET 33 (2011). collaboration, rd Proc.T. ICRC of Kobayashi (Rio the de 34th Janeiro) ICRC, ID: thisO. 0248 conference Adriani (2013). (2015). M. Aguilar O. Adriani M. Ackermann L. Accord P.S. Marrocchesi P.S. Marrocchesi for the CALET collaboration,(2013). Proc. of the 33T. rd Niita ICRC (Rio de Janeiro) ID: 0362 B.E. Rauch for the CALET collaboration, Proc. of the 34th ICRC, this conference (2015). The CALET mission is conducted by Japanese space agency, JAXA, in collaboration with CALET mission is proposed to perform observations of electrons, gamma rays, and H, He and The data down link will be done by two telemetry channels: One is the Ethernet channel [9] [4] [5] [6] [7] [8] [1] [2] [3] [14] [15] [10] [11] [12] [13] NASA and ASI. This work is partially supported by JSPS KAKENHIReferences Grant Number 21224006. heavy ions at theobserving high energy the frontier. energy spectrum Nearbycandidates and sources will the of be anisotropy electrons searched will in withray a be the spectra. sensitivity directly TeV expected identified region. The by by mechanism hadron theory Signatures of in observation transport of both has in dark the the the Galaxy.and matter electron potential CALET solar and will to modulation. gamma be reveal CALET useful the is forwith anticipated monitoring a origin gamma to mission of ray life begin transients the of operations 5 on "knee" years. the and ISS-JEM the inAcknowledgments August, 2015 team based on the data delivered from the WCOC. 5. Summary and Future Prospects which is operated at afor, on medium average, rate approximately 70 of % 600 ofprovides kilobits each low day, per and rate the second data other (kbps) at isISS functions a 50 MIL-STD-1553B will in kbps. channel real be which In time the transferred mode the medium to event. rate the mode, The Tsukuba an data Space eventlater that observed Center replay. are by The (TKSC) CALET not low of on available rate the viakeeping JAXA mode data the a is plus real used few a as time seconds sample a linkto of following redundant are the the channel cosmic-ray recorded NASA for events.. link on-board telemetering A mentioned the thethe Japanese above. ISS CALET United link house for State, The will and be CALET prepared are datamonitoring in sent will the addition to be events the transmitted Waseda to CALET [ TKSC Operations via Center MSFC (WCOC) in in real time for CALET 4.2 Ground Support Equipment