Ichimura, M

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29th International Cosmic Ray Conference Pune (2005) 3, 321324CALET Observation of Nuclear Components in Primary Cosmic RaysM. Ichimura , S. Kuramata , S. Torii, T. Tamura, K. Yoshida, K. Kasahara, J. Chang,H. Fuke, K. Hibino, T. Kashiwagi, Y. Katayose  , H. Kitamura, T. Kobayashi,Y. Komori	, F. Makino, K. Mizutani, H. Murakami  , J. Nishimura, S. Okuno,Y. Saito, M. Shibata  , M. Takayanagi, N. Tateyama, T. Terasawa  , S. Tomida,Y. Uchihori, S. Ueno, T. Yamagamiand T. Yuda(a) Department of Earth and Environmental Science, Hirosaki University, Japan(b) Advanced Research Institute for Science and Engineering, Waseda University, Japan(c) Faculty of Engineering, Kanagawa University, Japan(d) Department of Electronic and Information Systems, Shibaura Institute of Technology, Japan(e) Purple Mountain Observatory, Chinese Academy of Science, China(f) Institute of Space and Astronautical Science, JAXA, Japan(g) Department of Physics, Yokohama National University, Japan(h) National Institute of Radiological Sciences, Japan(i) Department of Physics, Aoyama Gakuin University, Japan(j) Kanagawa University of Human Services, Japan(k) Space Environment Utilization Center, JAXA, Japan(l) Department of Physics, Saitama University, Japan(m) Department of Physics, Rikkyo University, Japan(n) Department of Earth and Planetary Physics, University of Tokyo, JapanPresenter: M. Ichimura (ichimu@cc.hirosaki-u.ac.jp), jap-ichimura-M-abs2-og15-posterAlthough CALET is originally designed for detections of electrons and gamma rays, nuclear components ofprimary cosmic rays, from protons to iron nucleus and more, are also observable by CALET, utilizing the totalabsorption calorimeter (TASC). TASC has 1.6 m.f.p. for protons which is enough to measure the energy ofprotons up to 1000 TeV. Using the observed spectra, the following items will be discussed:(1) the detailed structure of the spectrum, checking the change of the spectrum index and comparing indicesof various components. More than 300 iron nuclei with the energy greater than 1 TeV/n will be observed.(2) secondary/primary ratio. Especially we can observe the both of B/C ratio and sub-Fe/Fe ratio. At the spacestation, the observation is free from the atmospheric contamination corrections.These observations are essential for the acceleration mechanisms and the propagation of cosmic rays.1. IntroductionThe CALET mission is proposed for observation of very high energy cosmic rays on the International SpaceStation. Although the detector is basically designed for detections of electrons and gamma-rays with useof electro-magnetic calorimeter, it can detect nuclear components because the total absorption calorimeter isenough thick for detection of protons up to 1000 TeV which is close to the Knee region.The energy spectra of nuclear components in proximity of the Knee region is very important to resolve theproblems of the acceleration limit and of the propagation of cosmic rays. The capability of the CALET missionfor the observations of nuclear components are discussed in this report.2. DetectorThe CALET detector has two parts, an imaging calorimeter (IMC) in upper part, and a total absorptioncalorimeter (TASC) in lower part. The IMC has 36 layers of scintillating fiber belts for tracking of chargedparticles, and the TASC is composed of BGO logs with 32 r.l. of thickness for energy measurement. A siliconpad module is set at the top of the IMC to measure the precise charge of incident heavy nuclei.322 M. Ichimura et al.The incident nuclei with the energy more than 1 TeV will be triggered by electro-magnetic cascade shower inthe TASC with 0.1 Hz of the trigger rate. The particle identification of each event will be done in the IMC. Theincident nuclei can make nuclear interactions and cascade showers in the TASC because it has 1.6 m.f.p. forprotons which is enough thickness. The details of our detector are explained in other paper in this conference.3. Expected Results3.1 Exposure FactorThe number of detected nuclei  is given byﬁﬀﬂﬃ ﬁ!"!#whereis the intensity of nuclei  ,ﬀis the area of detector andﬂis the time of observation.ﬃ ﬁ!"! is thefactor of geometrical solid angle including detection efficiency which depends on nuclear species  . We areplanning 3 years observation by CALET, soﬂ$&%' (*),+.-0/21sec. The area of TASC is/'43m 5 . Although thesimulation calculations will be necessary to know the accurate value of detection efficiency for each nucleus,hereﬃ ﬁ!"!/' 6is used for all species for rough estimation. The expected numbers which will be detected byCALET, will be demonstrated as follows with use of above factors.3.2 Energy SpectraThe energy spectra for proton and helium which are expected to be observed by CALET operation are shownin Fig. 1, including the data obtained by several groups[1, 2, 3, 4, 5, 6]. Single power law is assumed forestimation with 798';:of power index for both of proton and helium, and expected statistical errors are showntogether. More than)<+=->/*?of protons with the energy above 1 TeV will be observed. Both of spectra willextend to just below the Knee with small statistical errors. It means that we can confirm the spectrum changingdue to the acceleration limit which is predicted around there, if exists. These data will make clear the problemon the acceleration limit of cosmic rays.The same type of plots for heavy component groups are shown in Fig. 2 with the data obtained by pastexperiments[3, 6, 7, 8, 9, 10]. The power indices are assumed to be 798' )@6for CNO and NeMgSi groups,798' 3@)for iron nuclei respectively, for calculation of expected points. More than 300 iron nuclei with energyabove 1 TeV/n will be detected. The detailed structure of the spectrum for each nuclear component will beobtained up to->/@/@/TeV/n region. Rigidity dependence of acceleration and propagation processes will bechecked basing on these data.3.3 Secondary/Primary RatioThe energy dependence of the ratio of secondary nuclei relative to primaries is important for understanding thepropagation mechanism of cosmic rays. Especially the observation in high energy region , more than 1 TeV/n,is important for the checking of the difference between some propagation models. We show the observed ratioof boron relative to carbon obtained by previous experiment[7, 11, 12] in Fig. 3, and the ratio of sub-Fe relativeto iron [7, 13] in Fig. 4.We made rough estimations of expected ratio which will be observed in CALET, assuming both of these ratiosare simply decreasing by single power law. The CALET mission will provide unique results for these ratiosCALET Observation of Nuclear Components in Primary Cosmic Rays 3231 10 210 310 410 510 610 710210310410510BESSRyan et al.SOKOLJACEEMUBEERUNJOBCALET(expected)Figure 1. Expected proton and helium spectra which will be observed in CALET mission(lled circles). Other points areobserved data by various kinds of balloon borne experiments[1, 2, 3, 4, 5, 6].210 310 410 510 610-310-210-110110210310HEAO3CRNSOKOLJACEERUNJOBKamioka et al.CALET(expected)CNONeMgSi(x1/10)iron(x1/100)Figure 2. The energy spectra for CNO group, NeMgSi group and iron nuclei. Filled circles are expected points for CALETmission, others are obtained by past direct observations[3, 6, 7, 8, 9, 10].324 M. Ichimura et al.up to several TeV/n. We are considering to lower the triggering energy threshold from 1 TeV down to severaltimes 10 GeV for these observation, because there are no observed data in the energy region above 100 GeV/nup to now. The estimated points are plotted in Figs. 3 and 4 for the energy more than 10 GeV/n with filledcircles. They will put severe restriction on the current propagation models.1 10 210 310 410-210-1101HEAO3Chappel et al.Simon et al.CALET(expected)l and Webber)Figure 3. The energy dependence of the ratio of boronrelative to carbon. The expected data for CALET missionare plotted with lled circles in TeV/n region. The previousmeasurements [7, 11] are covering the energy region lessthan 100 GeV/n.1 10 210 310 410-210-1101HEAO3Hareyama et al.CALET(expected)Figure 4. The ratio of sub-Fe group ( ACB=DFE0GHD>DFGHDJI ) rela-tive to iron nuclei. The expected points for CALET mission(lled circles) are plotted with the observed data obtainedby HEAO3[7] and Hareyama et al.[13].3.4 SummaryThe energy spectra for nuclear components and the secondary/primary ratios which will be observed inCALET mission are roughly estimated with simple assumptions. The variation of spectra in the energy regionjust below the Knee will be obtained for many species. Also the unique data for B/C ratio as same as sub-Fe/Feratio will be obtained in TeV/n region. The CALET will provide such important informations for nuclearcomponent which are very important to solve the problems on acceleration and propagation mechanisms ofcosmic rays.References[1] S. Haino et al., Phys. Lett. B 594, 35(2004).[2] M.J. Ryan et al., Phys. Rev. Lett. 28, 985(1972).[3] I.P. Ivanenko et al., Proc. 23rd Cosmic Ray Conf. 2, 17(1993).[4] K. Asakimori et al., Ap. J. 502, 278(1998).[5] V.I. Zatsepin et al., Yad. Fiz. 57, 684(1994).[6] V.A. Derbina et al., Ap. J. 628,L41(2005).[7] J.J. Engelmann et al., Astron. and Astrophys. 233, 96(1990).[8] D. Mu¨ller et al., Ap. J. 374, 356(1991).[9] K. Asakimori et al, astro-ph, 9509091(1995).[10] E. Kamioka et al., Astropart. Phys. 6, 155(1997).[11] J.H. Chappell and W.R. Webber, Proc. 17th Int. Cosmic Ray Conf. 2, 59(1981).[12] M. Simon et al., Ap. J. 239, 712(1980).[13] M. Hareyama et al., Proc. 26th Int. Cosmic Ray Conf. 3, 105(1999).

CALET Observation of Nuclear Components in Primary Cosmic Rays

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