Tsuji, S

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29th International Cosmic Ray Conference Pune (2005) 8, 233236The Observation System of EAS Muon Component with the EAS Arrayand the Muon SpectrometerS. Tsuji , T. Wada, N. Ochi, A. Iyono, S. Lan, M. Okita, N. Takahashi, K. Okei,Y. Yamashita, T. Katayama, M. Tokiwa, S. Liang, H. Matsumoto, T. Morita,T. Nakatsukaand I. Yamamoto(a) Department of Information Sciences, Kawasaki Medical School, Kurashiki 701-0192, Japan(b) Department of Physics, Okayama University, Okayama 700-8530, Japan(c) Yonago National College of Technology, Tottori 683-8502, Japan(d) Department of Computer Simulation, Okayama University of Science, Okayama 700-0005, Japan(e) Okayama Shoka University, Okayama 700-8601, Japan(f) Faculty of Engineering, Okayama University of Science, Okayama 700-0005, JapanPresenter: S. Tsuji (tsuji@med.kawasaki-m.ac.jp), jap-tsuji-S-abs1-he15-posterThe observation system of muons associated with the compact extensive air shower (EAS) array and the solidiron magnet spectrometer (Okayama telescope) was at work in Okayama University. This telescope enables usto measure the atmospheric muon flux at sea level and the incident direction, the momentum and the chargesign of incident cosmic-ray muons. The EAS array which is a part of Large Area Air Shower experiment isalso operated, and the telescope is located almost right under of this array. From January 2004, we startedcoincidence observation between the EAS array and Okayama telescope.1. IntroductionFigure 1. A photograph of Okayama telescope.The OU (plastic scintillator) array has beenoperating to observe extensive air show-ers (EAS) in the campus of Okayama Uni-versity since September 1996 and belongsto the Large Area Air Shower experiment(LAAS) [1, 2]. The muon spectrometer(Okayama telescope) is also installed tomeasure the atmospheric muon flux in thebuilding of Okayama University since April1990 [3, 4].The OU array is situated on rooftops ofthe building and the Okayama telescope un-der the same roof as shown in figure 2.The magnet spectrometer and the array of 8scintillators have been used to measure themomentum spectrum of the muon compo-nent of EAS since January 2004. The ordinal atmospheric muons are initiated from the primary particleswhich energies are below 	 eV. On the other hand, muons associated EAS are initiated from the primaryparticles which energies are 		 eV called the ”knee” region.This observation is able to study the muon component of EAS at sea level. Bennett and Greisen reported muonspectra using both the EAS array and the magnet spectrometer [5]. We have study muon flux associated withEAS using both the EAS array and the magnet spectrometer.234 S.Tsuji et alZthickness of roof : 20cmScint403.85(m)Scint120 0 -5(m)100-5(m)YZ14253678X50cm50cm5cm scintillator,8 detectorsNFigure 2. The arrangement of detectors. Left: Top view of detectors. The squares with numbers indicate positions of eachscintillation counters. The lled square indicates the position of Okayama telescope. Right: Side view in the broken circle.2. Observation systemThe EAS array and the telescope are situated as shown in figure 2. The OU array is a part of Large Area AirShower (LAAS) group arrays [1, 2]. The OU array is equipped with 8 detectors, each consist of a plastic scin-tillator (50 cm  50 cm  5 cm) and fast photomultiplier tube (PMT). The distance between the two triggering(No.1&No.4) is 5 m, and other detectors are located at 5-30 m from them. The array’s angular resolution isevaluated at 7 degrees by the Monte Carlo simulation [2]. The arrangement is shown in figure 2. The OU arrayare put on the top of the building and the Okayama telescope are set up in the building. The angular resolu-tion of the telescope is 1 ﬀﬂﬁ , MDM is about 150 ﬃ !#"$ . The geometrical acceptance is 21.5 %& ('  . Thetelescope consists of trigger counters (2 scintillation counters), position chambers (3 multi-wire proportionalchamber sets used as drift chambers), an iron core magnet, and a theodolite and azimuthal boards. The maincharacteristics are summarized in the reference [4]. The OU array is put on the rooftops the building and theOkayama telescope is under the same roof. The OU array is used to observe EAS electrons and muons withthe primary energy range 	 )	* eV. The Okayama telescope is operated to observe atmospheric muonswith the energy range 	,+-.	*/ eV. The majority of muons detected by the Okayama telescope are producedfrom the primary particle with the energy below 	0 eV. Each observation system is operated independently.The trigger signal of the OU array circuit is sent to the Okayama telescope system as shown with the empha-sized line in figure 3. The signal as the ”coincidence” between the OU array and the telescope is recorded inthe telescope data when the trigger signal of the OU array comes within 1 1 2 sec from the trigger signal of thetelescope.The Observation System of EAS Muon Component ... 235#&%)256&%%TCVG%QPVTQNNGT%#/#%/QFWNGU.GXGN#FCRVGT0+/KP66.QWV2%VQ65#P[HQNF%QKPEKFGPEGUVCTV)CVG)GPGTCVQT%(&KUETGOKPCVQT&GNC[UQWV KPQWVKPQWV)CVG&GNC[U&GNC[U0Q 0QKP0+//QFWNGUKPQWVQWVKP&4+8'4UEKPV2%2%2%2%UEKPV6TKIIGTWPKV%#/#%6&%OUENQEMNCVEJENQEM#\KOWVJCNCPINGEQPVTQNOQVQT<GPKVJCPINGEQPVTQNOQVQT5GTXQ%QPVTQNNGT5GTXQ%QPVTQNNGTKPVGTHCEG2%51.#56TCEKPIEQPVTQN2%%15/1'ZVGTCN$WUKPVGTHCEG)2+$$WUKPVGTHCEG5NCXG$WUKPVGTHCEG5[UVGOEQPVTQNNGT2%.CVEJ14%#/#%KPVGTHCEG%.1%-KPVGTHCEG%.1%-KPVGTHCEGJOUNCVEJ%NGCT5VCTV5VQR%NGCT$WU[)2+$Figure 3. Block diagram of the observation system. Left side is shown the OU array system and right side is shown theOkayama telescope system. The emphasized line is connected both system to send the OU array coincidence signals to theOkayama telescope system.3. ObservationElectron eventsIncident angel㧦ǰZ4.6r1.3qǰ[10.9r1.5qTime 㧦20/1/2004 2:8:36SC1SC2PC1PC2PC3PC4(A)(T)(M)Theodolite boardMagnetAzimuthal board      Okayama  telescope                      &               OU arrayTickness of roof㧦20cmMuon eventIncident angle㧦ǰZ4.2qǰ[2.8qMomentum㧦3.4GeV/cTime㧦20/1/2004 15:17:02(a) (b) (c)Figure 4. The particles of EAS fall in detectors. The events are shown in the track-checking system. Figure (b) shows twotrack events which are estimated electron events, since they do not penetrate the magnet. Figure (c) shows a single trackevent which is estimated single muon event, since it penetrates the magnet.We have observed coincidence events between the OU array and the Okayama telescope from 18th January2004 to 30th April 2005, total observation time is 380.2 days.Typical event tracks are shown in figure 4. Figure 4-(a) shows that particles in the air shower incident the OUarray and the Okayama telescope. Figure 4-(b) and (c) show the track-checking system. Figure 4-(b) showstwo track events. They are estimated to be electrons, since they do not penetrate the magnet. The thickness of236 S.Tsuji et althe iron core magnet is 32 cm. Figure 4-(c) shows the single track event. It is estimated to be a single trackmuon, since it penetrates the magnet. In case of single track muons, we can measure the momenta of themfrom bending in the magnet. The total number of coincidences and single muon events are shown in table 1.The event rate of recorded all events in the telescope is 156,815 per day. The event rate of recorded all singleTable 1. Number of associated events.no.of events rate / daycoincidence 299306 787.3single muon 195 0.513muon events is 10,732 per day. The coincidence event rate is 0.50 % and the associated single muon event rateis 304 35	67 % compared with recorded all events.The physical results are presented as “Momentum Spectrum of Muons Associated with Cosmic-Ray AirShower at Sea Level” in this conference [6].References[1] T.Wada et al., Nuclear Physics (Proc. Suppl.) 75A, 330 (1999).[2] N.Ochi et al., J. Phys. G:Nucl. Part. Phys. 29, 1169 (2003).[3] S.Tsuji et al., J. Phys. G:Nucl. Part. Phys. 24, 1805 (1998).[4] M.Tokiwa et al., 28th ICRC, Tsukuba(2003) HE2, 1171.[5] S.Bennett and K.Greisen, Phys. Rev. 6, 1982 (1961)[6] S.Tsuji et al., 29th ICRC, Pune(2005) HE. 1. 2,Proceeding in this conference,“Momentum Spectrum of Muons Associated with Cosmic-Ray Air Showerat Sea Level”

The Observation System of EAS Muon Component with the EAS Array and the Muon Spectrometer

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