Investigation of the background sources of muography László Oláh 1 , Hiroyuki Tanaka 1 , Dezső Varga 2 1 Earthquake Research Institute, The University of Tokyo 2 Wigner Research Centre for Physics of the HAS 15th July 2017
Outline I. Motivation: Muography II. Study of the Soft Component of Cosmic Rays III. MWPC-based Muographic Observation System for Volcano Imaging L. Oláh ICRC2017 2
I. Motivation: Cosmic-ray Physics Experiments The Standard Model describes the material world and the interactions, however ... ● Several open questions: ● How the Universum was created? ● Where is the origin of cosmic rays? ● Where is the missing antimatter? ● ... ● Cosmic-ray physics expriments are ongoing in the space, in the atmosphere, underground: ● C osmic rays/particle collisions + particle detectors The AMS Collaboration: The Pierre Auger Collaboration: The ALICE Collaboration: JINST 3 (2008) S08002 PRL 110 (2013) 141102 Phys. Lett. B. 685 (2010) 239-246 L. Oláh ICRC2017 3
I. Motivation: Muography I. Cosmic muons are energetic, non-invasive and loss their energy across materials: ● → imaging of objects at the size scale of 10-5000 m by the measurement of muon flux Large social benefits can be resulted by muography: ● prediction of volcano eruption, nuclear security, etc. The nuclear fuel was melted down in Reactor No. 2 of Fukushima H. Tanaka et al.: Earth Pl. Sci. Let. 263 (2007) 104 Physical Society of Japan meeting, Kunihiro Morishima et al. ( 2015): L. Oláh ICRC2017 4
I. Motivation: Muography II. Physical background noise of muography: ● Low energy muons and electrons (< 1 GeV) and high energy hadrons create background ● Signal-to-Noise ratio depends on the detector arrangement (absorbers, position resolution) ● and the target of interest (thickness) Maximization of Signal-to-Noise ratio of muography: ● Development of dedicated simulation framework for muography ● (it includes correlated particle showers, detector effects, target of interest) Application oriented development of paticle detectors for muography ● using low cost technologies L. Oláh ICRC2017 5
II. Study of the Soft Component of Cosmic Rays L. Oláh ICRC2017 6
A Simulation Framework for Muography A GEANT4-based simulation framework: S. Agostinelli et al.: NIM A506 (2003) 250-303 ● US1976 atmosphere model http://ccmc.gsfc.nasa.gov/modelweb/atmos/us standard.html ● Muons are injected vertically above 6 km asl with power law energy distribution (N(E)~ E -2.7 ) ● Low-material budget tracking detectors are deployed at sea level ● Muons and electrons (E > 10 MeV) are tracked in the atmosphere and in the detectors: ● IDs, energy, momentum and position information are recorded and analysed Sources of soft component: ● All of the sources are relevant, muon decay becomes more abundant with increasing energy ● Electrons/positrons (E >10 MeV) are created at the last 1-1.5 km (3-5 X 0 ) above sea level ● L. Oláh and D. Varga: Astroparticle Physics 93 (2017) 17-27 L. Oláh ICRC2017 7
Spectra and Ratios of Secondary Cosmic-ray Particles Spectra and ratios of secondary cosmic rays are in agreement with the ● earlier measurements, the theory, and other simulations Theory: R. R. Daniel and S. A. Stephens: Rev. Geophys., 233-257, 1974 Measurement: R. Golden et al.: J. Geophys. Res., 100, 515-523, 1995 CRY: C. Hagmann et al.: Nucl. Sci. Symp. Conf. Rec. (2007) 1143-1146 L. Oláh and D. Varga: Astroparticle Physics 93 (2017) 17-27 L. Oláh ICRC2017 8
Spatial and Directional Correlations Particle pairs are observed within low relative angle (< 25 o ) and small distances (< 10 m) ● Correlation measurement was performed with two MWPC-based trackers: ● simulation reproduces the measurements Conclusion: realistic, correlated physical background casued by the soft component can ● be simulated by single muons started from the altitude of 6-30 km L. Oláh and D. Varga: Astroparticle Physics 93 (2017) 17-27 L. Oláh ICRC2017 9
Spatial and Directional Correlations Particle pairs are observed within low relative angle (< 25 o ) and small distances (< 10 m) ● Correlation measurement was performed with two MWPC-based trackers: ● simulation reproduces the measurements Conclusion: realistic, correlated physical background casued by the soft component can ● be simulated by single muons started from the altitude of 6-30 km L. Oláh and D. Varga: Astroparticle Physics 93 (2017) 17-27 Slave Distance Master L. Oláh ICRC2017 10
Soft Component at Underground Soft component is created in the soil/rock at the last few radiation lengths (10-50 cm) ● Electrons are produced mostly by ionization and the decay of muons does not contribute ● Spatial and directional correlations are also observed ● Qualitatively the same results are observed as under open sky, ● but the charachteristic lengths are smaller due to the reduced radiation length L. Oláh and D. Varga: Astroparticle Physics 93 (2017) 17-27 (detector depth) (detector depth) L. Oláh ICRC2017 11
III. MWPC-based Muographic Observation System for Volcano Imaging L. Oláh ICRC2017 12
MWPC Technology for Cosmic Particle Tracking A new variant of MWPC detector ● MWPC measures the position of electron avalanche created by a charged particle ● Requires the flow of Ar - CO 2 gasmixture (non-flammable, environmental friendly) ● 2D position information: field wires and pick-up wires, self-triggering by anode wires ● Low material budget (15 kg /m 2 ), tolerance against small (~ 100 μm) mechanical shocks ● Reasonable position resolution: 4 mm, angular resolution: ~ 10 mrad ● Stable detector operation in varying environmental ● D. Varga, G. Hamar, G. Nyitrai, L. Oláh: Advances in High Energy Physics 2016 (2016) 1962317 L. Oláh ICRC2017 13
MWPC-based Muographic Observation System (mMOS) Joint development of the Wigner RCP of the ● HAS and Earthquake Research Institute, UT 7 layers of MWPCs (surface of 0.6 m 2 , ● length of 2 m) and 5 layers of 2 cm lead absorbers, angular resolution of 10 mrad, low power (< 6 W) Raspberry Pi controlled DAQ → Low noise and high precisional muography G. Hamar, T. Kusagaya, L. Oláh, H.. Tanaka, D. Varga: Muographic Observation System, PTZATA153 L. Oláh ICRC2017 14
Test of mMOS at the Sakurajima Volcano, Kyusu, Japan Imaging with near-horizontal muons: flux of 10 -3 -10 -1 m -2 sr -1 s -1 after 1-5 km SiO 2 ● The mMOS reliably operates at the Sakurajima from the January of 2017: ● resonable trigger rate of 5-7 Hz, detection efficiency above 95 %, and stable gas gain are observed The measured flux is in aggrement with the expected one calculated from Modified Gaisser model ● A. Tang et al.: Phys. Rev. D 74 (2006) 053007 Next steps: ● First images of the volcano with 30 m × 30 m resolution (2017) ● Online detector monitoring and imaging system (2018) ● Development and construction of large size (~10 m ₂ ) detector system (2017-2020) ● L. Oláh ICRC2017 15
Summary Muography is a promising technique for various applications ● Investigation of the soft component of cosmic rays: ● GEANT4-based simulation framework: correlated showers + detector ● Simulation well reproduces particle spectra and ratios ● Spatial and directional correlations are observed: ● particles typically arrive in pairs within a small distance and small relative angle MWPC-based Muographic Observation System (mMOS): ● Based on lightweight, low power gaseous detectors ● mMOS performs low noise and high precisional muography ● mMOS applicability was demonstrated at Sakurajima volcano, Kyusu, Japan ● Thank You for your attention! Our supporters: MTA Lendület program (LP2013-60); MEXT Integrated Program for the Next Generation Volcano Research and Human Resource Development. L. Oláh ICRC2017 16
Back up slides L. Oláh ICRC2017 17
Consistency tests of creation altitude and exponent of energy distribution L. Oláh ICRC2017 18
Consistency tests of zenith angle and magnetic field L. Oláh ICRC2017 19
Comparison of proton and muon induced air showers L. Oláh ICRC2017 20
Measurement of directional correlations under open sky L. Oláh ICRC2017 21
Creation altitude of electrons at shallow depth L. Oláh ICRC2017 22
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