Investigation of the background sources of muography Lszl Olh 1 , - - PowerPoint PPT Presentation

Investigation of the background sources of muography

László Oláh1, Hiroyuki Tanaka1, Dezső Varga2

1Earthquake Research Institute, The University of Tokyo

2Wigner Research Centre for Physics of the HAS

15th July 2017

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Outline

• I. Motivation: Muography
• II. Study of the Soft Component of Cosmic Rays
• III. MWPC-based Muographic Observation System for Volcano Imaging

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• 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:

Cosmic rays/particle collisions + particle detectors

The ALICE Collaboration: JINST 3 (2008) S08002 The AMS Collaboration: PRL 110 (2013) 141102 The Pierre Auger Collaboration:

• Phys. Lett. B. 685 (2010) 239-246

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• 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.

• H. Tanaka et al.: Earth Pl. Sci. Let. 263 (2007) 104

The nuclear fuel was melted down in Reactor No. 2 of Fukushima Physical Society of Japan meeting, Kunihiro Morishima et al. ( 2015):

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• 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

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• II. Study of the Soft Component of Cosmic Rays

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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 X0) above sea level
• L. Oláh and D. Varga: Astroparticle Physics 93 (2017) 17-27

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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

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Spatial and Directional Correlations

• L. Oláh and D. Varga: Astroparticle Physics 93 (2017) 17-27
• Particle pairs are observed within low relative angle (< 25o) 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

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Spatial and Directional Correlations

• Particle pairs are observed within low relative angle (< 25o) 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

Master Slave Distance

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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)

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• III. MWPC-based Muographic Observation System

for Volcano Imaging

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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 - CO2 gasmixture (non-flammable, environmental friendly)
• 2D position information: field wires and pick-up wires, self-triggering by anode wires
• Low material budget (15 kg /m2), 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

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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 m2,

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

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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 SiO2
• 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 m₂) detector system (2017-2020)

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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

Our supporters: MTA Lendület program (LP2013-60); MEXT Integrated Program for the Next Generation Volcano Research and Human Resource Development.

Thank You for your attention!

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Back up slides

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Consistency tests of creation altitude and exponent of energy distribution

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Consistency tests of zenith angle and magnetic field

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Comparison of proton and muon induced air showers

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Measurement of directional correlations under open sky

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Creation altitude of electrons at shallow depth