Investigation of the background sources of muography

Transcription

1 Investigation of the background sources of muography László Oláh1, Hiroyuki Tanaka1, Dezső Varga2 1 Earthquake Research Institute, The University of Tokyo 2Wigner Research Centre for Physics of the HAS 15th July 2017

2 Outline I. Motivation: Muography II. Study of the Soft Component of Cosmic Rays III. MWPC-based Muographic Observation System for Volcano Imaging 2

3 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 AMS Collaboration: PRL 110 (2013) The Pierre Auger Collaboration: Phys. Lett. B. 685 (2010) The ALICE Collaboration: JINST 3 (2008) S

4 I. Motivation: Muography I. Cosmic muons are energetic, non-invasive and loss their energy across materials: imaging of objects at the size scale of 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): 4

5 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 5

6 II. Study of the Soft Component of Cosmic Rays 6

7 A Simulation Framework for Muography A GEANT4-based simulation framework: S. Agostinelli et al.: NIM A506 (2003) US1976 atmosphere model 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 km (3-5 X 0) above sea level L. Oláh and D. Varga: Astroparticle Physics 93 (2017)

8 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: Measurement: CRY: R. R. Daniel and S. A. Stephens: Rev. Geophys., , 1974 R. Golden et al.: J. Geophys. Res., 100, , 1995 C. Hagmann et al.: Nucl. Sci. Symp. Conf. Rec. (2007) L. Oláh and D. Varga: Astroparticle Physics 93 (2017)

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)

10 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) Slave Distance Master 10

11 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) (detector depth) (detector depth) 11

12 III. MWPC-based Muographic Observation System for Volcano Imaging 12

13 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)

14 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 14

15 Test of mmos at the Sakurajima Volcano, Kyusu, Japan Imaging with near-horizontal muons: flux of 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) 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 ( ) 15

16 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 (LP ); MEXT Integrated Program for the Next Generation Volcano Research and Human Resource Development. 16

17 Back up slides 17

18 Consistency tests of creation altitude and exponent of energy distribution 18

19 Consistency tests of zenith angle and magnetic field 19

20 Comparison of proton and muon induced air showers 20

21 Measurement of directional correlations under open sky 21

22 Creation altitude of electrons at shallow depth 22