Muography is a novel imaging technology to reveal density structure of hill-sized objects. The cosmic muons predictably lose their energy and penetrate hundreds of meters into the ground, thus their differential local flux correlates with the crossed density-length. The Sakurajima Muography Observatory in Kagoshima, Japan, is the largest muography experiment targeting an active volcano. A set of multilayered gaseous detectors are used to reconstruct the muon tracks, thus by measuring the flux, imaging of the inner part of the volcano become possible. The paper focuses on the technical challenges of such a particle tracking system, the designed multi-wire proportional chambers, and the recent results from the measurements

Balogh, Szabolcs J.

Gera, Ádám

Hamar, Gergő

Nyitrai, Gábor

Oláh, László

Tanaka, Hiroyuki K.M.

Varga, Dezső

Repository of the Academy's Library

Gaseous tracking detectors at the SakurajimaMuography ObservatoryG Hamar 1,4, H K M Tanaka 2,4, L Oláh 2,4, D Varga 1,4 G Nyitrai 1,3,Sz J Balogh 1, Á Gera 11 Wigner Research Centre for Physics, Budapest, Hungary2 Earthquake Research Institute, The University of Tokyo, Tokyo, Japan3 Technical University Budapest, Hungary4 Virtual Muography InstituteE-mail: hamar.gergo@wigner.huAbstract. Muography is a novel imaging technology to reveal density structure of hill-sizedobjects. The cosmic muons predictably lose their energy and penetrate hundreds of metersinto the ground, thus their differential local flux correlates with the crossed density-length. TheSakurajima Muography Observatory in Kagoshima, Japan, is the largest muography experimenttargeting an active volcano. A set of multilayered gaseous detectors are used to reconstruct themuon tracks, thus by measuring the flux, imaging of the inner part of the volcano becomepossible. The paper focuses on the technical challenges of such a particle tracking system, thedesigned multi-wire proportional chambers, and the recent results from the measurements.1. IntroductionMuography is a novel field of research where the detector technology and instrumentationof particle physics meets applications in geo-sciences and industry to reveal inner structure oflarge solid volumes.As cosmic rays encounter high-energy hadronic interactions in the upper atmosphere thesecondary particles decay, and the produced muons could reach the penetrate the surface ofEarth. The energy of the muon defines its penetration depth in units of density-length, thus theattenuation of the flux correlates with the overall mass along its track. Measuring the attenuationof the angular-dependent flux an imaging of the interior structure of hill-sized objects becamepossible.Muography got first known for archaeological inspections of a pyramid [1]. Nowadays themost highlighted application is the survey of volcanoes [2, 3, 4, 5, 6, 7, 8], while it is also usedto locate unknown cave systems [9, 10], disclose various ore-bodies in mines [11], in culturalheritage exploits [12], or directly in industry [13, 14].Several groups involved in R&D of detectors for HEP use cosmic muons for calibration, and afew started to use these state-of-the-art devices for muography. Muographs based in solid stateemulsion (eg. [8]) or scintillator devices (eg. [2]) are used, while various gaseous detectors asMicromegas [15] Resistive Plate Chambers [4] or Close Cathode Chambers [16] [17] had beenproven usable.2. Modified MWPC Detectors for MuographyGaseous detectors offer high efficiency particle detection with an extremely well knowntechnology [18]. Numerous realizations exist for the challenges in high energy physics, optimizedfor resolution (DC), rate capability (MPGD), excellent timing (MRPC), or gigantic volumes(TPC).Muography being typically moderate-scale outdoor experiments, the focus of design anddevelopments shifted towards simplicity, robustness, out-of-the-lab operability, low-powerconsumption, and cost efficiency.The sharpness of the muographical image depends on the detector’s angular resolution; thuswhen large lever arm shall be used the position resolution can be degraded, which could reducethe number of electronic channels relieving power-consumption and cost issues.Our Group has designed a modified multi-wire proportional chamber, that is optimized to beused in large-area muographic trackers [19]. Spacing of sense-wires is 12 mm, while connectedall-together to get an instant trigger if a muon is crossed. Field wires are applied to reducesensitivity to cathode flatness and serves as individual readout elements. As the etching oflarge-area (≈ 1 m2) PCB would be cumbersome, requiring expensive high-end-infrastructureand/or extra gluing steps; thus instead an extra plane of pickup-wires has been introducedserving as 1 dimensional pads. The projective readout is applicable due to the low occupancy,and thus reducing the number of channels to twice-of-squareroot, namely 160 channels for a120×80 cm2 chamber.Figure 1 shows a photo of the MWPC tester setup in the Laboratory at Wigner RCP inBudapest, where eight 80×80 cm2 chambers are tested for tracking performance, in a realisticclose-to-final (lead sheets are not included) setup.In most cases muographs shall be autonomous and low-power devices, as power source islimited (usually from batteries and solar panels). While the detector layers themselves donot require large currents (especially for gaseous ones), the crucial part is the data acquisitionsystem. The tasks of the DAQ includes powering the chambers and front-end electronics, readoutof the raw data, storage of recorded data, control of runs and user interactions, and monitoringof environmental parameters. Figure 2 shows a photo of a full DAQ plane with the maincomponents listed below. The total power consumption of a portable Muographs of WignerRPCis 6-10 W, all functions included.Figure 1. Tester setup for the ModifiedMWPC detectors in close-to-final layoutin the Laboratory at Wigner RCP inBudapest.Figure 2. Photo of the DAQ plane of a MMOS,containing DaqBoard and the RPi (middle), theHigh Voltage supply (left), LV regulator (middledown), and THP sensor (right).3. MMOS at Sakurajima Muography ObservatoryThe Sakurajima Muography Observaroty (SMO) is the world’s largest muography experiment[21], that targets an active volcano, Sakurajima, in south Japan in Kyushu. While SMO startedas a scintillator based experiment, the modified MWPC technology of the previous section hasbeen tested there, and soon became the main component of the system. Right now, in 2021, thereare 11 working gaseous trackers there, called MWPC-based Muography Observatory System(MMOS), each with mostly 8 layers of the described MWPC chambers and DAQ. Figure 3presents a close-up photo of an MMOS, where the individual chambers, the scattering leadplates, and its DAQ is visible.SMO, as all other volcano muography experiments, shall deal with extreme low flux, as close-to-horizontal muons are required and the absorption is high during the order-of-mile long muonpaths inside the hills. The imaging time and/or image resolution can be enhanced using largersurface, practically including multiple muographs into a combined system. At SMO all theMMOS modules measure individually, and regularly sending their data to a local server, whichis in connection with a remote data storage and analysis computer. Figure 4 presents a fartherphoto inside SMO building, showing 2+2 MMOS in their containers.The SMO based on the modified MWPC tracking units have shown an excellent performancein the last years [21], with roughly 99% efficiency on the individual MMOS units. With theMWPC based system the increase in effective area was such, that the images projected ontothe volcano showed localization better than 8 m, and density changes around the three craterscould be measured [20].In a separate study a similar single-MMOS-like system has been used to determine theimaging capabilities behind gigantic objects, namely the distortion of resolution behind/insidea hill/volcano [21]. The measurements at Sakurajima Muography Observatory could first proofformation of a volcanic plug via the novel method of muography [22].The experiment of SMO is still active, data is analysed and correlations to effects of geo-scientific and volcanologic interest are now in focus.Figure 3. An MMOS with 8 ModifiedMWPC detectors (green and copper coloursare visible) and the lead plates inbetweenthem, while the corresponding DAQ ismounted to a well-accessible side.Figure 4. Photo where 2+2 MMOS-es arevisible within their container boxes, all insidethe simple builing of SMO on the hillside ofSakurajima.AcknowledgmentsThe authors would like to acknowledge the support of the Hungarian OTKA Grant FK-135349and the János Bolyai Research Scholarship of the Hungarian Academy of Sciences, the Ministryof Education, Culture, Sports, Science and Technology, Japan (MEXT) Integrated Program forthe Next Generation Volcano Research, the support of the Joint Usage Research Project (JURP)of the University of Tokyo, Earthquake Research Institute (ERI) under project ID 2020-H-05,and the ”INTENSE” H2020 MSCA RISE project under Grant Agreement No. 822185. Theauthors would like to thank the work and support of the members of the REGARD DetectorPhysics Research Group of the Winger RCP.References[1] Alvarez L W et al. 1970 Search for hidden chambers in the pyramids Science 167 832[2] Tanaka H K M et al. 2013 Development of a two-fold segmented detection system for near horizontallycosmic-ray muons to probe the internal structure of a volcano Nucl.Instrum.Meth. A 507 657[3] Tanaka H K M, Kusagaya T, and Shinohara H 2014 Radiographic visualization of magma dynamics in anerupting volcano Nature Communication 5 3381[4] Carloganu C et al. 2013 Towards a muon radiography of the Puy de Dome Geosci.Inst.Meth.Data Syst. 2 55[5] Oláh L, Tanaka H K M, Hamar G and Varga D 2019 Muographic observation of density variations in thevicinity of Minami-dake crater of Sakurajima volcano Journal of Disaster Research 14 701[6] Saracino G et al. 2017 The MURAVES muon telescope: technology and expected performances Annals ofGeophysics 60 1[7] Lo Presti D et al. 2018 The MEV project: Design and testing of a new high-resolution telescope for muographyof Etna Volcano Nucl.Instrum.Meth. A 904 195[8] Tioukov V et al. 2019 First muography of Stromboli volcano Scientific Reports 9 6695[9] Cimmino L et al. 2019 3D Muography for the Search of Hidden Cavities Scientific Reports 9 2974[10] Surányi G, Molnár G, Barnaföldi G G, Hamar G, Melegh H G, Oláh L and Varga D 2016 Locating of densityanomalies using highly penetrating cosmic muons Karsztfejlődés 2016 203[11] Schouten D W and Ledru P 2018 Muon tomography applied to a dense uranium deposit at the McArthurRiver mine Journal of Geophysical Research: Solid Earth 123 8637[12] Morishima K et al. 2017 Discovery of a big void in Khufu’s pyramid by observation of cosmic-ray muonsNature 552 386[13] Thompson L F et al. 2020 Muon tomography for railway tunnel imaging Phys. Rev. Research 2 023017[14] Oláh L, Hamar G, Miyamoto S, Tanaka H K M and Varga D 2018 The first prototype of an MWPC-basedborehole-detector and its application for muography of an underground pillar Geophys. Exploration 71 113[15] Bouteille S et al. 2016 A micromegas-based telescope for muon tomography: the watto experimentNucl.Instrum.Meth. A 834 223[16] Oláh L, Barnaföldi G G, Hamar G, Melegh H G, Surányi G and Varga D 2012 CCC-based Muon Telescopefor Examination of Natural Caves Geosci. Instrum. Method. Data Syst. 1 229[17] Barnaföldi G G, Varga D, Oláh L, Hamar G, Melegh H G and Surányi G 2012 Portable Cosmic MuonTelescope for Environmental Applications Nucl.Instrum.Meth. A 689 60[18] Blum W and Rolandi L 1993 Particle Detection with Drift Chambers (Springer-Verlag)[19] Varga D, Nyitrai G, Hamar G and Oláh L 2016 High efficiency gaseous tracking detector for cosmic muonradiography Advances in High Energy Physics 2016 1962317[20] Oláh L, Tanaka H K M, Ohminato T, and Varga D 2018 High-definition and low-noise muography of theSakurajima volcano with gaseous tracking detectors Scientific Reports 8 3207[21] Varga D, Hamar G, Nyitrai G, Gera Á, Oláh L, and Tanaka H K M 2019 Tracking detector for highperformance cosmic muon imaging Journal of Instrumentation 5 C05007[22] Oláh L, Tanaka H K M, Ohminato T, Hamar G, and Varga D 2019 Plug Formation Imaged Beneath theActive Craters of Sakurajima Volcano With Muography Geophysical Research Letters 46 10417

Gaseous Tracking Detectors at the Sakurajima Muography Observatory

http://real.mtak.hu/150308/1/Tipp2021Proc_SMO_20210624.pdf

Gaseous Tracking Detectors at the Sakurajima Muography Observatory

Abstract

Similar works

Full text

Available Versions

Repository of the Academy's Library