International Workshop on "Muon and Neutrino Radiography 2012"

17 avr. 2012, 08:00 → 20 avr. 2012, 18:00 Europe/Paris

Chapelle des Cordeliers

Aldo Zollo (Universita degli studi di Napoli), Annarita Margiotta (Sezione INFN and Universita Bologna), Christophe De La Taille (IN2P3/CNRS), Hiroyuki Tanaka (ERI/U Tokyo), Jean-Francois LENAT (LMV/UBP), Laurent Desbat (UJF Grenoble)

The conference website.

mar. 17 avril

11:00 Registration

12:30 Lunch

Round table: Detectors for muon tomography

1 Physics case for the detectors in volcanology, seismic fault, industry and extraterrestrial planetary explorations

Orateur: Prof. Hiroyuki Tanaka (University of Tokyo)

Transparents RoundTable-Tanaka-Intro.pdf

2 Emulsion detectors

Orateur: Dr Andrea Russo (INFN Napoli)

Transparents RoundTable-Russo.pdf

3 Scintillation based detectors with MAPMTs DAQ

Orateur: Prof. Hiroyuki Tanaka (University of Tokyo)

Transparents Roundtable-Tanaka-Scintillator.pdf

4 Scintillation based detectors with SiPM DAQ

Orateur: Fabio Ambrosino (Dipartimento di Scienze Fisiche Università degli Studi di Napoli "Federico II" e Sezione INFN, Napoli)

Transparents RoundTable-Ambrosino-Scintillator.pdf

5 Gazeous detectors

Orateur: Dr Cristina Carloganu (LPC Clermont Ferrand)

Transparents RoundTable-Carloganu.pdf

6 VFE electronics for high segmentation detectors : Spiroc, Hardroc ASICs

Orateurs: Dr Cristina Carloganu (LPC Clermont Ferrand), Fabio Ambrosino (Dipartimento di Scienze Fisiche Università degli Studi di Napoli "Federico II" e Sezione INFN, Napoli)

Transparents RoundTable-Ambrosino-FEE.pdf

7 Constraints on the detectors in situ (tropicalisation, power consumption, remote control, etc)

Orateur: Dominique GIBERT (Institut de Physique du Globe de Paris)

Transparents ROundTable-Gibert.pdf

15:30 Registration and coffee break

mer. 18 avril

Registration

Poster Session

8 Development and evaluation of a time-dependent radiographic technology by using a muon read out module

We will present a real-time monitoring system for cosmic-ray muon radiography as an application of a readout module developed by T. Uchida et al [1,2]. The readout module was developed originally for probing the internal structure of volcanoes in 2008 [3]. Its features are small in size, low power consumption, and the capability to access remotely via Ethernet. The current statistics data of cosmic-ray muons can be read from a PC placed far from the module at anytime. By using this feature, we constructed a real-time monitoring system. As a test experiment, we observed fluid movement in a cylinder with a diameter of 112 meters water equivalent. In this work, we succeeded to resolve the fluid movement in the cylinder. We varied the fluid level inside the cylinder and measured the muon intensity. We found that the muon intensity correlates inversely with the fluid level: the muon intensity increases for the lower fluid level and decreases for the higher fluid level. Although the time resolution of muon radiography was sufficient to resolve changes in the fluid level, an adequate time window has to be chosen for different operating conditions. We anticipate that this system will be applicable to exploring high-speed phenomena in a gigantic object. References [1] T. Uchida, H. K. M. Tanaka, and M. Tanaka, Space Saving and Power Efficient Readout System for Cosmic-Ray Muon Radiography, IEEE Transactions on Nuclear Science, Vol. 56, No.2, pp. 448-452, Apr., 2009. [2] T. Uchida, H K. M. Tanaka, and M. Tanaka, Development of a muon radiographic imaging electronic board system towards a stable solar power operation, Earth Planets Space, Vol. 62, No. 2, pp. 167-172, Feb., 2010. [3] H.K.M. Tanaka, T. Uchida, M. Tanaka, and H. Shinohara, Cosmic-ray muon imaging of magma in a conduit: Degassing process of Satsuma-Iwojima Volcano, Japan, Geophysical Research Letters, Vol. 36, L01304, pp. 1-5, Jan., 2009.

Orateur: M. Taro Kusagaya (Earthquake Research Institute, University of Tokyo)

9 Development of a joint inversion technique using gravity and muon-radiographic data for resolving three-dimensional density structure of a gigantic body

We have developed a method of analyzing gravity and muon-radiographic data for resolving a three-dimensional density structure of a volcano. In the method, we search for a density structure that explains the muon and gravity data by using a linear inversion scheme. As a demonstration, we applied this method to Mt. Showa-Shinzan lava dome, Hokkaido, Japan. At this site, muon observation has already been performed with emulsion cloud chamber(ECC). The effective area of ECC was 1200 cm2, and the exposure time was four month. Tanaka et al. [2007] calculated the amount of matter on the muon trajectories in the unit of gcm^{-2} (density times length). In addition to the muon data, we newly collected gravity data at 35 stations on/around the dome. The gravity data were measured by using a LaCoste Romberg Gravimeter (G-875). Positions of gravity stations were determined by GPS interferometry. First, we performed a so-called checkerboard test with a synthetic data to test the resolution. We concluded from the result of the test that a horizontal spatial resolution is about 200 m in our configuration. Based on the conclusion, we conducted joint inversion of the actual muon and gravity data. The joint inversion yielded us the three-dimensional density profile of Mt. Showa-Shinzan. The density profile suggested the two features of the dome. Firstly, we could visualize the high density magma which had intruded beneath the dome at an altitude of 220 - 260 m. Secondly, we found an ultra high density region which was suspected to be a spine spreading vertically near the top of the dome.

Orateur: M. Ryuichi Nishiyama (Earthquake Research Institute, University of Tokyo)

10 Development of a Logging Tool for Muon Radiography

A research for high level radioactive waste disposal should investigate geological structure and saturation change of rock mass around a disposal cavern. In the CO2 geological storage and the underground storage of crude oil, natural gas or liquefied petroleum gas (LPG), it is necessary to monitor an upward migration of a gaseous fluid which is stored in underground. For an investigation of slope stability, it is effective to evaluate a high saturation area in the ground's pore space as the area should be the same as that of a rainfall infiltration. Since these phenomena could be evaluated by a measurement of a density variation in underground rock, an application of muon radiography is highly prospective. The Central Research Institute of Electric Power Industry (CRIEPI) has a plan to conduct a field experiment to evaluate an applicability of the muon radiography to engineering geology in cooperation with Electric Power Development Co., Ltd. (J-POWER). The field experiment will be performed this year in slope topography. If the applicability will be revealed as a result of the field experiment, CRIEPI will start a research on development of a logging tool which can measure muon in a borehole. We plan to build a prototype of the logging tool in around three years and will put it into practical use in around five years.

Orateur: Hiroshi Suenaga (Central Research Institute of Electric Power Industry)

11 Development of a simple-material discrimination method with three plastic scintillator strips for visualizing nuclear reactors

The Fukushima Daiichi nuclear disaster is a series of equipment failures and nuclear meltdowns, following the T¯ohoku earthquake and tsunami on 11 March 2011. We present a new method for visualizing nuclear reactors. Muon radiography based on the multiple Coulomb scattering of cosmic-ray muons has been performed. In this work, we discuss experimental results obtained with a cost-effective simple detection system assembled with three plastic scintillator strips. Actually, we counted the number of muons that were not largely deflected by restricting the zenith angle in one direction to 0:8o. The system could discriminate Fe, Pb and C. Materials lighter than Pb can be also discriminated with this system. This method only resolves the average material distribution along the muon path. Therefore the user must make assumptions or interpretations about the structure, or must use more than one detector to resolve the three dimensional material distribution. By applying this method to time-dependent muon radiography, we can detect changes with time, rendering the method suitable for real-time monitoring applications, possibly providing useful information about the reaction process in a nuclear reactor such as burnup of fuels. In nuclear power technology, burnup (also known as fuel utilization) is a measure of how much energy is extracted from a primary nuclear fuel source. Monitoring the burnup of fuels as a nondestructive inspection technique can contribute to safer operation. In nuclear reactor, the total mass is conserved so that the system cannot be monitored by conventional muon radiography. A plastic scintillator is relatively small and easy to setup compared to a gas or layered scintillation system. Thus, we think this simple radiographic method has the potential to visualize a core directly in cases of normal operations or meltdown accidents. Finally, we considered only three materials as a first step in this work. Further research is required to improve the ability of imaging the material distribution in a mass-conserved system.

Orateurs: Prof. Hiroyuki Tanaka (University of Tokyo), Dr Kuniyoshi Takamatsu (JAEA)

12 Introduction of a test measurement for a monitoring technology inside a large-scale civil engineering structure using muon radiography

Introduction The technology that enables us to observe the internal structure of a volcano and the city foundation is being developed by utilizing the muon’s significant penetration power. From the possibility to use this technology for the surveillance inside a large-scale civil engineering structure, we are planning an experimental measurement. General Instruction A final target is safety judgment of the condition of a large-scale civil engineering structure. It is important for safety judgment to grasp the internal density contract, such as the crack and slack levels of a base rock or the structure, and degradation and groundwater levels. However, feasibility of application of muon radiography to monitoring inside the large-scale civil engineering structure has not confirmed yet. Therefore, as a test experiment, we attempt to measure the fluctuation of the groundwater level in order to evaluate and examine the method. Measurement will be carried out from the inside of a scupper tunnel in the base rock. The result will be compared with the independent groundwater level measurement in order to perform quantitative evaluation of muon radiography. In addition, this test measurement will start the near future. About a detailed plan, it is under examination now.

Orateur: Dr Akira Sannomiya (Electric Power Development)

13 Rapid-time sequential muon radiography for repetitional phenomena

The time resolution of dynamic muon radiography is defined by achieving the appropriate angular resolution, detection area, and cosmic ray muon flux (=70 muons/m2 sr sec). For example, at an angular resolution of 30 mrad, we need a detection area of 3.9 m2 to collect 100 muons in 8 hours for each bin. However, a space of this size in the correct position may be unavailable in an industrial plant system. In this work, we developed a new technique to dynamically image a high speed phenomenon using a more practically sized detector adapted to relieve some of these restraints on the present system . This technique can be applied to any repetitional phenomena by superimposing radiographs collected during different intervals of time. In the coarse of these experiments, we collected muon data every 10 minutes in order to analyze the internal density distribution of an electric furnace for different operating conditions. Here we report the results for different (a) electric load conditions, (b) electric resistance conditions, and (c) production efficiencies. We clearly distinguished the variation in the spatial distribution of the melt objects inside the furnace collected between the daytime and the nighttime.

Orateur: Prof. Hiroyuki Tanaka (University of Tokyo)

14 The lava dome tomography in Unzen : the discussion about the observation and data treatment

S. Miyamoto (7), C Bozza (6), N D’Ambrosio (1), G De Lellis (4), A Di Crescenzo (4), N Di Marco (1), U Kose (5), N Naganawa (3), M Nakamura (3), R Rescigno (6), A Russo (4), H Shimizu (2), C Sirignano (1), S Stellacci (6), P Strolin (4), H Tanaka (7), and V Tioukov (4) (1) INFN , Gran Sasso, Italy, (2) SEVO, Kyushu University Japan, (3) F-lab, Nagoya University, Japan, (4) INFN, Napoli, Italy, (5) INFN , Padva, Italy, (6) INFN , Salerno, Italy, (7) ERI, The Univesity of Tokyo, Japan The observation of the lava dome density 2D map was performed by using cosmic-ray muon and muon detector in Unzen. The muon detector, nuclear emulsion films which has high position resolution and 0.85m2 effective area, was installed in a natural cave from early December 2010 to the end of March. The developed nuclear emulsion films has been scanned by automated muon readout system. In this session, the flow of data acquisition, basic treatment of the data, and density calculation will be shown. A lot of discussions about this observation and data treatment are welcome.

Orateur: Dr Seigo Miyamoto (University of Tokyo)

Welcome

Volcanology

Président de session: Prof. Aldo Zollo (Univ Naples)

15 Earthquake tomography on volcanoes with a probabilistic regularization approach

Muon radiography of volcanoes aims at estimating the density of rocks constituting the volcanic edifice from muon fluxes. Earthquake tomography aims at estimating the seismic velocity of the same rocks from the travel times of seismic waves. Muon radiography and earthquake tomography are inverse problems that share some similar features - muon flux variation and travel time may be both written as the integral of elementary flux variations or travel times across elementary volumes of rocks that are sampled by muon trajectories or seismic rays. In this talk we will present our experience in seismic tomography, emphasizing on the aspects that may be later used in muon radiography. In both cases the whole volume of the volcanic edifice may be incompletely or insufficiently sampled by muon trajectories or seismic rays. Inferring parameters characterizing elementary volumes from an integral measure therefore leads to evidence trade-offs between this parameters. These trade-off relations feature the correlation existing between the parameters, which is inherent to the nature of the inverse problem. Incomplete or insufficient sampling and trade-offs lead to find unphysical parameter values, which may spread over trajectories or rays. Noise may therefore propagate along these trajectories or rays, from poorly sampled elementary volumes to neighbouring elementary volumes due to the integral nature of the muon flux variation or seismic travel time, lowering the resolution of the parameter estimation. Mitigating the problems due to the incomplete sampling of the studied volume is performed by regularizing the inversion. In this talk we will follow a probabilistic, bayesian approach for performing this regularization, in the frame of seismic tomography. We therefore perform the Maximum a posteriori Probability (MAP) estimation of the model parameters. Data and parameters are assumed to follow a gaussian distribution, and a priori information is used to limit the values taken by parameters to physical intervals. The correlation between parameters is explicitely taken into account by defining correlation kernels and correlation lengths. Optimal standard deviation and correlation length are found by minimizing a cost function. It leads to find the minimal-norm model fitting the data. It will be shown that (1) introducing a limited bias in the estimation strongly limits its variance, (2) contrarily to what is often thought, increasing the correlation length does not lead to bias the model and to lower the resolution – instead, using the optimal correlation length leads to increase the resolution by solving the bias-variance trade-off (improving the physical value of the parameter while reducing the noise).

Orateur: Prof. Jean-Luc GOT (ISTERRE, CNRS, Université de Savoie)

Transparents Volcanology-Got.pdf

16 From conduit processes to surface emissions: constraints from seismic and Doppler radar data

We have investigated the dynamics of volcanic explosive eruptions, from the sub-surface source mechanisms through to the surface emission dynamics. To this end, we carried out a cross-correlation of broadband seismic data and ground-based Doppler radar data (VOLDORAD) recorded at Arenal (Costa Rica). Arenal is a small stratovolcano ca. 1.1 km in height, characterized by a mildly-explosive activity which commonly expels both ash plumes and ballistic projections that can rise up to a few hundred meters above the vent. The radar data inform on the mass loading and velocimetry of the expelled ejecta through time and space, while the seismic data inform on volcanic processes operating within the edifice. A conceptual model is proposed to account for the complex interplay of both data, whereby fractures through a rigid lava cap control the system’s degassing, which in turn governs both the seismic and radar signals.

Orateur: Dr Sebastien Valade (LMV, Université Blaise Pascal)

Transparents Volcanology-Valade.pdf

17 Crustal structure of Guadeloupe Islands and the Lesser Antilles Arc from a new gravity and magnetic synthesis

Guadeloupe Island (West French Indies) is one of the twenty islands that compose the Lesser Antilles Arc, which results from the subduction of the Atlantic Ocean plate beneath the Caribbean one. The island lies in a complex volcano-tectonic system and the need to understand its geological context has led to numerous on- and offshore geophysical investigations. This work presents the compilation and processing of available, on-land, airborne and marine, gravity and magnetic data acquired during the last 40 years on Guadeloupe Islands and at the scale of the Lesser Antilles Arc. The overall dataset provides new Bouguer and reduced to the pole magnetic anomaly maps at the highest achievable resolution. Regionally, the main central negative gravity trend of the arc allows defining two subsident areas. The first one is parallel to the arc direction (~N160°E) to the north, whereas the second unexpected southern one is oriented parallel to oceanic ridges (N130°E). Along the Outer Arc, the long wavelength positive anomaly is interpreted, at least along the Karukera Spur, as an up-rise of the volcanic basement in agreement with the seismic studies. To the NE of Guadeloupe, the detailed analysis of the geophysical anomalies outlines a series of structural discontinuities consistent with the main bathymetric morphologies, and in continuity of the main fault systems already reported in this area. Based on geophysical evidences, this large scale deformation and faulting of the Outer Arc presumably primarily affects the Atlantic subducting plate and secondarily deforms the upper Caribbean plate and the accretion prism. At the scale of Guadeloupe Island, joined gravity and magnetic modeling has been initiated based on existing interpretation of old seismic refraction profiles, with a general structure in three main layers. According to our geophysical anomalies, additional local structures are also modeled in agreement with geological observations: i) the gravity and magnetic signals confirm an up-rise of the volcanic basement below the limestone platforms outcropping on Grande-Terre Island ; ii) the ancient volcanic complexes of Basse-Terre Island are modeled with high density and reverse magnetized formations; iii) the recent volcanic centre is associated with formations consistent with the low measured density and the underlying hydrothermal system. The EW models coherently image a NNW-SSE depression structure in half-graben beneath Basse-Terre Island, its western scarp following the arc direction in agreement with bathymetric and seismic studies to the north of the island. The so-defined depressed area, and particularly its opening in half-graben toward the SW, is interpreted as the present-day front of deformation of the upper plate associated with the recent volcanic activity on and around Guadeloupe. Based on this regional deformation model, perspectives are given for further integrated investigation of key targets to address the internal structure and evolution of the Lesser Antilles Arc and Guadeloupe volcanic system.

Orateur: Lydie Gailler (LMV-BRGM)

Transparents Volcanology-Gailler-Guadeloupe.pdf

18 Internal architecture of La Réunion (Indian Ocean) inferred from geophysical data

The island of La Réunion (Indian Ocean) is a large oceanic volcanic system of which most of the volume is submerged. We present a study of its internal structure using geophysical methods. Subaerial and marine gravity and magnetic measurements have been compiled with terrestrial-based electromagnetic surveys. Geophysical models have been constructed using geological constraints and results from previous geophysical interpretations. The magnetic data allow us to differentiate the structures pre- and post-dating the Brunhes-Matuyama magnetic reversal (0.78 Ma). The main gravity features are used to detect and characterize the dense intrusive complexes, and to derive the internal structure of the coastal formations and of the submarine flanks. The electromagnetic data allow us to determine the distribution of electrical resistivities which we interpret in terms of water saturation of rocks, hydrothermal alteration and the presence of hydrated mineral. At Piton de La Fournaise, the dense gravity coverage allows us to unambiguously distinguish the shallow and deep sources. The shallow ones correspond to the filling of ancient depressions by dense lavas flows, to the Central Cone, largely composed of low density material, and to a level of breccias at the base of the large southern valleys. The deep structures are associated with intrusive complexes within Les Alizés volcano and the Ancient Shield of the Piton de la Fournaise. Gravity variations associated with the collapse of the Dolomieu crater in April 2007 are studied in terms of mass displacements within the edifice. The analysis of magnetic anomalies suggests that the products from Piton de la Fournaise are rather thin to the north and to the east of the massif. It also indicates the presence of a body of weakly magnetized rocks underneath the central zone, correlated with the presence of a hydrothermal system, well characterized by a dome of rocks with low resistivity, and with an inferred shallow magma reservoir. Beneath the Ancient Shield, a region of weak resistivity may correspond to an ancient hydrothermal system. The Piton des Neiges is depicted as a huge volcano structured around a large hypovolcanic system (~20 km in diameter and ~4 km thick). The blanket of Brunhes formations is not continuous over Piton des Neiges and shows large thickness variations. Only the western flank, the summit zone and, to a lesser degree the northern flank, present significant thicknesses of these products. Topographical barriers predating Bruhnes-Matyama reversal, such as those created by collapses, or subsequent large landsides could explain the discontinuous distribution of these formations at the scale of the massif. In addition, we observe a close correlation between the extent of the intrusive complex and the topographical depressions of the massif. This suggests a possible relationship between a subsidence of the complex and that of the overlying formations. On the immerged part of the volcanic system, two large ancient volcanic constructions are identified in the continuation of sub-aerial ones: (1) to the east of the Piton de la Fournaise (the eastern flank of Les Alizés volcano) and (2) to the south-west of Piton des Neiges (Etang Salé Submarine Ridge). At the land-sea transition, the coastal shelf is interpreted in terms of accumulation of hyaloclastites and pillow-lavas, such as the examples of La Montagne Massif, to the north, or of the offshore continuation of the rift zones, to the north-east and south-east of Piton de la Fournaise. On the immerged flanks, gravity and magnetic analyses show that the four submarine bulges are mostly composed of low density and brecciated material which correspond well to accumulations of mass wasting deposits as proposed by geological studies. At the scale of the entire construction, we have been able to reconstruct the morphology of the top of the submarine volcanic constructions and that of the top of the island at the Brunhes-Matuyama reversal.

Orateur: Mlle Lydie Gailler (LMV-BRGM)

Transparents Volcanology-Gailler-LaRéunion.pdf

10:40 Registration and coffee break

19 Structure of Puy de Dôme volcano (Chaîne des Puys, France): towards a revised model

The project TOMUVOL, aimed at developing a method for muonic tomography of volcanic edifices, has chosen the Puy de Dôme as an experimental test site. In fact, this volcano with a simple external shape has a complex internal structure that may allow testing the performances of this new method. The Puy de Dôme is a composite lava dome, about 11 ka old. It is composed of two distinct morphological units. The first one would consist of a classic bristled lava-dome whereas the second one would be a dome erected on the eastern flank of the first one, after a large flank collapse. However, between 2004 and 2011, fresh outcrops revealed by the building of touristic facilities on the summit and at the basis of the mountain, afforded the collection of new data inducing new questions. The field was then more systematically explored and the results of a LiDAR survey centred on the Puy de Dôme and recorded in March 2011 were examined. As a result, the following key-points were set to the forth. (i) The volcanic sequence was initiated by a small explosion which perforated the geological basement. (ii) The slopes of the eastern edifice display long and thick (up to ~6 m) lava slabs which can be considered as true lava flows, not included in the simple dome model. Also, the amount of accumulated ash and blocks at the eastern foot of the volcano is too small to fit the wide flank-collapse hypothesis. (iii) Alteration of the dome by fumaroles and/or hydrothermal processes was previously underestimated. Actually, not only the summit of the volcano is deeply affected by colored alteration and silicification, sometimes connected with marked fissures, but the hydrothermal system, localised below the dome, is suspected to have triggered a late small eruption through an open vent atop the volcano. Now, the challenge consists in establishing a new model able to account for these new data. In this perspective, the geophysical investigation, including muon tomography, should play a prominent role.

Orateur: M. Didier Miallier (Laboratoire de Physique Corpusculaire Clermont Université - Université Blaise Pascal CNRS-IN2P3)

Transparents volcanology-Miailler.pdf

20 Inner structure of the Puy de Dôme: cross-comparison of geophysical models (ERT, Gravimetry, Muonic Imagery)

Muon imagery of volcanoes and other types of geological structures is presently actively developed by several groups in the world. It has the potential capability to provide the 2D or 3D distribution of density with an accuracy of a few percent. However, at this stage of the development of the method, comparisons with the results from established geophysical methods are necessary to validate its results. An experience is presently carried out at the Puy de Dôme volcano involving the concurrent acquisition of muon imagery, electrical resistivity, 2D tomography (ERT) and gravity survey. Here we present the preliminary results for the last two methods. The Puy de Dôme is an 11,000 years old, 1465 m high composite dome in the Chaîne des Puys (France). Geological studies suggest an evolution with at least two pulses of lava extrusion, separated by a partial destruction of the first construction. This interpretation is in good agreement with the present morphology, as, for example, it can be observed in the new high precision LIDAR elevation model (50 cm resolution). In addition, Miallier and al., (2010) suggest that a final explosive episode formed a small crater on the summit at 10,700 years. Hydrothermal alteration is widespread on the outcrops in the summit area of the dome. A first south-north resistivity section has been obtained in June 2011 using a 2200 m long line of electrodes (electrode spacing of 35 m and of 5 m in the summit area). A second west-east similar profile is planned for April 2012. These electric data will provide models of the distribution of the resistivity values down to the base of the dome. Because the resistivity of the rocks varies significantly (several orders of magnitude) according to their water and clay contents, a resistivity section can be interpreted as a geological section. A detailed gravity survey has also been carried out in March 2012. The dome and its surroundings are now covered with more than 250 gravity stations. The computed Bouguer anomaly can be interpreted by models of the density distribution within the dome. This will be directly comparable with the results from the muons imagery. Our ultimate goal is to derive a model of the dome using the joint interpretation of all the sets of data.

Orateur: Angélie PORTAL (OPGC-LMV)

Transparents Volcanology-Portal.pdf

21 Towards a muon radiography of the Puy de Dome

High energy (10^11+ eV) atmospheric muons are a natural probe for geophysical studies. They can travel through hundreds to kilometers of rocks allowing for a radiography of the density distributions within large structures, the like mountains or volcanoes. A collaboration between volcanologists, astroparticle- and particle physicists, TOMUVOL, has been formed in 2009 to study tomographic muon imaging of volcanoes with high-resolution, large-scale tracking detectors. We report on two campaigns of radiographic measurements of the Puy de Dôme using Glass Resistive Plate Chambers (GRPCs) developped for Particle Physics R&D, within the CALICE collaboration.

Orateur: M. Valentin Niess (LPC, Clermont)

Transparents Volcanology-Niess.pdf

22 Visualizing the internal structure of a cryptodome with cosmic ray muon radiography

We have developed a multilayer, scintillator based, segmented muon hodoscope with the capacity to create up to 8 layers. One of the most important processes of cosmic ray muon radiography is the ability to select muon trajectories with precision from simultaneously arriving, vertical electromagnetic (EM) background components. As the size of the target increases, the muon path length of the target lengthens and significantly decreases the flux of the penetrating muon. Accordingly, the effect of background (BG) noise becomes more exaggerated as the length of the muon path increases. To address this issue, we attempted to reduce the vertical EM shower originated background events and to screen the low energy muons (muons with energies below 10 GeV) by constructing a multi-layered, rotational muon hodoscope called GDM (gradient of density measurement). Along with other adjustments, this GDM hodoscope was also designed to effectively cancel artifacts in the PMT and scintillator individually as well as facilitating corrections for the horizontal east-west effect. The maximum detectable thickness (MDT) of the present GDM was found to be 4 km.w.e. Four or more position sensitive detector (PSD) layers measured the trajectory of the cosmic-ray muons while low energy muons were screened using GDM analysis. Conventional muon radiography methods require one to two months for data collection, however we were able to measure the internal structure of the 1910 cryptodome of Usu volcano located in Hokkaido, Japan in 290 hours with +/-2% precision in the density measurement. The obtained image indicates the existence of high density magma that is hidden inside the structure of a hill.

Orateur: Prof. Hiroyuki Tanaka (University of Tokyo)

Transparents Volcanology-Tanaka-Calorimeter.pdf

12:30 lunch

Volcanology

Président de session: Prof. Aldo Zollo (Univ Naples)

23 Density Muon Radiography of Soufrière of Guadeloupe Volcano: Comparison with Geological, Electrical Resistivity and Gravity data

We present density radiographies obtained for the Soufrière of Guadeloupe lava dome, both in the North-South and East-West planes. These radiographies reveal the highly heterogeneous density structure of the volcano, with low-density regions corresponding to recognized hydrothermally altered areas. The main structures observed in the density radiographies correlate with anomalies in electrical resistivity cross-sections and density model derived from gravity data

Orateur: Prof. Dominique GIBERT (Institut de Physique du Globe de Paris)

Transparents Volcanology-Gibert.pdf

24 Muon radiography of the Unzen volcano with a nuclear emulsion detector.

The improvements of automated scanning systems have produced an impressive revival of the nuclear emulsion technique, thus allowing their large scale application in particle physics experiments. The portability of a nuclear emulsion based detector makes it well suitable also for the muon radiography of internal structures of volcanoes. We present the application of this technique to the study of the Unzen and Stromboli volcanoes. We will report preliminary results on the analysis of emulsion films exposed in Japan and being currently scanned in Italian and Japanese laboratories. For the Stromboli we present the design of the emulsion detector and the plans for the future analysis.

Orateur: Dr Andrea Russo (INFN Napoli)

Transparents Volcanology-Russo.pdf

25 The MU-RAY telescope

The MU-RAY project aims at the construction of muon telescopes and the development of new analysis tools for muon radiography. The telescopes are required to be able to work in harsh environment and to have low power consumption, good angular and time resolutions, large active area and modularity. A high background suppression is required. A prototype telescope has been constructed. The detector is composed of three stations, each consisting of two planes of one square meter area for the measurement of the X-Y coordinates. The three stations are assembled on a frame where their relative distance can be modified. The frame can be easily rotated to change the azimuth angle. Each plane consists of two modules made by 32 scintillator strips of triangular cross section coupled with WLS fibres. The light emitted from fibres is read by Silicon Photomultipliers, produced by FBK-IRST, mounted on a custom printed circuit board. A dedicated front-end electronic, based on SPIROC ASIC, and data acquisition system have been developed. The prototype is under test in the Physics Department in Naples. The detector design, construction and preliminary performances results will be shown.

Orateur: Fabio Ambrosino (Dipartimento di Scienze Fisiche Università degli Studi di Napoli "Federico II" e Sezione INFN, Napoli)

Transparents Volcanology-Ambrosino.pdf

26 Exploring muon radiography as an asset in the characterisation of activity at dome-forming volcanoes

Orateur: Dr Joachim Gottsmann (University of Bristol)

Transparents Volcanology-Gottsman.pdf

27 Looking into Ngauruhoe volcano; - can we use muons to get a density profile

Ngauruhoe (2287 m high) was New Zealand’s most active volcano for over a century until 1975, when after a series of Vulcanian eruptions, it became quiescent. It is a steep conical volcano, which had an open vent about 200 metres deep in late 1973, which has since filled up. It is important in considering the hazard of future eruptions, and in interpreting any possible eruption precursors, to know whether its former vent is blocked by solid lava or just soft fill material. Muon tomography offers a method to measure the density within the upper part of the volcano, and can potentially answer this question. Based on measurements of the deep open vent that existed in late 1973, and using the current topography, we calculated the effect on the muon attenuation profile of a density anomaly in the old vent region. This showed that if a film type muon detector could be installed at a suitable location high on the slopes of Ngauruhoe, it would be able to detect whether there is a significant density difference associated with the old vent. Work has continued on trying to find a suitable location to install the detectors. Difficulties include the steep topography, as well as getting permission to use an area of importance to both outdoor enthusiasts and the indigenous population. Possible sites have been identified on the less visited southern side, and will be investigated next summer. The trade-off between a lower site which can see deeper into the volcano versus a higher site with less attenuation can only be decided once the characteristics of the detector film are known.

Orateur: Dr Tony Hurst (GNS Science)

Transparents Volcanology-Hurst.pdf

28 Volume slicing with multi-directional muon radiography

Additional strategies to modify the rapid time measurement system of muon radiography may make it possible to survey a target without knowledge of its exterior shape. Examples of such targets would be an activated volcano with a growing lava dome or the geology of extraterrestrial exploration. Established techniques of muon radiography rely on precise exterior shape data because the method exclusively focuses on the integral density along the muon path. However, the exterior shape specific targets may be changeable (as a lava dome grows) or may be unknown. To resolve this point we need either (1) a time-sequential three dimensional exterior shape of the target (e.g., as obtained by synthetic aperture rader measurement); or (2) a method to resolve the internal density structure without the knowledge of an exterior shape. Unlike other phenomenon utilized in geophysical techniques, muons pass through targets without diverging. Therefore, a tomographic analysis method using radon transformation can be applied. A new, portable, battery-operated muon detector system with the capacity to create three-dimensional images of targets without the aid of external shape information is described in this paper. Mt. Omuro was chosen as an example in this survey because the structure is well known and, unlike other volcanoes, it is encircled with road and parking areas that are conveniently situated. A battery-operated muon detector was set up in a compact car and the target was measured by moving the car to different vantage points. The measurement time at each point was 20 minutes, a suitable time frame to assess a growing lava dome or to conduct an investigation at an extraterrestrial exploration point. Once the reconstructed slice of the target was obtained, it was found to be consistent with the known contours of the main structure and crater.

Orateur: Prof. Hiroyuki Tanaka (University of Tokyo)

Transparents Volcanology-Tanaka-VolSlices.pdf

16:00 Registration and coffee break

Volcanology: Volcanology Round Table

Président de session: Prof. Aldo Zollo (Univ Naples)

29 Introduction to the round table - Geophysical vs muon imaging techniques applied to volcanoes : advantages, limitations and perspectives

Orateur: Prof. Aldo Zollo (Univ Naples)

Transparents Volcanology-RoundTable-Zollo.pdf

30 Seismic tomography vs muon radiography to image the structure of volcanoes

Orateur: Jean-Luc GOT (ISTERRE)

Transparents Volcanology-RoundTable-Got.pdf

31 Geological and volcanological relevance/potential of muon radiography to investigate and to understand the shallow volcanic processes

Orateur: Jean-François Lénat (UMR 6524 CNRS "Magmas et Volcans")

Transparents Volcanology-Roundtable-Lenat.pdf

32 Applications and perspectives of Muon radiography: the experience in Japan

Orateur: Prof. Hiroyuki Tanaka (University of Tokyo)

Transparents Volcanology-Tanaka-RoundTable.pdf

33 Applications and perspectives of Muon radiography: the experience in Italy

Orateur: Prof. Paolo Emilio Strolin (Univ. Napoli and INFN)

Transparents Volcanology-RoundTable-Strolin.pdf

34 Applications and perspectives of Muon radiography: the experience in France

Orateur: Dominique GIBERT (Institut de Physique du Globe de Paris)

jeu. 19 avril

35 Opening

Poster Session

Atmospheric Muons and Neutrinos

Président de session: Annarita Margiotta (Sezione INFN and Universita' Bologna)

36 Atmospheric muons and neutrinos

Primary cosmic-protons and nuclei interact in the atmosphere and produce cascades of secondary hadrons, some of which decay to produce muons and neutrinos. Production of pions, kaons and other hadrons occurs at the level of nucleon-nucleon interactions. For example, the excess of positive muons is a consequence of the excess of protons over neutrons in the primary spectrum of cosmic-ray nucleons. On average, the most energetic pion from interaction of a high-energy proton is positively charged, while the opposite is the case for a neutron. Thus the charge asymmetry in the primary cosmic radiation persists in the muons observed at the surface and deep underground. In this talk I will start with a review of the primary spectrum and then discuss the consequences for the muon charge ratio and the ratio of neutrinos to antineutrinos. These ratios are sensitive to the relative contribution of pions and kaons. The response of the muon and neutrino fluxes to changes in the stratosphere can also be used as a probe of flavor content, including the contribution from decay of charmed hadrons at very high energy. I will discuss seasonal variations in rates as a probe of kaon and charm contributions to the flux of muons and neutrinos. Finally, I will comment on the shape of the spectrum of atmospheric neutrinos around 100 TeV and above where the influence of the “knee” in the primary cosmic ray spectrum appears. Understanding the atmospheric neutrino spectrum in this energy region is important because it is the background in the search for neutrinos of astrophysical origin as well as a probe of density structure of the Earth.

Orateur: Thomas Gaisser (University of Delaware)

Transparents AtmoMN-Gaisser.pdf

37 Atmospheric muons: experimental aspects

At sea level the flux of charged particles is dominated by muons, which originated by the decay of mesons produced by the interactions of primary cosmic rays at the top of the atmosphere. Due to their relative stability and small cross sections, these particle are able to arrive deep under-ground, -water or -ice. As a consequence, their penetration properties opens the possibility of radiography of thick and very thick objects. The muon flux is strongly dependent on energy and zenith angle and, at low energies, also on altitude, geomagnetic latitude, solar activity and atmospheric conditions. Finally, the study of the muon flux covers many aspects of particle and cosmic ray physics. The talk will review some experimental aspects and results obtained in the last decades using different methods. These methods can be combined into direct measurements of the muon energy spectrum at the sea level (or shallow depths) using magnetic spectrometers and the measurements of the depth–intensity curve deep under-ground,-water and -ice. The measurements cover a large interval of the muon momentum at the sea level (from a fraction of GeV/c up to tens of TeV) and the different experimental techniques are shortly illustrated. The correlation between some observable quantities with their systematic uncertainties and the underlying physical processes are described. Finally, underground and underwater events contain a large fraction of multiple muons; the characteristics of muon bundles are presented.

Orateur: Prof. maurizio spurio (Università Bologna)

Transparents AtmoMN-Spurio.pdf

38 Geoneutrinos

Electron anti-neutrinos produced by natural radioactivity inside the Earth - geoneutrinos - can be used as a unique direct probe in order to determine the amount of long-lived radioactive elements inside our planet and to constrain the radiogenic contribution to the terrestrial heat. The composition of the Earth's interior, the heat sources driving the mantle convection, the generation of the Earth's magnetic field are all not well understood, but in many models the abundance of radioactive elements is one of the key points. Geoneutrinos with extremely small interaction cross sections propagate undisturbed through the Earth and today represent the only possibility how to trace down radioactivity in the deep Earth. The large volume liquid scintillator detectors, originally built to measure neutrinos or anti-neutrinos from other sources, are capable to detect them, as was demonstrated by KamLAND (Japan) in 2005 for the first time. Since then geoneutrinos were measured with high statistical significance both by KamLAND and by the Borexino underground experiment (central Italy) designed to measure low energy solar neutrinos. Several future projects of large volume detectors have geoneutrinos among their scientific goals, as SNO+ (in construction phase) or LENA and HanoHano. The status-of-art and scientific potential of this new inter-disciplinary field will be presented.

Orateur: Dr Livia Ludhova (INFN Milano)

Transparents AtmoMN-Lhudova.pdf

10:45 Coffee break

39 Neutrino Radiography of the Earth’s Core with the IceCube neutrino observatory

In spring of 2011, the world's largest neutrino observatory, IceCube, was completed within deep glacial ice at the South Pole. IceCube is designed to detect Cherenkov light emitted by secondary charged particles generated from high-energy neutrinos. The primary mission of IceCube is to discover the origin of cosmic neutrinos, while detailed studies of the atmospheric neutrino background have been performed in the last five years. For example, we observed ~35 atmospheric neutrino events per day in 2008 with a half-size detection volume of completed IceCube. From the point of view of geosciences, using atmospheric neutrinos seen by IceCube is currently the unique solution to perform neutrino radiography for the Earth’s core. This is the direct measurement of Earth's core density, while the body-wave and the free oscillation studies based on seismic wave measurements cannot reduce substantial uncertainties that depend on geophysical models of Earth. Two challenges to be overcome for IceCube are sufficient event statistics and improved energy resolution. Our current knowledge about Earth’s density profile, the Preliminary Reference Earth Model (PREM), indicates sensitivity to neutrino energies above 10TeV. However, the atmospheric neutrino energy spectrum decreases steeply with increasing energy. This constraint results in a requirement of long-term measurement even with a cubic kilometer neutrino observatory. Using 10 years of full-size IceCube data, we currently expect at least 3-sigma separation in averaged density between core and mantle. On the other hand, the energy resolution of event reconstruction affects separation efficiency of neutrinos with energy over 10TeV. With a better energy resolution and detailed understandings of systematic errors, the required measurement period is minimized. Our short-term goal is thus understanding systematic errors and improving our energy reconstructions. In this talk we present the current status of neutrino radiography of the Earth's Core with IceCube one year data. The talk will contain results performed with data obtained in 2008 or later.

Orateur: Dr Kotoyo Hoshina (ERI University of Tokyo)

Transparents AtmoMN-Hoshina.pdf

40 Atmospheric showers simulation and preliminary background estimation

The main source of background for the radiography of volcanoes with atmospheric muons comes from the accidental coincidences produced in the telescopes by the atmospheric showers. In order to quantify this background, the showers were investigated using two MonteCarlo packages, Corsika[1] and Geant4[2]. The talk will describe the simulation chain and give very preliminary results on the shower topology as well as on the background estimation. [1] http://www-ik.fzk.de/corsika/ [2] http://geant4.cern.ch/

Orateur: Samuel Béné (LPC Clermont-Ferrand - Tomuvol)

Transparents AtmoMN-Bene.pdf

12:30 Lunch

Applications of muon imaging in geophysics, archeology, civil and industrial engineering

Président de session: Prof. Hiroyuki Tanaka (University of Tokyo)

41 Application of Muon Geotomography to Mineral Exploration

A novel geophysical imaging method using muon tomography is being developed for mineral exploration. This nondestructive technique, similar in principle to computed tomography, can be used to identify massive ore bodies underground. A proof-of-concept trial has been conducted using a known volcanic massive sulfide deposit at Mt. Myra located on Vancouver Island in British Columbia. Muon flux data from the experimental survey were used to obtain mass lengths from the sensors to the surface. Using an accurate topographical map, the mass lengths were inverted to reconstruct an image of the deposit in good agreement with the known drill-data. Simulations and calculations were also performed to test the inversion software and design the survey. This work demonstrates that muon tomography can be a valuable approach for identifying mineral deposits with high-density contrast compared to the host rock.

Orateur: Zhiyi Liu (AAPS@TRIUMF)

Transparents Application_Liu.pdf

42 Pyramids: a case study for muon tomography

In 1969, Luis Alvarez ruled out the existence of an extra room in Khephren's pyramid, using a muon detector installed in the only known room, which is close to the ground level. Several studies have pointed out the possible existence of an extra room in Khufu's pyramid, which could be located below the level of known rooms. It would be detectable by modern muon detectors installed outside of the pyramid.

Orateur: M. Eric Aubourg (APC)

Transparents Application-Aubourg.pdf

Technical developments for muon and neutrino imaging

Président de session: Christophe de LA TAILLE (LAL)

43 The KM3NeT project: status and perspectives

KM3NeT is an international consortium involving more than 300 scientists from 10 EU countries. Its main objective is the construction of a multi-km3 high-energy neutrino telescope in the Mediterranean Sea that will also host an interdisciplinary observatory for devices dedicated to marine sciences. KM3NeT has been included in the roadmap of the European Strategy Forum of Research Infrastructures (ESFRI). Very high energy neutrinos are important messengers to study non-thermal phenomena in the Universe and their detection will help to answer astrophysical questions, such as those related to the origin of the cosmic rays and the mechanisms of particle acceleration. The pioneering ANTARES, NEMO and NESTOR underwater neutrino telescope projects comprise the extensive R&D knowledge base behind the KM3NeT project. A Technical Design Report has been published which describes the technological solutions chosen for the detector. European-wide funding is available now to start a first construction phase. The present status of the project and the steps towards construction are presented and the physics potential discussed.

Orateur: Annarita Margiotta (Sezione INFN and Universita' Bologna)

Transparents Detector-Margiotta.pdf

44 The MEUST Project

The Mediterranean Eurocentre for Underwater Sciences and Technologies (MEUST) plans to deploy a second generation deep sea cabled infrastructure offshore of Toulon, France, within the framework of the European networks of neutrino telescopes KM3NeT and deep sea observatories EMSO. The project will be presented with emphasis on the layout of the deep sea infrastructure, its regional context and its multidisciplinary applications in environmental sciences.

Orateur: Dr Claude Vallee (Centre de Physique des Particules de Marseille)

Transparents Detector-Vallee.pdf

45 The Diaphane project: readout design and telescopes upgrades

The DIAPHANE project is dedicated to the density tomography of geological structures, focusing on active volcanoes like the ones in the Lesser Antilles belt. The aim of the project is to provide high resolution profiles, complementary to standard tomographic methods, to constrain the various evolution models of those volcanoes. In this talk we review the opto-electronics readout scheme of the telescopes used to measure the muon flux attenuation through the structures under study. We detail present state of the readout chain, based on solid scintillator and multi-anode PMT's and the current upgrades under development using MPPC and FPGA-embedded TDC technology.

Orateur: Claude GIRERD (CNRS)

Transparents Detector-Girerd.pdf

46 Old and new perspectives for the readout system of the MuRay muon telescope

Muon telescopes, which detect atmospheric muons produced from cosmic ray showers, are providing an invaluable tool to volcanologists the world over by imaging the cone structure of the volcanoes. An instrument of this type has been assembled in Italy by the MuRay collaboration. The MuRay telescope uses scintillator rods to detect and track atmospheric muons. One of the novelties with respect to other instruments developed for this purpose consists in the use Silicon Photomultipliers (SiPM) to convert the scintillator light output in electrical signals. In this paper a detailed description will be given of the electronics designed and built for this detector based on the SPIROC chip, also new developments for the future using the new EASIROC chip will be presented.

Orateur: Raffaello D'Alessandro (Università di Firenze - INFN Firenze)

Transparents Detector-Dalessandro.pdf

16:00 Coffee break

47 Progress of the collaboration T2DM2

T2DM2 SUMMARY OF OBJECTIVES AND SCIENTIFIC The aim of this project is to develop a new field of study in the geosciences, using a detector very promising and innovative coming from particle physics, applied to the temporal tomography of subsurface a few hundred meters thickness of rock. The field of applications concerns the stability of rocks, the monitoring of rheological properties, as for example: monitoring of landslides, collapse of a tunnel or a cliff, or the evolution of a volcanic cone. We propose to develop the methodology (measurement instrumentation, measurement protocol, forward modeling and tomographic inversion) needed to achieve: • The density map of the rock mass geological objects, with a lateral extension mileage under a blanket multi hectometric. • Measurement of density variations related to spatial and temporal changes in the fluid saturation or the evolution of the rock porosity along its state of stress. T2DM2 (Temporal Tomography Densitometric by the Measure of Muons), we propose to develop a range of 80 muon telescopes to measure the density and extent of variations in density, in order to have a new operational tool for the characterization and monitoring of basements. This tool will complement innovative exploration geophysics (eg, seismic, electrical and electromagnetic imaging of the basement), in the various fields of application: • Monitoring of water resources and reserves, • Monitoring the stability of volcanoes, • Monitoring of oil fields, gas storage CO2 or active reserve, • Monitoring the stability of tunnels and underground cavities, • Monitoring of rock mass instabilities in the context of the cliff and monitoring of landslides.

Orateur: Pierre Salin (GEOAZUR-LSBB(UMS3538)-CNRS-IN2P3)

Transparents Detector-Salin.pdf

48 Development of large GRPC with a very fine segmentation readout electronics

Glass Resistive Plate Chambers (GRPC) are excellent candidates to study volcanoes structure. They provide high efficiency and excellent homogeneity to detect the muons crossing the volcanoes. Few chambers of 1m2 equipped with an embedded readout electronics of 1 cm2 segmentation that were developed to be the active medium of a sampling hadronic calorimeter proposed for the future International Linear Collider experiments were used to perform a preliminary study of the Puy De Dôme structure. The output of this study confirms the capability of these detectors and allows one to envisage using them for future studies of the volcanoes structure.

Orateur: M. imad laktineh (in2p3-ucbl)

Transparents Detector-Laktineh.pdf

49 Muon tomography with resistive plate chambers

Resistive Plate Chambers are widely used in high energy physics experiments as reliable trigger systems due to their excellent time resolution and rate capability, while generally the track spatial information is obtained by means of different detectors. Studies show that it is possible to produce RPC with good spatial resolution (~ 0.5 mm) by appropriate choice of the pitch of the readout strips. High resolution RPC (HRPC) can be economically produced to cover large area and represent a valid alternative to more expensive detectors in applications when a spatial resolution of 0.5 mm is sufficient. Our group has successfully produced a Muon Scattering Tomography (MST) prototype based on 12 HRPCs which provide 3D information on muons scattering in a volume ~ 50 cm x 50 cm x 80 cm (suitable for scanning a suitcase). Both the incoming and the outgoing tracks of the muon are reconstructed. The required spatial granularity is achieved using ~300 readout strips per HRPC, with a pitch of 1.5 mm. All the strips from an HRPC are multiplexed into a single differential analog line by four Helix 3.0 chips daisy chained on a hybrid circuit. The detector has been collecting data since June 2011, with the HRPC showing an efficiency above 99% and purity above 98%. The spatial resolution on the tracks is ~0.8 mm. This is a preliminary measurement and includes the intrinsic detector resolution as well as the extrapolation errors due to multiple scattering in the detectors and separation of the planes. Additional results will be presented.

Orateur: M. Christian Thomay (University of Bristol)

Transparents DEtector-Thomay.pdf

50 CCC-based Muon Telescope for Examination of Natural Caves

The REGARD group (Eötvös Loránd University and Wigner RCP RMI collaboration for R&D of gaseous detectors) developed a portable detector for environmental application: searching for large scale underground rock/soil inhomogenities [1]. The designed muontomograph is based on the newly developed Closed Cathode Chamber (CCC) technology [2], which provide an cheap, easy handling, portable, high-resolution detector system, able to work even at extreme conditions (e.g. high humidity, low/high temperature). The developed muontomograph has about 0.1 square meters of detection surface with 10 mrad angular resolution, but it is small enough to deploy within difficultly-accessible cavern system where we used searching for hidden caverns. Cosmic muon flux measurements had been performed using our muon telescope in natural caves: (1) the relief reconstruction of the hill above the Molnár János cave in Budapest were done, (2) unknown cavern searches in Ajándék Cave (Ariadne Cave System), Pilis Mountain, Hungary is under investigation. [1] G. G. Barnaföldi et al.: Portable Cosmic Muon Telescope for Environmental Applications, Submitted to Nucl. Instrum. Meth. A (March 2012) [2] D. Varga, G. Hamar and G. Kiss: Asymmetric multi-wire proportional chamber with reduced requirements to mechanical precision Nucl. Instrum. Meth. A648, 163 (2011).

Orateur: M. László Oláh (Eötvös University)

Transparents Detector-Olah.pdf

51 The non-destructive measurement of soil water content of upper part of the cave using soft component of air shower

We have developed a new radiographic method to measure the time variation of the water content of the soil with soft component of air shower. Air shower produced by a primary cosmic ray consists of hard component and soft component. Hard component is mainly consists of muon, and soft components is consists of electron, positron and photon. The penetration power of soft component is weaker than that of hard component, so soft component is suitable for small scale structure thinner than 2 kg/cm^2 equivalent to 20m thick water, like buildings and small hills. But it requires particle identification which means distinguishing hard component and soft component. Particle identification can be done with strong magnets and dense detectors, but it is very hard to use that kind of detector for radiography because of their weight and cost. We established the cheap and effective method to distinguish soft component and hard component statistically. We also performed measurements in Arimura observation pit of Mt. Sakurajima, Japan. As a result of this observation, we found there is an anti-correlation between soft component flux and rainfall. If the water content of the soil became larger, the amount of absorption increases. So this result can be interpreted as detecting the increase of the water content by soft component flux. This method can be applied for the quantitive compensation of the measurement data like absolute gravitymeter data and tiltmeter data which is easy to receive turbulence by rain. It is also expected that the quantitive compensation leads to the improvement in accuracy of diastrophism measurement and the improvement in presumed accuracy of magma movement inside a volcano. We will report this newly developed radiography method using soft component for small scale structure in detail and the result of measurement. Further improvement and possible application are also discussed.

Orateur: M. Akimichi Taketa (ERI, University of Tokyo)

Transparents Detector-Taketa.pdf

52 Requirements for a survey system of active volcanoes based on muon radiography

Muon imagery techniques, that use cosmic-ray muons generated in the upper atmosphere, are currently intensively being developed by several international groups to probe the internal structures of volcanic edifices to depths up to several kilometers. These techniques may be used to construct precise 3D models of rock density distribution, and, even more, its variation with time, within active volcanoes. The development and validation of this innovative imaging method are currently being pursued by the multidisciplinary TOMUVOL collaboration that involves both particle and astroparticle physicists, volcanologists and geophysicists. The next step of the project concerns the application of muon tomography to the monitoring of active volcanoes, when validated on the experimental site, the Puy de Dôme volcano (Massif Central, France). To achieve this goal, the main challenge is the design, development and construction of a mobile instrument platform. Monitoring volcanoes using muon tomography is challenging, since it requires using cutting-edge particle physics detectors, previously used mostly in the laboratory, in harsh environments.The field muon telescope system has to be transportable, autonomous in energy and connected via a two-way communication channel (remote control of the system and data transmission). The definition of the specifications will constrain the project in all the technical aspects: the gas systems (for GRPC detectors), the design of the detectors, the autonomy in energy, the communication and data transmission, the instrument mobility and portability, the operation centre, the adaptation to local conditions, the design of the instrument platform prototype.

Orateur: Dr Philippe Labazuy (Laboratoire Magmas et Volcans, OPGC, Clermont Université, Université Blaise Pascal, CNRS, IRD)

Transparents Detector-Labazuy.pdf

53 social diner

ven. 20 avril

Poster Session

Tomographic reconstruction methods

Président de session: Laurent Desbat (UJF-Grenoble 1 / CNRS / TIMC-IMAG UMR 5525,)

54 Introduction to Muon and Neutrino Radiography

Orateur: Prof. Hiroyuki Tanaka (University of Tokyo)

Transparents Math-Tanaka.pdf

55 Integral Equation Methods for Electrical Impedance Tomography

Electrical Impedance Tomography (EIT) is a non-invasive, low cost technology developed to image the electrical conductivity distribution of a conductive medium. The technique works by performing simultaneous measurements of electric currents and voltages on the boundary of an object. These are the data used by an image reconstruction algorithm to determine the electrical conductivity distribution within the object. Different materials display different electrical properties, so a map of the internal conductivity can be used to infer the internal structure of the object under consideration. EIT can therefore be used as a method of industrial, geophysical and medical imaging. In this talk we present integral equation reconstruction methods suitable for smooth conductivity distributions.

Orateur: Dr CRISTIANA SEBU (OXFORD BROOKES UNIVERSITY)

Transparents Math-Sebu.pdf

56 Non-parametric regularization of tomographic problems

The purpose of the talk is to present an approach of tomographic inverse problems based on regularization by covariance type norm in a stochastic framework. By using Bochner’s characterization of definite positive functions, some useful classes of covariance kernels can be displayed, and I will indicate how to assign values to the regularization parameters through L-curve analysis. I will also give insights on the resolution and uncertainty analysis. Finally the approach will be illustrated by synthetic examples of 2-D tomography through ray analysis, and by the example of inferring spatial distribution of interstellar dust from opacity data in Astrophysics.

Orateur: Dr Bernard Valette (IRD)

Transparents Math-Valette.pdf

10:15 Coffee break

57 Inverse problems for reconstruction in tomography

Iterative reconstruction in tomography, based on inverse problems approaches, have long proven their potential to enhance reconstruction quality, compared to the filtered backprojection (FBP). The drawback of iterative methods is their expensive computation time. However ongoing researches on algorithms and recent enhancements in computational power, call for a re-evaluation of the potential of iterative reconstruction in this domain. I will present the advantages of using the inverse approach in tomographic reconstruction. A key point is the data modelization, i.e. the numerical model of projection, which has to be sufficiently accurate to ensure accordance to the data, while not enhancing too much the computational burden. Combining the minimization of data residuals with an adequate regularization term can allow to drastically reduce the angular sampling of projections without any loss of quality.

Orateur: Fabien Momey (Centre de Recherche Astrophysique de Lyon - UCB Lyon 1 / Laboratoire Hubert Curien - UJM Saint Étienne)

Transparents Math-Momey.pdf

58 Spinning Registration Reconstruction Quantization, a new reconstruction method for electron tomography

SRRQ (Spinning Registration Reconstruction Quantization) is a reconstruction method alternating projections alignment and segmentation of reconstructed volume. This method reconstructs alternately and iteratively an object complying a priori constraints, and an object which some projections comply registrated projections known experimentally. A priori constraints are derived for an object to reconstruct which is piecewise constant and which has a known limited number of phases. SRRQ well manages missed wedge reconstruction and misaligned projections which are typical constraints of electron tomography. In this talk, we present the SRRQ method and give some results on 2D simulations.

Orateur: Dr Maxime Moreaud (IFP Energies nouvelles)

Transparents Math-Moreaud.pdf

59 Region-of-interest tomography from incomplete data

Analytic two dimensional tomography aims at reconstructing a function from its line integrals, based on the exact inversion of the Radon operator. Until 2002 it was believed that no exact reconstruction was possible if any line integral was missing. Indeed, the reconstructions based on the FBP algorithm, used a non-local filter. Surprisingly, new results were published in 2002 (see [Clackdoyle et al. 2010], for a review) demonstrating that for some particular cases of incomplete data there exist region-of-interests that could be exactly reconstructed. Since that, two main approaches - that are not equivalent - were developed: the virtual-fan-beam (VFB) approach and the differentiated-back-projection (DBP) approach. Inverse analytic formulae were established for both. In a first part, we will present the classical approach in 2D tomography reconstruction and will introduce the incomplete data reconstruction problem. Then we will explain why and how the VBP and DBP approaches can solve some incomplete data problem. Numerical results will be shown. [Clackdoyle et al. 2010]: R. Clackdoyle and M. Defrise, Tomographic Reconstruction in the 21st Century, Region-of-interest reconstruction from incomplete data, IEEE signal processing magazine, p. 60-80, July 2010.

Orateur: Dr Catherine Mennessier (CPE Lyon)

Transparents Math-Mennessier.pdf

60 Monte Carlo image reconstruction for medical applications

Physical effects degrading the quality of reconstructed medical images have been corrected during a while using analytical methods, applied to projections or directly to reconstructed images but those methods are still aproximative. An alternative approach is to correct those effects using iterative methods during the reconstruction of images.vThe principal is to model the physical and technological effects degrading the image directly in the so called projector describing mathematically the process of image creation .During the tomographic reconstruction, which consists into inversing the matrix system to estimate the distribution of the radiopharmaceutical from the measured data, parasital effects are implicitly compensated because they are considered as full part of the process of images creation. Using this approach, one of the difficulties consists into modeling correctly the process of image creation including to it all the parasitical phenomena. Monte Carlo simulations are powerfull and efficient to conceptualize and optimize detectors but also to model realistic physical phenomena occuring during nuclear medicine exam reconstruction such as single photon emission tomography (SPECT) or Positron Emission Tomography (PET).

Orateur: Dr Lydia Maigne (University Blaise Pascal)

Slides MNT2012_Maigne.pdf

12:30 Lunch

Round Table Applied Mathematics

Président de session: Laurent Desbat (UJF-Grenoble 1 / CNRS / TIMC-IMAG UMR 5525,)