3D cosmic-ray muon tomography using portable muography detector

A feasibility demonstration of three-dimensional (3D) muon tomography was performed for infrastructure equivalent targets using the proposed portable muography detector. For the target, we used two sets of lead blocks placed at different heights. The detector consists of two muon position-sensitive detectors, made of plastic scintillating fibers (PSFs) and multi-pixel photon counters (MPPCs) with an angular resolution of 8 msr. In this work, the maximum likelihood-expectation maximization (ML-EM) method was used for the 3D imaging reconstruction of the muography. For both simulation and experiment, the reconstructed positions of the blocks produce consistent results with prior knowledge of the blocks' arrangement. This result demonstrates the potential of the 3D tomographic imaging of infrastructure by using seven detection positions for portable muography detectors to image infrastructure scale targets.

A portable muon telescope for multidisciplinary applications

Muon tomography or “muography” is an emerging imaging technique that uses cosmogenic muons as the radiation source. Due to its diverse range of applications and the use of natural radiation, muography is being applied across many fields such as geology, archaeology, civil engineering, nuclear reactor monitoring, nuclear waste characterization, underground surveys, etc. Muons can be detected using various detector technologies, among which, resistive plate chambers (RPC) are a very cost effective choice. RPCs are planar detectors which use ionization in a thin gas gap to detect cosmic muons, already used since years in major particle accelerator experiments. We have developed a muon telescope (or “muoscope”) composed of small scale RPCs. The design goal for our muoscope is to be portable and autonomous, in order to take data in places that are not easily accessible. The whole setup is light and compact, such to be easily packed in a car trunk. Individual RPCs are hosted in gas-tight aluminium cases. There is no need for gas bottles, once the chambers are filled. The muoscope can be controlled from a reasonable distance using wireless connection. In this paper we summarize the guiding principles of our project and present some recent developments and future prospects, including a long-term stability study of the resistivity of the semiconductive coating obtained with serigraphy.

The use of muon radiography in safeguarding geological repositories

Muon radiography is a technique that harnesses naturally occurring cosmic radiation to noninvasively determine the density of an object of interest. The technique has many similarities to that of medical X-ray examinations and can supply detailed density maps of the object. We propose the application of muon radiography to aspects of the long-term monitoring of nuclear waste. In particular, muon radiography would provide valuable information on the overburden of a prospective underground geological repository and would be able to identify unknown features, such as undocumented underground passages. Similarly, muon tomography is capable of confirming that containers that have nominally been emptied are in fact empty. Such safeguard measures are important to maintain continuity of knowledge and to develop robust deterrent strategies against the removal of monitored nuclear material. The presentation focuses on the results of simulations that address some of these questions. Details of assumptions regarding the detector requirements and run times necessary to perform the imaging are discussed and results from the various removal and misuse scenarios are presented.

SMAUG v1.0 – a user-friendly muon simulator for transmission tomography of geological objects in 3D

Knowledge about muon tomography has spread in recent years in the geoscientific community and several collaborations between geologists and physicists have been founded. As the data analysis is still mostly done by particle physicists, we address the need of the geoscientific community to participate in the data analysis, while not having to worry too much about the particle physics equations in the background. The result hereof is SMAUG, a toolbox consisting of several modules that cover the various aspects of data analysis in a muon tomographic experiment. In this study we show how a comprehensive geophysical model can be built from basic physics equations. The emerging uncertainties are dealt with by a probabilistic formulation of the inverse problem, which is finally solved by a Monte Carlo Markov Chain algorithm. Finally, we benchmark the SMAUG results against those of a recent study, which however, have been established with an approach that is not easily accessible to the geoscientific community. We show that they reach identical results with the same level of accuracy and precision.

Feasibility study of muon tomography application in a non-invasive representation of tumulus

Within the frame of the EKATϒ programme, whose purpose is the innovative imaging of the subsurface of archaeological sites and the interior of structural elements of monuments in “three” and “four” dimensions, the applicability of Muon Tomography technique in the representation of a tumulus is tested in the present work. The scanning of its internal structure is accomplished by measuring the flux deficit of cosmic muon tracks in the presence of an object inside the tumulus, compared to the muon flux when traversing a uniform tumulus (transmission muography). The feasibility study of the method is achieved with a simulation of the tumulus geometry and the structure under investigation. Following the simulation process, a tracking telescope, consisting of four MicroMegas detectors and two trigger plastic scintillators, will be placed near Apollonia’s tumulus to collect data. For the specific latitude where the Apollonia’s tumulus is located, the energy and angular muon distribution at sea level is studied. Implementing the dimensions of the telescope in the simulation, the back-projection method is examined for the localization of the hidden object and the estimation of its dimensions. The method is tested for the telescope optimal position, placed under the tumulus, and the realistic one, placed near the tumulus at the level of its base.