In order to establish accurate leptonic CP violation at 3 σ level for a significant fraction of the possible δCP values, the T2K collaboration plan to upgrade the beam intensity and to upgrade the ...near detector ND280.
The T2K experiment consists of a totally active Super-Fine-Grained-Detector, two High Angle Time Projection Chamber and six time of flight planes. The HA-TPC will be used for 3D track reconstruction, momentum measurement and particle identification. These time projection chambers, with overall dimensions of 2 × 2 × 0.8 m3, will be equipped with 32 encapsulated resistive anode bulk Micromegas detectors. The thin field cage (3 cm thickness, 4% radiation length) will consist of composite material with a Kapton foil with copper strips as inner layer. The 42 × 34 cm2 ERAM detector will use a 400 kΩ/sq diamond-like carbon foil to spread the charge over the pad plane, each pad being approximately 1 cm2. New front-end electronic cards, based on the AFTER chip, directly mounted on the back of the detector and parallel to its plane have been developed and used for the signal readout.
The first production ERAM detector modules have been tested in a lab using a X-ray bench and a cosmic bench. In July 2021, data have also been taken in a test beam at DESY in 0.2 T magnetic field. Performance characterization and results from these measurement campaigns will be shown.
Khufu's Pyramid is one of the largest archaeological monument all over the world, which still holds many mysteries. In 2016 and 2017, the ScanPyramids team reported on several discoveries of ...previously unknown voids by cosmic-ray muon radiography that is a non-destructive technique ideal for the investigation of large-scale structures. Among these discoveries, a corridor-shaped structure has been observed behind the so-called Chevron zone on the North face, with a length of at least 5 meters. A dedicated study of this structure was thus necessary to better understand its function in relation with the enigmatic architectural role of this Chevron. Here we report on new measurements of excellent sensitivity obtained with nuclear emulsion films from Nagoya University and gaseous detectors from CEA, revealing a structure of about 9 m length with a transverse section of about 2.0 m by 2.0 m.
The Great Pyramid, or Khufu's Pyramid, was built on the Giza plateau in Egypt during the fourth dynasty by the pharaoh Khufu (Cheops), who reigned from 2509 bc to 2483 bc. Despite being one of the ...oldest and largest monuments on Earth, there is no consensus about how it was built. To understand its internal structure better, we imaged the pyramid using muons, which are by-products of cosmic rays that are only partially absorbed by stone. The resulting cosmic-ray muon radiography allows us to visualize the known and any unknown voids in the pyramid in a non-invasive way. Here we report the discovery of a large void (with a cross-section similar to that of the Grand Gallery and a minimum length of 30 metres) situated above the Grand Gallery. This constitutes the first major inner structure found in the Great Pyramid since the nineteenth century. The void, named ScanPyramids' Big Void, was first observed with nuclear emulsion films installed in the Queen's chamber, then confirmed with scintillator hodoscopes set up in the same chamber and finally re-confirmed with gas detectors outside the pyramid. This large void has therefore been detected with high confidence by three different muon detection technologies and three independent analyses. These results constitute a breakthrough for the understanding of the internal structure of Khufu's Pyramid. Although there is currently no information about the intended purpose of this void, these findings show how modern particle physics can shed new light on the world's archaeological heritage.
Several muon telescopes have been developed in the last years at CEA-Saclay. Benefitting from 15 years of R&D on Micro-Pattern Gaseous Detectors (MPGDs) and from several recent innovations, these ...telescopes yield unprecedented resolution for real-time instruments, and allow for high-definition muography imaging. As a first application, three of them were deployed around Khufu's Pyramid from 2015 to 2017, showing very good performance and stability in harsh conditions. They also provided the first-ever detection of internal structures of a pyramid from the outside, and participated in the discovery of a large void above the Grand Gallery.
Plusieurs télescopes à muons ont été mis au point ces dernières années au CEA-Saclay. Bénéficiant de 15 années de R&D sur les détecteurs gazeux à micro-pistes (MPGDs) et de plusieurs innovations récentes, ces télescopes offrent une résolution inégalée pour des instruments temps réel, et ouvrent la voie à la muographie haute définition. Trois de ces instruments ont été déployés autour de la pyramide de Khéops entre 2015 et 2017, démontrant de très bonnes performances et une grande stabilité dans des conditions particulièrement difficiles. Ils ont également fourni la toute première détection de structures internes d'une pyramide depuis l'extérieur et participé à la découverte d'un grand vide situé au-dessus de la Grande Galerie.
Micromegas (MICRO-MEsh GAseous Structure) detectors have found common use in different applications since their development in 1996 by the group of I. Giomataris and G. Charpak. In this review ...article, we present implementations of Micromegas sub-detectors in different physics experiments and highlight the current state of development for innovative detection concepts with Micromegas.
Transmission muography is a non-invasive and non-destructive imaging method which allows to estimate the integrated density of a volume in a given direction (also referred as opacity). It relies on a ...reconstruction of muons tracks that crossed the studied volume compared to the corresponding open sky expectation. The experimental setup of the muography developed at CEA Irfu consists in portable muon telescopes. Each of these instruments has four Micromegas gaseous detectors, power and acquisition electronics, and an embedded computer connected to the network allowing remote control. It is then well adapted to deploy them in constrained environments. A muography measurements campaign has been carried out in the decommissioned nuclear reactors G2 and G3 at CEA Marcoule (France) which are expected to be dismantled. We were able to conduct 2D muographies and 3D analyses of inside G2’s airtight concrete chamber. In this paper we describe the measurement protocol at the G2 and G3 reactors. We explain what was developed to improve the measurements between G2 and G3 campaigns. It shows how potential improvements were identified in the proof of concept and why we expect a better reconstruction for G3. Among the improvements, we describe how simulations prior to the measurements, denoising and in general automation play an important role to have a precise 3D image in reasonable time.
The inspection of very large or thick structures represents one of the biggest challenges for nondestructive techniques. For such objects, a particularly powerful technique is muography, which makes ...use of free, natural cosmic-ray muons. Among other applications, this technique has been applied to provide two-dimensional (2D) images of nuclear reactors, pyramids, or volcanos. Recently, 3D algorithms developed for medical applications were adapted to the special case of muon imaging to derive density maps. The main difficulties relate to the size of the object and to the limited number of available projections. Here, we report on the first 3D imaging of a whole nuclear reactor, obtained without any prior information on its structure and using the largest set of muographic projections ever made in this field.
The R&D activities for the linear collider TPC (LC-TPC) are currently working on the adoption of the micro pattern devices for the gaseous amplification stage. Several beam tests have been carried ...out at DESY with a 5 GeV electron beam in a 1 T superconducting magnet. We worked on a large prototype TPC with an end-plate that was built, for the first time, using seven resistive bulk Micromegas modules. During experiments, reduced signal sensitivity was observed at the boundary of these modules. Electrostatic field distortion near the module boundaries was considered to be the possible major reason behind these observations. In the present work, we will explore this hypothesis through numerical simulation. Our aim has been to understand the origin of distortions observed close to the edges of the test beam modules and to explore the possibility of using the Garfield simulation framework for investigating a phenomenon as complex as distortion.
A time projection chamber (TPC) can be used to measure the polarization of gamma rays with excellent angular precision and sensitivity in the MeV-GeV energy range through the conversion of photons to ...e+e− pairs. The Hermetic ARgon POlarimeter (HARPO) prototype was built to demonstrate this concept. It was recently tested in the polarized photon beam at the NewSUBARU facility in Japan. We present this data-taking run, which demonstrated the excellent performance of the HARPO TPC.
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