Evaluation of Gadolinium's Action on Water Cherenkov Detector Systems with EGADS
Ll. Marti, M. Ikeda, Y. Kato, Y. Kishimoto, M. Nakahata, Y. Nakajima, Y. Nakano, S. Nakayama, Y. Okajima, A. Orii, G. Pronost, H. Sekiya, M. Shiozawa, H. Tanaka… 展开作者
Ll. Marti, M. Ikeda, Y. Kato, Y. Kishimoto, M. Nakahata, Y. Nakajima, Y. Nakano, S. Nakayama, Y. Okajima, A. Orii, G. Pronost, H. Sekiya, M. Shiozawa, H. Tanaka, K. Ueno, S. Yamada, T. Yano, T. Yokozawa, M. Murdoch, J. Schuemann, M. R. Vagins, K. Bays, G. Carminati, N. J. Griskevich, W. R. Kropp, S. Locke, A. Renshaw, M. B. Smy, P. Weatherly, S. Ito, H. Ishino, A. Kibayashi, Y. Koshio, T. Mori, M. Sakuda, R. Yamaguchi, P. Fernandez, L. Labarga, I. Bandac, J. Perez, J. Amey, R. P. Litchfield, A. Sztuc, Y. Uchida, W. Y. Ma, A. Goldsack, C. Simpson, D. Wark, L. H. V. Anthony, N. McCauley, A. Pritchard, F. Di Lodovico, B. Richards, A. Cole, M. Thiesse, L. Thompson, J. Imber, S. V. Cao, K. Ito, Y. Takeuchi, R. Akutsu, Y. Nishimura, K. Okumura, S. Hirota, F. Muto, M. Yokoyama, Y. Suda, H. Zhang
Used for both proton decay searches and neutrino physics, large water Cherenkov (WC) detectors have been very successful tools in particle physics. They are notable for their large masses and charged particle detection capabilities. While current WC detectors reconstruct charged particle tracks over a wide energy range, they cannot efficiently detect neutrons. Gadolinium (Gd) has the largest thermal neutron capture cross section of all stable nuclei and produces an 8 MeV gamma cascade that can be detected with high efficiency. Because of the many new physics opportunities that neutron tagging with a Gd salt dissolved in water would open up, a large-scale R&D program called EGADS was established to demonstrate this technique's feasibility. EGADS features all the components of a WC detector, chiefly a 200-ton stainless steel water tank furnished with 240 photo-detectors, DAQ, and a water system that removes all impurities in water while keeping Gd in solution. In this paper we discuss the milestones towards demonstrating the feasibility of this novel technique, and the features of EGADS in detail.
Okayama University（冈山大学）；Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo（东京大学宇宙射线研究所神冈观测站）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, University of Tokyo（东京大学基础物理学与数学柯尔维特研究所（WPI））
Monitoring of high energy cosmic ray neutrons is of particular interest for cosmic ray water Cherenkov detectors as intense bundles of delayed neutrons have been found to arrive after the initial passage of a high energy air shower. In this paper we explore the possibility of building large-area high-energy neutron monitors using gadolinium-loaded Water Cherenkov Detectors (WCDs). GEANT4 simulations of photon production in WCDs are used to estimate the maximum detection efficiency for a hypothetical system. Requiring a series of neutron induced gamma ray flashes distributed over an extended pe…
Antineutrino detectors are practical, non-intrusive tools capable of remotely monitoring the activity of nuclear reactors. Here we explore the sensitivity of the Super-Kamiokande water-Cherenkov detector, following gadolinium loading, to antineutrinos from a nuclear reactor complex at a distance of approximately 190 km. The livetimes required to observe the two currently operating cores in the reactor complex depend on the activity of other reactors in the vicinity, as well as on estimates of detection efficiency and background rates. Under reasonable assumptions, we find that gadolinium-loade…
Antineutrinos are an unavoidable byproduct of the fission process. The kiloton-scale KamLAND experiment has demonstrated the capability to detect reactor antineutrinos at few-hundred-km range. But to detect or rule out the existence of a single small reactor over many km requires a large detector. So large in fact that the optical opacity of the detection medium itself becomes an important factor. If the detector is so large that photons cannot traverse across the detector medium to an optical detector, then it becomes impractical. For this reason, gadolinium-doped-water Cherenkov detectors ha…
Large water Cherenkov detectors have been successfully used for decades in high- and low-energy particle physics. Nevertheless, detecting neutrons remains a challenge for such detectors since a neutron capture on a hydrogen atom doesn't release a sufficient amount of gamma energy to be observed efficiently. The use of gadolinium in the form of soluble salts has been explored extensively to remedy this issue, as gadolinium exhibits both a very large neutron capture cross section and a subsequent high-energy gamma cascade. However, in order for large gadolinium-loaded detectors to operate stably…
Antineutrinos from a nuclear reactor comprise an unshieldable signal which carries information about the core. A gadolinium-doped, water-based Cherenkov detector could detect reactor antineutrinos for mid- to far-field remote reactor monitoring for non-proliferation applications. Two novel and independent reconstruction and analysis pathways have been developed and applied to a number of representative reactor signals to evaluate the sensitivity of a kiloton-scale, gadolinium-doped Cherenkov detector as a remote monitor. The sensitivity of four detector configurations to nine reactor signal co…
Remote detection of undeclared nuclear reactors remains one of the key goals concerning global nuclear security. To meet this goal the WATCHMAN collaboration has proposed the construction of a water based antineutrino detector, sited 13 to 25 kilometres from a nuclear reactor complex. Antineutrinos from the reactor interact in the water of the detector via an inverse beta decay interaction resulting in two distinct cones of Cherenkov light tens of milliseconds apart. Using this interaction WATCHMAN (WATer Cherenkov Monitor for ANtineutrinos) will be the first detector to determine the active/i…
Water Cherenkov detectors like Super-Kamiokande, and the next generation Hyper-Kamiokande are adding gadolinium to their water to improve the detection of neutrons. By detecting neutrons in addition to the leptons in neutrino interactions, an improved separation between neutrino and anti-neutrinos, and reduced backgrounds for proton decay searches can be expected. The neutron signal itself is still small and can be confused with muon spallation and other background sources. In this paper, machine learning techniques are employed to optimize the neutron capture detection capability in the new i…
To date, antineutrino experiments built for the purpose of demonstrating a nonproliferation capability have typically employed organic scintillators, were situated as close to the core as possible -typically a few meters to tens of meters distant and have not exceeded a few tons in size. One problem with this approach is that proximity to the reactor core require accommodation by the host facility. Water Cherenkov detectors located offsite, at distances of a few kilometers or greater, may facilitate non-intrusive monitoring and verification of reactor activities over a large area. As the stand…
The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) is designed to serve as a test bed for new detector technologies in future water and liquid scintillator based neutrino experiments. Located on the Booster Neutrino Beam at Fermilab, ANNIE will be the first gadolinium-loaded water Cherenkov detector on a neutrino beam and will provide high statistics measurements of neutron yields from neutrino interactions in water. It is also the first particle physics application of the new photosensor technology: Large Area Picosecond Photodetectors (LAPPDs). With single photon time resolution…
Gadolinium-loading of large water Cherenkov detectors is a prime method for the detection of the Diffuse Supernova Neutrino Background (DSNB). While the enhanced neutron tagging capability greatly reduces single-event backgrounds, correlated events mimicking the IBD coincidence signature remain a potentially harmful background. Neutral-Current (NC) interactions of atmospheric neutrinos potentially dominate the DSNB signal especially in the low-energy range of the observation window that reaches from about 12 to 30 MeV. The present paper investigates a novel method for the discrimination of thi…
Numerous experimental efforts have shown that antineutrino-based monitoring provides a non-intrusive means to estimate the fissile content and relative thermal power of nuclear reactors for nonproliferation. Until now, there have been no experimental demonstrations dedicated to exploring the nonproliferation potential of large detectors required for long-range monitoring. The goal of the Advanced Instrumentation Testbed (AIT) program is to test novel methods for the discovery of reactor cores, specifically in the mid-field to far-field, beyond 200 meters and out to tens or hundreds of kilomete…
Neutron multiplicity measurement in muon capture on oxygen nuclei in the Gd-loaded Super-Kamiokande detector
Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo（东京大学宇宙线研究所神冈观测站）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, University of Tokyo（东京大学前沿研究机构宇宙物理与数学研究 Kavli 研究所（WPI））
