6 research outputs found
First navigation with wireless muometric navigation system (MuWNS) in indoor and underground environments
Summary: Navigation in indoor and underground environments has been extensively studied to realize automation of home, hospital, office, factory and mining services, and various techniques have been proposed for its implementation. By utilizing the relativistic and penetrative nature of cosmic-ray muons, a completely new wireless navigation technique called wireless muometric navigation system (MuWNS) was developed. This paper shows the results of the world’s first physical demonstration of MuWNS used on the basement floor inside a building to navigate (a person) in an area where global navigation satellite system (GNSS)/ global positioning system (GPS) signals cannot reach. The resultant navigation accuracy was comparable or better than the positioning accuracy attainable with single-point GNSS/GPS positioning in urban areas. With further improvements in stability of local clocks used for timing, it is anticipated that MuWNS can be adapted to improve autonomous mobile robot navigation and positioning as well as other underground and underwater practical applications
Muon Imaging of Volcanic Conduit Explains Link Between Eruption Frequency and Ground Deformation
Understanding the physical mechanism of ground deformation at a volcano supports the use of deformation data as a monitoring tool. An inverse correlation was observed between eruption frequency and ground deformation of Sakurajima volcano from November 2018 to April 2021. Over the same period, the mass density of magma in the conduit was monitored via muography. Mass density increased during inflation, when eruption frequency was low, and decreased during deflation, when eruption frequency was high. Periods of low eruption frequency are associated with the formation of a dense plug in the conduit, which we infer caused the inflation of the edifice by trapping pressurized magmatic gas. Conversely, periods of high eruption frequency are associated with the absence of the plug, which we infer allows gas to escape, leading to deflation. Muography thus reveals the in-conduit physical mechanism for the observed correlation, with implications for interpretation of deformation at other volcanoes
Muographic Detection of Seasonal Variations in Astronomical Tides With Hyper Kilometric Submarine Deep Detector (HKMSDD)
Tidal amplification or tidal reduction as a response to sea-level variations can potentially amplify or mitigate the flood risk associated with future sea-level rise caused by global climate change. Tokyo Bay Seafloor Hyper Kilometric Submarine Deep Detector (TS-HKMSDD), the world’s first detector array located underneath the seafloor, has operated without intermittency for more than one year collecting cosmic-ray muon data, which revealed the seasonal variations in astronomical tides in Tokyo Bay. By comparing onshore tide gauge seasonal mean sea level data with offshore-subseafloor TS-HKMSDD data, it was found that seasonal water level rises in Tokyo Bay played a negative role in the local tidal amplification, indicating that future sea-level rise may potentially mitigate the flood risk in the Tokyo Bay area. With its cosmic sensors, which can monitor aquatic environments without requiring them to be in direct contact with water and in conjunction with the availability of globally increasing urban underground spaces (UUS) for installation (including pre-existing underwater tunnels and commercial buildings that offer reliable utilities in coastal areas) we anticipate that the robustness and versatility of HKMSDD as a long-term stable tide monitor will make it a world standard measurement tool for coastal tide monitoring to complement pre-existing tide gauge stations worldwide
First results of undersea muography with the Tokyo-Bay Seafloor Hyper-Kilometric Submarine Deep Detector
Abstract
Tidal measurements are of great significance since they may provide us with essential data to apply towards protection of coastal communities and sea traffic. Currently, tide gauge stations and laser altimetry are commonly used for these measurements. On the other hand, muography sensors can be located underneath the seafloor inside an undersea tunnel where electric and telecommunication infrastructures are more readily available. In this work, the world’s first under-seafloor particle detector array called the Tokyo-bay Seafloor Hyper-Kilometric Submarine Deep Detector (TS-HKMSDD) was deployed underneath the Tokyo-Bay seafloor for conducting submarine muography. The resultant 80-day consecutive time-sequential muographic data were converted to the tidal levels based on the parameters determined from the first-day astronomical tide height (ATH) data. The standard deviation between ATH and muographic results for the rest of a 79-day measurement period was 12.85 cm. We anticipate that if the length of the TS-HKMSDD is extended from 100 m to a full-scale as large as 9.6 km to provide continuous tidal information along the tunnel, this muography application will become an established standard, demonstrating its effectiveness as practical tide monitor for this heavy traffic waterway in Tokyo and in other important sea traffic areas worldwide
Periodic sea-level oscillation in Tokyo Bay detected with the Tokyo-Bay seafloor hyper-kilometric submarine deep detector (TS-HKMSDD)
Abstract
Meteorological-tsunami-like (or meteotsunami-like) periodic oscillation was muographically detected with the Tokyo-Bay Seafloor Hyper-Kilometric Submarine Deep Detector (TS-HKMSDD) deployed in the underwater highway called the Trans-Tokyo Bay Expressway or Tokyo Bay Aqua-Line (TBAL). It was detected right after the arrival of the 2021 Typhoon-16 that passed through the region 400 km south of the bay. The measured oscillation period and decay time were respectively 3 h and 10 h. These measurements were found to be consistent with previous tide gauge measurements. Meteotsunamis are known to take place in bays and lakes, and the temporal and spatial characteristics of meteotsunamis are similar to seismic tsunamis. However, their generation and propagation mechanisms are not well understood. The current result indicates that a combination of muography and trans-bay or trans-lake underwater tunnels will offer an additional tool to measure meteotsunamis at locations where tide gauges are unavailable