Cosmic Ray Muons Research Articles

A cosmic ray muons telescope based on bar plastic scintillator detectors

A cosmic ray muons telescope (CORMT) was designed to monitor the distribution of cosmic ray muons in the environment. CORMT is made of three main components: the mechanical structure, the detector, and the readout electronics. The mechanical structure consists of a support structure and a rotating moving platform that ensures the stability and accuracy of the test. The detector consists of four bar-shaped plastic scintillators each coupled with a silicon photomultiplier (SiPM). The readout electronics design uses Xilinx Artix 7 series field-programmable gate array (FPGA), combined with peripheral circuit design, to complete the readout of detector cosmic ray muons hit information. CORMT has the advantage of adjustable thresholds, real-time output, and the use of Coordinated Universal Time (UTC) to record events. The CORMT test results show that the detection efficiency can reach over 90%, the accidental compliance count rate is around 0.02, and the muon flux conforms to the distribution law. This article will discuss the design and performance of the CORMT.

The cosmic ray muons tomography system with wavelength shifting fiber and plastic scintillator plane and vertical borehole detectors and improved 3d image reconstruction algorithm: a simulation study

In this paper, a cosmic ray muon plane detector tomography system based on wavelength shifting fiber and scintillation is built in GEANT4, and the relevant experimental platform is established, then the image reconstruction experiment based on the muon scattering imaging principle is carried out. Finally, based on the research above, a vertical drilling muon detector system is proposed and the simulation studies is completed. The position resolution of the fiber-scintillation detector system is studied in detail, and the chamber position resolution of parallel fiber-optic grid with different parameters is described and compared. Based on the experimental data of the plane detector system, an image reconstruction algorithm and correction method based on muon scattering are proposed, and some engineering applications of the vertical borehole detector system are simulated. The general guiding theory applicable to fiber-scintillation detectors has not been established and detailed simulation studies are required through simulation programs. By using GEANT4, the photon-photon yield of optical light in WLS fiber can be extracted and compared with the existing experiments. The simulation results are in good agreement with the experimental results, indicating that the detector system modeled in the simulation study has high reliability and practical value.

Calibration of Cosmic Watch Desktop Muon Detector: Evaluating the Effects of Atmospheric Pressure and Material Interaction on Detection Accuracy

This study focuses on the analysis of data obtained from Cosmic Watch (CW) muon detectors. The objective is to establish a standardised procedures for the enhancement of accuracy of muon detection in varying environments. By applying correlation analysis, the linear regression line is used to addresses the impact of atmospheric pressure on muon detection rates, which is clarified in the dissertation. A significant aspect of the research involves the rectification of systematic errors, which includes inconsistencies in pressure and temporal discrepancies across groups of Cosmic Watch (CW) detectors. Furthermore, the study investigates the influence of diverse materials on muon penetration, with the detectors being covered with lead, iron, and no material, respectively. The corrected data provide more reliable detection of double- and triple-coincident events and insights into the interactions between certain material and muons. Although there are limitations, the developed calibration model provides a robust framework for future experiments involving muon detection, with potential applications in studying the properties of cosmic-ray muons, and angular distribution.

Measurements of the charge ratio and polarization of cosmic-ray muons with the Super-Kamiokande detector

We present the results of the charge ratio (R) and polarization (P0μ) measurements using decay electron events collected between September 2008 and June 2022 with the Super-Kamiokande detector. Because of its underground location and long operation, we are able to perform high-precision measurements by accumulating cosmic-ray muons. We measured the muon charge ratio to be R=1.32±0.02(stat+syst) at EμcosθZenith=0.7−0.2+0.3 TeV, where Eμ is the muon energy and θZenith is the zenith angle of incoming cosmic-ray muons. This result is consistent with the Honda flux model while indicating a tension with the πK model of 1.9σ. We also measured the muon polarization at the production location to be P0μ=0.52±0.02 (stat+syst) at the muon momentum of 0.9−0.1+0.6 TeV/c at the surface of the mountain; this also suggests a tension with the Honda flux model of 1.5σ. This is the most precise measurement ever to experimentally determine the cosmic-ray muon polarization near 1 TeV/c. These measurement results are useful to improve atmospheric neutrino simulations. Published by the American Physical Society 2024

Joint measurement of cosmic-ray muons and seismic waves at laboratory scale

SUMMARY Current geophysical exploration methods face challenges in accurately determining gas saturation levels and elastic constants with adequate spatial resolution. Seismic wave velocity is a critical physical property in these techniques, but it introduces uncertainties because of its composite nature involving density and two elastic constants (e.g. bulk and shear modulus), which exhibit a trade-off relationship. We propose a novel approach that integrates cosmic-ray muon detection with seismic exploration to independently resolve P- and S-wave velocities into their constituent elastic constants and densities. First, we utilized a fluid substitution approach based on Gassmann's model to illustrate the benefits of incorporating density information in predicting gas saturation levels in pores. This supports the advantage of decomposing seismic wave velocity into density and two elastic constants. Second, to validate the applicability and performance of the proposed method, which involves separating seismic wave velocity into density and two types of elastic constants, muon and ultrasonic data were collected in laboratory experiments on two different targets: an acrylic block and an aluminium block. Upon muon observation, a relationship is established to convert muon flux into density length, considering the characteristics of the building housing the laboratory and the direction of muon arrival at specific positions within the building. Although there is potential for enhancing the accuracy of the derived physical properties such as density, bulk modulus, and shear modulus, the feasibility of this method has been successfully demonstrated at the laboratory scale.

Development of 10 m<sup>2</sup> hodoscope made of drift tubes for cosmic ray muon registration

The 10 m2 muon hodoscope made of drift tubes with length 3.7 m and diameter 52 mm is under development and construction in NRC “Kurchatov institute” — IHEP. Totally 768 drift tubes are grouped into 6 identical multilayers, each consisting of two tube layers with parallelly placed tubes. Tube orientation in adjacent multilayers is orthogonal, thus the hodoscope has six X and six Y tube layers. Detailed mechanical structure, on-chamber electronic and data acquisition systems are described. Expected technical characteristics and some test results are presented.

Rapid cargo verification with cosmic ray muon scattering and absorption tomography

Cosmic ray muon tomography is considered a promising method for the non-invasive inspection of shipping containers and trucks. It utilizes highly penetrating cosmic-ray muons and their interactions with various materials to generate three-dimensional images of large and dense materials, like inter-modal shipping containers, typically not transparent with conventional X-ray radiography techniques. The commonly used methods for imaging with muons are based on muon scattering or absorption-transmission data analysis. Due to large thickness of cargo material in shipping container substantial scattering and absorption occur when muons are passing through cargo. One of the key tasks of customs and border security is to verify shipping container declarations to prevent illegal trafficking, and muon tomography could be a viable choice for this task. In this paper, we demonstrate through Monte Carlo simulations using the GEANT4 toolkit that a combined analysis of muon scattering and absorption data can improve the identification of cargo materials compared to using scattering or absorption data alone. The statistical differences in scattering and absorption data for several cargo materials are quantified. For a particular smuggling scenario where tobacco declared as paper towel rolls, it is demonstrated that the combined analysis can accurately distinguish between tobacco and paper towel rolls with 5.5σ accuracy for detector spatial resolution (FWHM) of 0.235 mm, 4.5σ for 1.175 mm resolution (FWHM), and 3.9σ accuracy for 2.35 mm spatial resolution (FWHM), in a short scanning time of 10 seconds. This rapid detection capability has significant implications for anti-smuggling efforts and cargo inspection.

Real-time portable muography with Hankuk Atmospheric-muon Wide Landscaping : HAWL

Cosmic ray muons prove valuable across various fields, from particle physics experiments to non-invasive tomography, thanks to their high flux and exceptional penetrating capability. Utilizing a scintillator detector, one can effectively study the topography of mountains situated above tunnels and underground spaces. The Hankuk Atmospheric-muon Wide Landscaping (HAWL) project successfully charts the mountainous region of eastern Korea by measuring cosmic ray muons with a detector in motion. The real-time muon flux measurement shows a tunnel length accuracy of 6.0%, with a detectable overburden range spanning from 8 to 400 meter-water-equivalent depth. This is the first real-time portable muon tomography.

The potential of in situ cosmogenic 14CO in ice cores as a proxy for galactic cosmic ray flux variations

Abstract. Galactic cosmic rays (GCRs) interact with matter in the atmosphere and at the surface of the Earth to produce a range of cosmogenic nuclides. Measurements of cosmogenic nuclides produced in surface rocks have been used to study past land ice extent as well as to estimate erosion rates. Because the GCR flux reaching the Earth is modulated by magnetic fields (solar and Earth's), records of cosmogenic nuclides produced in the atmosphere have also been used for studies of past solar activity. Studies utilizing cosmogenic nuclides assume that the GCR flux is constant in time, but this assumption may be uncertain by 30 % or more. Here we propose that measurements of 14C of carbon monoxide (14CO) in ice cores at low-accumulation sites can be used as a proxy for variations in GCR flux on timescales of several thousand years. At low-accumulation ice core sites, 14CO in ice below the firn zone originates almost entirely from in situ cosmogenic production by deep-penetrating secondary cosmic ray muons. The flux of such muons is almost insensitive to solar and geomagnetic variations and depends only on the primary GCR flux intensity. We use an empirically constrained model of in situ cosmogenic 14CO production in ice in combination with a statistical analysis to explore the sensitivity of ice core 14CO measurements at Dome C, Antarctica, to variations in the GCR flux over the past ≈ 7000 years. We find that Dome C 14CO measurements would be able to detect a linear change of 6 % over 7 ka, a step increase of 6 % at 3.5 ka or a transient 100-year spike of 190 % at 3.5 ka at the 3σ significance level. The ice core 14CO proxy therefore appears promising for the purpose of providing a high-precision test of the assumption of GCR flux constancy over the Holocene.

Performance simulation study of plastic scintillator arrays for stability monitoring applications

The characteristics of high energy cosmic-ray muons make them strongly penetrative in materials. It has great potential to monitor the stability of buildings by reconstructing the tracks of cosmic-ray muons. In this work, a buildings stability monitoring system based on plastic scintillator strips is proposed. The monitoring system consists of a single-plane upper telescope to record the incoming track of a muon, and a three-plane lower telescope to track its outgoing trajectory. Every detector plane is formed by orthogonally placed scintillator strips. The impacts of the scintillator geometry and spatial placement on the stability monitoring precision are carefully studied using Geant4 simulations. A sub-millimeter position resolution is achievable by selecting a proper data taking time. The triangular scintillator strips always outperform rectangular ones of the same size and placement. Two empirical formulas have been derived to quantitatively estimate the position resolution with respect to the abovementioned influential factors. In addition, the comprehensive effects of multiple parameters are also studied. Accordingly, triangular scintillator strips will be utilized in the construction of a real monitoring system with better performance and less detection channels. The simulation study in this work can provide good guidance for the manufacturing of triangular strips and their experimental configurations.

Proposed Peking University muon experiment for muon tomography and dark matter search

A set of new methods are proposed here to directly detect light mass dark matter through its scattering with abundant atmospheric muons or accelerator beams. A first plan is to use the free cosmic-ray muons interacting with dark matter in a volume surrounded by tracking detectors, to trace the possible interaction between dark matter and muons. Secondly, the same device can be interfaced with domestic or international muon beams. Due to the much larger muon intensity and focused beam, it is anticipated that the detector can be made further compact, and the resulting sensitivity on dark matter searches will be improved. Furthermore, it may also be possible to measure precisely directional distributions of cosmic-ray muons, either at mountain or sea level, and the differences may reveal possible information about dark matter distributed near the Earth. Specifically, methods described here can have advantages over “exotic” dark matters that are either muonphilic or slowed down due to some mechanism, and the sensitivity on dark matter and muon scattering cross section can reach as low as microbarn level. Published by the American Physical Society 2024

TomOpt: differential optimisation for task- and constraint-aware design of particle detectors in the context of muon tomography

We describe a software package, TomOpt, developed to optimise the geometrical layout and specifications of detectors designed for tomography by scattering of cosmic-ray muons. The software exploits differentiable programming for the modeling of muon interactions with detectors and scanned volumes, the inference of volume properties, and the optimisation cycle performing the loss minimisation. In doing so, we provide the first demonstration of end-to-end-differentiable and inference-aware optimisation of particle physics instruments. We study the performance of the software on a relevant benchmark scenario and discuss its potential applications. Our code is available on Github (Strong et al 2024 available at: https://github.com/GilesStrong/tomopt).

Automated object detection for muon tomography data analysis

In recent years, there have been ongoing efforts to improve screening technologies to improve security and prevent terrorist threats. The most widely used technologies for scanning shipping containers are gamma and X-ray radiography, which can be harmful to operators and the environment. Muon tomography screening systems are considered as a potential tool to enhance border security and prevent terrorist threats or smuggling, especially in the context of shipping container inspections. Muon tomography uses naturally occurring cosmic ray muons to create detailed images of the inside of objects, such as shipping containers, without the need for physical intervention. Various realistic smuggling scenarios were simulated using the GEANT4 toolkit. The implemented filtering algorithms successfully reduce background noise from the surrounding cargo, enabling the detection of concealed threats and contraband. With the tools provided by the ROOT data analysis package, prohibited items can be automatically detected and localized in a cargo container.

Omnidirectional borehole detector for muography: Design and performance evaluation

Muography using cosmic ray muons is a non-invasive and environmentally friendly imaging technique with comprehensive applicability across various fields such as mineral exploration, archaeology, and engineering, etc. Given characteristics of high penetration and broad energy spectrum of cosmic ray muons, three-dimensional density distribution of objects up to hundreds of meters can be well reconstructed. In mineral exploration and archaeology applications, conventional planar detectors are too large and usually deployed in spacious rooms like tunnels or outdoors, which seriously limits the deeper and broader applications of muography. A type of borehole muon detector is highly desired to address this. In the work, we introduce a novel borehole-type muography detector comprising annular and prismatic plastic scintillators, allowing for its deployment in boreholes. In the paper, the structural design of the detector is described in details and its performance is evaluated numerically and experimentally. Comprehensive investigation on components and on the system as a whole were conducted. According to our commissioning tests, the detector we propose has an omnidirectional field of view without blind spots, with an angular uncertainty of 27.4 mrad and a position uncertainty of 2.29 mm in the azimuthal direction, an angular uncertainty of 20.6 mrad and a position uncertainty of 10.31 mm in the zenithal direction. Detection efficiencies for both annular and prismatic scintillators were measured as 90.3 ± 0.53% and 92.27 ± 0.82%. In addition, an underground location was investigated, survival rate distributions being calculated from above-ground and underground measurements. The results indicate its capability to successfully address muography applications This novel borehole-type detector has the potential to address industry demand for lower-cost, more flexible muography solutions.

Second gadolinium loading to Super-Kamiokande

The first loading of gadolinium (Gd) into Super-Kamiokande in 2020 was successful, and the neutron capture efficiency on Gd reached 50%. To further increase the Gd neutron capture efficiency to 75%, 26.1 tons of Gd2(SO4)3⋅8H2O was additionally loaded into Super-Kamiokande (SK) from May 31 to July 4, 2022. As the amount of loaded Gd2(SO4)3⋅8H2O was doubled compared to the first loading, the capacity of the powder dissolving system was doubled. We also developed new batches of gadolinium sulfate with even further reduced radioactive impurities. In addition, a more efficient screening method was devised and implemented to evaluate these new batches of Gd2(SO4)3⋅8H2O. Following the second loading, the Gd concentration in SK was measured to be 333.5±2.5 ppm via an Atomic Absorption Spectrometer (AAS). From the mean neutron capture time constant of neutrons from an Am/Be calibration source, the Gd concentration was independently measured to be 332.7 ± 6.8(sys.) ± 1.1(stat.) ppm, consistent with the AAS result. Furthermore, during the loading the Gd concentration was monitored continually using the capture time constant of each spallation neutron produced by cosmic-ray muons, and the final neutron capture efficiency was shown to become 1.5 times higher than that of the first loaded phase, as expected.

Accurate in situ rock density measurement with cosmic ray muon radiography

Muon radiography, which relies on measuring the absorption and attenuation of muons as they pass through matters, offers a new imaging technique capable of revealing the internal structure of large objects. Recent technological advancement allows for the application or testing of muon radiography in various fields, including mining, civil engineering, security check, etc. This study investigates the factors that influence muon radiography, which is used in density inversion, through simulations and experiments. The materials considered for density inversion include water, standard rock, and iron. Our simulation studies show that the number of events detected and selected has an impact on the reconstruction results, and several factors, such as multiple Coulomb scattering processes, recording time, and spatial resolution, which influence the number of muons, must be taken into account when measuring the rock density. We design and conduct a laboratory scale experiment based on the simulation results. We filter the 220 h of recording signals through time coincidence and straight-line fitting to obtain the selected events. Our results reveal that the statistical error of muons survival ratio in recording time significantly impacts the inversion result and decreases the error can improve accuracy greatly. In the experiment, the deviation between the inversion mean value and the expected value can be reduced to 2.4%–2.9% for iron, 7% for water, and 1.5% for standard rock. This density inversion approach provides insight into future density detection of underground structures.

A method of three-dimensional muon imaging using cosmic ray ground array

Cosmic ray muon imaging technology is an effective non-destructive imaging technique. It is currently used to survey the internal structure of large-scale objects such as active volcanoes, pyramids, and some buildings. Additionally, it is used to detect high-Z materials in scenarios such as border security, nuclear reactor monitoring, and container inspection. All applications of cosmic ray muons require a detector to reveal and measure the flux or angular variations of muons. However, detectors may have specific characteristics for each application depending on the detection requirements. Unlike single-point track detectors, we propose using ground array detectors to investigate how ground array detection technology can be used for 3D reconstruction of objects. We use ground array detection technology for simulation studies and apply the Iterative Correction Algorithm (ICA) to reconstruct two-dimensional projections and obtain three-dimensional images of density distribution. We have also addressed the convergence problem and analyzed and optimized some parameters that may affect the detection results. The advantages of using ground arrays include their ability to simultaneously measure the transmittance flux data of muons in different directions, achieve multi-angle detection, and have a large field of view, enabling the collection of sufficient data for more accurate detection results. To verify the feasibility of our new method, we conducted a simple experimental validation on a cylindrical cement building located in the Large High Altitude Air Shower Observatory (LHAASO). By comparing the experimental results with the cement building in the array, we found that their shape structure and density information are basically consistent, demonstrating the effectiveness of our method.

Enhanced material identification via momentum-integrated muon scattering tomography

Background Cosmic ray muons, originating from interactions in the upper atmosphere, possess high energy and unique penetrative capabilities suitable for non-traditional radiographic inspection. This study explores their application in various fields such as nuclear fuel cask monitoring, nuclear reactor imaging, and archaeology, leveraging the principle of multiple Coulomb scattering for imaging dense materials. While muon scattering tomography has shown promise, accurately measuring muon momentum remains challenging. Methods This research introduces the Momentum Integrated Point-of-Closest Approach (mPoCA) algorithm, integrating muon momentum data into the traditional Point-of-Closest Approach (PoCA) framework. Utilizing the Cherenkov muon spectrometer, renowned for precise muon momentum estimation, the mPoCA algorithm offers a novel imaging approach. Results Simulations conducted with GEANT4 evaluate the mPoCA algorithm’s performance against the standard PoCA method, demonstrating superior image resolution and enhanced material identification capabilities, particularly in distinguishing materials like uranium and lead. Conclusions These findings underscore the potential of the mPoCA algorithm for advancing muon scattering tomography applications.

Lateral distribution cosmic ray muon coincidences up to 36 m

Primary cosmic ray particles comprise about 85 % protons, 12 % helium, 3 % iron, and heavier elements. These particles interact with the Earth's atmosphere, generating the Extensive Air Showers (EAS). Among the particles produced are pions and kaons, which decay into cosmic ray muons. In this research, the lateral distribution of cosmic ray muons was measured using two-fold coincidences. Four NaI (Tl) detectors and the associated electronics were used in the measurements of cosmic ray muons. The detectors were positioned from 0 to 36 m at regular intervals. The muon count rate was observed to decrease as the distance between the detectors increased. The measurements were fitted to the Nishimura–Kamata–Greisen (NKG) function to analyze the lateral distribution. Monte Carlo (MC) simulations of EAS were performed using the Cosmic Ray Simulations for the KAscade Grande (CORSIKA) program. The simulations made use of EPOS and GHEISHA models for high and lower energies respectively.•The measurements for the two-fold coincidence are consistent with the NKG function.•The simulated and measured data were found to be in agreement.•The knowledge gained from the lateral distribution of cosmic ray muons is essential for the understanding of the development of extensive air showers.

First characterization of a novel grain calorimeter: the GRAiNITA prototype

A novel type of calorimeter based on grains of inorganic scintillating crystal readout by wave length shifting fibers is proposed. The concept and main features as well as the prototype design are introduced and the first results obtained using cosmic rays are presented. The number of photo-electrons generated by cosmic rays muons in the prototype detector is estimated to be of the order of 10000 photo-electrons per GeV, validating the concept of this next-generation shashlik calorimeter.