Cosmic Ray Muon Flux Research Articles

Image reconstruction algorithm for momentum dependent muon scattering tomography

Nondestructive radiography using cosmic ray muons has been used for decades to monitor nuclear reactor and spent nuclear fuel storage. Because nuclear fuel assemblies are highly dense and large, typical radiation probes such as x-rays cannot penetrate these target imaging objects. Although cosmic ray muons are highly penetrative for nuclear fuels as a result of their relatively high energy, the wide application of muon tomography is limited because of naturally low cosmic ray muon flux. This work presents a new image reconstruction algorithm to maximize the utility of cosmic ray muon in tomography applications. Muon momentum information is used to improve imaging resolution, as well as muon scattering angle. In this work, a new convolution was introduced known as M-value, which is a mathematical integration of two measured quantities: scattering angle and momentum. It captures the objects’ quantity and density in a way that is easy to use with image reconstruction algorithms. The results demonstrate how to reconstruct images when muon momentum measurements are included in a typical muon scattering tomography algorithm. Using M-value improves muon tomography image resolution by replacing the scattering angle value without increasing computation costs. This new algorithm is projected to be a standard nondestructive radiography technique for spent nuclear fuel and nuclear material management.

Muon Flux Variations Measured by Low‐Cost Portable Cosmic Ray Detectors and Their Correlation With Space Weather Activity

AbstractWe present a comparison of the measured cosmic ray (CR) muon fluxes from two identical portable low‐cost detectors at different geolocations and their sensitivity to space weather events in real time. The first detector is installed at Mount Wilson Observatory, CA, USA (geomagnetic cutoff rigidity Rc ∼ 4.88 GV), and the second detector is running on the downtown campus of Georgia State University in Atlanta, GA, USA (Rc ∼ 3.65 GV). The variation of the detected muon fluxes is compared to the changes in the interplanetary solar wind parameters at the L1 Lagrange point and geomagnetic indexes. In particular, we have investigated the muon flux behavior during three major interplanetary shock events and geomagnetic disturbances that occurred during July and August of 2022. To validate the interpretation of the measured muon signals, we compare the muon fluxes to the measurement from the Oulu neutron monitor (NM, Rc ∼ 0.8 GV). The results of this analysis show that the muon detector installed at Mount Wilson Observatory demonstrates a stronger correlation with a high‐latitude NM. Both detectors typically observe a muon flux decrease during the arrival of interplanetary shocks and geomagnetic storms. Interestingly, the decrease could be observed several hours before the onset of the first considered interplanetary shocks at L1 at 2022‐07‐23 02:28:00 UT driven by the high‐speed Coronal Mass Ejection and related geomagnetic storm at 2022‐07‐23 03:59:00 UT. This effort represents an initial step toward establishing a global network of portable low‐cost CR muon detectors for monitoring the sensitivity of muon flux changes to space and terrestrial weather parameters.

Application of Geant4 simulation in measurement of cosmic-ray muon flux and studies of muon-induced background

Application of Geant4 simulation in measurement of cosmic-ray muon flux and studies of muon-induced background

Search for Neutrino Radiation from the Collapse of Stellar Cores Using LVD Detector

The article presents the latest results with the experiment of the Large Volume Detector located in the Gran Sasso Laboratory at the depth of 3650 m.w.e. LVD has been in operation since 1992 on the program a search for neutrino bursts from stellar core colapses, variations of the cosmic ray muon flux, and investigations of background sources at detecting rare events. According to the data of the LVD neutrino telescope for 29 years of operation (1992–2021), an experimental limitation on the frequency of neutrino bursts from gravitational collapses of stars in the Galaxy was obtained: less than 1 event in 12.6 years (f=0.08 year{}^{-1}) at a 90% confidence level.

A new semi-empirical model for cosmic ray muon flux estimation

Abstract Cosmic ray muons have emerged as a non-conventional high-energy radiation probe to monitor dense and large objects. Muons are the most abundant cosmic radiation on Earth; however, their flux at sea level is approximately 104 min−1m−2, much less than that of induced radiation. In addition, cosmic ray muon flux depends on not only various natural conditions, e.g., zenith angle, altitude, or solar activity, but also the geometric characteristics of detectors. Since the low muon flux typically results in long measurement times, an accurate estimation of measurable muon counts is important to improve the efficiency of muon applications. Here we propose a simple and versatile semi-empirical model to improve the accuracy in muon flux estimation at all zenith angles by incorporating the geometric parameters of detectors, and we name this the ‘effective solid angle model.’ To demonstrate the functionality of our model, it is compared with (i) the cosine-squared model, (ii) the PARMA model, (iii) Monte Carlo simulations, and (iv) experimental measurements. Our results show that the muon count rate estimation capability is significantly improved, resulting in increasing a mean C/E level from 0.7 to 0.95. In addition, by selecting an appropriate intensity correlation, the model can be easily extended to estimate muon flux at various altitudes and also underground.

Cosmic ray flux and lockdown due to COVID-19 in Kolkata - Any correlation?

Cosmic ray muon flux is measured by the coincidence technique using plastic scintillation detectors in the High Energy Physics Detector Laboratory at Bose Institute, Kolkata. Due to the COVID-19 outbreak and nationwide complete lockdown, the laboratory was closed from the end of March 2020 till the end of May 2020. After lockdown, although the city is not in its normal state, we still were able to take data on some days. The lockdown imposed a strict restriction on the transport service other than the emergency ones and also most of the industries were shut down in and around the city. This lockdown has significant effect on the atmospheric conditions in terms of change in the concentration of air pollutants. We have measured the cosmic ray flux before and after the lockdown to observe the apparent change if any, due to change in the atmospheric conditions. In this article, we report the measured cosmic ray flux at Kolkata (22.58^{circ }N 88.42^{circ }E and 11 m above the Sea Level) along with the major air pollutants present in the atmosphere before and after the lockdown.

Measurement of cosmic-ray muon flux in the underground laboratory at UCIL, India, using plastic scintillators and SiPM

A measurement of cosmic muon flux, in the newly established underground laboratory at the Uranium Corporation of India Limited (UCIL), Jaduguda, Jharkhand, India, has been carried out. Several future low background experiments are planned in this laboratory.The experimental set up for muon flux measurements consists of four plastic scintillators, with three of these coupled to photomultiplier tubes (PMT) to generate a coincidence trigger for acquiring data. The fourth scintillator has been coupled to a Silicon Photomultiplier (SiPM) whose signals were processed with respect to the coincidence trigger. In this scintillator, a mean light yield of 22 photoelectrons per muon event was observed and the measured time resolution was 1.3 ns. The muon flux measurement at the underground laboratory at 555 m (1554±45 m w.e.) depth level was (2.79±0.13(stat)±.20(syst))×10−7cm−2sec−1sr−1. This agrees well with model predictions.This paper describes the detector system, analysis techniques, and results of measurement at the surface and the underground laboratory.

The Effects of Atmospheric Attenuation on Cosmic Ray Muons: How is Surface Level Cosmic Ray Muon Flux Affected by Atmospheric Attenuation?

Cosmic rays are high-energy astronomical particles originating from various sources across the universe. After undergoing nuclear reactions in the upper atmosphere, the primary form they take on the Earth’s surface is in the form of muons. Here, we sought to understand how surface-level cosmic-ray muon flux is affected by atmospheric attenuation by measuring the variation in relative muon-flux rate relative to zenith angle, testing the hypothesis that muons follow an exponential attenuation model. Using a QuarkNet cosmic ray muon detector (CRMD), we collected relative muon-flux data while varying the rotational orientation of the CRMD with respect to the magnetic east-west axis. We then calculated a sensitivity function for the detector with respect to muon entry angle. We parameterized a relative muon angular-density function based on the model of exponential attenuation through the Earth’s atmosphere. Then, we convolved these functions and fitted parameters to experimental data using least-squares regression. The attenuation model predicts an attenuation length of 6.3 km. This result implies that only a maximum of 24% of muons can reach the Earth’s surface, due to both decay and atmospheric interactions. The agreement between data and model (χ2=0.351) provides evidence of exponential muon attenuation through the atmosphere.

Advanced Readout Electronics System for Portable Cosmic Ray Muon Detection

Ground cosmic ray muon measurements have extensive applications in weather and climate change prediction and muon tomography. However, for comprehensive understanding of the relationship between cosmic ray muon and various weather phenomena, the cosmic ray muon flux needs to be determined accurately at various geographical locations. Toward this objective, this report presents an advanced readout electronics system with a multichannel application-specific integrated circuit (ASIC) chip for a portable cosmic ray muon detector. This ASIC chip consists of high-speed comparators and an excellent time-resolution digital circuit module. Furthermore, it can provide all-digital outputs associated with the flux and zenith angles of incident cosmic ray muons. A 32-channel prototype readout ASIC chip was designed and fabricated in a 180-nm mixed-signal CMOS process, and the chip size was 3.9 mm2. A double-layer plastic scintillator muon detector was used to test the performance of this chip. The time resolution of the chip was approximately 5 ns, and its power consumption was only 1.6 mW/channel. Compared with the existing muon readout electronics system, the proposed system has advantages such as low cost, low power, high reliability, small size, and lightweight and is highly suitable for portable real-time cosmic ray muon detection. The final version of this chip will be used to construct a ground cosmic ray muon measurement network for long-term monitoring of cosmic ray muon flux variations around the world.

Muon flux measurement at China Jinping Underground Laboratory * *Supported in part by the National Natural Science Foundation of China (11620101004, 11475093), the Key Laboratory of Particle & Radiation Imaging (Tsinghua University), the CAS Center for Excellence in Particle Physics (CCEPP), and Guangdong Basic and Applied Basic Research Foundation (2019A1515012216). Portion of this work performed at Brookhaven National Laboratory is

China Jinping Underground Laboratory (CJPL) is ideal for studying solar, geo-, and supernova neutrinos. A precise measurement of the cosmic-ray background is essential in proceeding with R&D research for these MeV-scale neutrino experiments. Using a 1-ton prototype detector for the Jinping Neutrino Experiment (JNE), we detected 264 high-energy muon events from a 645.2-day dataset from the first phase of CJPL (CJPL-I), reconstructed their directions, and measured the cosmic-ray muon flux to be cm s . The observed angular distributions indicate the leakage of cosmic-ray muon background and agree with simulation data accounting for Jinping mountain's terrain. A survey of muon fluxes at different laboratory locations, considering both those situated under mountains and those down mine shafts, indicates that the flux at the former is generally a factor of larger than at the latter, with the same vertical overburden. This study provides a convenient back-of-the-envelope estimation for the muon flux of an underground experiment.

Monte Carlo characterization of the cosmic ray muon flux in shallow subsurface geological repositories intended for disposal of radioactive materials

Recent challenges in monitoring subsurface geological repositories intended for disposal of radioactive materials such as spent nuclear fuel call for new, innovative concepts that are facility independent, cost-effective, passive, and reliable. Once nuclear material is in place at these facilities, reverifying the inventory may no longer be feasible if continuity of knowledge is lost or unavailable to the inspectors. Using cosmic ray muons may present several potential advantages over conventional photon/neutron signatures, and their use in safeguards applications have only received attention in the past decade. However, there have been limited efforts to explore the integration of cosmic ray muons into repository safeguards and study potential gains, risks, and costs. This paper presents a Monte Carlo-based methodology to characterize the cosmic ray muon flux, including muon angular and energy differential distributions at depths representative of subsurface geological repositories. Since there have been limited measurements at these sites and a measurement made in one site is not always transferable to another site, the objective is to develop an efficient simulation method and useful parametrizations to provide a convenient tool for enabling muon simulations at any geological repository site. It is expected these results will provide a better understanding of how muons can be integrated into an existing geological repository safeguards framework.

Variations of cosmic ray muon flux during thunderstorms as a tool for studying electric field distribution and particle production processes in the atmosphere

The recently published result of GRAPES-3 (a strong thunderstorm muon intensity change) and conclusions made on its basis by this collaboration are discussed and compared with the Baksan observations of muon variations during thunderstorms performed much earlier. It is demonstrated that generally both experiments are quite consistent as far as characteristic patterns of events are concerned, as well as conclusions about direct connection between amplitude of muon intensity disturbance and electric field strength in the atmosphere. However, the GRAPES-3 conclusion about gigavolt potentials associated with their event is doubtful and seems to contradict the fundamental limits on electric fields that can exist in the atmosphere.

Forbush Decreases During 2007–2018 According to the Muon Hodoscope URAGAN Data

Results of the study of variations of cosmic ray muon flux at the Earth surface during Forbush decreases registered in 2007–2018 by means of the muon hodoscope URAGAN are presented. The dynamics of the amplitude spectral index at different stages (the decrease, the minimum, and the recovery), which correspond to different phases of the influence of heliospheric disturbances on the flux of cosmic rays for the period 2012 to 2018, is considered. To investigate possible regularities in the behavior of the projection of the relative local anisotropy vector of the muon flux to the South and to the East (rS and rE) during 2007–2018, the distributions of these parameters for four phases (immediately before FD, decrease phase, minimum phase, recovery phase) were calculated.

Invesigation of the Local Anisotropy of Cosmic Ray Muon Flux During Coronal Mass Ejections in 2007–2018

Coronal mass ejections are among the most powerful disturbances of the interplanetary space. They can influence the state of the near-Earth space, including magnetosphere of the Earth. In addition, such disturbances modulate the flux of cosmic rays and penetrate both the heliosphere and the Earth’s magnetosphere. In order to find an early alert of such events, it is necessary to investigate the flux of particles arriving to the Earth and providing information about events in the heliosphere. The paper presents the results of investigation of the anisotropy of the cosmic ray muon flux by means of the muon hodoscope URAGAN in the period from 2007 to 2018.

Measurement of the cosmic ray muon flux seasonal variation with the OPERA detector

The OPERA experiment discovered muon neutrino into tau neutrino oscillations in appearance mode, detecting tau leptons by means of nuclear emulsion films. The apparatus was also endowed with electronic detectors with tracking capability, such as scintillator strips and resistive plate chambers. Because of its location in the underground Gran Sasso laboratory, under 3800 m.w.e., the OPERA detector has also been used as an observatory for TeV muons produced by cosmic rays in the atmosphere. In this paper the measurement of the single muon flux modulation and its correlation with the seasonal cycle of atmospheric temperature is reported.

Annual change in forest grouse in southern Norway: variation explained by temperatures, bilberry seed production and the lunar nodal phase cycle

Forage quality is rarely the focus of studies on grouse performance. The plant stress hypothesis predicts that the protein digestibility of a focal food plant for grouse in Norway, the bilberry Vaccinium myrtillus should be highest after a peak in seed production. Protein digestibility may also be affected positively by cosmic ray (muon) fluxes, which fluctuate with the 9.3-year lunar nodal phase cycle, and negatively by high temperatures in the preceding summers. The annual change (first difference) in ln-transformed black grouse Tetrao tetrix and capercaillie T. urogallus hunting statistic indices from southern Norway 1999–2017 was positively related to the mean June temperature, which is assumed to have a direct positive impact on chick survival. In multiple regression models, there was also a positive relationship with the seed production of bilberry in the preceding year, the lunar nodal phase index with a two-year time lag, and a negative relationship with the combined mean June–September temperature of the two preceding years. Small rodent numbers did not contribute significantly in these models. In further monitoring of grouse populations, the seed production of bilberry or other important food plants should also be recorded.

Investigation of acoustic signals correlated with the flow of muons of cosmic rays, in connection with seismic activity of the north Tien Shan

The work is aimed at revealing a possible connection between seismic activity and cosmic-ray muon fluxes capable of penetrating into the Earth’s crust and generating a nuclear electromagnetic cascade in a tense seismically active medium, leading to the formation of microcracks, the opening of which is accompanied by the generation of acoustic and, under certain conditions, seismic energy as predicted by Tsarev and Chechin (Atmospheric muons and high-frequency seismic noise. In: Preprint of the FIAN, vol 179, 1988). The data of the underground installation (in a well at a depth of 52 m) for monitoring geoacoustic signals correlated in time with the flow of high-energy cosmic-ray muons generated in extensive atmospheric showers implemented on the basis of the experimental complex “ATHLET” in the Tien Shan High-Altitude Scientific Station of the Physical Institute of the Russian Academy of Sciences were used. It is found that the daily number of acoustic pulses increases significantly before and during appreciable regional earthquakes. The most pronounced pulsed emissions of acoustic energy, correlated in time with the flow of high-energy cosmic-ray muons generated in extensive atmospheric showers, are followed by an increasing seismic activity in the region, that support idea that penetrating into Earth’s crust the flux of cosmic-ray muons may become a “trigger” of earthquake.

Studying Powerful Coronal Mass Ejections That Occurred in September 2017, According to Data from the URAGAN Muon Hodoscope

At the beginning of September 2017, the Sun was characterized by anomalously high solar activity (SA), which was unusual for the region of the minimum of the 11-year cycle. A great many powerful flares of the M- and X-classes were observed; these were accompanied by powerful coronal mass ejections (CMEs). These events caused strong magnetic storms on the Earth (the Kp index was as high as 8; the Dst index was <−140 nT). In this work, the effect these ejections had on the flux of cosmic rays (CRs) is considered using data from the URAGAN muon hodoscope at the Moscow Engineering Physics Institute. The study is based on an analysis of variations in the cosmic ray muon flux. Results are presented from processing flux intensity via flicker-noise spectroscopy in order to identify geoeffective disturbances of the Earth’s magnetosphere. A predictor that precedes by more than one day the emergence in near-Earth space of disturbances related to CME propagation is obtained.

Estimation of cosmic-muon flux attenuation by Monserrate Hill in Bogota

When designing an experimental setup for measuring the flux of cosmic ray muons through a geological structure, it is crucial to make detailed estimates about the expected muon flux attenuation by the structure studied. In this way, the coverage area of the detectors, the data acquisition system and the time length of data taking can be planned accordingly to the aimed accuracy of the measurements. We present here a computational study of the cosmic muon flux at the location of Monserrate Hill in Bogota, Colombia, using the CORSIKA cosmic ray simulator. We use ArcGIS package to estimate the mean depth muons have to travel through the mountain to reach the detector. We consider two different uniform densities of rock for the mountain to make estimates of the muon flux. Through the interpolation of stopping power available data, one can then determine the attenuation as a function of the muon incident energy. Our final result provides an estimation for the muon flux attenuation as a function of the location of the mountain where the muons pass through. We also supply estimated values for the time needed to reach an accuracy of about 3% in the measurement of the muon flux through Monserrate Hill. Our strategy can be easily adapted for muon flux studies at any other location in the world.

Investigating the Apparent Link between Cosmic Ray Muon Flux, Sudden Stratospheric Warming and Dry Season Rainfall over Jamaica

The Jamaican primary dry season extends from November-April with the driest period being January-March each year. Examination of the rainfall records over several decades reveal months that experienced a sharp increase in rainfall while sometimes they are drier than normal. During this dry season, some of the weather systems that impact the island significantly are cold fronts, highs pressure systems and troughs that migrate from the mainland USA. Major Sudden Stratospheric Warmings (SSW) occur routinely north of 60°N and severely impact weather over the North American continent. The islands of the Greater Antilles also experience inclement weather during this period as weather systems migrate southwards and impact the Caribbean. Severe winter weather due to the increase frequency and intensity of storms related to SSW events over North America is important to the Jamaican economy as tourists escape harsh winters by travelling to the island. Predicting the variability of rainfall during the primary dry season is therefore important as it has significant implications for event planning, tourism and agriculture. Cosmic-ray Muon flux has been found to be positively correlated with the atmospheric effective temperature used to indicate the occurrence of SSW events. Current research investigates the relationship between cosmic-ray Muon flux, SSW events and primary dry season rainfall. Our findings suggest that a significant change in rainfall occur over Jamaica during the primary dry season on average 29 days after the central date or on average 15 days after the SSW events end. Our study also suggests apparent similarities in the behaviour of cosmic-ray Muon flux over Jamaica to those when major SSW occurs at high latitudes. We therefore argue that the Muon detectors at low latitudes have practical use with respect to identifying SSWs and merits further study.