Muon Counters Research Articles

Geant4 software application for the simulation of cosmic ray showers in the Earth’s atmosphere

Galactic cosmic rays and solar energetic particles with sufficient rigidity to penetrate the geomagnetic field, enter the Earth’s atmosphere and interact with the electrons and the nuclei of its atoms and molecules. From the interactions with the nuclei, cascades of secondary particles are produced that can be detected by ground-based detectors such as neutron monitors and muon counters. The theoretical study of the details of the atmospheric showers is of great importance, since many applications, such as the dosimetry for the aviation crews, are based on it. In this work, a new application which can be used in order to study the showers of the secondary particles in the atmosphere is presented. This application is based on the Monte Carlo simulation techniques, performed by using the well-known Geant4 toolkit. We present a thorough analysis of the simulation’s critical points, including a description of the procedure applied in order to model the atmosphere and the geomagnetic field. Representative results obtained by the application are presented and future plans for the project are discussed.

Digital electronics for the Pierre Auger Observatory AMIGA muon counters

The ``Auger Muons and Infill for the Ground Array'' (AMIGA) project provides direct muon counting capacity to the Pierre Auger Observatory and extends its energy detection range down to 0.3 EeV. It currently consists of 61 detector pairs (a Cherenkov surface detector and a buried muon counter) distributed over a 23.5 km2 area on a 750 m triangular grid. Each counter relies on segmented scintillator modules storing a logical train of `0's and `1's on each scintillator segment at a given time slot. Muon counter data is sampled and stored at 320 MHz allowing both the detection of single photoelectrons and the implementation of an offline trigger designed to mitigate multi-pixel PMT crosstalk and dark rate undesired effects. Acquisition is carried out by the digital electronics built around a low power Cyclone III FPGA. This paper presents the digital electronics design, internal and external synchronization schemes, hardware tests, and first results from the Observatory.

A Prototype of Readout Electronics Based on an Unified Altera Platform for Underground Muon Counters Triggered by Surface Detectors

The paper describes the prototype of a synchronous (Master/Slave) data acquisition system for underground muon counters triggered by surface detectors. A water Cherenkov surface detector (Master) when hit by extensive air showers generates and transmits the trigger to the underground system (Slave) to register the muon fraction of the showers which survived the propagation through 3 m layer of soil. The surface and underground segments are built on the Altera field-programmable gate array (FPGA) CycloneIII/CycloneIV platforms, respectively. Both FPGAs are equipped with NIOS processors, which makes previously used external microcontrollers unnecessary. They also generate necessary interfaces: SDRAM controller, UART, SPI, DMA; interfaces which were previously implemented by means of logic elements. Moving several time-consuming tasks from the logic block (coded in the Altera Hardware Description Language) to the NIOS (coded in “C”) dramatically simplifies the system and increases its flexibility. The time margin for all processes managed by the soft-core NIOS for the 100 Hz T1 trigger rate remains sufficient. NIOS processors communicate with each other via UART protocol and by the RS485 standard. The underground CycloneIV FPGA is programmed remotely via additional MAXII CPLD with nonvolatile programmable memory. Tests have shown that a full string of data processing goes smoothly. The above-mentioned string involves the following processes: the transfer of the trigger with a time stamp from the surface detector into the underground segment via a dedicated line with a galvanic barrier, freezing data from 64 channels at 320 MHz sampling in internal DPRAMs, writing/reading data into/from external SDRAM, extracting physical data identified by GPS time stamps sent from Central Data Acquisition System (CDAS) and the data transfer from the underground NIOS via the surface NIOS to CDAS.

AMIGA at the Auger observatory: the telecommunications system

AMIGA is an extension of the Pierre Auger Observatory that will consist of 85 detector pairs, each one composed of a surface water-Cherenkov detector and a buried muon counter. Each muon counter has an area of 30 square meters and is made of scintillator strips, with doped optical fibers glued to them, which guide the light to 64 pixel photomultiplier tubes. The detector pairs are arranged at 433 m and 750 m array spacings. In this paper we present the telecommunications system designed to connect the muon counters with the central data processing system at the observatory campus in Malarg"ue. The telecommunications system consists of a point-to-multipoint radio link designed to connect the 85 muon counters or subscribers to two coordinators located at the Coihueco fluorescence detector building. The link provides TCP/IP remote access to the scintillator modules through router boards installed on each of the surface detectors of AMIGA. This setup provides a flexible LAN configuration for each muon counter connected to a WAN that links all the data generated by the muon counters and the surface detectors to the Central Data Acquisition System, or CDAS, at the observatory campus. We present the design parameters, the proposed telecommunications solution and the laboratory and field tests proposed to guarantee its functioning for the whole data traffic generated between each surface detector and muon counter in the AMIGA array and the CDAS.

Effects of massive photons from the dark sector on the muon content in extensive air showers

Inspired by recent astrophysical observations of leptonic excesses measured by satellite experiments, we consider the impact of some general models of the dark sector on the muon production in extensive air showers. We present a compact approximative expression for the bremsstrahlung of a massive photon from an electron and use it within Monte Carlo simulations to estimate the amount of weakly interacting photon-like massive particles that could be produced in an extensive air shower. We find that the resulting muon production is by many orders of magnitude below the average muon count in a shower and thus unobservable.

KASCADE-Grande measurements of energy spectra for elemental groups of cosmic rays

The KASCADE-Grande air shower experiment [1] consists of, among others, a large scintillator array for measurements of charged particles, Nch, and of an array of shielded scintillation counters used for muon counting, Nμ. KASCADE-Grande is optimized for cosmic ray measurements in the energy range 10PeV to about 2000PeV, where exploring the composition is of fundamental importance for understanding the transition from galactic to extragalactic origin of cosmic rays. Following earlier studies of the all-particle and the elemental spectra reconstructed in the knee energy range from KASCADE data [2], we have now extended these measurements to beyond 200PeV. By analysing the two-dimensional shower size spectrum Nch vs. Nμ for nearly vertical events, we reconstruct the energy spectra of different mass groups by means of unfolding methods over an energy range where the detector is fully efficient. The procedure and its results, which are derived based on the hadronic interaction model QGSJET-II-02 and which yield a strong indication for a dominance of heavy mass groups in the covered energy range and for a knee-like structure in the iron spectrum at around 80PeV, are presented. This confirms and further refines the results obtained by other analyses of KASCADE-Grande data, which already gave evidence for a knee-like structure in the heavy component of cosmic rays at about 80PeV [3].

地下μ粒子計数率の時間変動に関わる因子ごとの効果係数

地下μ粒子計数率の時間変動に関わる因子ごとの効果係数

Cosmic ray measurement and experimental temperature analysis with a muon detector

The Basic Atomic Energy Research Institute (BAERI) of Hanyang University in Korea constructed and operates a cosmic ray detection system. In this study, a muon detector composed of a plastic scintillator and a wavelength shifter was used to obtain data over a total of six experimental periods. Using the collected data, we analyzed the response dependence of the developed muon detector on the laboratory’s environmental temperature. The detection results showed a correlation coefficient of over 0.7, as well as a negative proportional correlation in the experiments in which the thermostat did not operate. We performed a correction for the laboratory’s environmental temperature and analyzed the correlation between the muon count rate and the atmospheric pressure. As a result, we obtained a barometric coefficient of −0.1191 ± 0.0054%/hPa. The analyzed data were compared with data from the eighteen NM64 type neutron monitors at our station. The correlation coefficient between the two detection systems was approximately 0.8046, confirming that the response changes were roughly identical to response of neutron monitors.

Conduit magma convection of a rhyolitic magma: Constraints from cosmic-ray muon radiography of Iwodake, Satsuma-Iwojima volcano, Japan

Quantitative re-evaluation of the muon radiography data obtained by Tanaka et al. (2009) was conducted to constrain conduit magma convection at the Iwodake rhyolitic cone of Satsuma-Iwojima volcano, Japan. Re-evaluation of the measurement error considering topography and fake muon counts confirms the existence of a low-density body of 300m in diameter and with 0.9–1.0gcm−3 at depths of 135–190m from the summit crater floor. The low-density material is interpreted as rhyolitic magma with 60% vesicularity on average, and existence of this unstable highly vesiculated magma at shallow depth without any recent eruptive or intrusive activity is considered as evidence of conduit magma convection. The structure of the convecting magma column top was modeled based on density calculations of vesiculated ascending and outgassed descending magmas, compared with the observed density anomaly. The existence of the low-density anomaly was confirmed by comparison with published gravity measurements, and the predicted degassing at the shallow magma conduit top agrees with observed heat discharge anomaly distribution localized at the summit area. This study confirms that high viscosity of silicic magmas can be compensated by a large size conduit to cause the conduit magma convection phenomena. The rare occurrence of conduit magma convection in a rhyolitic magma system at Iwodake is suggested to be due to its specific magma features of low H2O content and high temperature.

Search for a simultaneous signal from small transient events in the Pierre Auger Observatory and the Tupi muon telescopes

We present results of a search for a possible signal from small scale solar transient events (such as flares and interplanetary shocks) as well as possible counterparts to Gamma-Ray Burst (GRB) observed simultaneously by the Tupi muon telescope Niteroi-Brazil, 22.90S, 43.20W, 3 m above sea level) and the Pierre Auger Observatory surface detectors (Malargue-Argentina, 69.30S, 35.30W, altitude 1400 m). Both cosmic ray experiments are located inside the South Atlantic Anomaly (SAA) region. Our analysis of several examples shows similarities in the behavior of the counting rate of low energy (above 100 MeV) particles in association with the solar activity (solar flares and interplanetary shocks). We also report an observation by the Tupi experiment of the enhancement of muons at ground level with a significance higher than 8 sigma in the 1-sec binning counting rate (raw data) in close time coincidence (T-184 sec) with the Swift-BAT GRB110928B (trigger=504307). The GRB 110928B coordinates are in the field of view of the vertical Tupi telescope, and the burst was close to the MAXI source J1836-194. The 5-min muon counting rate in the vertical Tupi telescope as well as publicly available data from Auger (15 minutes averages of the scaler rates) show small peaks above the background fluctuations at the time following the Swift-BAT GRB 110928B trigger. In accordance with the long duration trigger, this signal can possibly suggest a long GRB, with a precursor narrow peak at T-184 sec.

Reconstruction of muon tracks in a buried plastic scintillator muon telescope (Batata)

The Batata muon counter was designed as one of the foreseen detector upgrades of the Pierre Auger Observatory with the main goal of quantifying the electromagnetic contamination of the muon signal as a function of the depth for cosmic ray shower energies above 10PeV. Nevertheless Batata offers also the possibility of measuring the incoming direction of secondary muons from both GeV and PeV primary cosmic rays. Large efforts have been already done to quantify from simulations the amount of the electromagnetic contamination and the expected muon identification performances. The present work is focused on the evaluation of the detector performances for muon track reconstruction. To this aim and in view of the detector installation in the field, expected to be completed by the first half of current year, we performed a Geant4 end-to-end simulation of such device and set up a track reconstruction procedure. Typical results concerning achieved acceptance and angular resolution for muons are presented.

Estimation of the Most Probable Muon Energy at Sea Level Using Two-Paddle Cosmic Ray Detectors

We present a measurement of the most probable cosmic muon energy at near sea level using a two-paddle cosmic ray detector. Muon rates at two different elevations (27 and 326 m) were measured. Data were collected for 2–3 h for each data set at 1 min intervals in the afternoon of successive days. Muon counts were extracted from a Gaussian fit to the distributions of both sets. Despite the fact that only a limited amount of data were collected and measurements were performed at relatively close altitudes, we observed good agreement between the 2.28 ± 0.21 GeV energy measured in this work and the value of 2 GeV that is reported in the literature.

The KACST muon detector and its application to cosmic-ray variations studies

A single channel cosmic ray muon detector was constructed and installed in Riyadh, central Saudi Arabia, for studying the variations in the cosmic ray (CR) muon flux. The detector has been in operation since July 2002. The recorded data correspond to muons that primarily have energies between 10 and 20GeV. The detector will be used to continuously measure the intensity of the muon components of the cosmic rays, exploring its variations and possible correlations with environment parameters. The technical aspects of this detector will be presented. Some results obtained by the detector so far will be given. These include the modulation of the CR flux on different time scales (diurnal, 27-day, and long-term variations). Additionally, the effect of a severe dust storm on the muon count rate was investigated.

Triggers, Data Flow and the Synchronization Between the Auger Surface Detector and the AMIGA Underground Muon Counters

The aim of the AMIGA project (Auger Muons and Infill for the Ground Array) is an investigation of Extensive Air Showers at energies lower than those accesible with the standard Auger array, where the transition from galactic to extragalactic sources is expected. The paper describes the working principle of the Master/Slave (standard Auger surface detector/the underground muon counters) synchronous data acquisition and general triggering applied in two prototypes: with 12.5 ns resolution built from 4 segments (2 FPGAs and 2 standard micro-controllers) and 3.125 ns resolution built from two segments only (2 FPGAs with implemented NIOS <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> processors).

Observation of the February 2011 Forbush decrease by the EEE telescopes

The Forbush decrease following the large X2 solar flare on mid-February 2011 has been observed by the muon telescopes of the EEE Project, which are located in several Italian sites and at CERN. Data from two different telescopes of the EEE network have been analyzed and compared to those measured by neutron monitor stations. The variation of the muon counting rate during the Forbush decrease was also extracted for different intervals of the azimuthal angle of the incoming muons.

AMIGA at the Auger Observatory: the scintillator module testing system

AMIGA is an extension of the Pierre Auger Observatory thatwill consist of 85 detector pairs each one composed of a surfacewater-Cherenkov detector and a buried muon counter. Each muoncounter has an area of 30 m2 and is made of scintillator stripswith doped optical fibers glued to them, which guide the light to64 pixels photomultiplier tubes. The detector pairs are arranged at433 m and 750 m array spacings. In this paper we present the testing and initialcalibration system for the scintillator modules that constituteeach muon counter of AMIGA. The scintillator modules are testedwith a “scanner” that consists of an x−y positioning systemthat moves a 5 mCi 137Cs radioactive source over the moduletaking data at fixed locations. The scanner both tests the modulefor possible fabrication defects and stores the light-attenuationcurve parameters. A complete scanning process of a 64 stripscintillator module has been performed and results are presented. Also,attenuation curves obtained with scanner and with background muons arecompared with satisfactory results.

Extending the Pierre Auger Observatory to explore the ankle of the cosmic ray spectrum

There are currently two enhancements of the Pierre Auger Observatory under construction or taking first data. AMIGA extends the surface detector by a denser array of water Cherenkov stations each accompanied by a muon counter. Furthermore, the fluorescence detector is extended by three telescopes, called HEAT, with a field of view chosen to observe lower atmospheric depths. Together they will lower the energy threshold of the Observatory by an order of magnitude from 1018eV to about 1017eV, and make it possible to study the interesting energy region around the second knee and the ankle with high precision and statistic. As the hybrid technique is best suited for determining the mass composition of cosmic rays, these enhancements will help to enlighten the questions around the transition from galactic to extragalactic cosmic rays.

Background and muon counting rates in underground muon measurements with a plastic scintillator counter based on a wavelength shifting fibre and a multi-pixel avalanche photodiode readout

Abstract In this short note we present results of background measurements carried out with polystyrene based cast plastic 12.0×12.0×3.0 cm3 size scintillator counter with a wavelength shifting fibre and a multi-pixel Geiger mode avalanche photodiode readout in the Baksan underground laboratory at a depth of 200 metres of water equivalent. The total counting rate of the scintillator counter measured at this depth and at a threshold corresponding to ∼0.37 of a minimum ionizing particle is approximately 1.3 Hz.

The BESIII muon identification system

The muon identification system of BESIII experiment at the IHEP is described. The muon counter (MUC) is composed of resistive plate chambers (RPCs) working in self-quenching streamer mode with the gas mixture Ar/C 2F 4H 2/C 4H 10=50/42/8. The design, the construction, the mass production and the quality control result of the detectors are described in detail. The paper also presents the performance of the bare RPCs and the superlayer modules with cosmic rays. Finally, the subsystems of MUC, including the RPC superlayer modules, the gas systems, the HV and LV system and the readout electronic system, are also presented.

Track reconstruction in the BESIII muon counter

The reconstruction algorithm for BESIII Muon Counter, MucRecAlg, is developed with the object-oriented language C++ in BESIII offline software environment. MucRecAlg consists of the following functions: to find track seeds either from extrapolation of tracks in the main drift chamber or from the fired strips in muon counter, to select fired strips associated to the candidate tracks, to fit the candidate tracks with a linear or quadratic function and to calculate other parameters of the tracks for muon identification. Monte Carlo samples are generated to check the performance of the reconstruction package, such as reconstruction efficiency, muon remaining rate and pion rejection rate, etc. The preliminary results show that the pion rejection rate is around 3%–4% while the muon remaining rate is better than 90% in 0.4–1.6 GeV/c momentum region, which meets the requirement as shown in the design report.