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The Time-Of-Propagation (TOP) counter is a ring-imaging Cherenkov detector designed to identify the charged hadrons in the barrel region of the Belle II detector. The Belle II experiment collected data delivered by the SuperKEKB accelerator from March 2019 to June 2022. After the first run period (Run1), a long shutdown (LS1) was dedicated to implement several accelerator and detector upgrades. The second collision period (Run2) was started in January 2024. The components of the TOP detector and the performance during the Run1 will be reported and the detector upgrade during LS1 and future upgrades will be described. [ABSTRACT FROM AUTHOR]

Transparent silica aerogel, serving as one typical porous and transparent material, possesses various unique features (e. g. large amounts of pores and interfaces, super‐lightweight, super thermal insulation, low refractive index similar to gas), and it has attracted great attention in the fields of science, technology, engineering, art, and others. Transparency is one important evaluation index of transparent silica aerogel, and it was influenced by various factors such as raw materials, sol‐gel reactions, phase separation, and drying methods. The structure design and fabrication of transparent silica aerogel is one huge and fine engineering. In this review, the optical/chemical guidance and design for the preparation of transparent silica aerogels are discussed, and typical applications, such as Cherenkov detectors, solar energy collection, lighting systems, and transparent fabric, were also discussed. Finally, a future outlook on the opportunities and challenges of transparent silica aerogels was proposed. [ABSTRACT FROM AUTHOR]

Photodetectors used in future high-energy physics experiments will need to keep sufficient performance during a few years of data-taking despite radiation load, which, for example, in the planned upgrade of the Ring Imaging Cherenkov detectors in Large Hadron Collider beauty (LHCb) experiment is estimated at about 10 13 1-MeV neutron equivalent per cm 2 (neq/cm 2 ). Silicon photomultipliers (SiPMs) are considered as candidates for photodetectors for this application. However, their sensitivity to neutron irradiation may seriously compromise their operation, with the increase in dark count rates being the primary limitation after the irradiation. In this work, 1 × 1 mm 2 15 μ m pitch NUV-HD-RH silicon photomultipliers developed by the Fondazione Bruno Kessler were characterized before and after the irradiation. In total, 5 SiPMs were irradiated at the Jožef Stefan Institute TRIGA nuclear reactor with different fluences from 10 9 neq/cm 2 up to 10 13 neq/cm 2 . The SiPMs were also annealed at high temperatures and re-characterized after the annealing. For the SiPM characterization in all the cases, current–voltage (I-V curve) measurements, dark count rate measurements, and waveform analysis, including single photon time resolution, were carried out at different controlled temperature steps from room temperature down to the liquid nitrogen temperature. While cooling to − 20 ∘ C was enough for the SiPM irradiated at 10 9 neq/cm 2 to recover the ability to resolve single photons, by 10 13 neq/cm 2 , cooling to liquid nitrogen temperature was necessary. With sufficient cooling, the measured single photon time resolution was around 90 ps FWHM for all irradiation levels. [ABSTRACT FROM AUTHOR]

The Latin American Giant Observatory (LAGO) is a ground-based extended cosmic rays observatory designed to study transient astrophysical events, the role of the atmosphere on the formation of secondary particles, and space-weather-related phenomena. With the use of a network of Water Cherenkov Detectors (WCDs), LAGO measures the secondary particle flux, a consequence of the interaction of astroparticles impinging on the atmosphere of Earth. This flux can be grouped into three distinct basic constituents: electromagnetic, muonic, and hadronic components. When a particle enters a WCD, it generates a measurable signal characterized by unique features correlating to the particle's type and the detector's specific response. The resulting charge histograms from these signals provide valuable insights into the flux of primary astroparticles and their key characteristics. However, these data are insufficient to effectively distinguish between the contributions of different secondary particles. In this work, we extend our previous research by using detailed simulations of the expected atmospheric response to the primary flux and the corresponding response of our WCDs to atmospheric radiation. This dataset, which was created through the combination of the outputs of the ARTI and Meiga simulation frameworks, simulated the expected WCD signals produced by the flux of secondary particles during one day at the LAGO site in Bariloche, Argentina, situated at 865 m above sea level. This was achieved by analyzing the real-time magnetospheric and local atmospheric conditions for February and March of 2012, where the resultant atmospheric secondary-particle flux was integrated into a specific Meiga application featuring a comprehensive Geant4 model of the WCD at this LAGO location. The final output was modified for effective integration into our machine-learning pipeline. With an implementation of Ordering Points to Identify the Clustering Structure (OPTICS), a density-based clustering algorithm used to identify patterns in data collected by a single WCD, we have further refined our approach to implement a method that categorizes particle groups using advanced unsupervised machine learning techniques. This allowed for the differentiation among particle types and utilized the detector's nuanced response to each, thus pinpointing the principal contributors within each group. Our analysis has demonstrated that applying our enhanced methodology can accurately identify the originating particles with a high degree of confidence on a single-pulse basis, highlighting its precision and reliability. These promising results suggest the feasibility of future implementations of machine-leaning-based models throughout LAGO's distributed detection network and other astroparticle observatories for semi-automated, onboard and real-time data analysis. [ABSTRACT FROM AUTHOR]

Gamma-ray burst (GRB), GRB 221009A, a long-duration GRB, was observed simultaneously by the Water Cherenkov Detector Array (WCDA) and the Kilometer Squared Array (KM2A) of the Large High Altitude Air Shower Observatory (LHAASO) during the prompt emission and the afterglow periods. Characteristic multi-TeV photons up to 13 TeV were observed in the afterglow phase. The observed very high-energy (VHE) gamma-ray spectra by WCDA and KM2A during different time intervals and in different energy ranges can be explained very well in the context of the photohadronic model with the inclusion of extragalactic background light models. In the photohadronic scenario, interaction of high-energy protons with the synchrotron self-Compton (SSC) photons in the forward shock region of the jet is assumed to be the source of these VHE photons. The observed VHE spectra from the afterglow of GRB 221009A are similar to the VHE gamma-ray spectra observed from the temporary extreme high-energy peaked BL Lac (EHBL), 1ES 2344+514 only during the 11th and the 12th of August, 2016. Such spectra are new and have been observed for the first time in a GRB. [ABSTRACT FROM AUTHOR]

The ASHIPH (Aerogel, SHifter, PHotomultiplier) Cherenkov counters are considered as a particle identification system alternative option for the detector on future Super Charm-Tau factory. The ASHIPH counters have been operating successfully in the KEDR and SND experiments in Novosibirsk at the Budker Institute of Nuclear Physics. Previously in our experiments Micro Channel Plate PMTs were used for the photon detection in the ASHIPH counters. Now, we have developed a prototype of the ASHIPH counter with SiPM (Silicon PMTs) array as a photodetector. Such an upgrade will increase the number of detected photoelectrons by 2.5 times and consequently improve the quality of particle separation. The results of testing the ASHIPH counter prototype on the electron test beam facility of the VEPP-4M accelerator is presented. [ABSTRACT FROM AUTHOR]

The global challenge of on-site detection of highly enriched uranium (HEU), a substance with considerable potential for unauthorized use in nuclear security, is a critical concern. Traditional passive nondestructive assay (NDA) techniques, such as gamma-ray spectroscopy with high-purity germanium detectors, face significant challenges in detecting HEU when it is shielded by heavy metals. Addressing this critical security need, we introduce an on-site detection method for lead-shielded HEU employing a transportable NDA system that utilizes the 252Cf rotation method with a water Cherenkov neutron detector. This cost-effective NDA system is capable of detecting 4.17 g of 235U within a 12 min measurement period using a 252Cf source of 3.7 MBq. Integrating this system into border control measures can enhance the prevention of HEU proliferation significantly and offer robust deterrence against nuclear terrorism. [ABSTRACT FROM AUTHOR]

Objective. Prompt gamma timing (PGT) uses the detection time of prompt gammas emitted along the range of protons in proton radiotherapy to verify the position of the Bragg peak (BP). Cherenkov detectors offer the possibility of enhanced signal-to-noise ratio (SNR) due to the inherent physics of Cherenkov emission which enhances detection of high energy prompt gamma rays relative to other induced uncorrelated signals. In this work, the PGT technique was applied to 3 semiconductor material slabs that emit only Cherenkov light for use in a full scale system: a 3 × 3 × 20 mm3 TlBr, a 12 × 12 × 12 mm3 TlBr, and a 5 × 5 × 5 mm3 TlCl. Approach. A polymethyl methacrylate (PMMA) target was exposed to a 67.5 MeV, 0.5 nA proton beam and shifted in 3 mm increments at the Crocker nuclear laboratory (CNL) in Davis, CA, USA. A fast plastic scintillator coupled to a photomultiplier tube (PMT) provided the start reference for the proton time of flight. Time of flight (TOF) distributions were generated using this reference and the gamma-ray timestamp in the Cherenkov detector. Main results. The SNR of the proton correlated peaks relative to the background was 20, 29, and 30 for each of the three samples, respectively. The upper limit of the position resolutions with the TlCl sample were 2 mm, 3 mm, and 5 mm for 30k, 10k, and 5k detected events, respectively. The time distribution of events with respect to the reference reproduced with clarity the periodicity of the beam, implying a very high SNR of the Cherenkov crystals to detect prompt gammas. Background presence from the neutron-induced continuum, prompt gammas from deuterium, or positron activation were not observed. Material choice and crystal dimensions did not seem to affect significantly the outcome of the results. Significance. These results show the high SNR of the pure Cherenkov emitters TlBr and TlCl for the detection of prompt gammas in a proton beam with current of clinical significance and their potential for verifying the proton range. The accuracy in determining shifts of the BP was highly dependent on the number of events acquired, therefore, the performance of these detectors are expected to vary with different beam conditions such as current, pulse repetition, and proton bunch width. [ABSTRACT FROM AUTHOR]

Isotopic composition measurements of singly charged cosmic rays (CR) provide essential insights into CR transport in the Galaxy. The Alpha Magnetic Spectrometer (AMS-02) can identify singly charged isotopes up to about 10 GeV/n. However, their identification presents challenges due to the small abundance of CR deuterons compared to the proton background. In particular, a high accuracy for the velocity measured by a ring-imaging Cherenkov detector (RICH) is needed to achieve a good isotopic mass separation over a wide range of energies. The velocity measurement with the RICH is particularly challenging for Z = 1 isotopes due to the low number of photons produced in the Cherenkov rings. This faint signal is easily disrupted by noisy hits leading to a misreconstruction of the particles' ring. Hence, an efficient background reduction process is needed to ensure the quality of the reconstructed Cherenkov rings and provide a correct measurement of the particles' velocity. Machine learning methods, particularly boosted decision trees, are well suited for this task, but their performance relies on the choice of the features needed for their training phase. While physics-driven feature selection methods based on the knowledge of the detector are often used, machine learning algorithms for automated feature selection can provide a helpful alternative that optimises the classification method's performance. We compare five algorithms for selecting the feature samples for RICH background reduction, achieving the best results with the Random Forest method. We also test its performance against the physics-driven selection method, obtaining better results. [ABSTRACT FROM AUTHOR]

Air compressors are widely used in industrial fields. Compressed air systems aggregate air flows and then supply them to places of demand. These huge systems consume a significant amount of energy and generate heat internally. Machine components in compressed air systems are vulnerable to heat, and, in particular, a radiator to cool the heat of the overall air compressor is the core component. Dirty radiators increase energy consumption due to anomalous cooling. To reduce the energy consumption of air compressors, this mechanism emphasizes a machine learning-based radiator fault detection, using features such as RPM, motor power, outlet pressure, air flow, water pump power, and outlet temperature with slight true fault labels. Moreover, the proposed system adds an LSTM-based motor power prediction model to point out the initial judgment of radiator fault possibility. Via the rigorous analysis and the comparison among machine learning models, this meticulous approach improves the performance of radiator fault prediction up to 93.0%, and decreases the mean power consumption of the air compressor around 2.24%. [ABSTRACT FROM AUTHOR]

Because gadolinium (Gd) has the highest thermal neutron capture cross section, resulting in an 8 MeV gamma cascade upon capture, it has been proposed for dissolution in water Cherenkov detectors to achieve efficient neutron tagging capabilities. Whereas metallic Gd is insoluble in water, several compounds are very easy to dissolve. Gadolinium sulfate, Gd2(SO4)3, has been thoroughly tested and proposed as the best candidate. Accurate measurement of its concentration, free of doubt from impurities in water, is crucial. An atomic absorption spectrophotometer (AAS) is a device that suits this purpose and is widely used to measure the concentration of many elements. In this study, we describe three different approaches to measure Gd sulfate concentrations in water using an AAS: doping samples with potassium and lanthanum, and employing tantalum and tungsten platforms. [ABSTRACT FROM AUTHOR]

The Trans-Iron Galactic Element Recorder (TIGER) family of instruments is optimized to measure the relative abundances of the rare, ultra-heavy galactic cosmic rays (UHGCRs) with atomic number (Z) Z ≥ 30. Observing the UHGCRs places a premium on exposure that the balloon-borne SuperTIGER achieved with a large area detector (5.6 m2) and two Antarctic flights totaling 87 days, while the smaller (∼1 m2) TIGER for the International Space Station (TIGERISS) aims to achieve this with a longer observation time from one to several years. SuperTIGER uses a combination of scintillator and Cherenkov detectors to determine charge and energy. TIGERISS will use silicon strip detectors (SSDs) instead of scintillators, with improved charge resolution, signal linearity, and dynamic range. Extended single-element resolution UHGCR measurements through 82Pb will cover elements produced in s-process and r-process neutron capture nucleosynthesis, adding to the multi-messenger effort to determine the relative contributions of supernovae (SNe) and Neutron Star Merger (NSM) events to the r-process nucleosynthesis product content of the galaxy. [ABSTRACT FROM AUTHOR]

This paper presents the results of the sky survey with the TAIGA–HiSCORE installation, an array of 120 wide-angle Cherenkov light detectors spread over an area of 1 km2. Data analysis is made for 2 winter seasons (2019–2021) at cosmic ray energies above 200–500 TeV. A modified method of background estimation is tested. Signal significance is estimated using classical Li-Ma method. [ABSTRACT FROM AUTHOR]

The next-generation water Cherenkov Hyper-Kamiokande detector will be able to detect thousands of neutrino events from a galactic Supernova explosion via Inverse Beta Decay processes followed by neutron capture on Gadolinium. This superb statistics provides a unique window to set bounds on neutrino properties, as its mass and lifetime. We shall explore the capabilities of such a future detector, constraining the former two properties via the time delay and the flux suppression induced in the Supernovae neutrino time and energy spectra. Special attention will be devoted to the statistically sub-dominant elastic scattering induced events, normally neglected, which can substantially improve the neutrino mass bound via time delays. When allowing for a invisible decaying scenario, the 95% CL lower bound on τ / m is almost one order of magnitude better than the one found with SN1987A neutrino events. Simultaneous limits can be set on both m ν and τ ν , combining the neutrino flux suppression with the time-delay signature: the best constrained lifetime is that of ν 1 , which has the richest electronic component. We find τ ν 1 ≳ 4 × 10 5 s at 95% CL. The tightest 95% CL bound on the neutrino mass we find is 0.34 eV, which is not only competitive with the tightest neutrino mass limits nowadays, but also comparable to future laboratory direct mass searches. Both mass and lifetime limits are independent on the mass ordering, which makes our results very robust and relevant. [ABSTRACT FROM AUTHOR]

• We characterized the pressure wave produced by the Tonga volcano using cosmic rays. • We believe this is the first time that a Lamb wave is studied using cosmic rays. • Our high-altitude data provides additional information about this unique event. High-energy cosmic rays that hit the Earth can be used to study large-scale atmospheric perturbations. After a first interaction in the upper parts of the atmosphere, cosmic rays produce a shower of particles that sample it down to the detector level. The HAWC (High-Altitude Water Cherenkov) gamma-ray observatory in Central Mexico at 4,100 m elevation detects air shower particles continuously with 300 water Cherenkov detectors with an active area of 12,500 m2. On January 15th, 2022, HAWC detected the passage of the pressure wave created by the explosion of the Hunga volcano in the Tonga islands, 9,000 km away, as an anomaly in the measured rate of shower particles. The HAWC measurements are used to determine the propagation speed of four pressure wave passages, and correlate the variations of the shower particle rates with the barometric pressure changes. The profile of the shower particle rate and atmospheric pressure variations for the first transit of the pressure wave at HAWC is compared to the pressure measurements at the Tonga island, near the volcanic explosion. By using the cosmic-ray propagation in the atmosphere as a probe for the pressure, it is possible to achieve very high time-resolution measurements. Moreover, the high-altitude data from HAWC allows to observe the shape of the pressure anomaly with less perturbations compared to sea level detectors. Given the particular location and the detection method of HAWC, our high-altitude data provides valuable information that contributes to fully characterize this once-in-a-century phenomenon. [ABSTRACT FROM AUTHOR]

According to observations of the radiation situation in space from the Meteor-M No. 2 satellite, which is in a sun-synchronous circular orbit with a height of ~832 km, 25 anomalous increases in electron fluxes with a duration of ~6–8 min each were detected. These rare events were recorded in 2014–2022 in Oceania at low latitudes in the morning hours of local time under quiet geomagnetic conditions, at energies from ~100 keV to several MeV. Electron fluxes in the channel of the Cherenkov counter were observed at the level of fluxes of galactic cosmic rays in the polar caps, and in the channels of other counters, at the level of fluxes at the maximum of the outer radiation belt. It is assumed that precipitation of electrons from the inner radiation belt was observed: during bounce oscillations, electrons fell into cyclotron resonance with radio emission initiated by ground and/or ship transmitters in the morning hours of local time. [ABSTRACT FROM AUTHOR]

The IceCube Neutrino Observatory is a cubic-kilometer Cherenkov detector that is deployed deep in the Antarctic ice at the South Pole. A square kilometer companion surface detector, IceTop, located directly above in the in-ice array, measures cosmic-ray initiated extensive air showers with primary energies between 100 TeV and 1 EeV. By combining the events measured by IceTop and the in-ice detectors of IceCube in coincidence, we can reconstruct the energy spectra for different primary mass groups. Therefore, we provide information about the origin of cosmic rays, in particular, in the transition region from galactic to extra-galactic origin of high-energy cosmic rays. In this contribution we present recent experimental results, as well as prospects by the foreseen enhancement of the surface detectors of IceTop and the future IceCube-Gen2 surface array. [ABSTRACT FROM AUTHOR]

The upcoming LHCb calorimetry upgrade implies significant modifications to the present detector system. These changes include modifications to the Electromagnetic Calorimeter (ECAL) and possible removal of the Hadron Calorimeter. Such changes require detailed studies, including the test beam campaign. This paper presents the results of the hadron beam particle composition analysis performed at CERN SPS H8 testbeam line. The analysis is based on the data recorded with a single-cell LHCb ECAL module, threshold Cherenkov detector and tracking system based on delay-wire chamber stations. [ABSTRACT FROM AUTHOR]

Numerous particle physics experiments utilize gadolinium (Gd), a rare earth element with the most significant neutron capture cross-section among all elements, to detect anti-neutrinos via inverse beta decays or to remove neutron-induced background events. For example, to load Gd into water Cherenkov detectors, Gd2(SO4)3 · 8H2O is dissolved and rare event search experiments are required to screen for radioactive impurities in Gd2(SO4)3 · 8H2O before dissolution. This study developed a new method to rapidly measure the radium-226 (226Ra) concentration in Gd2(SO4)3 · 8H2O. This method requires only 3 days to measure a batch of samples, as opposed to the usual method using high-purity germanium detectors, which takes approximately 20 days after arrival. The detection limit for the measurement of 226Ra concentration in Gd2(SO4)3 · 8H2O is 0.43 mBq/kg. This method has been already used for Gd2(SO4)3 · 8H2O screening at the Super-Kamiokande Gd (SK-Gd) project, and it can be applied to future experiments. [ABSTRACT FROM AUTHOR]

The parameters of scintillator veto detectors that should be installed in an intermediate water Cherenkov detector of the Hyper-Kamiokande project have been measured. The veto detectors are disc scintillators with embedded wavelength-shifting fibers and with compact photosensors, i.e., silicon photomultipliers. It is shown that the detection efficiency of these detectors for cosmic muons is larger than 99%. [ABSTRACT FROM AUTHOR]

Direct evidence of inertially confined fusion ignition appears in the abrupt temperature increase and consequent rapid increase in the thermonuclear burn rate as seen in the reaction history. The Gamma Reaction History (GRH) and Gas Cherenkov Detector (GCD) diagnostics are γ-based Cherenkov detectors that provide high quality measurements of deuterium–tritium fusion γ ray production and are, thus, capable of monitoring the thermonuclear burn rate. Temporal shifts in both peak burn time and burn width have been observed during recent high-yield shots (yields greater than 1017 neutrons) and are essential diagnostic signatures of the ignition process. While the current GRH and GCD detectors are fast enough to sense the changes of reaction history due to alpha heating, they do not have enough dynamic range to capture the onset of alpha heating. The next generation of instrumentation, GRH-15m, is proposed to increase the yield-rate coverage to measure the onset of alpha-heating. [ABSTRACT FROM AUTHOR]

We analyze the expected arrival time spectrum of supernova neutrinos using simulated luminosity and compute the expected number of events in future detectors such as the DUNE Far Detector and Hyper-Kamiokande. We develop a general method using minimum square statistics that can compute the sensitivity to any variable affecting neutrino time of flight. We apply this method in two different situations: First, we compare the time spectrum changes due to different neutrino mass values to put limits on electron (anti)neutrino effective mass. Second, we constrain Lorentz invariance violation through the mass scale, M Q G , at which it would occur. We consider two main neutrino detection techniques: 1. DUNE-like liquid argon TPC, for which the main detection channel is ν e + 40 Ar → e − + 40 K ∗ , related to the supernova neutronization burst; and 2. HyperK-like water Cherenkov detector, for which ν ¯ e + p → e + + n is the main detection channel. We consider a fixed supernova distance of 10 kpc and two different masses of the progenitor star: (i) 15 M ⊙ with neutrino emission time up to 0.3 s and (ii) 11.2 M ⊙ with neutrino emission time up to 10 s. The best mass limits at 3 σ are for O (1) eV. For ν e , the best limit comes from a DUNE-like detector if the mass ordering happens to be inverted. For ν ¯ e , the best limit comes from a HyperK-like detector. The best limit for the Lorentz invariance violation mass scale at the 3 σ level considering a superluminal or subluminal effect is M Q G ≳ 10 13 GeV ( M Q G ≳ 5 × 10 5 GeV) for linear (quadratic) energy dependence. [ABSTRACT FROM AUTHOR]

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• New water Cherenkov detector at the Antarctic Peninsula for cosmic ray flux. • Analysis of atmospheric pressure and temperature effects on data. • Solar diurnal anisotropy of cosmic ray flux is observed. A new water-Cherenkov radiation detector, located at the Argentine Marambio Antarctic Base (64.24S-56.62 W), has been monitoring the variability of galactic cosmic ray (GCR) flux since 2019. One of the main aims is to provide experimental data necessary to study interplanetary transport of GCRs during transient events at different space/time scales. In this paper we present the detector and analyze observations made during one full year. After the analysis and correction of the GCR flux variability due to the atmospheric conditions (pressure and temperature), a study of the periodicities is performed in order to analyze modulations due to heliospheric phenomena. We can observe two periods: (a) 1 day, associated with the Earth's rotation combined with the spatial anisotropy of the GCR flux; and (b) ∼ 30 days due to solar impact of stable solar structures combined with the rotation of the Sun. From a superposed epoch analysis, and considering the geomagnetic effects, the mean diurnal amplitude is ∼ 0.08% and the maximum flux is observed in ∼ 15 h local time (LT) direction in the interplanetary space. In such a way, we determine the capability of Neurus to observe anisotropies and other interplanetary modulations on the GCR flux arriving at the Earth. [ABSTRACT FROM AUTHOR]

We recently proposed a new approach for the real-time monitoring of particle therapy treatments with the goal of achieving high sensitivities on the particle range measurement already at limited counting statistics. This method extends the Prompt Gamma (PG) timing technique to obtain the PG vertex distribution from the exclusive measurement of particle Time-Of-Flight (TOF). It was previously shown, through Monte Carlo simulation, that an original data reconstruction algorithm (Prompt Gamma Time Imaging) allows to combine the response of multiple detectors placed around the target. The sensitivity of this technique depends on both the system time resolution and the beam intensity. At reduced intensities (Single Proton Regime—SPR), a millimetric proton range sensitivity can be achieved, provided the overall PG plus proton TOF can be measured with a 235 ps (FWHM) time resolution. At nominal beam intensities, a sensitivity of a few mm can still be obtained by increasing the number of incident protons included in the monitoring procedure. In this work we focus on the experimental feasibility of PGTI in SPR through the development of a multi-channel, Cherenkov-based PG detector with a targeted time resolution of 235 ps (FWHM): the TOF Imaging ARrAy (TIARA). Since PG emission is a rare phenomenon, TIARA design is led by the concomitant optimisation of its detection efficiency and Signal to Noise Ratio (SNR). The PG module that we developed is composed of a small PbF 2 crystal coupled to a silicon photoMultiplier to provide the time stamp of the PG. This module is currently read in time coincidence with a diamond-based beam monitor placed upstream the target/patient to measure the proton time of arrival. TIARA will be eventually composed of 30 identical modules uniformly arranged around the target. The absence of a collimation system and the use of Cherenkov radiators are both crucial to increase the detection efficiency and the SNR, respectively. A first prototype of the TIARA block detector was tested with 63 MeV protons delivered from a cyclotron: a time resolution of 276 ps (FWHM) was obtained, resulting in a proton range sensitivity of 4 mm at 2 σ with the acquisition of only 600 PGs. A second prototype was also evaluated with 148 MeV protons delivered from a synchro-cyclotron obtaining a time resolution below 167 ps (FWHM) for the gamma detector. Moreover, using two identical PG modules, it was shown that a uniform sensitivity on the PG profiles would be achievable by combining the response of gamma detectors uniformly distributed around the target. This work provides the experimental proof-of-concept for the development of a high sensitivity detector that can be used to monitor particle therapy treatments and potentially act in real-time if the irradiation does not comply to treatment plan. [ABSTRACT FROM AUTHOR]

The Muon Telescope, MuTe, is an instrument for imaging volcanoes in Colombia. It consists of a scintillator tracking system and a water Cherenkov detector for particle energy measurement. The Muon Telescope operates autonomously in high-altitude environments where the temperature gradient reaches up to 10 °C. In this work, we characterize the telescope silicon photomultipliers' breakdown voltage, gain, and noise for temperature variations spanning 0 to 40 °C. We demonstrate that the discrimination threshold for the Muon Telescope hodoscope must be above 5 photo-electrons to avoid contamination due to dark count, crosstalk, and afterpulsing. We also assess the detector counting rate depending on day-night temperature variations. [ABSTRACT FROM AUTHOR]

We report the results of the Monte Carlo simulation of electron dynamics in stationary and space- and time-dependent electric fields in compensated GaN samples. We have determined the frequency and wavevector dependencies of the dynamic conductivity, σ ω , q (i.e., the electron response to high-frequency electrical signals). We have found that the spatially dependent dynamic conductivity of the drifting electrons can be negative under stationary electric fields of moderate amplitudes, 2..5 kV / cm. This effect is realized in a set of frequency windows. The low-frequency window with negative dynamic conductivity is due to the Cherenkov mechanism. For this case, the time-dependent field induces a "traveling wave" of the electron concentration in real space and a "standing wave" in the energy/momentum space. The higher frequency windows of negative dynamic conductivity are associated with the optical phonon transient time resonances. For this case, the time-dependent field is accompanied by oscillations of the electron distribution in the form of the "traveling" waves in both the real space and the energy/momentum space. We discuss the optimal conditions for the observation of these effects. We suggest that the studied negative dynamic conductivity can be used to amplify electromagnetic waves at the expense of energy of the stationary field and current. [ABSTRACT FROM AUTHOR]

The Liquid Argon Time Projection Chamber (LAr-TPC) technology was conceived at the end of the 1970s as a way to combine the excellent spatial and calorimetric performance of the traditional bubble chambers with the electronic read-out of the TPCs, obtaining the so-called "electronic bubble chambers". This technology was intended to be applied in particular to neutrino physics as an alternative to Ring Water Cherenkov detectors. The main technological issues of such an innovative technique were investigated from the very beginning within the ICARUS program, with staged R&D starting from prototypes of increasing mass to arrive, at the end of 1990s, at the largest LAr-TPC detector ever built at that time: ICARUS-T600, with almost 500 tons of active LAr. The successful operations of the ICARUS-T600 LAr-TPC in its more than twenty years of life, from the first run at surface in Pavia (Italy) in 2001 to the LNGS (Italy) underground run being exposed to the CNGS beam from CERN to Gran Sasso (2010–2013) and finally to the ongoing run at Fermilab (USA) for sterile neutrino searches (2020–), have demonstrated the huge potential of the LAr-TPC technique, paving the way to future larger LAr-TPCs detectors as DUNE. [ABSTRACT FROM AUTHOR]

The only method for assessing the fusion power throughput of a deuterium–tritium (DT) reactor presently relies on determining the absolute number of 14 MeV neutrons produced in the DT plasma. An independent method, developed and investigated during the recent DT campaign at the Joint European Torus, is based on the absolute counting of 17 MeV gamma rays produced by the competing T(D, γ)5He reaction that features a very weak branching ratio (about 3–6 × 10−6) when compared to the main T(D, n)4He reaction. The state-of-the-art spectrometer used for gamma-ray measurements in magnetic confinement fusion plasmas is LaBr3(Ce) scintillator detectors, although they require significant neutron shielding to extract a relatively weak gamma-ray signal from a much more abundant neutron field. A better approach relies on a gamma-ray detector that is intrinsically insensitive to neutrons. We have advanced the design of a gamma-ray counter based on the Cherenkov effect for gamma-rays whose energy exceeds 11 MeV, optimized to work in the neutron-rich environment of a steady-state, magnetically confined fusion plasma device. The gamma-rays interact with an aluminum window and extract electrons that move into the radiator emitting photons via the Cherenkov effect. Since the Cherenkov light consists of few photons (25 on average) in the far UV band (100–200 nm), a pre-amplifier is required to transport the photons to the neutron-shielded location, which may be a few meters away, where the readout elements of the detector, either a silicon or standard photomultiplier tube, are placed. The present work focuses on the development of a scintillating GEM (Gas Electron Multiplier) based pre-amplifier that acts as a Cherenkov photon pre-amplifier and wavelength shifter. This paper presents the result of a set of Garfield++ simulations developed to find the optimal GEM working parameters. A photon gain of 100 is obtained by biasing a single GEM foil to 1 kV. [ABSTRACT FROM AUTHOR]

We first discuss and determine the isospin mixing of the two 2− states (12.53 MeV and 12.97 MeV) of the16O nucleus using inelastic electron scattering data. We then evaluate the cross section of 4.4-MeV γ rays produced in the neutrino neutral-current (NC) reaction 16O(ν, ν ′)16O(12.97 MeV, 2−) in a water Cherenkov detector at a low energy, below 100 MeV. The detection of γ rays for E γ > 5 MeV from the NC reaction 16O(ν, ν ′)16O(Ex > 16 MeV, T = 1) with a water Cherenkov detector in supernova neutrino bursts has been proposed and discussed by several authors previously. In this article, we discuss a new NC reaction channel from 16O(12.97 MeV, 2−) producing a 4.4-MeV γ ray, the cross section of which is more robust and even larger at low energy (E ν < 25 MeV) than the NC cross section from 16O(Ex > 16 MeV, T = 1). We also evaluate the number of such events induced by neutrinos from supernova explosion which can be observed by the Super-Kamiokande, an Earth-based 32-kton water Cherenkov detector. [ABSTRACT FROM AUTHOR]

Spectrum difference was used to study the dependence of Cherenkov light yields of complex and simple substances added to liquid radiators on their concentration. The radiation was generated by cosmic muons and 194-MeV positrons produced at the S-25R electron synchrotron. Dependence of the characteristics of Cherenkov radiation spectra of simple substances on their position in the periodic system of elements has been studied. Cherenkov light yields as a function of the ratio of atomic numbers Z and the volume of atoms of these substances have been estimated. Based on the results of the study, use of Cherenkov radiation is suggested as a method for determining the type of substances (Cherenkov spectrometry). [ABSTRACT FROM AUTHOR]

To observe supernova relic neutrino events, 13 tons of gadolinium sulfate octahydrate (Gd2(SO4)3·8H2O), corresponding to 0.01% Gd solution, was dissolved in the Super-Kamiokande water Cherenkov detector in 2020. The aim is to improve the detection efficiency of neutrons from inverse β decay involving electron antineutrinos. However, Gd3+ ions can be excited by the Cherenkov light from cosmic muons, and the subsequent emission at 312 nm is a possible background (BG) source for Cherenkov signal detection. In this work, we constructed an experimental setup based on time-resolved laser-induced luminescence spectroscopy to investigate the emission characteristics of Gd3+ ions in water. The excitation laser wavelength was tuned in the range of 245–255 nm, and large resonant peaks were observed at 246.2 nm and 252.3 nm with measured emission lifetimes of around 3 ms. Good linearity was observed between Gd concentration and emission intensity for these two wavelengths, indicating that our setup is useful for remote monitoring of Gd concentration. According to the simulation results using our spectroscopic data and reference values, the Gd3+ emission BG rate from cosmic muons is expected to be 10−1 counts/μs or less, which seems small but not negligible. [ABSTRACT FROM AUTHOR]

In 1980, detecting the evidence of the so-called Grand Unified Theory (GUT) became a major challenge for experimentalists. The GUT predicted that protons would decay, and M. Koshiba proposed the Kamioka Nucleon Decay Experiment (Kamiokande), which was originally conceived and designed for the detection of proton decay signals. Kamiokande was a 3000-t water Cherenkov detector located 1000 m underground in the Kamioka mine. The unique feature of this experiment was the use of 1000 photomultiplier tubes with the world's largest diameter of 20 in (∼51 cm). This article describes the story of the Kamiokande experiment from the preparation stage to the observation of the first candidate events for proton decays. [ABSTRACT FROM AUTHOR]

With the start of LHC Run 3 the upgraded LHCb experiment, designed to run at an instantaneous luminosity five times larger with respect to previous running periods, is aiming to collect L = 50 f b − 1 of p p collisions data by the end of Run 4. In addition, thanks to a trigger-less readout and a full software trigger, the selection efficiency for fully hadronic decay channels of heavy hadrons increases up to a factor two. The LHCb RICH detectors have been renewed to manage the increased detector occupancy, ensuring outstanding charged hadron discrimination in the more demanding Run 3 environment and at the maximum LHC interaction rate. This process is detailed, outlining the automated calibration procedures of the RICH system to achieve optimal signal efficiency and background rejection during the initial stages of the Run 3 data-taking. The early performance of the newly installed detectors is presented, including the determination of performance parameters such as the Cherenkov angle resolution. It is also reported that the particle identification capabilities are already approaching the design level and outperforming those of Run 1 and 2. [ABSTRACT FROM AUTHOR]

EUSO-TA is a ground-based fluorescence telescope built to validate the design of ultra-high energy cosmic ray fluorescence detectors to be operated in space with the technology developed within the Joint Exploratory Missions for Extreme Universe Space Observatory (JEM-EUSO) program. It operates at the Telescope Array (TA) site in Utah, USA. With an external trigger provided by the Black Rock Mesa fluorescence detectors of the Telescope Array experiment, with EUSO-TA we observed air-showers from ultra-high energy cosmic rays, as well as laser events from the Central Laser Facility at the TA site and from portable lasers like the JEM-EUSO Global Light System prototype. Since the Black Rock Mesa fluorescence detectors have a ∼ 30 times larger field of view than EUSO-TA, they allow a primary energy reconstruction based on the observation of a large part of the shower evolution, including the shower maximum, while EUSO-TA observes only a part of it, usually far away from the maximum. To estimate the detection limits of EUSO-TA in energy and distance, a method was developed to re-scale their energy, taking into account that EUSO-TA observes only a portion of the air-showers. The method was applied on simulation sets with showers with different primaries, energy, direction, and impact point on the ground, as well as taking into account the experimental environment. EUSO-TA was simulated with an internal trigger and different elevation angles and electronics. The same method was then applied also to real measurements and compared to the simulations. In addition, the method can also be used to estimate the detection limits for experiments that are operated at high altitudes and in most cases can see the maximum of the showers. This was done for EUSO-SPB1, an instrument installed on a super-pressure balloon. Finally, the expected detection rates for EUSO-TA were also assessed using the prepared simulated event sets. The rates correspond to a few detections per recording session of 30 h of observation, depending on the background level and the configuration of the detector. [ABSTRACT FROM AUTHOR]

The next generation of Ring Imaging CHerenkov detectors in high energy physics experiments may use SiPMs as photon sensing elements. This upgrade is necessary to achieve greater detector granularity and speed, however SiPMs need to be cooled down to cryogenic temperatures to detect single photons in high-radiation environments and avoid being overwhelmed by the presence of "dark signals". It is therefore necessary to study and characterize SiPM models in dedicated campaigns, using a custom-built amplifying chain that can also operate in an extended temperature range, between 80 K and 300 K, for detector characterization purposes. The proposed amplifier configuration consists of two amplifying stages and achieves low jitter values (< 10 − 20 ps RMS ) thanks to the low electronic noise and the high amplifier bandwidth. The circuit achieves a signal bandwidth of 500 MHz < BW < 1 GHz , a phase margin of approximately 45° and a power consumption of about 65 − 135 mW. The amplifier prototype unit can be adjusted to cover the considered temperature range and still achieve low jitter values. [ABSTRACT FROM AUTHOR]

Muography is an innovative imaging technique using naturally produced elementary particles – atmospheric muons – used to determine the distribution of density inside massive objects. The modification of the particles flux – by scattering or absorption – reflects the contrasts in density within the medium and therefore offers the possibility for an image of the crossed volumes. In most muography setups the imaging process is based on the tracking of the particles which accounts for the absorption or the scattering of the muons trajectories. Neither the energy nor the identity of the particles (the so-called PID) is exploited since this information traditionally relies on the use of calorimeters and/or high intensity magnetic fields. Both these techniques hinder detector portability which in the case of muography is important and this renders them impractical for its purpose. In this paper we characterize the performance of a simple and small water Cherenkov detector capable of providing some insights on the energy of muons and the PID for the crossing particles that could potentially improve the background rejection for a muography survey when operating in conjunction with a muon telescope. We tested a prototype of such water Cherenkov detector in combination with two small muon hodoscopes. Both systems are using the same opto-electronics chain – optical fibers and pixellized photosensors – and the same data acquisition (DAQ) readout system which ensures an easy integration and implementation within presently running systems. This article presents the test setup, the detector response to cosmic muons and its performance evaluation against a basic simulation of its geometry and detection principle. [ABSTRACT FROM AUTHOR]

The DIRC-like time-of-flight detector (DTOF) at the Super Tau-Charm Facility (STCF) in China is a Cherenkov light detector that uses the TOF technique to identify charged particles. To achieve the expected target that provides a $3\sigma \pi $ /K separation at 2-Ge/c momentum, a single-photon time resolution of better than 50 ps is required, while the contribution from electronics should be lower than 15 ps. To meet the requirements with high channel count integration, the timing electronics using leading-edge discrimination and field-programmable gate array (FPGA)-based time-to-digital converters (TDCs) are employed in the DTOF detector. This article reports the results of the first phase of project where the timing electronics with 128 channels has been constructed and its performance has been evaluated. Including the uncertainty of system clock distribution and synchronization, the intrinsic timing resolution of the electronics is better than 10-ps rms. Taking fast microchannel plate photomultiplier tubes (MCP-PMTs) as Cherenkov photodetectors and adopting time-over-threshold (TOT) measurement for time walk correction, the measured single-photon time resolutions are better than 40-ps rms. The test results confirm that the proposed timing electronics has advantages of high precision and high integration, which is highly demanded in future picosecond timing detectors. [ABSTRACT FROM AUTHOR]

Time measurements with sub-nanosecond time resolution (aiming at values of few picoseconds) are of paramount importance for a wide variety of applications. In the field of particle physics, measuring with increasing precision the time taken by a particle to travel between two points (Time-of-Flight, ToF) gives information on the particle' (relativistic) velocity, contributing to identifying the type of particle (Particle Identification Detectors, PID). Among this category of detectors are also Cherenkov counters, based on the emission of light when a charged particle travels in a transparent medium with a velocity exceeding the light velocity in that medium. Here we discuss a special category of ToF counters using the properties of Cherenkov light to determine the passage of the particles through the detectors with unprecedented precision. Results obtained with test beams are described and analysed, demonstrating the excellent timing resolution that can be obtained. Such detectors may be used to provide a 'precision time reference' for calibrating other types of timing detectors. Other applications are, for instance, time-tagging of 'pile-up' events in high-luminosity Large Hadron Collider (LHC), and identification of events with anomalous timing properties (for instance, long-lived particles, LLP). [ABSTRACT FROM AUTHOR]

Inertial confinement fusion experiments at both the National Ignition Facility (NIF) and the Laboratory for Laser Energetics OMEGA laser facility currently utilize Cherenkov detectors, with fused silica as the Cherenkov medium. At the NIF, the Quartz Cherenkov Detectors improve the precision of neutron time-of-flight measurements; and at OMEGA, the Diagnostic for Areal Density provides measurements of capsule shell areal densities. An inherent property of fused silica is the radiator's relatively low energy threshold for Cherenkov photon production (Ethreshold < 1 MeV), making it advantageous over gas-based Cherenkov detectors for experiments requiring low-energy γ detection. The Vacuum Cherenkov Detector (VCD) has been specifically designed for efficient detection of low energy γ's. Its primary use is in implosion experiments, which will study reactions relevant to stellar and big-bang nucleosynthesis, such as T(4He,γ)7Li, 4He(3He,γ)7Be, and 12C(p,γ)13N. The VCD is compatible with LLE's standard Ten-Inch Manipulator diagnostic insertion module. This work will outline the design and characterization of the VCD as well as provide results from recent experiments conducted at the OMEGA laser facility. [ABSTRACT FROM AUTHOR]

Gas Cherenkov detectors provide a time resolved measurement of the fusion burn in inertial confinement fusion experiments. The fusion rate delivers critical benchmark figures, such as burn width and bang time. Recent detector improvements pushed temporal resolution to 10 ps to make burn width measurements on igniting targets possible. First high temporal resolution measurements using CO2 gas fills had a background signal with a long decay length (tail), which was caused by gas scintillation. This gas scintillation limits the ability of the detector to resolve short burn width and high frequency features in the fusion rate measurements. A thorough investigation of the cause of the tail and mitigation options for gas scintillation is presented here. As a near-term resolution, neon gas is being used to extract fusion burn histories. Paths forward for the next generation of gas Cherenkov detectors are identified including the usage of oxygen as a Cherenkov medium. [ABSTRACT FROM AUTHOR]

The concept of a small, single-layer water Cherenkov detector, with three photomultiplier tubes (PMTs), placed at its bottom in a 120 ∘ star configuration (Mercedes Water Cherenkov Detector) is presented. The PMTs are placed near the lateral walls of the stations with an adjustable inclination and may be installed inside or outside the water volume. To illustrate the technical viability of this concept and obtain a first-order estimation of its cost, an engineering design was elaborated. The sensitivity of these stations to low energy Extensive Air Shower (EAS) electrons, photons and muons is discussed, both in compact and sparse array configurations. It is shown that the analysis of the intensity and time patterns of the PMT signals, using machine learning techniques, enables the tagging of muons, achieving an excellent gamma/hadron discrimination for TeV showers. This concept minimises the station production and maintenance costs, allowing for a highly flexible and fast installation. Mercedes Water Cherenkov Detectors (WCDs) are thus well-suited for use in high-altitude large gamma-ray observatories covering an extended energy range from the low energies, closing the gap between satellite and ground-based measurements, to very high energy regions, beyond the PeV scale. [ABSTRACT FROM AUTHOR]

Cosmic rays that strike the top of the Earth’s atmosphere generate a shower of secondary particles that move toward the surface with relativistic speeds. Water Cherenkov detectors (WCDs) on the ground can detect charged muons, which are one of the many particles generated in the shower, with the Cherenkov imaging technique. A large number of these muons travel in WCD tanks near the speed of light in a vacuum, faster than the speed of light in water, and so trigger isotropic Cherenkov radiation, which is detected by the photomultiplier tubes (PMTs) placed inside the tanks. When the radial component of the speed of the muon toward a PMT drops from superluminal to subluminal, the PMT records Cherenkov light from an optical phenomenon known as relativistic image doubling (RID), which causes two Cherenkov images of the same muon to appear suddenly, with both images moving in geometrically opposite directions on the original muon track. The quantities associated with the RID effect can be measured experimentally with a variety of detector types and can be used to find various points on the original trajectory of the muon. In this paper, a detailed study of reconstructing the trajectory of a muon entering a WCD using the RID technique has been presented. It is found that the measurements of standard RID observables enables a complete reconstruction of the trajectory of the muon to a high degree of accuracy with less than 1% error. [ABSTRACT FROM AUTHOR]

The ion temperature varying during inertial confinement fusion implosions changes the amount of Doppler broadening of the fusion products, creating subtle changes in the fusion neutron pulse as it moves away from the implosion. A diagnostic design to try to measure these subtle effects is introduced—leveraging the fast time resolution of gas Cherenkov detectors along with a multi-puck array that converts a small amount of the neutron pulse into gamma-rays, one can measure multiple snapshots of the neutron pulse at intermediate distances. Precise measurements of the propagating neutron pulse, specifically the variation in the peak location and the skew, could be used to infer time-evolved ion temperature evolved during peak compression. [ABSTRACT FROM AUTHOR]

This paper presents the standardization of 90Y solution using the Cherenkov method measuring in the TDCR counters. The counting efficiencies for the production of Cherenkov light were applying the Frank and Tamm theory. The detection efficiency for the TDCR counter was calculated in a home-made code. The calculation took into account the PMT's asymmetry in the detector and the anisotropy of Cherenkov light propagation. The solution was measured in two different TDCR detectors using the Cherenkov and Liquid Scintillation Counting methods. The agreement of the two methods results was below 0.1%. [ABSTRACT FROM AUTHOR]

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For research on cosmic gamma rays with energies in the range of several tens of teraelectronvolts or more, we investigated a method to improve the angular resolution of an air shower. In an air shower, the density of secondary gamma rays is several times higher than that of electrons and those measurement is important for determining the shower direction. It was found that the angular resolution in the shower front-fit method decreases in inverse proportion to the square root of the number of measured particles. Even if the total number of measured particles is the same, secondary gamma rays contribute more to the improvement of angular resolution than electrons. If secondary gamma rays could be measured at an altitude of 4,740 m with a sensitivity of 100 %, an improvement of approximately 40 % was determined for a 500 TeV shower. A water Cherenkov detector with high gamma-ray sensitivity was investigated through Monte Carlo simulation. Detection efficiencies of approximately 0.38 and 0.76 were obtained for vertically incident gamma rays and electrons, respectively, using 19 8-inch diameter PMTs inside a detector installed in a water tank of radius 4.5 m and water depth 1.6 m. The detection time error for secondary gamma rays is approximately 2.18 ns at an incident angle of 0∘ and the standard error in the detection time for shower front particles was found to be approximately 10 times lower than that obtained by using a plastic scintillation detector with an area of 1 m2. [ABSTRACT FROM AUTHOR]

In the last decade, an increasing number of datasets have revealed a consistent discrepancy between the number of muons measured in ultra-high-energy extensive air showers (EAS) and the numbers predicted by simulations. This gap persists despite incorporating Large Hadron Collider (LHC) data into the tuning of current hadronic interaction models, leading to the phenomenon often termed the "muon puzzle". To gain a deeper understanding of the potential origins of this muon puzzle, we have developed Sibyll ★ , a series of phenomenologically modified versions of Sibyll 2.3d. In these models, we have increased muon production by altering ρ 0 , baryon–antibaryon pair, or kaon production in hadronic multiparticle production processes. These variants remain within bounds from provided by accelerator measurements, including those from the LHC and fixed-target experiments, notably NA49 and NA61, showing a level of consistency comparable to Sibyll 2.3d. Our findings show that these modifications can increase the muon count in EAS by up to 35%, while minimally affecting the depth of shower maximum (X max) and other shower variables. Additionally, we assess the impact of these modifications on various observables, including inclusive muon and neutrino fluxes and the multiplicities of muon bundles in deep underground and water/ice Cherenkov detectors. We aim for at least one of these model variants to offer a more accurate representation of EAS data at the highest energies, thereby enhancing the quality of Monte Carlo predictions used in training neural networks. This improvement is crucial for achieving more reliable data analyses and interpretations. [ABSTRACT FROM AUTHOR]

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 Gd 2 (SO 4) 3 ⋅ 8H 2 O was additionally loaded into Super-Kamiokande (SK) from May 31 to July 4, 2022. As the amount of loaded Gd 2 (SO 4) 3 ⋅ 8H 2 O 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 Gd 2 (SO 4) 3 ⋅ 8H 2 O. 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. [Display omitted] • We conducted additional loading of 26.1 tons of Gd 2 (SO 4) 3 ⋅ 8H 2 O to Super-Kmaioknade in 2022. • Developed new batches of gadolinium sulfate with reduced radioactive impurities. • Gd concentration in SK measured to be 333. 5 ± 2. 5 ppm by an AAS. • Gd concentration derived from the neutron capture time is consistent with AAS. • Demonstrated a 1.5 times higher neutron capture efficiency as expected. [ABSTRACT FROM AUTHOR]

The Excess Noise Factor (ENF) of a Photomultiplier Tube (PMT) is basically the additional noise introduced because of the statistical nature of electron multiplication inside PMT. In the field of Very High Energy (VHE) gamma-ray astronomy, PMT is used as a Cherenkov photon detector. Hence, the noise of PMT plays an important role in estimating the energy of VHE gamma rays. Conventionally, estimation of ENF of PMT requires a very low-intensity, tunable light source experiment in a lab where no external light background interferes. In this study, we propose the application of a novel Machine Learning (ML) technique, the Gaussian Mixture Model (GMM) to estimate the ENF of the telescope camera for an in-situ observation. [Display omitted] • The statistical noise introduced by a PMT is known as the Excess Noise Factor (ENF). • GMM is used to decompose any distributions into a few Gaussians. • By decomposing the simulated and the actual charge spectrum, one can determine the ENF. • ENF measured by GMM agrees well with the value obtained by SPE experiment. [ABSTRACT FROM AUTHOR]