Estimation of Fluor Emission Spectrum through Digital Photo Image Analysis with a Water-Based Liquid Scintillator

In this paper, we performed a feasibility study of using a water-based liquid scintillator (WbLS) for conducting imaging analysis with a digital camera. The liquid scintillator (LS) dissolves a scintillating fluor in an organic base solvent to emit light. We synthesized a liquid scintillator using water as a solvent. In a WbLS, a suitable surfactant is needed to mix water and oil together. As an application of the WbLS, we introduced a digital photo image analysis in color space. A demosaicing process to reconstruct and decode color is briefly described. We were able to estimate the emission spectrum of the fluor dissolved in the WbLS by analyzing the pixel information stored in the digital image. This technique provides the potential to estimate fluor components in the visible region without using an expensive spectrophotometer. In addition, sinogram analysis was performed with Radon transformation to reconstruct transverse images with longitudinal photo images of the WbLS sample.

Application research on neutron-gamma discrimination based on BC501A liquid scintillator

Liquid organic scintillators are widely used in non-destructive analysis, which plays an important role in nuclear disarmament verification. This paper focused on studying the neutron-gamma discrimination technology in the fast neutron multiplicity measuring counter based on BC501A liquid scintillation detector. First, the charge comparison method, the zero-crossing time method and the rise time method were compared via the Geant4 and Matlab algorithm, and the result shows that charge comparison has the highest Figure of Merit. Then, a neutron-gamma discrimination system based on the six-probe fast neutron multiplicity counter was built and tested with a conclusion that the mean value of Figure of merit is 1.08, which verify the satisfactory neutron-gamma discriminating capability of the system. Finally, for the uranium samples, the mass are detected by fast neutron multiplicity counter, and the enrichment are measured by the characteristic gamma-ray signals using the system. The experimental results are in good agreement with the actual data.

Unambiguously Resolving the Potential Neutrino Magnetic Moment Signal at Large Liquid Scintillator Detectors

Non-vanishing electromagnetic properties of neutrinos have been predicted by many theories beyond the Standard Model, and an enhanced neutrino magnetic moment can have profound implications for fundamental physics. The XENON1T experiment recently detected an excess of electron recoil events in the 1–7 keV energy range, which can be compatible with solar neutrino magnetic moment interaction at a most probable value of μν = 2.1 × 10−11 μ B. However, tritium backgrounds or solar axion interaction in this energy window are equally plausible causes. Upcoming multi-tonne noble liquid detectors will test these scenarios more in depth, but will continue to face similar ambiguity. We report a unique capability of future large liquid scintillator detectors to help resolve the potential neutrino magnetic moment scenario. With O(100) kton⋅year exposure of liquid scintillator to solar neutrinos, a sensitivity of μν < 10−11 μ B can be reached at an energy threshold greater than 40 keV, where no tritium or solar axion events but only neutrino magnetic moment signal is still present.

Neutrino physics with an opaque detector

In 1956 Reines & Cowan discovered the neutrino using a liquid scintillator detector. The neutrinos interacted with the scintillator, producing light that propagated across transparent volumes to surrounding photo-sensors. This approach has remained one of the most widespread and successful neutrino detection technologies used since. This article introduces a concept that breaks with the conventional paradigm of transparency by confining and collecting light near its creation point with an opaque scintillator and a dense array of optical fibres. This technique, called LiquidO, can provide high-resolution imaging to enable efficient identification of individual particles event-by-event. A natural affinity for adding dopants at high concentrations is provided by the use of an opaque medium. With these and other capabilities, the potential of our detector concept to unlock opportunities in neutrino physics is presented here, alongside the results of the first experimental validation.

Identification of neutron sources and background levels in the polyethylene room of the China Jinping Underground Laboratory

The neutron backgrounds induced by supplementary experimental materials can result in contaminations in rare event search experiments. To address this, we present the neutron background levels arising from ambient materials in the polyethylene room of the China Jinping Underground Laboratory; particularly, we compare simulated spectra with measured neutron spectra unfolded using a genetic algorithm. The genetic algorithm optimizes the continuity of the energy spectra and obtains a reasonable spectral result. A good agreement between the unfolded and simulated spectra is achieved. Moreover, estimated neutron background levels of representative ambient materials such as polyethylene, aluminum, and lead are obtained using an exposure time of 511.27 days via a 28 liter 0.5%-gadolinium-doped liquid scintillator detector. The identification of rare neutron sources can aid in background reduction in next-generation large-scale rare event experiments.

20-inch photomultiplier tube timing study for JUNO

Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator neutrino detector now under construction at Jiangmen, Guangdong, China for determination of neutrino mass ordering with 3% energy resolution at 1 MeV, a precise measurement of neutrino oscillation parameters, and other neutrino physics. The central detector is made up of a 35.4-meter diameter acrylic sphere which contains 20 kton of liquid scintillator and is surrounded by about 18k 20-inch photomultiplier tubes (PMTs). The PMTs performance is one of the JUNO’s key successes to reach the high resolution goal. In this study, the PMT characteristic and its timing related responses were determined via the PMT generated signals, extracted from the PMT in a scanning station system. About 2,400 of micro-channel plate PMTs (MCP-PMTs) and dynode PMTs were analyzed for their responses with LED source such as rise time, fall time, transit time spread (TTS), gain, etc., which relate to photon incident on different positions of PMT’s glass surface. Furthermore, we also observed the fluctuation of PMT performance under magnetic field which can decrease the PMT photon detection efficiency (PDE).

The stress measurement system for the JUNO Central Detector acrylic panels

The Jiangmen Underground Neutrino Observatory (JUNO) Central Detector (CD) is a huge acrylic spherical vessel containing 20,000 tons of liquid scintillator; the sphere is composed of 263 pieces of acrylic spherical panels bonded by the mass polymerization. The operation life time of the JUNO CD is 20 years. To ensure the structural safety during the JUNO CD life time, the acrylic stress of CD is required not to be greater than 3.5 MPa. The stresses of acrylic spherical panels are required to be measured during the installation on-site; unfortunately there is no suitable commercial measurement equipment that can meet JUNO's requirements. Therefore, a measurement setup based on photo-elastic principle and spectrometric methods was designed, developed and tested for on-site measurements. The measurement system performs accurate calibration of stress-optical coefficient of acrylic in JUNO, and gives reliable results of acrylic stresses. The measurement system has been tested in the Taixing Donchamp Acrylic Ltd mechanical workshop, and the achieved results meet the JUNO's requirements. The measurement principle, the system components, and the tooling design are introduced in the paper. Moreover, the calibration of stress-optical coefficient of the acrylic and measurements results on JUNO acrylic spherical panels are discussed in the following.

Sterile Neutrinos with Neutrino Telescopes

Searches for light sterile neutrinos are motivated by the unexpected observation of an electron neutrino appearance in short-baseline experiments, such as the Liquid Scintillator Neutrino Detector (LSND) and the Mini Booster Neutrino Experiment (MiniBooNE). In light of these unexpected results, a campaign using natural and anthropogenic sources to find the light (mass-squared-difference around 1 eV2) sterile neutrinos is underway. Among the natural sources, atmospheric neutrinos provide a unique gateway to search for sterile neutrinos due to the broad range of baseline-to-energy ratios, L/E, and the presence of significant matter effects. Since the atmospheric neutrino flux rapidly falls with energy, studying its highest energy component requires gigaton-scale neutrino detectors. These detectors—often known as neutrino telescopes since they are designed to observe tiny astrophysical neutrino fluxes—have been used to perform searches for light sterile neutrinos, and researchers have found no significant signal to date. This brief review summarizes the current status of searches for light sterile neutrinos with neutrino telescopes deployed in solid and liquid water.