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Register a new userIn-Situ Measurement of Relative Attenuation Length of Gadolinium-Loaded Liquid Scintillator Using Source Data at RENO Experiment
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We present an in-situ method of measuring the relative attenuation length of gadolinium-loaded liquid scintillator in the RENO detectors using radioactive source calibration data without requiring any PMT performance model. We observed the degradation of the attenuation length of the gadolinium-loaded liquid scintillator in the RENO detectors by ~50% over a period of about 4 years.
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A new experiment, which is called as NEOS (NEutrino Oscillation at Short baseline), is proposed on the site of Hanbit reactors at Yonggwang, South Korea, to investigate a reactor antineutrino anomaly. A homogeneous NEOS detector having a 1000-L target volume has been constructed and deployed at the tendon gallery ~25 m away from the reactor core. A linear alkylbenzene (LAB) is used as a main base solvent of the NEOS detector. Furthermore, a di-isopropylnaphthalene (DIN) is added to improve the light output and pulse shape discrimination (PSD) ability. The ratio of LAB to DIN is 90:10. PPO (3 g/L) and bis-MSB (30 mg/L) are dissolved to formulate the mixture of LAB- and DIN-based liquid scintillator (LS). Then, ~0.5% gadolinium (Gd) is loaded into the LS by using the solvent-solvent extraction technique. In this paper, we report the characteristics of Gd-loaded LS (GdLS) for the NEOS detector and the handling during mass production.
Scintillator doped with a high neutron-capture cross-section material can be used to detect neutrons via their resulting gamma rays. Examples of such detectors using liquid scintillator have been successfully used in high-energy physics experiments. However, a liquid scintillator can leak and is not as amenable to modular or complex shapes as a solid scintillator. Polystyrene-based scintillators from a variety of gadolinium compounds with varying concentrations were polymerized in our laboratory. The light output, emission spectra, and attenuation length of our samples were measured and light collection strategies using a wavelength shifting (WLS) fiber were evaluated. The measured optical parameters were used to tune a Geant4-based optical Monte Carlo, enabling the trapping efficiency to be calculated. This technology was also evaluated as a possible neutron veto for the direct detection dark matter experiment, Super Cryogenic Dark Matter Search (SuperCDMS).
This paper describes the design and performance of a 50 liter, two-segment $^{6}$Li-loaded liquid scintillator detector that was designed and operated as prototype for the PROSPECT (Precision Reactor Oscillation and Spectrum) Experiment. The two-segment detector was constructed according to the design specifications of the experiment. It features low-mass optical separators, an integrated source and optical calibration system, and materials that are compatible with the $^{6}$Li-doped scintillator developed by PROSPECT. We demonstrate a high light collection of 850$pm$20 PE/MeV, an energy resolution of $sigma$ = 4.0$pm$0.2% at 1 MeV, and efficient pulse-shape discrimination of low $dE/dx$ (electronic recoil) and high $dE/dx$ (nuclear recoil) energy depositions. An effective scintillation attenuation length of 85$pm$3 cm is measured in each segment. The 0.1% by mass concentration of $^{6}$Li in the scintillator results in a measured neutron capture time of $tau$ = 42.8$pm$0.2 $mu s$. The long-term stability of the scintillator is also discussed. The detector response meets the criteria necessary for achieving the PROSPECT physics goals and demonstrates features that may find application in fast neutron detection.
A measurement is reported for the response to charged particles of a liquid scintillator named EJ-335 doped with 0.5% gadolinium by weight. This liquid scintillator was used as the detection medium in a neutron detector. The measurement is based on the in-situ $alpha$-particles from the intrinsic Uranium and Thorium contamination in the scintillator. The $beta$-$alpha$ and the $alpha$-$alpha$ cascade decays from the U/Th decay chains were used to select $alpha$-particles. The contamination levels of U/Th were consequently measured to be $(5.54pm0.15)times 10^{-11}$ g/g, $(1.45pm0.01)times 10^{-10}$ g/g and $(1.07pm0.01)times 10^{-11}$ g/g for $^{232}$Th, $^{238}$U and $^{235}$U, respectively, assuming secular equilibrium. The stopping power of $alpha$-particles in the liquid scintillator was simulated by the TRIM software. Then the Birks constant, $kB$, of the scintillator for $alpha$-particles was determined to be $(7.28pm0.23)$ mg/(cm$^{2}cdot$MeV) by Birks formulation. The response for protons is also presented assuming the $kB$ constant is the same as for $alpha$-particles.
This work reports the production and characterization of lithium-loaded liquid scintillator (LiLS) for the Precision Reactor Oscillation and Spectrum Experiment (PROSPECT). Fifty-nine 90 liter batches of LiLS (${}^6{rm Li}$ mass fraction 0.082%$pm$0.001%) were produced and samples from all batches were characterized by measuring their optical absorbance relative to air, light yield relative to a pure liquid scintillator reference, and pulse shape discrimination capability. Fifty-seven batches passed the quality assurance criteria and were used for the PROSPECT experiment.
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