Gd-doped Liquid Scintillator Research Articles

Flux measurement of fast neutrons in the Gran Sasso underground laboratory

Neutron energy spectrum for energies extending up to 15 MeV has been measured in the Hall A of INFN Laboratori Nazionali del Gran Sasso in Italy, by using a mathrm {1.5~m^3} stainless-steel tank filled with 1.2 ton Gd-doped liquid scintillator. A two-pulse signature, due to proton recoils and delayed gammas from neutron capture on Gd, has been used for event selection. The neutron energy spectrum has been obtained from the detected proton-recoil spectrum, after unfolding the detector response, which had been simulated with GEANT4. Although this spectrum has been measured previously, the present work represents an improvement in the energy resolution with respect to previously published results. The results obtained with this technique are compared with other measurements existing in literature.

Double Chooz: Results and Perspectives

The Double Chooz experiment has been observing ν¯e from two reactor cores at the Chooz nuclear power station in Ardennes, France, with a single 10.3 m3 fiducial volume Gd-doped liquid scintillator detector at a flux-weighted average baseline of ∼1050 m. This article reviews results achieved with a detector live time of 227.93 days and exposure of 33.71 GW-ton-years. A total of 8,249 candidate ν¯e events have been observed, compared to an expected 8,937 events in the null-oscillation case: this deficit is interpreted as evidence for ν¯e disappearance. A fit to the observed neutrino rate and spectral shape gives a best-fit value of sin2(2θ13)=0.109±0.030(stat.)±0.025(syst.) at a mass-squared splitting of Δm312=2.32×10−3 eV2. The null-oscillation hypothesis is excluded by the data at 99.8% CL (2.9σ). The Double Chooz Near Detector is under construction, and analysis efforts to measure neutrino directionality, test Lorentz violation, and measure backgrounds in situ are underway.

A Mineral Oil Monitoring System for the Daya Bay Neutrino Experiment

The Daya Bay Reactor Neutrino Experiment expects to determine the neutrino mixing angle θ13 with a sensitivity of sin2(2θ13)=0.01 in a three-year run. Eight three-zone cylindrical Anti-neutrino Detector (AD) modules with Gd-doped Liquid Scintillator are arranged in two near halls and a far hall. In the outermost zone of each AD, 192 PMTs are mounted in Mineral Oil (MO). The stability of the optical properties of the liquids is very important for controlling the systematic uncertainties of the experiment and thus will be monitored online. The design of a monitoring system for the MO and results from a prototype system is presented.

Overview of the Aberdeen Tunnel Laboratory

An underground laboratory (Aberdeen Tunnel Laboratory) was built inside a traffic tunnel (Aberdeen Tunnel) in the Hong Kong Island in the early 80ʼs for the study of cosmic-ray muon anisotropy. The laboratory has an overburden of about 250 m of rock, which is comparable to those of the detector halls proposed for the Daya Bay Neutrino Experiment in Guangdong Province, China. Given the very similar geographical location, the geology and background radiation to those in Daya Bay, the Aberdeen Tunnel Laboratory is an ideal testing ground for the Daya Bay Experiment. This project aims to study the neutrons initiated from cosmic muons by detecting the neutrons with a 0.5 ton neutron detector comprising of Gd-doped liquid scintillators viewed by PMTs. The events will be triggered by a muon tracker consisting of 3 horizontal layers of crossed stainless steel proportional counters and plastic scintillators, with 2 layers above and 1 layer below the neutron detector. It is hoped that the results will help in understanding and minimizing the neutron background in Gd-doped liquid scintillator based neutrino detectors. This paper presents an overview of the laboratory, the geology and radiation background, and the proposed detectors.

Evaluation of the neutron background in a direct WIMP detector with neutron vetosystem based on Gd-doped liquid scintillator

A direct WIMP (Weakly Interacting Massive Particle) detector with aneutron veto system is designed to better reject neutrons. Twoexperimental configurations are studied in the present paper: one isfor an Xe detector enclosed in a Gd-loaded scintillator and theother one is for an Xe detector placed inside a reactor neutrinodetector. The Gd-doped liquid scintillator (or the neutrinodetector) is used as a neutron veto device. The neutron backgroundsfor the two experimental designs have been estimated using Geant4simulations. The results show that the neutron backgrounds candecrease to O(0.1) events per year per tonne of liquid Xenon. Wecalculate the sensitivities to spin-independent WIMP-nucleon elasticscattering. An exposure of one tonne × year could reach across-section of about 6 × 10−11 pb.

Reactor Neutrino Detection for Non-Proliferation With the NUCIFER Experiment

The major advances achieved over the last decades in the understanding of fundamental neutrino physics allow us to apply the detection of reactor antineutrino signals to automatic and nonintrusive nuclear power plant surveys. Here, we present the NUCIFER experiment, a 1-ton Gd-doped liquid scintillator detector to be installed a few 10 m from a reactor core for measurements of its thermal power and plutonium (Pu) content. The design of such a small volume detector has been focused on high detection efficiency (~ 50% and good background rejection. Detailed simulations of reactor-emitted antineutrino spectrum and detector response have been developed and used to calculate the NUCIFER sensitivity to illicit retrieval of Pu from the core. These results have been presented in October 2008 to the International Atomic Energy Agency (IAEA), which has expressed its interest in the potentialities of this detector as a new safeguard tool.

Performances and stability of a 2.4 ton Gd organic liquid scintillator target for ν̄e detection

In this paper we report the performance and the chemical and physical properties of a 2 × 1.2 ton organic liquid scintillator target doped with Gd up to ∼ 0.1%, and the results of a 3 year long stability survey of the target. In particular we have measured and monitored the optical and fluorescent properties of the Gd-doped liquid scintillator (LS), the amount of both Gd and primary fluor in solution, and the performance of the two Gd doped targets as neutron detectors, namely neutron capture efficiency and average capture time. The experimental survey is ongoing, the targets being continuously monitored. From the spectrophotometric measurements performed on samples periodically extracted along the three years, we can exclude, at 99% C.L. level, a degradation of the light transmittance of the Gd-doped liquid scintillator larger than 1% y-1; from the in-tank measurements no significant decrease of the neutron capture efficiency and neutron capture time is observed. This is the largest stable Gd-doped organic liquid scintillator target ever produced and continuously operated for a long period.

Reactor neutrino detection for non proliferation with the Nucifer experiment

The idea of using a neutrino detector to monitor nuclear reactors was first proposed in 1977 by L.A.Mikaelian. Tremendous progresses have been achieved since then in both detection technology and understanding of fundamental neutrino physics. This allows us to apply reactor antineutrino detection to thermal power measurement and survey of isotopic composition of reactor fuel. Here we present the Nucifer experiment, a 1 ton Gd-doped liquid scintillator detector to be installed a few 10 m from the core for reactor surveillance. The design of such a small surface detector has been focused on high detection efficiency (~50%) and good background rejection. Detailed simulations of reactor emitted antineutrino spectrum and detector response have been developed and used to calculate the Nucifer sensitivity to illicit retrieval of Pu from the core as it will be discussed. These results have been presented in October 2008 to the International Atomic Energy Agency (IAEA) which has expressed its interest in the potentialities of this detector as a new safeguard tool.

Updated results from the 3-ton Gd loaded liquid scintillator target after 2 years of data taking at LNGS

We performed a 3-m3 Gd experiment by doping (up to 0.1% in weight) two counters of the LVD experiment, at LNGS, with a Gd organic salt developed and produced as the result of a joint INFN/INR research activity. Feasibility of the experiment and performances of the Gd doped liquid scintillator (Gd-LS) have been presented. The chemical and physical properties of the Gd-LS and its performance as a neutron detector, namely neutron capture efficiency and average capture time are being monitored since the doping time in 2005. From laboratory survey we can state the stability of the trasmittance (T) at the reference wavelength (425 nm) with a C.L. of 81% and 96% respectively for the first and the second doped counter. This is the largest stable Gd-doped organic liquid scintillator target ever produced and continuously operated for a long period.

252Cf: neutron multiplicities in correlation with fission-fragment mass and energy

The number of neutrons emitted in the spontaneous fission of 252Cf has been measured, using a large Gd-doped liquid scintillator tank. A total of 1.7 × 107252Cf fission events were assayed, and the correlations between the number of neutrons emitted by the fission fragments and the total kinetic energy (TKE) released in a particular fission event were investigated. From these correlations, spontaneous-fission parameters were derived and compared to exit-channel predictions given by the multi-modal random neck-rupture model of Brosa and co-workers.