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Register a new userCharacteristics of a thermal neutrons scintillation detector with the [ZnS(Ag)+$^6$LiF] at different conditions of measurements
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A construction of a thermal neutron testing detector with a thin [ZnS(Ag)+$^6$LiF] scintillator is described. Results of an investigation of sources of the detector pulse origin and the pulse features in a ground and underground conditions are presented. Measurements of the scintillator own background, registration efficiency and a neutron flux at different objects of the BNO INR RAS were performed. The results are compared with the ones measured by the $^3$He proportional counter.
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A neutron detector based on EJ301 liquid scintillator has been employed at EAST to measure the neutron energy spectrum for D-D fusion plasma. The detector was carefully characterized in different quasi-monoenergetic neutron fields generated by a 4.5 MV Van de Graaff accelerator. In recent experimental campaigns, due to the low neutron yield at EAST, a new shielding device was designed and located as close as possible to the tokamak to enhance the count rate of the spectrometer. The fluence of neutrons and gamma-rays was measured with the liquid neutron spectrometer and was consistent with 3He proportional counter and NaI (Tl) gamma-ray spectrometer measurements. Plasma ion temperature values were deduced from the neutron spectrum in discharges with lower hybrid wave injection and ion cyclotron resonance heating. Scattered neutron spectra were simulated by the Monte Carlo transport Code, and they were well verified by the pulse height measurements at low energies.
A new type of neutron detector, named Stack Structure Solid organic Scintillator (S$^4$), consisting of multi-layer plastic scintillators with capability to suppress low-energy $gamma$ rays under high-counting rate has been constructed and tested. To achieve $it{n}$-$gamma$ discrimination, we exploit the difference in the ranges of the secondary charged particles produced by the interactions of neutrons and $gamma$ rays in the scintillator material. The thickness of a plastic scintillator layer was determined based on the results of Monte Carlo simulations using the Geant4 toolkit. With layer thicknesses of 5 mm, we have achieved a good separation between neutrons and $gamma$ rays at 5 MeV$_{rm ee}$ threshold setting. We have also determined the detection efficiencies using monoenergetic neutrons at two energies produced by the $it{d}$+$it{d}toit{n}$+$^{3}$He reaction. The results agree well with the Geant4 simulations implementing the Li$grave{rm e}$ge Intranuclear Cascade hadronic model (INCL++) and the high-precision model of low-energy neutron interactions (NeutronHP).
A neutron lifetime measurement conducted at the Japan Proton Accelerator Research Complex (J-PARC) is counting the number of electrons from neutron decays with a time projection chamber (TPC). The $gamma$ rays produced in the TPC cause irreducible background events. To achieve the precise measurement, the inner walls of the TPC consist of $^6$Li-enriched lithium-fluoride ($^6$LiF) tiles to suppress the amount of $gamma$ rays. In order to estimate the amount of $gamma$ rays from the $^{6}{rm LiF}$ tile, prompt gamma ray analysis (PGA) measurements were performed using germanium detectors. We reconstructed the measured $gamma$-ray energy spectrum using a Monte Carlo simulation with the stripping method. Comparing the measured spectrum with a simulated one, the number of $gamma$ rays emitted from the$^{6}{rm LiF}$ tile was $(2.3^{+0.7}_{-0.3}) times 10^{-4}$ per incident neutron. This is $1.4^{+0.5}_{-0.2}$ times the value assumed for a mole fraction of the $^{6}{rm LiF}$ tile. We concluded that the amount of $gamma$ rays produced from the $^{6}{rm LiF}$ tile is not more twice the originally assumed value.
We present the results of neutron detection in a laser plasma experiment with a CD$_2$ nanowire target. A hybrid semiconductor pixel detector Timepix3 covered with neutron converters was used for the detection of neutrons. D-D fusion neutrons were detected in a polyethylene converter through recoiled protons. Both the energy of recoiled protons and the time-of-flight of neutrons (and thus their energy) were determined. We report $(2.4 pm 1.8) times 10^7$ neutrons generated for 1~J of incoming laser energy. Furthermore, we proved that Timepix3 is suitable for difficult operational conditions in laser experiments.
A simple model for the estimation of the light yield of a scintillation detector is developed under general assumptions and relying exclusively on the knowledge of its optical properties. The model allows to easily incorporate effects related to Rayleigh scattering and absorption of the photons.The predictions of the model are benchmarked with the outcomes of Monte Carlo simulations of specific scintillation detectors. An accuracy at the level of few percent is achieved. The case of a real liquid argon based detector is explicitly treated and the predicted light yield is compared with the measured value.
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