Measurement and simulation of the new liquid organic scintillator response to fast neutrons

Liquid organic scintillators are important devices for measurements of neutron radiation. This work aims to develop and optimize the composition of liquid organic scintillators so it can be used for fast neutron spectrometry. As the neutron radiation is usually accompanied with γ ray radiation, it is important to have quality γ/n discrimination. The new cocktail for house made liquid organic scintillator is prepared and studied with intention of being able to separate gamma and neutron for neutron energies above 0.5 MeV while keeping lower constraints on practical use (e.g., sealing because of oxygen) than commercial liquid scintillators. In preceding work the composition of liquid scintillators was optimized. Two twocomponent scintillators were selected for further studies. Solvent DIPN (Di-iso-propyl-naphthalene Mixed Isomers) is selected for both. First is mixed with luminophore PYR (1-Phenyl-3-(2,4,6-trimethyl-phenyl)-2-pyrazoline) of concentration 5 g/l. Second is mixed with luminophore THIO (2,5-Bis(5-tert-butyl-benzoxazol-2-yl)thiophene) of concentration 5 g/l. In this work the response of scintillator to monoenergetic beam of neutrons was measured for multiple neutron energies at PTB in Braunschweig. The two parameter spectrometric system NGA-01 is used to analyze the energy and discrimination characteristics. 137 Cs and 60 Co are used as radiation sources for calibration with pure γ rays. Then the response of scintillator for same neutron energies was simulated using GEANT4. The dissipated energy in the scintillator in response to monoenergetic neutrons is obtained. Both, measured and simulated responses are compared. Functional dependence for yield of recoiled products is estimated. It is seen that main recoil product hydrogen proton is well observed in both. From the edge of proton response one can assume the yield for given neutron energy. The recoiled carbon ion (from elastic collision) is on the other side difficult to observe in measured results but clearly seen in dissipated energy plots. It suggests that yield of carbon ion is very small relatively to proton yield. These results will serve as basis for response function evaluation of scintillator which is necessary for evaluation of unknown neutron spectra from measurements with scintillator.

Neutron production from thick LiF, C, Si, Ni, Mo, and Ta targets bombarded by 13.4-MeV deuterons

Double-differential thick target neutron yields from LiF, C, Si, Ni, Mo, and Ta targets bombarded by 13.4-MeV deuterons were measured by using an EJ-301 liquid organic scintillator at the Center for Accelerator and Beam Applied Science, Kyushu University. The measured (d, xn) spectra were compared with the (t, xn) spectra measured by the other group at the same incident energy per nucleon (6.7 MeV/u) and theoretical model calculations by Particle and Heavy Ion Transport code System (PHITS) and DEUteron-induced Reaction Analysis Code System (DEURACS). Some bumps are observed in the (d, xn) spectra for low-Z target elements, while no specific structure was seen in the (t, xn) spectra. The PHITS calculation, in which the intra-nuclear cascade of Liége (INCL) and generalized evaporation model (GEM) were used, generally overestimates neutron spectra while the DEURACS calculation agrees with experimental ones fairly well.

Cинтез и испытания 1 m-=SUP=-3-=/SUP=- жидкого сцинтиллятора на основе линейного алкилбензола

The stability of a liquid organic scintillator based on linear alkylbenzene in a volume of 1 m^3 was measured. The measurements were performed using an iDREAM reactor antineutrino detector at the National Research Center Kurchatov Institute. No systemic degradation of the scintillator light yield within an observation time of 225 days was observed. These long-term stability measurements of a large-volume liquid organic scintillator based on linear alkylbenzene are the first in Russia.

Изучение стабильности образцов гадолинизированного жидкого органического сцинтиллятора

The technology of preparing a linear-alkylbenzene-based gadolinium-doped liquid organic scintillator (Gd-LOS) as a target material in reactor antineutrino detectors has been developed. Results of longterm measurements of the light yield of Gd-LOS in contact with acryl and stainless steel are presented, which confirm the compatibility of Gd-LOS with these materials. The measurements were performed for two otherwise identical LOS detectors only differing in wall materials of the sensitive volume: acryl versus stainless steel. The results of measurements over about one year showed almost the same, relatively small decreases in the light yield of both detectors. It is concluded that both structural materials can be used in detector parts contacting with Gd-doped scintillator. Such a long-term parallel comparative test was carried out for the first time.