Measurement of neutron-induced proton-production energy spectra with NE213 scintillator

Many benchmark data are required for the improvement of theoretical model implemented in a Monte Carlo code for particle transport. To acquire the benchmark data, we measured energy spectra of protons emitted from graphite, aluminum, and iron targets bombarded with continuous-energy neutrons, which enable simultaneous measurements at the incident energies from 100 to 600 MeV at a time. The neutron flux incident on the target was measured with a ²³⁸U fission ionization chamber. Protons emitted from the target were measured with three ΔE–E detectors consisting of a thin NE102A scintillator and a thick NE213 liquid scintillator. In the analysis, the pulse shape discrimination of the NE213 scintillator enable us to distinguish events for a charged particle stopping in the scintillator from events for a charged particle penetrating the scintillator. Experimental results were compared with calculations by the PHITS code coupled with the JENDL-HE file, the Bertini model implemented in the PHITS code, and the PEANUT model in the FLUKA code.     

Measurement of the neutron spectrum of a Pu-C source with a liquid scintillator

The neutron response function for a BC501A liquid scintillator （LS） has been measured using a series of monoenergetic neutrons produced by the p-T reaction. The proton energies were chosen such as to produce neutrons in the energy range of 1 to 20 MeV. The principles of the technique of unfolding a neutron energy spectrum by using the measured neutron response function and the measured Pulse Height （PH） spectrum is briefly described. The PH spectrum of neutrons from the Pu-C source, which will be used for the calibration of the reactor antineutrino detectors for the Daya Bay neutrino experiment, was measured and analyzed to get the neutron energy spectrum. Simultaneously the neutron energy spectrum of an Am-Be source was measured and compared with other measurements as a check of the result for the Pu-C source. Finally, an error analysis and a discussion of the results are given.     

Measurement of the neutron spectrum of a Pu-C source with a liquid scintillator

The neutron response function for a BC501A liquid scintillator (LS) has been measured using a series of monoenergetic neutrons produced by the p-T reaction. The proton energies were chosen such as to produce neutrons in the energy range of 1 to 20 MeV. The principles of the technique of unfolding a neutron energy spectrum by using the measured neutron response function and the measured Pulse Height (PH) spectrum is briefly described. The PH spectrum of neutrons from the Pu-C source, which will be used for the calibration of the reactor antineutrino detectors for the Daya Bay neutrino experiment, was measured and analyzed to get the neutron energy spectrum. Simultaneously the neutron energy spectrum of an Am-Be source was measured and compared with other measurements as a check of the result for the Pu-C source. Finally, an error analysis and a discussion of the results are given.     

Measurement of the response function and the detection effciency of an organic liquid scintillator for neutrons between 1 and 30 MeV

The light output function of a φ50.8 mm×50.8 mm BC501A scintillation detector was measured in the neutron energy region of 1 to 30 MeV by fitting the pulse height （PH） spectra for neutrons with the simulations from the NRESP code at the edge range. Using the new light output function, the neutron detection effciency was determined with two Monte-Carlo codes, NEFF and SCINFUL. The calculated effciency was corrected by comparing the simulated PH spectra with the measured ones. The determined effciency was verified at the near threshold region and normalized with a Proton-Recoil-Telescope （PRT） at the 8-14 MeV energy region.     

Measurement of the response function and the detection efficiency of an organic liquid scintillator for neutrons between 1 and 30 MeV

The light output function of a φ50.8 mm×50.8 mm BC501A scintillation detector was measured in the neutron energy region of 1 to 30 MeV by fitting the pulse height (PH) spectra for neutrons with the simulations from the NRESP code at the edge range. Using the new light output function, the neutron detection efficiency was determined with two Monte-Carlo codes, NEFF and SCINFUL. The calculated efficiency was corrected by comparing the simulated PH spectra with the measured ones. The determined efficiency was verified at the near threshold region and normalized with a Proton-Recoil-Telescope (PRT) at the 8-14 MeV energy region.     

ST-401薄塑料闪烁体中子能量响应测量技术研究

利用中国原子能科学研究院核工业放射性计量测试中心的5SDH-2串列加速器进行了ST-401薄塑料闪烁体的能量响应实验.选用T(p,n)³He反应和D(d,n)³He反应作为中子源，子源，中子束流采用复合屏蔽体进行准直，源强采用正比计数管和半导体望远镜进行监测，实验测量了厚度从0.16mm到2.00mm的八种规格薄闪烁体的能量响应曲线，对实验的结果的不确定度进行了分析.结果表明探测器的灵敏度随着晶体厚度的增加而增加，对于一定厚度的薄闪烁体，随着中子能量的增加，探测器的能量响应曲线坡度不大. 关键词： 塑料闪烁体 能量响应 正比计数器 半导体反冲质子望远镜     

Light response of a pure liquid Xenon scintillator irradiated with 2.5 MeV neutrons

In this paper the results obtained by exposing a pure liquid Xenon scintillator to 2.5 MeV neutrons are presented. In particular, the ratio of the measured amount of light from a recoil nucleus to the amount of light from an electron of the same kinetic energy has been investigated. Results substantially in agreement with previous determinations are obtained. A figure of r = 0.46 ± 0.10 is cumulatively obtained.     

掺钆液闪中子探测器的研制

中子在探测器中能产生与暗物质粒子（WIMPs）类似的核反冲信号,对于低背景的暗物质直接探测实验,精确测量和排除中子的干扰尤其重要。为测量中国锦屏地下实验室(CJPL)中子本底的通量,研制了高效的、具有很强中子-伽马分辨的掺钆液闪快中子探测器。介绍了掺钆液闪中子探测器的研制和性能,包括探测器形状和尺寸的设计,液体闪烁体类型、光电倍增管型号以及液闪容器材料的选择,探测器的伽马能量刻度以及中子与伽马信号的甄别。用Am-Be中子源对探测器进行探测效率刻度,得到阈值为0.2 MeV等效电子能量的中子探测效率为(6.300.30)%,满足中国锦屏地下实验室对中子通量测量的要求。     

Ground-state energy of the electron liquid in ultrathin wires

The ground-state energy and the density correlation function of the electron liquid in a thin one-dimensional wire are computed. The calculation is based on an approximate mapping of the problem with a realistic Coulomb interaction law onto exactly solvable models of mathematical physics. This approach becomes asymptotically exact in the limit of a small wire radius but remains numerically accurate even for modestly thin wires.     

掺钆液闪中子探测器的研制

中子在探测器中能产生与暗物质粒子(WIMPs)类似的核反冲信号,对于低背景的暗物质直接探测实验,精确测量和排除中子的干扰尤其重要。为测量中国锦屏地下实验室(CJPL)中子本底的通量,研制了高效的、具有很强"中子-伽马"分辨的掺钆液闪快中子探测器。介绍了掺钆液闪中子探测器的研制和性能,包括探测器形状和尺寸的设计,液体闪烁体类型、光电倍增管型号以及液闪容器材料的选择,探测器的伽马能量刻度以及中子与伽马信号的甄别。用Am-Be中子源对探测器进行探测效率刻度,得到阈值为0.2 MeV等效电子能量的中子探测效率为(6.30±0.30)%,满足中国锦屏地下实验室对中子通量测量的要求。     

Effect of dilution and temperature on the energy transfer and quenching in an organic liquid scintillator

The energy transfer and quenching rate parameters are determined as a function of temperature in the 30–70°C temperature range for a system 4,4'''-bis-(2-butyloctyloxy)-p-quaterphenyl in deoxygenated dilute solution containing a 1:9 mixture of toluene to cyclohexane using aniline as donor quencher. The data has been analysed using a compact equation. The energy transfer and quenching processes are due to molecular diffusion and migration but are not due to long-range interaction.     

平响应塑料闪烁体设计北大核心CSCD

通过采用北京同步辐射源标定了无镀膜闪烁体EJ232的能量响应曲线。该批次无镀膜闪烁体对于能量低于300eV的X射线的线性响应差。根据实验结果,进行了镀膜模拟设计,并通过真空磁控溅射法进行了闪烁体镀膜加工工艺。设计加工后的镀膜闪烁体经过实验标定后,其结果指标满足设计要求。该镀膜闪烁体对于能量低于1keV的X射线的平响应特性好,线性度高于99%。该闪烁体对普朗克谱的模拟输出结果表明,其输出谱与输入谱之间形变小,因此该镀膜闪烁体在Z-pinch实验中能有较好的适用性。     

飞秒激光与等离子体相互作用过程中超热电子能谱的测量

 报道了在3TW飞秒激光器上完成的激光 等离子体相互作用过程中产生的超热电子的能谱测量结果。能谱测量显示：在较低的能段，超热电子能谱先是呈现一个局部的平台，然后迅速衰减，呈现非类麦克斯韦分布，这是由于几种加热机制共同作用，其中占主导地位的是反射激光对电子的加速；在较高的能段，超热电子能谱呈类麦克斯韦分布，拟合的温度远远高于已知的温度定标律给出的温度，其原因在于超热电子分布的高能尾部本身的抬高和激光的自聚焦及成道。     

Vacancy formation energy related to liquid structure in a nonlinear scaled potential theory

Summary A scaling relation is derived for the vacancy formation energyE _v in a family of homologous systems at their melting temperatureT _m, using a pair potential theory which relatesE _v atT _m to liquid structure under the assumption that atomic relaxation round the vacancy can be neglected.

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Riassunto Il lavoro deriva una relazione di scala per l’energiaE _v di formazione di un posto vacante in una famiglia di sistemi omologhi alla loro temperatureT _m di fusione, nell’ambito di una teoria a potenziale di coppia che legaE _v aT _m alla struttura della fase liquida nell’ipotesi che rilassamenti atomici attorno al posto vacante possano essere trascurati.

     

Quenching of liquid scintillator fluorescence by chloroalkanes and chloroalkenes

The fluorescence quenching of 2,5-diphenyloxazole (PPO) by a series of chloroalkanes and chloroalkenes including carbon tetrachloride, chloroform, dichloroethane, tetrachloroethane, dichloroethylene, trichloroethylene and tetrachloroethylene was studied in toluene as solvent at room temperature. CCl₄ was found to be the most efficient quencher in the series. The quenching was found to be appreciable and a positive deviation from linearity was observed in the Stern–Volmer (SV) plots for all the quenchers in the concentration range studied. From the studies of effect of temperature, solvent viscosity and excitation wavelength dependence for the PPO–CCl₄ system, it was inferred that non-linearity is due to the presence of a minor static quenching component in an overall dynamic quenching. The static (K_S) and the dynamic (K_D) quenching constants were calculated from the modified SV equation using quadratic least square fits. Fluorescence quenching experiments with CCl₄ were done for four other scintillators (POPOP, α-NPO, BBO and PBBO). The mechanism of quenching was established to be via charge-transfer, with the direction of transfer being from the scintillators to the chloroalkanes and chloroalkenes.     

飞秒激光与等离子体相互作用过程中超热电子能谱的测量

报道了在3TW飞秒激光器上完成的激光 等离子体相互作用过程中产生的超热电子的能谱测量结果。能谱测量显示：在较低的能段,超热电子能谱先是呈现一个局部的平台,然后迅速衰减,呈现非类麦克斯韦分布,这是由于几种加热机制共同作用,其中占主导地位的是反射激光对电子的加速;在较高的能段,超热电子能谱呈类麦克斯韦分布,拟合的温度远远高于已知的温度定标律给出的温度,其原因在于超热电子分布的高能尾部本身的抬高和激光的自聚焦及成道。     

Aging of LAB-based liquid scintillator in stainless steel containers

Types 316 and 304 stainless steel are two candidates for the storage vessels and piping systems of LAB-based liquid scintillator (LS) in the JUNO experiment. LS aging experiments are carried out at temperatures of 40℃ and 25℃. After 192 days aging at 40℃, the attenuation length of LS was reduced by 6% in a glass container, 12% in a type 304 stainless steel tank, and 10% in a type 316 stainless steel tank. At 25℃ in 304 and 316 stainless steel tanks, the attenuation length was reduced by 6% after 307 days. The light yield and the absorption spectrum were practically the same as that of the unaged sample. The concentration of element Fe in the LAB-based LS did not show a clear change. Type 316 and 304 stainless steel can be used as vessels and transportation pipeline material for LAB-based LS.     

Study on gamma response function of E J301 organic liquid scintillator with GEANT4 and FLUKA

The gamma response function is required for energy calibration of EJ301 （5 cm in diameter and 20 cm in height） organic liquid scintillator detector by means of gamma sources. The GEANT4 and FLUKA Monte Carlo simulation packages were used to simulate the response function of the detector for standard 22Na, 60Co, 137Cs gamma sources. The simulated results showed a good agreement with experimental data by incorporating the energy resolution function to simulation codes. The energy resolution and the position of the maximum Compton electron energy were obtained by comparing measured light output distribution with simulated one. The energy resolution of the detector varied from 21.2% to 12.4% for electrons in the energy region from 0.341 MeV to 1.12 MeV. The accurate position of the maximum Compton electron energy was determined at the position 81% of maximum height of Compton edges distribution. In addition, the relation of the electron energy calibration and the effective neutron detection thresholds were described in detail. The present results indicated that both packages were suited for studying the gamma response function of EJ301 detector.