New Pulsed Cold Neutron Beam Line for Fundamental Nuclear Physics at LANSCE

The NPDGamma collaboration has completed the construction of a pulsed cold neutron beam line on flight path12 at the Los Alamos Neutron Science Center (LANSCE). We describe the new beam line and characteristics of the beam. We report results of the moderator brightness and the guide performance measurements. FP12 has the highest pulsed cold neutron intensity for nuclear physics in the world.     

Advantages and limitations of nuclear physics experiments at an ISIS-class spallation neutron source

Nuclear physics experiments have a long history of being conducted on spallation neutron sources. Like other experiments, these measurements take advantage of the identification of the incident neutron energy by the time-of-flight (ToF) technique. However, in some ways these experiments are often in direct conflict with other experiments. Especially in large (ISIS or SNS class) facilities, the design of the source often reflects a compromise between different experimental needs and requirements. It has been a long standing question for nuclear physics experiments how limiting these compromises are and how they can be dealt with. We have therefore calculated the incident neutron energy spectrum, along with the gamma background spectrum, for flight path (FP) 5 at the Los Alamos Neutron Science Center (LANSCE) Manuel Lujan Jr. Neutron Scattering Center (Lujan Center) including a detailed evaluation of the signal shape. We will discuss the advantages and limitations of the nuclear physics experiments at FP-5 in the light of our results.     

研究堆冷中子源冷包的强度分析

利用ANSYS软件包对某研究堆冷中子源（CNS）的冷包在内外压共同作用下的强度进行分析。分析结果表明，冷包的原设计不甚合理，冷包的局部应力超过了设计应力。变更原结构的几何尺寸后进行了进一步计算分析，并提出了相应的补强方案。改进后冷包的计算结果表明，补强后的结构很好地满足设计要求。研究结果为冷包的实际工程设计提供了依据。     

Violence conjugale et qualité de la relation mère-enfant: Effet médiateur ou modérateur de la santé des mères ?

Mothers' health and quality of mother–child relationship are often held as factors that predict the adaptation of children exposed to domestic violence, but the connection between these factors has not been analysed yet. This study verifies if mothers' health has a mediator or a moderator effect on the connection between domestic violence and mother–child relationship. The study was conducted with 111 abused women and their children aged 6 to 12 years. An indicator of physical health and a score of psychological distress were used to measure mothers' health. The mother–child relationship was evaluated from both the mother's and the child's perspective. The results show that the 2 indicators of mother's health have no mediator effect, but have a moderator effect when the mother–child relationship was evaluated by children themselves. The discussion underlines the importance of mother's health as a protective factor for mother–child relationship and the incidence of this result for intervention. The interest of having multiple informants is also underlined. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

一种降低CARR堆冷中子源氢系统中子慢化室内含气率的方法

CARR核功率达60MW;其慢化室中液氢产气量大,含气率高,对于系统的慢化能力、反应堆的安全等都有重大影响。为了降低慢化室与内筒间环形通道中的截面含气率,本文采取在慢化室内筒顶端开孔的措施,以导出慢化室内筒下部金属及液氢核发热产生的氢气。通过对一系列小直径短管的流量与压力关系的测量,获得了小直径短管的流量与压力关联式,并以此关联式为依据,得到了最佳开孔数与最佳直径。论证了此方法在核功率变化时的自我调节性与稳定性。     

在线中子活化分析系统关键参数的蒙特卡罗模拟

针对在线瞬发γ中子活化分析（PGNAA）系统的要求,利用MCNP程序对不同慢化材料（重水、石蜡、聚乙烯等）厚度、铅屏蔽厚度、样品厚度及大小进行模拟计算分析。计算结果表明,以厚9cm的石蜡作慢化材料,厚2cm的铅作γ屏蔽层,厚7cm、半径10cm的硫、钙和水泥类样品为最优设计方案,从而为实际设计在线PGNAA系统提供了科学依据。     

Neutron spectrum change with thermal moderator temperature in a compact electron accelerator-driven neutron source and its effects on spectroscopic neutron transmission imaging

Recently, Compact Accelerator-driven Neutron Sources (CANSs) are attracting attention. In CANSs, a simple thermal neutron moderator such as polyethylene is often used from the viewpoints of cost, simplicity and maintainability. In most cases, the temperature of such a moderator has not been controlled although it is natural that the moderator temperature and the neutron spectrum will change with accelerator-operation. Thus, we simultaneously measured neutron spectra and the temperature of a polyethylene moderator at the Hokkaido University Neutron Source (HUNS) driven by a compact electron accelerator to observe the effect of any temperature change on the reliability of spectroscopic transmission measurement. The ratio of the neutron effective temperature and the moderator temperature was constant in HUNS case, although both increased by 4–5 K within one hour after the start of accelerator-operation. This indicated that the neutron effective temperature was well estimated by the moderator temperature. The effect of the temperature change can be easily avoided by excluding data collection before the moderator warms up. These results suggested that the monitoring of moderator temperature is recommended in compact electron accelerator-driven neutron sources with a thermal neutron moderator to guarantee reliability of spectroscopic transmission measurement without sacrifices of cost, simplicity and maintainability.