共查询到20条相似文献,搜索用时 104 毫秒
1.
中子Soller准直器是中子散射谱仪一种常用部件,主要用于限制中子束流的发散度,提高中子谱仪的分辨率。准直器的准直角是描述其性能的一项重要技术指标,通过摇动曲线的实验测量获得。本文基于实验测量需求和方法,利用中子射线追踪模拟蒙特卡罗程序McStas对中子Soller准直器摇动曲线实验测量过程进行了蒙特卡罗模拟计算,并对计算结果进行实验对比和解析分析。分析结果表明,模拟计算、实验数据和理论解析三者符合较好,验证了模拟方法的可行性。通过多方法结合来研究摇动曲线,可提高测量分析结果的可靠性,类似的方法也可扩展应用于其他中子光学部件的测试分析。 相似文献
2.
能量分辨率是中子散射谱仪设计中需重点模拟计算的一项指标。本文阐述了基于反应堆中子源的两种冷中子非弹性散射谱仪——三轴谱仪和广谱谱仪的基本测量原理,利用MCSTAS软件分别建立两种谱仪的中子束追踪模型,完成了不同中子入射能量和出射能量下的谱仪整体能量分辨率的定量模拟计算。通过对比发现,广谱谱仪由于其测量原理即特殊的变异散射平面的限制,较三轴谱仪具有低的能量分辨率,但这种特殊的变异散射平面的中子散射轨迹却可优化广谱谱仪的分析器和探测器空间布局。通过分析模拟计算结果给出了适用于提高广谱谱仪能量分辨率的中子准直器类型。 相似文献
3.
中子单色器是中子散射谱仪的关键部件之一。使用效率更高的新型中子单色器将给中子散射谱仪带来极大的性能提升,垂直聚焦中子单色器可提高样品位置处中子束强度2~5倍,相应的中子散射实验测量时间将缩短2~5倍。显然,垂直聚焦中子单色器在提高反应堆中子源的利用效率上是一种经济有效的手段。考虑到新旧谱仪对于中子单色器的迫切需求,我们决定建立一个自主研发聚焦中子单色器工艺平台。 相似文献
4.
5.
讨论了中子散射实验中散射矢量分辨率问题,并根据目前谱仪通常的角度分辨和波长分辨参数,给出了常波长模式和飞行时间模式的分辨率曲线,并比较了不同模式的优缺点。分析表明,对于低q范围(〈0.4nm^-1)散射实验测量,飞行时间模式的分辨率更好;对于高q范围的中子散射测量,常波长模式更适合。 相似文献
6.
中子三轴谱仪分辨率的计算与分析 总被引:1,自引:0,他引:1
描述了中子三轴谱仪分辨率函数的计算方法,计算分析了中子波矢、准直器水平发散度、谱仪布局及能量和动量转移对分辨率函数的影响.谱仪分辨率随着入射波矢增大而降低,随着准直器水平发散度的减小而提高,谱仪最高能量分辨率能达到23μeV,计算值与实验测量和模拟计算结果符合得很好;谱仪布局只改变分辨率椭球在散射平面的方向,而不会影响... 相似文献
7.
单色器屏蔽系统是中子散射谱仪中的关键部件之一。大多数反应堆中子散射实验测量均须使用单色中子(具有特定能量或波长的中子)作探针。由反应堆引出的白光中子束的单色化过程由置于反应堆生物屏蔽外的晶体单色器来实现。当需要不同波长的中子时,可以通过改变单色器的起飞角2θM(入射束与出射束之间的夹角)来实现,为满足屏蔽要求并有效降低实验本底,必须在单色器周围和单色器之前中子的路径周围设置屏蔽,即设置单色器屏蔽系统。 相似文献
8.
本文目的是介绍中子技术在凝聚态物理研究中的应用。主要介绍中子散射的基本原理、实验方法及冷中子源、超冷中子源、中子导管和中子单色器。 相似文献
9.
中子散射谱仪计算机测控系统的研究初步实现了中子散射谱仪4个主要部件:样品台、探测器、单色器和准直器的运动控制,进行了现场控制实验,包括步进电机、伺服电机的控制及光栅编码器的数据获取,控制精度达到实验所需精度的要求,特别是对重达数吨的样品台的精确位置控制,实现了较 相似文献
10.
设计了一种多路准直器用于消除中子照相中的散射中子,利用MCNP5对准直器的中子吸收材料、长度进行了优化设计,利用该准直器对不同厚度的水层样品在不同样品探测器距离下进行了中子照相的MC模拟计算。计算结果表明选用25μm的Gd作为准直器的中子吸收涂层,准直器长度为1cm时可消除98%的散射中子,使用该准直器可以有效提高中子照相定量分析的精度。 相似文献
11.
医院中子照射器是基于微型反应堆而设计的专门用于硼中子俘获治疗(BNCT)的核反应堆装置,其额定功率为30 kW。在堆芯相对两侧分别设有一条热中子束流和超热中子束流用于病人照射,在热中子束流内引出一条实验用热中子束流,用于瞬发γ法测量病人血硼浓度。本工作利用235U裂变靶和白云母探测片测量了热、超热和实验用热中子束流出口处的热中子绝对注量率。结果显示,在30 kW额定功率运行时,热、超热和实验用热中子束流出口处的热中子注量率分别为1.67×109、2.44×107和3.03×106 cm-2•s-1。以上结果达到了BNCT设计要求,并能满足瞬发γ测量血硼浓度的要求。 相似文献
12.
实验室中的同位素Am-Be中子源在有关中子活化方法研究以及在核反应堆中子测量系统研制过程中的调试和刻度等方面都有着非常重要的作用.为使这些应用更有效并得到更准确的实验结果,需要知道Am-Be中子源在周围慢化介质中热中子通量密度的分布.用蒙特卡罗方法并结合中子源发射率计算得到了居里级Am-Be中子源在圆柱形水池中不同半径... 相似文献
13.
14.
15.
16.
17.
G. S. Bauer 《Journal of Fusion Energy》1989,8(3-4):169-180
The paper outlines the physics of the spallation reaction and the resulting rules of thumb with respect to neutron yield, heat deposition, and energy distribution. Technical problems and performance expectations are discussed on the basis of two high beam power spallation neutron source projects, namely, the German SNQ Project (not funded) and the Swiss SINQ Project (under construction). Since both of these projects were designed mainly for thermal neutron scattering application, emphasizing the production of a high flux of moderated neutrons, an alternative conceptual design is presented which, while still allowing the extraction of cold and thermal neutron beams, also offers the opportunity of placing samples into positions where the neutron spectrum has changed only very little due to transport in matter. The anisotropy of the high-energy neutron field can be taken advantage of to select, to some extent, how much of the high energy component will be seen by the specimens. No technical design concept exists so far for a spallation neutron source for fusion materials test purposes, and more detailed studies would be required to assess its value and usefulness. However, a source for combined use for different purposes seems to be feasible without too many compromises. 相似文献
18.
In order to achieve the goal of nuclear security, the neutron generator is used to image shielded nuclear material by non-destructive analysis method. In order to improve the imaging quality, it is necessary to collimate the slowed neutrons. In this paper, the Monte Carlo software Geant4 was used to theoretically model a new compact thermal neutron collimator based on gadolinium-doped silicate, and the thermal neutron transmittance and collimation ratio of the collimator were simulated and calculated. The calculation results will be used to guide the subsequent construction of neutron-based nuclear material imaging systems. 相似文献
19.
《Journal of Nuclear Science and Technology》2013,50(10):1050-1058
Abstract The JRR-3 has been upgraded to be a new high performance research reactor JRR-3M with neutron guide tubes on a large scale and a cold neutron source. The neutron fluxes and spectra were measured at the end of the two thermal and three cold neutron guide tubes. The gain of the cold neutron source is also found from these spectra. The neutron fluxes of thermal neutron guide tubes with characteristic wavelength 2 Å are 1.2x108 n/cm2.s at a reactor power of 20 MW. The neutron fluxes of cold guide tubes are 2.0x 108 n/cm2.s with characteristic wavelength 4 Å and 1.4x108 n/cm2.s with 6 A when the cold neutron source is operated. The neutron spectra measured by the time-of-flight method agree well with their designed ones. The gains of the cold neutron source are 8 for 4 Å and 20 for 6 Å at a reactor power of 20 MW. 相似文献
20.
Hirotaku Ishikawa Tetsuya Kai Hirotaka Sato Takashi Kamiyama 《Journal of Nuclear Science and Technology》2019,56(2):221-227
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. 相似文献