光幕靶测试系统测量不确定度分析

弹丸参数测试是靶场测试的一项主要内容,论文提出了一种激光光幕靶对弹丸速度进行测量的方法,介绍了激光光幕靶的测速原理,并对光幕靶测试系统的测量不确定度进行了分析,为试验布局提供理论依据.     

^59Co靶芯体厚度优化计算

采用比黑度理论更精确的ＡＮＩＳＮ方法,对ＨＦＥＴＲ堆芯“夹层式”结构的＾５９Ｃｏ靶的芯体厚度进行了优化设计计算。结果表明：芯体厚度在２．５ｍｍ至３．０ｍｍ间有一个比较宽的活度峰,最大活度对应的＾５９Ｃｏ靶芯体厚度约为２．９ｍｍ。     

电沉积法制备镉靶

对加速器生产111In所用镉靶制备工艺进行了研究.通过研究电沉积过程中影响Cd靶质量及厚度的各种因素,确定了最佳工艺条件.所研制的镉靶厚度大于57 mg/cm2,表面光亮、致密、牢固.     

同位素208Pb靶的制备

介绍了一种弧形靶框夹芯^208pb靶的制备工艺,包括核靶的制备装置和制备方法、核靶厚度和均匀性的控制和测量方法,并对结果进行了讨论.制备采用旋转蒸镀法,该法可以大大提高材料的利用率.所制靶的结构为30μg/cm^2 C＋361 μg/cm^2 ^208pb＋15 μg/cm^2 C,同一次所制的靶平均厚度为361μg/cm^2,不均匀性小于9.8%.其性能能够很好地满足超重核实验研究的要求.     

含表面层的厚靶D-T中子产额计算

本文给出一种含表面层氚钛靶D-T反应中子产额的计算方法,并开发了相应的数值计算程序。以氧化层为TiO2为例,定量计算了D核在TiO2中的深度分布统计及透过率、200keV的D核穿过不同厚度TiO2的能量分布函数、D核入射含不同厚度氧化层TiT1.0的D-T中子产额和不同能量D核入射固定厚度氧化层TiT1.0的D-T中子产额。结果显示,中子产额随氧化层厚度的增加而减小,对于200keV的D核入射到含TiO2氧化层的TiT1.0厚靶,当TiO2厚度为0.1μm时,损失约10%的中子产额,厚度为0.2μm时,损失约20%的中子产额。本方法可推广到其他类型表面层(如污染层、保护层等)的中子产额计算,可用于中子发生器用靶的结构设计和中子产额评估。     

自支撑同位素铬靶的制备方法

一、引言核物理实验需要各种厚度的自支撑同位素铬靶,首先我们用电镀法试制成0.5—2mg/cm~2的自支撑铬靶,为了获得更薄的自支撑铬靶,我们改用真空蒸发法进行试验,制成了厚度为0.2—0.4 mg/cm~2的自支撑铬靶。     

α能损法测厚仪的研制

α能损法测量靶膜的厚度是通过测量穿过薄膜的粒子能量的变化实现膜厚的测量。一束单能的α粒子穿过一定厚度的薄膜后由于能量损失的歧离效应会使能量有一定展宽，但中心能量是通过α能谱的峰位确定的，因此，用α粒子测量薄膜厚度有更小的测量误差。同时，这是一种无损的测量方法，采用计算机控制，方便易用。     

同位素208Pb靶的制备

介绍了一种弧形靶框夹芯208pb靶的制备工艺,包括核靶的制备装置和制备方法、核靶厚度和均匀性的控制和测量方法,并对结果进行了讨论.制备采用旋转蒸镀法,该法可以大大提高材料的利用率.所制靶的结构为30μg/cm2 C+361 μg/cm2 208pb+15 μg/cm2 C,同一次所制的靶平均厚度为361μg/cm2,不均匀性小于9.8%.其性能能够很好地满足超重核实验研究的要求.     

冷冻靶的环境热辐射屏蔽技术研究

通过建立三维柱腔冷冻靶计算模型,研究了外界环境辐射对间接驱动冷冻靶靶丸及燃料冰层温度场的影响。考虑柱腔内部激光入射孔（LEH）膜透光率对柱腔内靶丸和冰层温度场分布的影响,利用COMSOL软件对柱腔冷冻靶温度场进行了数值模拟计算。研究结果表明：受外界辐射影响,靶丸表面温度场呈两极热、赤道冷分布;LEH膜透光率越大,靶丸外表面温差和冰层内表面温差越大。当LEH膜透光率小于1%时,冰层内表面最大温差低于0.1 mK,可满足冰层均化和保持的要求。实验中,通过在LEH膜上镀不同厚度的铝层调控其透光率,并选择LEH膜镀铝层厚度为35 nm的冷冻靶开展了氘氘冷冻均化实验。结果表明：当LEH膜上的镀铝层厚度为35 nm时,冰层的保持能力得到大幅提升。从X射线相衬图像可知,冰层的厚度均匀性约为80.2%,粗糙度约为1.65 μm,平均厚度约为50.5 μm。     

单光电子谱测试中触发方式对比研究

光电倍增管(PMT)单光电子谱测试中触发方式的对比研究对PMT性能刻度具有很强的指导意义。通过搭建自触发、同步触发、异步触发三套测试系统,对比研究不同触发方式对PMT性能刻度的影响。实验结果表明:自触发只可用于初步性能刻度;而异步触发在信号触发频率小于触发门采样频率时,得到多光电子谱,刻度结果远偏离实际值;同步触发方式能更可靠地刻度出更多更精确的PMT参数,是PMT性能刻度的最佳触发方式。     

The Trigger System of the MAGIC Telescope

The MAGIC telescope aims at the detection of very low energy gamma rays (E>30 GeV) through the atmospheric emission of Cherenkov light. The high background rate originating from the night sky background, muons, hadronic showers and bright stars sets a serious challenge to this goal. Application of topological selection cuts at trigger level can have a big impact on background reduction allowing the telescope to operate at lower thresholds and reducing the minimum detectable energy. The trigger of the MAGIC telescope is a two-level system following a pipeline philosophy, similar to those adopted in high energy physics experiments. Operative since October 2002, the trigger system has been a key point in the commissioning of the MAGIC telescope that is now taking data. The trigger hardware is described in detail     

Energy loss of H and He in the semiconductors GaAs, ZnSe, InP and SiC

We have theoretically studied the electronic stopping cross section and the energy loss straggling of swift light ions (H⁺ and He⁺) moving through several compound semiconductors (GaAs, ZnSe, InP and SiC) as a function of the incident projectile energy. The calculations have been done using the dielectric formalism, in which the electronic structure of the projectile is described by the modified Brandt–Kitagawa model and the energy loss function (ELF) of the semiconductors is obtained using a linear combination of Mermin-type ELF to describe the outer electron excitations and generalized oscillator strengths to take into account the excitations of the inner-shell electrons. The different charge states that the projectile can acquire during its travel through the solid, as a result of electronic capture and loss processes, has been also considered. The contributions to the projectile energy loss from both the outer- and the inner-shell electron excitations are analyzed. The comparison of our calculated stopping cross sections with available experimental data shows a good agreement in a wide range of incident projectile energies.     

Calculation of the total force acting upon a rigid wall by projectiles

A numerical method is presented which allows for the calculation of the total force acting upon a building during impact of a projectile. The structural part to be hit by the projectile is assumed to be rigid; its surface is perpendicular to the direction of impact. Flight trajectory and projectile axes coincide. Variations of geometric and material properties across the projectile axis are replaced by proper average values. The computation algorithm is based on a difference method. The projectile model has to be divided into elements along the flight trajectory. Except for the elements at the beginning and end of the projectile each element is in equilibrium with its neigbour elements. Different elastic and plastic material properties for each element can be taken into account. Strongly deformed elements are assumed to become separated from the projectile. The impact of all debris is calculated as a part of the total force acting on the wall. The method is tailored to safety considerations. A parametric study of the force resulting from impact of a turbine of a military aircraft is discussed. It is shown that for safety considerations a simplified function between force and time can be established.     

A new large area scintillator screen for X-ray imaging

We report on the development of a new, large area, powdered scintillator screen based on Lu₂O₃(Eu). As reported earlier, the transparent ceramic form of this material has a very high density of 9.4 g/cm³, a high light output comparable to that of CsI(Tl), and emits in a narrow spectral band centered at about 610 nm. Research into fabrication of this ceramic scintillator in a large area format is currently underway, however the process is not yet practical for large scale production. Here we have explored fabrication of large area screens using precursor powders from which the ceramics are fabricated. To date we have produced up to 16 × 16 cm² area screens with thickness in the range of 18 mg/cm². This paper outlines the screen fabrication technique and presents its imaging performance in comparison with a commercial Gd₂O₂S:Tb (GOS) screen.     

Evaluation of Gd2O2S:Tb as a Phosphor for the Input Screen of X-Ray Image Intensifier

X-ray fluorescent screens consisting of a powder embedded in a silicone resin matrix and deposited on an aluminum plate have been prepared with the phosphors Gd2O2S:Tb and (ZnCd)S:Ag(P-20) at a series of different screen thicknesses. The x-ray conversion efficiency of the screens was measured using both radioisotopes and a dental radiography unit as x-ray sources. To simulate screen performance in an x-ray image intensifier tube, the screens were optically coupled to the photomultiplier which served as the detector. We found that Gd2O2S:Tb screens were substantially superior to P-20 screens in both x-ray conversion efficiency and x-ray energy absorption efficiency. Experimental screen efficiencies agree with those derived from theory by an analysis in which the efficiency of the conversion of absorbed x-ray energy to light is assumed equal to the energy efficiency of the phosphor under cathode ray excitation and optical parameters of the screens are used to estimate the efficiency with which the generated light is transmitted to the detector.     

板型燃料元件内部缺陷的无损检测

本文使用超声波水浸单探头反射法对不贴紧缺陷进行了检测,根据缺陷反射波的形状及在时域上的位置对缺陷的深度和类型进行了分析评价。使用²⁴¹Am源59.5 keV的单能窄缝γ射线,对芯体分布的均匀性进行了检测。根据特定检测频率下包壳厚度与涡流阻抗变化的对应关系对包壳厚度进行了分析评价。通过超声、射线和涡流检测方法对板型燃料元件内部缺陷检测并给予评价,保证产品质量。     

Determination of neutron-skin thickness using configurational information entropy

Configurational information entropy （CIE） theory was employed to determine the neutron-skin thickness of neutron-rich calcium isotopes.The nuclear density distributions and fragment cross sections in 350 Me V/u^40-60Ca+⁹Be projectile fragmentation reactions were calculated using a modified statistical abrasion-ablation model.CIE quantities were determined from the nuclear density,isotopic,mass,and charge distributions.The linear correlations between the CIE determined using ...     

Sputtering of Langmuir-Blodgett multilayers by keV C60 projectiles as seen by computer simulations

Fundamental processes induced in a thick organic system composed of long, well-organized linear molecules by an impact of 5-20 keV C₆₀ are investigated. The organic system is represented by Langmuir-Blodgett multilayers formed from bariated molecules of arachidic acid. The thickness of the system varies between 2 and 16 nm. Coarse-grained molecular dynamics computer simulations are applied to investigate the energy transfer pathways and sputtering yields as a function of the kinetic energy of the projectile and the thickness of the organic overlayer.The results indicate that an impact of keV C₆₀ projectiles leads to significant ejection of organic material. The efficiency of desorption increases with the kinetic energy of the projectile for a given layer thickness. For a constant primary kinetic energy, the sputtering yield goes through a maximum and finally saturates as the LB layer becomes thicker. Such behaviour is caused by a competition between signal enhancement due to increasing number of organic molecules and signal decrease due to lowering of the amount of the primary energy being backreflected into the organic overlayer by the receding organic/metal interface as the layer is getting thicker. When the sample thickness becomes much larger than the penetration depth of the projectile, the sputtering yield is independent of thickness. The deposited energy is channelled by an open and ordered molecular structure, which leads to abnormally long projectile penetration and ion-induced damage.     

BES-ⅢTOF子触发系统触发判选功能在可编程逻辑器件中的实现

北京正负电子对撞机谱仪的飞行时间计数器触发子系统,需从前端读出电子学接收368 bits快时间击中信号,按物理实验要求的触发逻辑产生7 bits触发条件信息,实时发送给主触发逻辑,以产生一级触发信号L1;并向径迹配对逻辑实时发送136 bits位置信息,以推算粒子飞行径迹;同时根据L1信号对事例进行判选、组装,向DAQ系统提供所有有效事例的数据包,以供离线分析.我们对该系统研制秉持可重构的设计理念,大量使用可编程逻辑器件FPGA,增加设计的灵活性和可靠性,减小印刷电路板设计的复杂度,节省PCB布板空间.本文介绍主触发处理FPGA中核心触发逻辑功能的设计与实现.     

基于OPC的凸度仪数据交互客户端开发

在凸度仪系统中,高温扫描仪用于实时测量热轧钢板的断面温度,所测得的温度数据用于对钢板厚度进行实时补偿,反馈给轧机调整板型。为实时获得钢板温度数据,需开发OPC客户端,与高温扫描仪的OPC服务器接口进行数据交互。本文介绍和分析了OPCDA规范,在VisualC++开发环境下,基于活动模板库实现了OPC客户端接口程序,可获取高温扫描仪的各数据项。温度数据传送给温度补偿模块进行厚度校正,获得了较好的校正效果。