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排序方式: 共有34条查询结果,搜索用时 15 毫秒
1.
LHAASO-WCDA is a large ground-based water Cherenkov detector array planned to be built at Shangri-La, Yunnan Province, China. As a major component of the LHAASO project, the main purpose of LHAASO-WCDA is to survey the northern sky for very-high-energy (above 100 GeV) gamma ray sources and measure the spectrum. To gain full knowledge of the water Cherenkov technique and to investigate the engineering issues, a 9-cell detector array has been built at the Yang-Ba-Jing site, neighboring the ARGO-YBJ experiment. With the array, charge calibration methods for both low and high ranges of the PMT readout are studied, whose result shows that a precision at several percentages can be reached, which can satisfy the requirement of the detector array. During the long term operation, the charge calibration stability and environmental affection are studied; in this paper, the results are discussed. These calibration methods are proposed to be applied in the future LHAASO-WCDA project.  相似文献   
2.
 采用傅里叶模方法,分析了单点金刚石铣削后KDP晶体表面小尺度波纹的周期和幅值对单层增透膜折射率、厚度以及透射率的影响。研究表明:膜层最佳折射率在1.22左右,在此折射率条件下,保证透射率大于99%的单层增透膜的理想厚度范围应为180~220 nm,并且折射率和膜厚值的选取基本不受晶体表面小尺度波纹周期和幅值的影响。若只考虑SPDT法加工后KDP晶体表面小尺度波纹周期和幅值的实际范围,透射率基本不受波纹周期的影响,但却会随波纹幅值的增大而加速下降。理想镀膜条件下透射率最大值大于99%,并且通常在99.67%~99.94%之间。  相似文献   
3.
LHAASO-WCDA is a large ground-based water Cherenkov detector array planned to be built at ShangriLa, Yunnan Province, China. As a major component of the LHAASO project, the main purpose of LHAASO-WCDA is to survey the northern sky for very-high-energy(above 100 GeV) gamma ray sources and measure the spectrum. To gain full knowledge of the water Cherenkov technique and to investigate the engineering issues, a 9-cell detector array has been built at the Yang-Ba-Jing site, neighboring the ARGO-YBJ experiment. With the array, charge calibration methods for both low and high ranges of the PMT readout are studied, whose result shows that a precision at several percentages can be reached, which can satisfy the requirement of the detector array. During the long term operation, the charge calibration stability and environmental afection are studied; in this paper, the results are discussed. These calibration methods are proposed to be applied in the future LHAASO-WCDA project.  相似文献   
4.
陈明君  张峰  王贻芳 《中国物理 C》2003,27(11):1015-1018
详细描述了作为中微子探测器的水基契伦科夫量能器单元的结构,并用GEANT4软件包对水箱单元契伦科夫光的光学过程做了仔细的蒙特卡罗模拟,结果显示水箱的设计是合理的,且此结果对探测器设计与优化具有重要意义.  相似文献   
5.
"采用分子动力学模拟的方法,运用镶嵌原子模型,研究了经过刻划后的单晶铜纳构件在不同拉伸速度条件下的力学行为. 通过原子位图、缺陷原子透视图、径向分布函数及应力-应变关系研究加工后纳构件在拉伸负载作用下的变化特性,并与理想单晶铜纳构件进行对比分析.模拟结果表明,加工后的纳构件的屈服强度较理想纳构件的屈服强度有明显下降,屈服强度随着刻槽深度的增加而下降,而且屈服强度对刻槽方向和拉伸速度敏感;纳结构在拉伸负载作用下,其应力应变关系出现了双峰形式,即工作硬化现象,二次屈服后表现为Z字形逐波下降形式.刻划深度、刻划  相似文献   
6.
"使用Brenner-LJ拟合势描述了金刚石与C36团簇原子间的相互作用,并用分子动力学模拟的方法研究单个C36(D6h)在金刚石(100)晶面的沉积机制.通过仿真实验分析了C36团簇的入射能量、入射点位置、入射姿势、入射角度等因素对其成核初期化学吸附过程以及沉积后其稳定性的影响.研究发现:由于C36入射点位置及入射姿势的不同,其在金刚石(100)晶面沉积时的沉积阈值最小值为20 eV,最大值为60 eV;在入射角不超过60o斜射时,由于水平运动分量的存在,C36可能翻滚及平滑至成键能量较小的区域后再成键  相似文献   
7.
李明全  陈明君  安晨辉  周炼  程健  肖勇  姜伟 《中国物理 B》2012,21(5):50301-050301
The low laser induced damage threshold of the KH2PO4 crystal seriously restricts the output power of inertial confinement fusion.The micro-waviness on the KH2PO4 surface processed by single point diamond turning has a significant influence on the damage threshold.In this paper,the influence of micro-waviness on the damage threshold of the KH2PO4 crystal and the chief sources introducing the micro-waviness are analysed based on the combination of the Fourier modal theory and the power spectrum density method.Research results indicate that among the sub-wavinesses with different characteristic spatial frequencies there exists the most dangerous frequency which greatly reduces the damage threshold,although it may not occupy the largest proportion in the original surface.The experimental damage threshold is basically consistent with the theoretical calculation.For the processing parameters used,the leading frequency of micro-waviness which causes the damage threshold to decrease is between 350-1 μm-1 and 30-1 μm-1,especially between 90-1 μm-1 and 200-1 μm-1.Based on the classification study of the time frequencies of microwaviness,we find that the axial vibration of the spindle is the chief source introducing the micro-waviness,nearly all the leading frequencies are related to the practical spindle frequency(about 6.68 Hz,400 r/min) and a special middle frequency(between 1.029 Hz and 1.143 Hz).  相似文献   
8.
在高功率激光系统中,精密微机械修复是减缓磷酸二氢钾(KDP)晶体表面缺陷增长的有效方法,使用精密微铣削机床可以加工出球面型与高斯型修复轮廓。为得到最优的修复结构参数,建立了晶体前表面球面型与高斯型修复轮廓的电磁场有限元模型,通过改变轮廓的宽度、深度等参数,对两种修复轮廓的光强调制能力进行对比研究。仿真结果表明光强调制能力主要是由修复轮廓的衍射效应及入射光在修复界面处的二次入射所引起的干涉作用共同决定;针对初始损伤点,建议采用宽深比大于5的修复轮廓,从而有效提高KDP晶体表面缺陷点的激光损伤阈值,对于宽深比大于10的修复轮廓建议选用高斯型;对宽1000μm,深20μm的两种修复表面的激光损伤实验表明,高斯型修复轮廓具有较高的抗损伤能力,实验与仿真结果相一致。  相似文献   
9.
The Large High Altitude Air Shower Observatory (LHAASO) project is proposed to study high energy gamma ray astronomy (40 GeV--1 PeV) and cosmic ray physics (20 TeV--1 EeV). The wide field of view Cherenkov telescope array, as a component of the LHAASO project, will be used to study the energy spectrum and composition of cosmic rays by measuring the total Cherenkov light generated by air showers and the shower maximum depth. Two prototype telescopes have been in operation since 2008. The pointing accuracy of each telescope is crucial for the direction reconstruction of the primary particles. On the other hand, the primary energy reconstruction relies on the shape of the Cherenkov image on the camera and the unrecorded photons due to the imperfect connections between the photomultiplier tubes. UV bright stars are used as point-like objects to calibrate the pointing and to study the optical properties of the camera, the spot size and the fractions of unrecorded photons in the insensitive areas of the camera.  相似文献   
10.
使用有限元方法分析了在激光辐照条件下,KDP晶体已加工表面存在的残余内应力、微裂纹及微孔等多种微纳米加工表层缺陷对晶体激光损伤阈值的影响。通过分析发现:KDP晶体微纳米加工表层缺陷的存在,会影响晶体表面的温度场及热应力场的分布,使入射激光的能量积聚在缺陷附近的很小范围内,造成晶体缺陷处产生局部熔融现象,从而使KDP晶体产生损伤,降低KDP晶体的激光损伤阈值。针对微纳米表层的微裂纹进行了损伤阈值测试实验,结果表明微裂纹的存在会降低KDP晶体的激光损伤阈值(约降低3J/cm2),实验结果与仿真结果符合得很好。  相似文献   
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