新型“Ca2F2（Eu）＋液闪”复俣WIMP探测器的实验研究

介绍北京组新近提出的“Ca2F2(Eu) 液闪”复俣WIMP探测器的设计特点。通过对探测器单元内部光收集效率的研究，初步确定了复合探测器的设计结构。另外，对探测器内部放射性杂质衰变在复合探测器单元中形成的本底情况进行模拟，结果表明了复合探测器具有良好的排除本底的能力。     

暗物质寻找实验中CsI(Tl)晶体反符合探测器实验研究

一个正在建设的位于韩国Y2L地下实验室的低能暗物质探测实验中, 采用了CsI(Tl)晶体反符合探测器作为主动屏蔽体. 本工作对CsI(Tl)晶体反符合探测器的实验性能进行了研究. 通过FADC系统记录的脉冲波形数据, 研究了探测器的能量分辨率和波形甄别的能力; 研究相同能量γ射线入射到反符合探测器不同位置的相对光输出将有助于选择探测器的工作参数; 为了解晶体自身放射性对暗物质测量的影响, 利用低本底HPGe探测器对CsI(Tl)晶体内部的放射性进行了测量, 得到晶体内部Cs同位素的放射性活度. 探测器系统进行了约18d的试运行取数. 实验数据表明, CsI(Tl)晶体探测器的反符合效率约为31% HPGe探测器的本底计数率水平约为133cpd. 为了进行暗物质探测研究, 需要采取有效的方法进一步降低探测器的本底水平.     

暗物质寻找实验中CsI（T1）晶体反符合探测器实验研究

一个正在建设的位于韩国Y2L地下实验室的低能暗物质探测实验中,采用了CsI（T1）晶体反符合探测器作为主动屏蔽体.本工作对CsI（T1）晶体反符合探测器的实验性能进行了研究.通过FADC系统记录的脉冲波形数据,研究了探测器的能量分辨率和波形甄别的能力;研究相同能量γ射线入射到反符合探测器不同位置的相对光输出将有助于选择探测器的工作参数;为了解晶体自身放射性对暗物质测量的影响,利用低本底HPGe探测器对CsI（T1）晶体内部的放射性进行了测量,得到晶体内部Cs同位素的放射性活度.探测器系统进行了约18d的试运行取数.实验数据表明,CsI（T1）晶体探测器的反符合效率约为31%,HPGe探测器的本底计数率水平约为133cpd.为了进行暗物质探测研究,需要采取有效的方法进一步降低探测器的本底水平.     

BEPCⅡ束流相关本底的蒙特卡罗模拟研究(Ⅱ)—束流-气体相互作用

介绍了用蒙特卡罗方法研究正常对撞模式下束流本底中的束流-气体相互作用的原理与效果.使用通用的模拟工具,研究了BEPCⅡ的束流-气体本底对设计中的BESⅢ的影响.结果显示,在储存环上设置挡板后,探测器的本底在允许的范围之内.模拟结果对BEPCⅡ-BESⅢ的设计建造具有指导意义.     

ANSYS在气体探测器电场分布计算中的应用

介绍了气体探测器电场分布的计算方法,以计算MSGC探测器单元电场分布为例说明了如何用ANSYS软件包来计算结构较复杂的气体探测器内部电场分布,同时讨论了电场分布对气体探测器性能的影响.     

BEPCⅡ束流相关本底的蒙特卡罗模拟研究(Ⅲ)——Touschek效应

介绍了Touschek效应本底研究的意义、Touschek效应的作用原理和建模方法. 使用自主开发及通用的模拟工具, 系统研究了BEPCⅡ工作条件下BESⅢ主要探测器的Touschek本底. 模拟和计算束流寿命的比较表明当前的模拟结果是有参考价值的, 建模方法是可行的. 探测器的模拟结果表明Touschek本底不会影响将来BESⅢ的正常稳定运行, 不会造成探测器的辐照损伤.     

HXMT准直器方案的优化设计

空间硬X射线调制望远镜(HXMT)的性能与探测器的总灵敏面积紧密相关. 利用蒙特卡罗工具对仪器的本底和点扩展函数进行计算分析, 提出了一种优化的准直器构造方案, 能减少探测单元总质量80多千克, 相当于至少5套新探测单元质量. 在同样的卫星载荷质量限制下, 新方案可以增加探测单元, 达到增大总探测灵敏面积, 提升HXMT灵敏度和角分辨率等性能的目的.     

新型太阳中微子闪烁探测器的研制

概述了一种新型太阳中微子闪烁探测器的研制,其中载钆(Gd)液体闪烁体的Gd浓度达到5%、光的衰减长度≥150cm、对60keV的Gamma-ray之能量分辨率为21%(σ);直径1cm、厚3cm的GSO:Ce晶体,其发光产额约为NaI(Tl)晶体的20%、光的衰减时间为60ns、对662keVGamma-ray之能量分辨率为9.2%(σ).文章讨论了由这两种闪烁体构成的复合探测器的特点及作为太阳中微子探测器其本底的降低措施.对直径10cm、厚50cm的这种复合探测器的模拟计算表明其光的收集效率可达20%.     

水基契伦科夫量能器单元的蒙特卡罗模拟

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.     

北京谱仪Ⅲ电磁量能器触发系统的模拟研究

利用北京谱仪Ⅲ探测器模拟和触发系统模拟程序,研究了北京谱仪Ⅲ电磁量能器的触发方案.根据物理目标设计了中性事例触发,巴巴事例判选和带电事例触发的方案,优化了各触发条件的参数,并仔细研究了对本底的排斥能力.研究了一批典型的物理道,给出了它们的触发效率,同时给出了预期的本底触发事例率.     

"Two-Photon" coincidence imaging with a classical source

Coincidence imaging is a technique that extracts an image of a test system from the statistics of photons transmitted by a reference system when the two systems are illuminated by a source possessing appropriate correlations. It has recently been argued that quantum entangled sources are necessary for the implementation of this technique. We show that this technique does not require entanglement, and we provide an experimental demonstration of coincidence imaging using a classical source. We further find that any kind of coincidence imaging technique which uses a "bucket" detector in the test arm is incapable of imaging phase-only objects, whether a classical or quantum source is employed.     

"猫眼"探测光学环路的功率密度计算

激光对光电传感器主动侦察是基于光学系统存在的"猫眼"效应.对包括"猫眼"镜头的回波功率和CCD光敏面照度的整个环路进行了推导.分析结果表明:CCD光敏面上的照度随发射激光束散角、照射距离的增大而降低,随大气能见度的提高而增大.同时,探测器探测面的离焦也对CCD光敏面的照度产生较大的影响,离焦量越大,接收到的光照度越小.     

基于红外光谱技术的混合气体检测系统概述

为了给从事红外混合气体检测领域的研究人员提供一定的借鉴与参考,针对红外混合气体检测系统中的光学复用结构以及检测方法进行了详细评述。目前,以量子级联激光器(QCL)、带间级联激光器(ICL)为代表的相干光源已逐渐取代热辐射红外光源、红外发光二极管(LED)等传统非相干光源,成为红外混合气体检测中的主流光源。相应地,具有超高探测度和极短响应时间的红外光探测器也逐渐超越以往的红外热探测器,占据红外探测器领域的主导地位。基于“复用思想”的光学复用结构则是红外混合气体检测系统的核心,主要包括单光源复用检测结构和多光源复用检测结构。其中,单光源复用检测结构以其体积小、集成度高等优点成为构建便携式混合气体检测系统的重要选择;而多光源复用检测结构是时分复用、频分复用、波分复用等思想的具体化,并凭借其较宽的光谱覆盖范围、较高的光谱分辨率等优势成为当前混合气体检测系统中的主导结构。应用于红外混合气体检测的检测方法主要有非分光红外(NDIR)光谱技术、波长/频率调制光谱技术、腔增强光谱技术以及光声光谱技术等。研究人员可通过对红外混合气体检测系统各组成部分充分了解后,设计出实用的红外混合气体检测系统,对工农业生产、环境监测、生命科学等诸多领域都具有重要意义。     

Search for solar <Emphasis Type="Italic">pp</Emphasis> neutrinos with an upgrade of CTF detector

The possibility of using ultrapure liquid organic scintillator as a low-energy solar neutrino detector is discussed. The detector with an active volume of 10 t and 4π coverage will count 1.8 pp neutrinos and 5.4 ⁷Be neutrinos per day with an energy threshold of 170 keV for the recoil electrons. The evaluation of the detector sensitivity and backgrounds is based on the results obtained by the Borexino collaboration with the Counting Test Facility (CTF). The detector can be build at the LNGS underground laboratory as an upgrade of the CTF detector using already developed technologies.     

Resonant "forbidden" reflections in magnetite

Resonant x-ray scattering was used to investigate electronic fluctuations of the octahedral iron atoms in magnetite. We measured the (002) and (006) "forbidden" x-ray diffraction reflections permitted by the anisotropy of the iron anomalous scattering factor. The energy and azimuthal angle dependencies of these reflections, and the polarization analysis, are shown and discussed. The results clearly show p and d iron empty states ordering in magnetite at room temperature. Moreover, the octahedral iron atoms are electronically equivalent in a time scale lower than 10(-16) sec. Therefore, magnetite should be considered as an itinerant magnet and not as a fluctuating mixed valence material.     

Kinematics,equilibrium, and shape in Hamiltonian systems: the "LAB" effect

We demonstrate that a system of a finite number of particles in a container with a "typical" shape does not get mixed in the sense that in an (asymptotic) steady state distribution the particles are not equally likely to occupy (almost) any position inside the container. Our incomplete mixing result should be contrasted with the complete mixing of noninteracting or elastically colliding particles in a box, which does occur because the box is not a "typical" shape. The effect we describe does not disappear in the limit of infinitely many particles. However, it is unlikely to be observed in nature but rather in laboratory (the "LAB" effect) experiments. Ideal gas in a container, which is a product of billiards, serves as a transparent model to understand the "LAB" (look at billiards) effect.     

Search for resonant absorption of solar axions emitted in an <Emphasis Type="Italic">M</Emphasis>1 transition in <Superscript>57</Superscript>Fe nuclei

The resonant absorption of solar axions by ⁵⁷Fe nuclei, which is accompanied by the excitation of the first excited nuclear level: A + ⁵⁷Fe → ⁵⁷Fe* → ⁵⁷Fe + γ(14.4 keV), is sought. To seek 14.4-keV photons, a Si(Li) detector and an enriched ⁵⁷Fe target are used. The detector and target are placed in a low-background setup equipped with passive and active shieldings. As a result, a new upper limit m _A ≤ 360 eV (at 90% C.L.) has been determined for the axion mass.     

Theoretical analysis for the apparent discrepancy between and pp data in charged particle forward–backward multiplicity correlations

The strength of charged particle forward–backward multiplicity correlation in and p+p collisions at is studied by PYTHIA 6.4 and compared to the UA5 and STAR data correspondingly. It is turned out that a factor of 3–4 apparent discrepancy between UA5 and STAR data can be attributed to the differences in detector acceptances and observing bin interval in both experiments. A mixed event method is introduced and used to calculate the statistical correlation strength and the dynamical correlation strengths stemming from the charge conservation, four-momentum conservation, and decay, respectively. It seems that the statistical correlation is much larger than dynamical one and the charge conservation, four-momentum conservation and decay may account for most part of the dynamical correlation. In addition, we have also calculated the correlation strength by fitting the charged particle multiplicity distribution from PYTHIA to the Negative Binomial Distribution and found that the result agrees well with the correlation strength calculated by mixed events.     

激光单脉冲时-空采样器的研究

分析了激光单脉冲时_空实时测量对时_空采样器的要求,提出了在高峰值功率密度下探测器设计的“梳导”思想,讨论了用不同长度的单模光纤束制作时_空采样器的关键技术和工艺。这种时_空采样器具有高带宽、高损伤阈值、高捕获率的优点。     

No "light shining through a wall": results from a photoregeneration experiment

Recently, axionlike particle search has received renewed interest. In particular, several groups have started "light shining through a wall" experiments based on magnetic field and laser both continuous, which is very demanding in terms of detector background. We present here the 2sigma limits obtained so far with our novel setup consisting of a pulsed magnetic field and a pulsed laser. In particular, we have found that the axionlike particle two photons inverse coupling constant M is >8 x 10{5} GeV provided that the particle mass m{a} approximately 1 meV. Our results definitively invalidate the axion interpretation of the original PVLAS optical measurements with a confidence level greater than 99.9%.