多光子Jaynes-Cummings模型中与Glauber-Lachs态相互作用原子的熵压缩

利用全量子理论,研究了多光子Jaynes-Cummings模型中与Glauber-Lachs态相互作用的混合态原子的信息熵压缩.讨论了相干平均光子数、热平均光子数、跃迁光子数、原子初态参量对原子信息熵压缩的影响.结果表明原子信息熵X分量没有熵压缩性质;相干平均光子数取值适当时,原子信息熵Y分量呈现熵压缩效应;热平均光子数、跃迁光子数会破坏原子信息熵Y分量的熵压缩效应;原子初态参量对原子信息熵Y分量能否呈现熵压缩效应没有决定性作用;伴随双光子跃迁时,原子的熵压缩因子的时间演化曲线呈现周期性.     

多像素光子计数器(MPPC)的性能测试

多像素光子计数器(Multi Pixel Photo Counter,简称MPPC)是近几年发展起来的一种新型信号读出设备.为了对这种设备制作的闪烁探测器有较深入的了解和认知,本文配合塑料闪烁体,与MPPC制成塑料闪烁探测器,对利用这种新型的光子计数器做成的探测器进行了研究.利用它测试了塑料闪烁体的时间和位置分辨率,将这方面数据与之前常用的配有光电倍增管的闪烁探测器的数据进行了比较,能够了解到用MPPC与塑料闪烁体做成的闪烁探测器在时间分辨和位置分辨方面能够达到实验的要求.在信价比和几何大小方面,MPPC优于光电倍增管,因此利用MPPC将在实验方面带来很大的优越性,为实验研究提供更大的方便.     

光子扣除(增加)压缩真空态与压缩猫态的保真度

解析推导了任意光子扣除(增加)压缩真空态与压缩猫态的保真度. 研究表明,无论是光子增加还是光子扣除,最大保真度都随光子增加或扣除数目的增加而增加,且最大保真度对应的叠加态振幅也增加;此外,对于相同数目的增加和扣除光子数,光子增加后的最大保真度所对应的叠加态振幅比光子扣除所对应的叠加态振幅要大,而最大保真度略小一些. 尽管目前从实验上实现光子增加比光子扣除困难较大,但光子增加也可以成为获得大振幅猫态的一个有力手段. 关键词： 光子扣除压缩真空态 光子增加压缩真空态 压缩猫态 保真度     

k光子Jaynes-Cummings模型光场的熵压缩

研究了k光子Jaynes-Cummings模型光场的熵压缩，讨论了光子数k和原子的初始状态对光场熵压缩的影响.结果表明，随光子数k的增大，光场的位置熵压缩愈趋明显，动量熵压缩量减小；当k≥3时，位置熵始终是被压缩的.原子的初态对光场的熵压缩也有一定的影响.     

60Coγ和高能电子在硅中NIEL的Monte Carlo计算

本文提出了计算高能电子和γ非电离能量损失(NIEL)的Monte Carlo方法,首次利用Monte Carlo方法计算了高能电子和⁶⁰Coγ的NIEL.给出了电子和⁶⁰Coγ在半导体硅材料中产生的NIEL和缺陷分布.计算结果与文献的比较表明模型是合理的.     

压缩奇偶相干态的量子统计性质

用压缩算子作用在奇偶相干态上即可得到压缩奇偶相干态.本文研究了这类量子态的统计特性.结果表明,压缩奇相干态和压缩偶相干态都能处于压缩状态,它们的光子亦都可能出现反聚束的现象.     

多光子Jaynes-Cummings模型中与Glauber-Lachs态相互作用原子的熵压缩

利用全量子理论,研究了多光子Jaynes-Cummings模型中与Glauber-Lachs态相互作用的混合态原子的信息熵压缩。讨论了相干平均光子数、热平均光子数、跃迁光子数、原子初态参量对原子信息熵压缩的影响。结果表明原子信息熵 分量没有熵压缩性质;相干平均光子数取值适当时,原子信息熵 分量呈现熵压缩效应;热平均光子数、跃迁光子数会破坏原子信息熵 分量的熵压缩效应;原子初态参量对原子信息熵 分量能否呈现熵压缩效应没有决定性作用;伴随双光子跃迁时,原子的熵压缩因子的时间演化曲线呈现周期性。     

辐射场的压缩的混沌态——Ⅰ. 特征函数和压缩性质

本文用Wigner特征函数方法将压缩的概念推广到一般量子态;详细讨论了一类新的光场状态——压缩的混沌态的量子统计性质,并提出辐射场与其共轭场的光子配组的概念作为其压缩性质的物理解释.     

单模加光子双模SU(2)相干态的非线性高阶差压缩

本文研究了单模加光子双模SU(2)相干态|M,ζ;m〉=Ama m|M,ζ〉的非线性高阶差压缩(即N次方X压缩)效应.数值计算结果表明:对于单模加光子双模SU(2)相干态,光场存在着非线性高阶差压缩??—N(=1,2,3,4,…)次方X压缩效应,且随着光场总光子数M的增加,N次方X压缩效应增强,但增大场模光子增加数m或增大N次方X压缩的压缩阶数N,N次方X压缩效应减弱.     

k光子Jaynes-Cummings模型光场的熵压缩

研究了k光子Jaynes-Cummings模型光场的熵压缩,讨论了光子数k和原子的初始状态对光场熵压缩的影响.结果表明,随光子数k的增大,光场的位置熵压缩愈趋明显,动量熵压缩量减小;当k≥3时,位置熵始终是被压缩的.原子的初态对光场的熵压缩也有一定的影响.     

Investigation of high resolution compact gamma camera module based on a continuous scintillation crystal using a novel charge division readout method

The objective of this study is to investigate a high performance and lower cost compact gammacamera module for a multi-head small animal SPECT system.A compact camera module was developed usinga thin Lutetium Oxyorthosilicate(LSO)scintillation crystal slice coupled to a Hamamatsu H8500 positionsensitive photomultiplier tube(PSPMT).A two-stage charge division readout board based on a novel subtractive resistive readout with a truncated center-of-gravity(TCOG)positioning method was developed for the camera.The performance of the camera was evaluated using a flood 99mTc source with a four-quadrant bar-mask phantom.The preliminary experimental results show that the image shrinkage problem associated with the conventional resistive readout can be effectively overcome by the novel subtractive resistive readout with an appropriate fraction subtraction factor.The response output area(ROA)of the camera shown in the flood image was improved up to 34%,and an intrinsic spatial resolution better than 2 mm of detector was achieved.In conclusion,the utilization of a continuous scintillation crystal and a flat-panel PSPMT equipped with a novel subtractive resistive readout is a feasible approach for developing a high performance and lower cost compact gamma camera.     

采用光纤和YAP晶体的小型γ相机的蒙特卡罗模拟

基于波长位移光纤(WSF)耦合YAP晶体中的光子传输特性,用GEANT4软件包建立了一个蒙特卡罗模拟程序.对采用波长位移光纤耦合平板式YAP晶体的小型单管γ相机的性能进行了计算机模拟.采用波长位移光纤耦合光电倍增管光阴极面的读出方式,和晶体直接耦合光电倍增管光阴极面相比,在相同的晶体面积大小条件下,PSPMT光阴极面积可大大缩小,使费用降低.模拟结果表明：γ射线与晶体发生作用的地方所对应的光纤输出的平均光子数最少为15个,位置灵敏光电倍增管完全可以探测到.说明采用闪烁晶体－WSF－位置灵敏光电倍增管的读出方式是可行的;在用硅油耦合波长位移光纤和YAP晶体的情况下,获得的空间分辨率为1.28 mm(FWHM).模拟结果也说明了增加平均光子数对提高空间分辨率的重要性.     

Experimental Study on Image Shrinkage in a Planar Crystal γ Camera

The effect of the crystal's type and treatment on the performance of gamma camera consisting of planar crystal and position sensitive photomulitiplier tube (PSPMT) is studied via experiment. The results demonstrate that: (1) treatment of the edge surface of the crystal is very sensitive to the shrinkage of image, and the side-absorptionsurface is the best choice; (2) the intrinsic spatial resolution of the CsI (T1) crystal camera is worse due to its low light yield: in the center part it is - 1cm (FWHM) for 2mm aperture collirnated 241Am source; while using NaI(T1) crystal, it is -4mm.     

Comparison of two position sensitive gamma-ray detectors based on continuous YAP and pixellated NaI(TI) for nuclear medical imaging applications

Dedicated position sensitive gamma-ray detectors based on position sensitive photomultiplier tubes (PSPMTs) coupled to scintillation crystals, have been used for the construction of compact gamma-ray imaging systems, suitable for nuclear medical imaging applications such as small animal imaging and single organ imaging and scintimammography. In this work, the performance of two gamma-ray detectors：a continuous YAP scintillation crystal coupled to a Hamamastu R2486 PSPMT and a pixellated NaI(TI) scintillation array crystal coupled to the same PSPMT, is compared. The results show that the gamma-ray detector based on a pixellated NaI(TI) scintillation array crystal is a promising candidate for nuclear medical imaging applications, since their performance in terms of position linearity, spatial resolution and effective field of view (FOV) is superior than that of the gamma-ray detector based on a continuous YAP scintillation crystal. However, a better photodetector (Hamamatau H8500 Flat Panel PMT, for example) coupled to the continuous crystal is also likely a good selection for nuclear medicine imaging applications.     

Comparison of two position sensitive gamma-ray detectors based on continuous YAP and pixellated NaI(TI) for nuclear medical imaging applications

Dedicated position sensitive gamma-ray detectors based on position sensitive photomultiplier tubes (PSPMTs) coupled to scintillation crystals, have been used for the construction of compact gamma-ray imaging systems, suitable for nuclear medical imaging applications such as small animal imaging and single organ imaging and scintimammography. In this work, the performance of two gamma-ray detectors: a continuous YAP scintillation crystal coupled to a Hamamastu R2486 PSPMT and a pixellated NaI(TI) scintillation array crystal coupled to the same PSPMT, is compared. The results show that the gamma-ray detector based on a pixellated NaI(TI) scintillation array crystal is a promising candidate for nuclear medical imaging applications,since their performance in terms of position linearity, spatial resolution and effective field of view (FOV) is superior than that of the gamma-ray detector based on a continuous YAP scintillation crystal. However, a better photodetector (Hamamatau H8500 Flat Panel PMT, for example) coupled to the continuous crystal is also likely a good selection for nuclear medicine imaging applications.     

Potential of GAGG:Ce scintillation crystals for synchrotron X-Ray micro-imaging

We examined the use of cerium-doped gadolinium aluminum gallium garnet (GAGG:Ce) as a material for scintillation screens in synchrotron X-ray radiography (SXR). Highlighted for gamma-ray detection, GAGG:Ce is also an attractive material for SXR because of its high X-ray stopping power and the high light yield at around 530?nm. A thin and transparent screen prepared from our grown ingot of GAGG:Ce was compared with commonly used scintillators of CdWO₄ and YAG:Ce in terms of image quality under monochromatic X-ray illumination. Micron spatial resolutions were achieved with comparable image quality, suggesting that a single crystal of GAGG:Ce is competent scintillation material for SXR.     

狭长CsI(Tl)闪烁体发光效率的研究

提出了基于狭长CsI（Tl）闪烁体和面阵CCD器件,采用光纤和光纤面板进行光耦合及传输,以扇形束线阵扫描方式实现对X射线探测与成像的工业X-CT系统探测器方案.基此,通过物理分析及数学建模,利用Matlab模拟研究了X光能量小于450 keV时狭长CsI（Tl）闪烁体的发光效率等性能指标.研究结果表明：当光电吸收截面μph和康普顿吸收截面μc分别为0.000313和0.0000295、反射层反射系数R和衬底反射系数Rs分别取0.95和0.8、荧光线性吸收系数σ取0.000222 μm－1时,得到狭长CsI(Tl)闪烁晶体的长度l、高度h和宽度w取值范围分别是926～4512 μm、242～5000 μm和242～5000 μm的结论.在此范围内,既可使闪烁晶体有较好的空间分辨率又可获得最高的发光效率.     

一种基于微通道板的脉冲X射线时间谱仪

为适应新型超快闪烁材料研究的需要,在原有脉冲X射线时间谱仪的基础上,通过改装微通道板光电倍增管(MCP-PMT),并采用具有快时间响应的前置放大器(FPA)和恒比甄别器(CFD)的方法,使谱仪的时间分辨极限提高到170 ps左右.BaF2晶体闪烁光快成分衰减时间谱的测量结果表明:该谱仪可很好地满足新型超快闪烁材料发光衰减时间特性的研究.     

Yb∶YAG晶体的红外闪烁特性

用脉冲电子束激发测量了不同Yb3+掺杂浓度的Yb∶YAG晶体的红外(IR)闪烁发光性能。Yb∶YAG晶体的IR闪烁发光具有高的光产额和长的衰减时间,但存在浓度猝灭效应和温度依赖关系。Yb∶YAG晶体的IR闪烁性能还与晶体品质有关,相同掺杂浓度的Yb∶YAG晶体,品质优异的会获得更高的光产额。这一初步的研究成果表明,部分掺Yb3+晶体有可能用于医学成像装置。