羊八井ARGO实验RPC模拟读出

羊八井ARGO实验正处于探测器安装及试运行阶段,整个阵列由1848个工作于流光模式的单层RPC探测器构成.依靠RPC读出条的数字读出只能测量小簇射事例的次级粒子数目,为了实现逐事例区分“膝区”原初宇宙线的成分及其能谱研究,对探测器增加了模拟读出,以实现对EAS芯区高达10⁴/m2的次级粒子数密度的精确测量.本文对RPC探测器性能及大动态范围模拟读出板的信号和性能做了初步的分析和研究     

BESⅢ端盖TOF时间分辨的束流测试

使用800MeV的电子束对BESⅢ端盖飞行时间探测器(TOF)模块的性能进行测试. 研究了塑料闪烁体的包装材料、光电倍增管(PMT)的工作电压、电子束入射位置对单个TOF模块的本征时间分辨的影响，并给出了测量时间与信号幅度和粒子击中位置的修正方法. 实验结果显示:使用Tyvek纸包装，闪烁体在安装PMT的一端有45°斜面, 电子击中在TOF模块不同位置其本征时间分辨在70—90ps范围内.     

大型激光原型装置低燃料面密度诊断技术

由于某大型激光原型装置内爆实验的燃料面密度很低,提出了利用充纯D燃料内爆产生的初级DD中子和次级DT中子的产额比值来诊断燃料面密度的方法。在该原型装置的首轮内爆实验中,利用研制的高灵敏塑料闪烁体探测器对初级DD中子产额和次级DT中子产额进行了测量。通过实验发现,当初级DD中子产额高于108时,可以测得次级DT中子实验数据。建立了均匀内爆模型,用初级和次级中子产额比值法对燃料面密度进行计算,获得的该原型装置首轮内爆实验燃料压缩的平均面密度小于4.0 mg/cm2。     

谱仪放大器参数对脉冲形状分析法鉴别轻带电粒子的影响

我们利用脉冲形状分析法,通过CsI(T1)闪烁体加光二极管读出探测器对¹²C(46.7/MeV/u)+⁵⁸Ni反应中出射的轻带电粒子进行了鉴别.实验中发现放大器成形时间常数的选取对轻带电粒子鉴别的结果有明显影响.本文基于信号转移函数的Laplace变换方法,对这个问题进行了计算和分析,成功地解释了所遇到的实验现象.     

μ子寿命测量实验

根据粒子的平均寿命测量原理,采用大面积塑料闪烁探测器和可编程逻辑器件设计了宇宙线μ子寿命测量的实验教学装置,使用该装置可实现对宇宙μ子寿命的直接测量.通过该实验,可使学生对高能物理理论、高能粒子探测器、高能粒子探测技术和数据获取、处理有整体的理解和认识.本文从实验教学内容和教学方法上对μ子寿命测量实验进行了探讨.     

HL-2M 装置初始放电可见光辐射测量系统

HL-2M 装置初始放电实验期间采用了一套 8 通道可见光辐射测量系统,4 个通道用于测量 Hα辐射, 其余分别测量 HeⅡ线、CⅢ线、OⅤ线和轫致辐射。该系统采用新型的雪崩放大二极管(APD)模块和光电倍增管 (PMT)模块作为光探测器,这些新型的探测器由于集成度高、供电方式简单而使得整个系统的后端具有体积小、 操作简单及可靠性强等优点。在 HL-2M 装置初始放电期间,该系统为控制运行人员提供了基本的等离子体信息。     

利用宇宙线对BESⅢ量能器CsI(Tl)晶体探测器单元的测量

利用宇宙射线进行探测器模型的性能测试是高能物理普遍采用的方法, 其中最重要的步骤之一就是确定宇宙线入射的准确位置和径迹. 多数采用丝室探测器来进行宇宙线的精确定位, 需要很高的造价和复杂的电子学系统. 本文介绍一种简单的定位方法, 采用塑料闪烁体条加波移剂光纤编码读出的方式, 可以实现精度为1cm的定位. 据此建立了一套实验装置, 对BESⅢ电磁量能器CsI(Tl)晶体探测器单元的光输出强度和不均匀性进行了测量.     

谱仪放大器参数对脉冲形状分析法鉴别轻带电粒子的影响

我们利用脉冲形状分析法,通过CsI(T1)闪烁体加光二极管读出探测器对~(12)C(46.7MeV/u)+~(58)Ni反应中出射的轻带电粒子进行了鉴别。实验中发现放大器成形时间常数的选取对轻带电粒子鉴别的结果有明显影响。本文基于信号转移函数的Laplace变换方法,对这个问题进行了计算和分析,成功地解释了所遇到的实验现象。     

闪烁体荧光传输特性对ETOF探测器性能的影响

为了对BESⅢ端盖飞行时间探测器(ETOF)的测试结果给出合理的解释, 采用Monte Carlo模拟软件包Geant4, 对该探测器测量高能带电粒子的性能进行模拟研究. 详细探讨了当粒子击中ETOF模块不同位置时, 其闪烁体荧光传输特性与探测器模块输出信号之间的关联, 以及PMT输出信号甄别阈值的选取对闪烁探测器本征时间分辨的影响, 并寻找可能的改善时间分辨的方法. 为进一步提高ETOF的性能提供参考.     

RIBLL束流诊断的发展

描述了重离子加速器放射性次级束流线束流诊断技术的新发展,它包括初级束流在线监测研制的非拦截式法拉第筒,监测低强度初级束流的塑料闪烁探测器,测量放射性次级束流剖面的大面积双维位置灵敏平行板雪崩室等.这些新研制的束流诊断装置的运用,明显提高了设置、调整、确定重离子加速器放射性次级束流线运行参数的速度和准确性,改善了放射性次级束流纯度和质量,并使得重离子加速器放射性次级束流线的运行更简洁、迅速和有效.     

折轴三反射镜成象光学系统结构研究

本文讨论了折轴式三块二次曲面反射镜成象光学系统结构,与非共轴三反射镜结构比较,该三反射镜结构其布置具有装调容易、杂散光影响小等优点.本文介绍了该系统中两个遮拦相匹配应满足的条件,以及改变结构参数和减小中心遮拦提高成象分辨率的简单且有效的方法.     

Non-static non-conformally flat fluid plates of embedding class one

In the present article four non-static perfect fluid solutions have been derived by considering a plane symmetric metric of embedding class one. Out of the solutions so obtained two solutions possess an acceleration free velocity vector field while the other two have flow with acceleration. As far as the authors are aware the solutions with non-vanishing acceleration are new.     

On the 3391 superstimulation and its competition with the 633 laser oscillations

Summary Competition between the 3391 radiation emitted by a long He−Ne tube and the 633 laser oscillations was investigated experimentally. the results were analysed by means of the balance equations of populations. The absolute values of populations of the 5s′[1/2] ₁ ⁰ and 4p′[3/2]₂ levels, the excitation rates of the levels and the rates of induced transitions were computed. A new experiment on the 3391 radiation generated by the long He−Ne tube showed a negligible value of the radiation in the middle of the tube.

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Riassunto Si è studiata sperimentalmente la competizione tra la radiazione 3391 emessa da un lungo tubo a He−Ne e l'oscillazione dellaser 633. I risultati sono stati analizzati per mezzo dell'equazioni di bilanciamento delle popolazioni. Sono stati calcolati i valori assoluti delle popolazioni dei livelli 5s′[1/2] ₁ ⁰ e 4p′[3/2]₂, i valori di eccitazione dei livelli e i valori delle transizioni indotte. Un nuovo esperimento sulla radiazione 3391 generata dal lungo tubo a He−Ne ha mostrato un valore trascurabile della radiazione nel centro del tubo.

     

Kroll-Watson-type theorem for potential scattering in a bichromatic laser field

Summary We show that for potential scattering of electrons in a bichromatic laser field a Kroll-Watson type of theorem can be derived in which the scatteringT-matrix element is composed of a renormalized on-shell matrix element for scattering without a field times a generalized Bessel function factor. The radiation field has two components of frequency ω₁ and sω₁ (s=2,3,…) and both components are out of phase by an angle ϕ. Our paper is a generalization of earlier investigations which were performed in the first-order Born approximation.     

3391 and 7699 laser generations and questions on the chaos

Summary In this report investigations are presented of laser generations at 3391 nm and 3391 and 7699 nm, or rather of changes induced by them in populations of the 5s′ [1/2] ₁ ⁰ , 4p′[3/2]₂ and 3d′[5/2] ₃ ⁰ levels, depending upon the angle of the tilted mirror of the He−Ne laser system. This writer has discovered that the above laser generations develop at a strongly tilted mirror, when the beam reflected from one mirror, in order to reach the other, has to be reflected many times on the inside walls of the discharge tube. The work was supported by CPBR 8.14.     

An approach to the study of strong-field laser-induced autoionization

Summary An approach is presented to the study of laser-induced autoionization which usescomplex dressed states as a basis, instead of the commonly used Fano eigenstates. The complex dressed states are the eigenstates of an effective Hamiltonian governing the equations of motion for the atomic probability amplitudes in the broad background assumption and in the rotating frame at the laser frequency. The electron and photon spectra are described in terms of the eigenvalues associated with the complex dressed states.

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Riassunto Viene presentato un approccio allo studio dell'autoionizzazione indotta da laser che, al posto degli autostati di Fano, utilizza quale base una coppia distati vestiti complessi. Tali stati sono gli autostati di una hamiltoniana effettiva che governa le equazioni di moto per le ampiezze di probabilità atomiche in un sistema di riferimento ruotante alla frequenza del laser e nell'ipotesi di continuo largo. Gli spettri di elettroni e fotoni sono descritti in termini degli autovalori associati agli stati vestiti complessi.

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Резюме Предлагается подход к исследованию автоионизации, индуцированной лазерным сильным полем, в котором используются, как, базис, комплексные “одетые” состояния, вместо обычных собственных состояний Фано. Комплексные “одетые” состояния представляют собственные состояния эффективного гамильтониана, определяющего уравнения движения для амплитуды вероятности атома во вращвющейся системе отсчета с лазерной частотой и в предположении широкого континуума. Электронные и фотонные спектры описываются в терминах собственных значений, связанных с комплексными “одетыми” состояниями.

     

Simultaneous multiphoton ionization by two radiation fields. Effects of the statistical properties of the radiation

Summary We report on calculations of differential and total ionization cross-sections of hydrogen atoms irradiated by two radiation fields with different properties. One of the fields is of low intensity and relatively high frequency, the other is of low frequency and high intensity. In particular, we show that the inclusion of the multimode structure of the low-frequency laser field modifies considerably the shape of the angular distribution of the photoelectrons and the rates of ionization into the different channels characterized by the number of low-frequency photons exchanged. Further, we find that the average energy exchanged between the photoelectrons and the low-frequency radiation field is independent of the statistical properties of the low-frequency laser field.     

Light-induced ejection of alkali atoms in polysiloxane coated cells

Summary An intense laser-induced fluorescence of sodium and of other alkali atoms (K, Rb) at room and lower temperatures has been observed in polysiloxanecoated cells, producing a vapor density of the metal which is much higher than that corresponding to the thermal equilibrium between the vapor and the condensed phase. This enhancement is attributed to the light-induced ejection of atoms absorbed by the polysiloxane coating. The atomic density of the vapor can be manipulated by changing either the laser power or frequency. The dependence of the atomic density on these and other parameters as well as its time-dependent behavior are studied experimentally. A tentative interpretation of the phenomenon is discussed in terms of the properties of solutions of the alkali metals in several solvents.     

Two-photon detachment cross-section of atoms in the extended asymptotic model

Summary A previously proposed one-electron model for photoionization, referred to as extended asymptotic model [J. Mol. Struct. (Teochem) 166, 369 (1988)], is further developed to cope with two-photon ionization processes. A simple application of the approach to the case of the negative ion H⁻ is investigated and discussed. The authors of this paper have agreed to not receive the proofs for correction.     

Realization of Dirac Bracket Algebras Through First-Class Functions and Quantization of Constrained Systems

It is shown that a Dirac bracket algebra is isomorphic to the original Poisson bracket algebra of first-class functions subject to first-class constraints. The isomorphic image of the Dirac bracket algebra in the star-product commutator algebra is found.