γ Mass Resolution versus Chamber Resolution in ALICE Dimuon Forward Spectrometer

The precisions and its sources of spatial resolutions of tracking chambers and mass resolutions of dimuon signals in ALICE Dimuon Forward Spectrometer are explored by tracking and reconstruction of AliRoot software. The dependences of γ mass resolution on spatial resolution of tracking chambers are presented with and without background events through simulations.     

二维位置灵敏探测器输出图像畸变的修正

高分辨(e,2e)谱仪采用二维位置灵敏探测器同时对能量和角度进行多道测量.二维位置灵敏探测器由级联使用的微通道板和电阻阳极板组成,由于电阻阳极板的边缘效应和制造工艺的缺陷,测量得到的位置图像与实际图像总会有一定的形变,存在一定的非线性.本文针对高分辨(e,2e)谱仪二维位置灵敏探测器输出图像的“桶形”畸变及位置非线性,采用一种简易的冷刻法(用脉冲信号来模拟真实电子束团),检验了二维位置灵敏探测器的Gear型电阻阳极板的线性好坏,并用分割成小三角形的方法找出测量得到的畸变图像与原始真实图像的映射关系,再用此关系对其它测量得到的畸变图像进行修正,并对修正的结果进行了评估.通过修正,由“桶形”畸变所造成的图像扭曲得到明显改善.修正后的x方向非线性由修正前的2.1%变为0.59%.这种检验和修正方法对其它领域类似探测器输出图像的修正也有一定的指导意义.     

Current and frequency modulation characteristics for continuous-wave quantum cascade lasers at 9.06 μm

We report the characteristics of current induced frequency modulation (FM) for two continuous-wave quantum cascade lasers (QCLs) at 9.06 μm. Both the frequency tuning rate and the phase shift between intensity modulation and FM are measured at different modulation frequencies from 10 Hz to 200 kHz. The frequency tuning rate of the QCLs depends on both the modulation frequency and amplitude. The tested QCL has been used to detect ambient water vapor with wavelength modulation spectroscopy for validation with a numerical model.     

强脉冲X射线辐照在Si-SiO2中感生的界面态及退火消除

 利用强脉冲X射线对Si-SiO₂界面进行了辐照，测量了界面态曲线和退火曲线。实验显示，经过强脉冲X射线对Si-SiO₂界面进行的辐照，在Si-SiO₂界面感生出新的界面态，感生界面态的增加与辐照剂量成正比，并且易出现饱和现象。总结出了感生界面态密度产额Dit随辐照剂量D变化的分布式，并定性分析了Dit随D变化的行为。随后进行的退火实验表明，强脉冲X射线辐照感生出的界面态越多，退火时这些界面态就消除得越快。退火过程显示有滞后现象，即辐照剂量大的阈电压漂移，在退火后恢复的绝对值，要小于辐照剂量小的阈电压漂移。导出了阈电压漂移随退火时间变化的关系，定性解释了滞后现象。     

Structural and spectroscopic properties of small Pun （n= 2-5） molecules

The equilibrium structures and the electronic, spectroscopic and thermodynamic properties of small Pu_n (n=2-5) molecules are systematically investigated using the methods of general gradient approximation (GGA) of density functional theory (DFT). The results show that the bond length of the lowest-energy structure of Pu₂ is 2.578 AA. The ground state structure of Pu₃ is a triangle with D_3h symmetry, whereas for Pu₄, the ground state structure is a square (D_4h) and the spin polarization of 16 for molecule Pu₅ with square geometry (D_4h) is the most stable structure. For the ground state structures, the vibrational spectra as well as thermodynamic parameters are worked out. In addition, the values for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) along with the energy gap of all the Pu_2-5 structures are presented. The relevant structural and chemical stabilities are predicted.     

A lattice scenario for a proton radiography accelerator

A proton radiography system is an accelerator-based facility.Especially high-energy proton radiography is an advanced hydrodynamics diagnostic tool,and it is the trend of radiography technology development.In this paper,a 20 GeV accelerator complex scenario,including a 35 MeV linac,a 1 GeV booster and a 20 GeV main ring,is introduced.The overall physics design of the proton radiography accelerator is described,including the design of each part of the accelerator and the choice of the main parameters.     

基于多角度偏振特性的云相态识别及验证

云相态识别是云参数研究的重要组成部分,为了有效识别水云和冰云,根据水云和冰云微物理性质的差别,研究了水云和冰云的单次散射特性,采用基丁倍加累加法的,人量辐射传输方程模拟了水云和冰云的多角度偏振特件.模拟结果表明,光谱的多角度偏振特件能够体现山水云粒子和冰云粒子微物理性质的差异,云在特定方向反射的偏振辐射强度对云相态非常敏感,可以用米进行云相念的识别,在模拟的基础上进行了云相态识别算法的研究,并利用多角度偏振卫星数据--POLDER 0.865μm通道数据进行了实例分析.识别结果与MODIS云相态产品及其1.38μm卷云榆测结果进行了比较.分析结果表明,基于多角度偏振特性云相态识别算法可以有效地进行云相态识别.     

Sender-controlled measurement-device-independent multiparty quantum communication

Multiparty quantum communication is an important branch of quantum networks. It enables private information transmission with information-theoretic security among legitimate parties. We propose a sender-controlled measurement-device-independent multiparty quantum communication protocol. The sender Alice divides a private message into several parts and delivers them to different receivers for secret sharing with imperfect measurement devices and untrusted ancillary nodes. Furthermore, Alice acts as an active controller and checks the security of quantum channels and the reliability of each receiver before she encodes her private message for secret sharing, which makes the protocol convenient for multiparity quantum communication.     

基于神光Ⅲ原型的激光直接驱动自由面准等熵实验研究

长脉冲激光打靶的直接驱动方式效率较高,但对激光强度变化非常敏感。利用测量自由面速度历史的方法对激光直接驱动准等熵压缩实验技术进行了分析,为改进激光直接驱动的准等熵压缩实验技术提供技术基础。介绍了国内在神光III原型装置上首次开展的激光直接驱动自由面准等熵压缩实验。对实验靶型、激光波形、典型实验结果以及实验中的关键技术进行了分析。在激光能量为1000 J的实验中,使用成像型速度干涉仪获得了较为理想的准等熵压缩条纹图。实验发现,自由面速度达到11.3 km/s时,自由面反射的探针光信号消失。通过对比Multi-1D软件的理论模拟数据与实验处理的结果,发现由于Al自由面缺少约束,这类实验会造成波系复杂化的问题,但是对主冲击的研究还是有意义的。对某些特殊材料,在很难找到阻抗匹配窗口的条件下,利用激光直接驱动方式研究材料高压响应特性提供了另一条可实施的技术途径。