CPT原子频标实验研究

介绍了相干布居囚禁（CPT）原子频标的小型、低功耗物理系统,并应用它开展实现了CPT原子频标的激光锁定、微波锁定方案的实验室研究.通过采用电流负反馈将激光频率锁定在原子对激光的吸收峰上,电压负反馈将微波频率锁定在电磁感应透明共振峰上,用该物理系统实现了闭环锁定的实验室桌面CPT频标实验系统.对该实验系统的频率稳定度测量获得200 s内优于5×10^-11τ^-1/2的结果. 关键词： CPT原子频标 频率稳定度 激光稳频     

LD抽运的Nd:YAG陶瓷/KTP绿光激光器

报道了一种LD端面抽运Nd:YAG陶瓷、KTP腔内倍频的全固态连续波绿光激光器.当抽运功率为21.6 W时,1064 nm基频输出达到11.3 W,光—光转换效率为52.3%.采用Ⅱ类切割的KTP晶体作为腔内倍频介质,在直腔结构下获得了最大功率为1.86 W的532　nm绿光输出,光—光转换效率为7%.输出光斑具有高斯型强度分布,1 W输出时的M²因子约为1.7. 关键词： 全固态绿光激光器 Nd:YAG陶瓷 KTP倍频 直腔     

基于神经网络的多联变频空调电子膨胀阀控制系统研究

空调制冷系统具有滞后大、非线性等特点,采用普通控制方式时效果不尽人意。采用BP-PID控制器对系统电子膨胀阀开度进行控制,并设计了BP-PID控制器。实践结果表明,该控制方法简单有效,很好地满足了用户的实际需要。     

脉冲激光入射下介质薄膜双频互相关散射截面及功率展宽

 结合特殊的镀金聚酯薄膜表面的粗糙度和半球反射率,依据基尔霍夫近似及粗糙面脉冲散射互相关函数,数值计算了脉冲激光（1.06 μm）在不同入射角照射下该材料薄膜双频互相关散射截面随相干带宽频差和散射角的变化情况。并给出δ脉冲和高斯脉冲波入射下,其散射功率随时间和散射角的波形分布。计算结果表明：该薄膜材料激光双频互相关散射截面在镜反射方向有最大的散射峰值,在非镜反射方向上,其散射值随相干带宽频差的增大迅速减小,当窄脉冲垂直入射时,粗糙面散射功率展宽现象明显。     

CuBr激光放电管声波共振现象的研究

为了使有广泛应用的CuBr激光器能稳定和高效运行,针对实验中出现的激光输出功率随放电频率起伏的情况,给出CuBr激光放电管内声波振动的数学模型。该模型选取圆柱形放电管轴为柱坐标轴对波动方程求解,通过数值计算,获得了放电管内声压分布的解析表达式。通过分析放电频率与激光管固有声振动频率的关系,明确了声共振会导致激光介质重新分布,它对激光输出功率有影响,理论计算结果和实验结果完全符合。     

重频激光对多壁碳纳米管悬浮液光限幅特性的影响研究

在激光以不同重复频率入射下,研究了直径分布为10～20 nm的多壁碳纳米管悬浮液对波长为1064 nm激光的光限幅效应,定性分析了不同重复频率激光对多壁碳纳米管悬浮液的光限幅影响。结果表明:碳纳米管悬浮液对波长为532 nm和1064 nm的激光都具有很强的光限幅响应;在多脉冲激光入射时,碳纳米管悬浮液的光限幅效应比单脉冲激光入射时更显著。     

80K高频无磁非金属脉冲管制冷机

介绍了高频脉冲管制冷机冷指无磁非金属材料的选择、加工以及实验优化工作.制作的高频无磁脉冲管制冷机冷指在风冷,2.3 MPa 充气压力,44 Hz,70 W 电功率输入条件下,最低达到 73.4 K 的无负荷最低温度;60 W 电功率输入,最低温度为 74.0 K,在 80 K 时可以提供 0.1 W 的制冷量.本文为高频脉冲管制冷机直接冷却相关低温超导器件提供了坚实的基础.     

Investigation on the fabrication of the 3rd harmonic superconducting cavity for the SSRF storage ring

A third harmonic superconducting niobium cavity has been proposed for installation in the Shanghai Synchrotron Radiation Facility （SSRF） storage ring to improve the Touschek lifetime. In order to investigate the feasibility of the superconducting cavity fabrication indigenously and the possibility to master the fabrica tion techniques, cavities were fabricated from copper and niobium sheets by deep drawing and electron-beam welding, and a series of measurements, such as resonant frequency, shape dimensions and wall thickness, were carried out during this process. After analysis of various problems existing in the fabrication process, technique improvements were proposed, and finally the precise shape as designed and resonant frequency within 1.2 MHz were achieved for the new completed cavities. In addition, full annealing was finally proved to be a good cure for niobium sheets＇ tearing up during deep drawing. By fabricating niobium cavities successfully, some problems to the next step were cleared. This paper introduces the process of cavity fabrication and its technique improvements towards forming, and the initial vertical test result of niobium cavity is also presented.     

Harmonic balancing approach to nonlinear oscillations of a punctual charge in the electric field of charged ring

The harmonic balance method is used to construct approximate frequency-amplitude relations and periodic solutions to an oscillating charge in the electric field of a ring. By combining linearization of the governing equation with the harmonic balance method, we construct analytical approximations to the oscillation frequencies and periodic solutions for the oscillator. To solve the nonlinear differential equation, firstly we make a change of variable and secondly the differential equation is rewritten in a form that does not contain the square-root expression. The approximate frequencies obtained are valid for the complete range of oscillation amplitudes and excellent agreement of the approximate frequencies and periodic solutions with the exact ones are demonstrated and discussed.     

Transverse Wave Propagation in Relativistic Two-Fluid Plasmas around Schwarzschild-de Sitter Black Hole

We investigate transverse electromagnetic waves propagating in a plasma influenced by the gravitational field of the Schwarzschild-de Sitter black hole. Applying 3+1 spacetime split we derive the relativistic two-fluid equations to take account of gravitational effects due to the event horizon and describe the set of simultaneous linear equations for the perturbations. We use a local approximation to investigate the one-dimensional radial propagation of Alfvén and high frequency electromagnetic waves. We derive the dispersion relation for these waves and solve it for the wave number k numerically.