Enhanced Extreme Ultraviolet Free Induction Decay Emission Assisted by Attosecond Pulses

We demonstrate the extreme ultraviolet free induction decay emission that can be significantly enhanced by employing isolated attosecond pulses.The near infrared pulses are applied to excite the neon atoms into Rydberg states coherently,and isolated attosecond pulses are used to manipulate populations of the Rydberg states and the subsequent free induction decay process.The time resolved experimental measurement of dependence of the resonance emission yield would help to understand the buildup dynamics of population of excited states.The enhancement assisted by attosecond pulses can serve as a mechanism to develop high-flux extreme ultraviolet light sources.

Intensity-Dependent Dipole Phase in High-Order Harmonic Interferometry

High-order harmonics are ideal probes to resolve the attosecond dynamics of strong-field recollision processes.An easy-to-implement phase mask is utilized to covert the Gaussian beam to TEM01 transverse electromagnetic mode,allowing the realization of two-source interferometry of high-order harmonics.We experimentally measure the intensity dependence of dipole phase directly with high-order harmonic interferometry,in which the driving laser intensity can be precisely adjusted.The classical electron excursion simulations reproduce the experimental findings quite well,demonstrating that Coulomb potential plays subtle roles on movement of electrons for harmonics near the ionization threshold.This work is of great importance for precision measurements of ultrafast dynamics in strong-field physics.

Chirp Compensation for Generating Ultrashort Attosecond Pulses with 800-nm Few-Cycle Pulses

We show that it is feasible to generate sub-40-attosecond pulses with near-infrared few-cycle pulses centered at 800 nm.With proper gating technique,super-broadband continuum spectrum extending from 50 eV to above 200 eV can be obtained,and the intrinsic atto-chirp can be satisfactorily compensated with C filter,producing isolated attosecond pulses with duration of 33 as.According to the wavelength scaling law of high-order harmonic generation,the proposed scheme is of great significance to develop high-flux ultrashort attosecond sources.

作动器连接耳环—关节轴承系统Link单元等效建模及结构分析

作动器连接耳环—关节轴承系统的结构与载荷的复杂性决定了其力学计算的复杂性。因为在完全润滑的条件下,关节轴承内外环之间的切向作用可以忽略,而其间的法向作用可用只能承受压力的Link单元来代替,同时这种方法避免了由于双曲率曲面接触、单元形状畸变及其他力学难题等带来的收敛困难。采取这种等效建模的方法对连接耳环的受力情况做了详尽的分析,计算了与之相连的关节轴承的载荷及变形状况,为结构设计的改进提供指导。

液压伺服系统产品测试生产流程优化

航天液压伺服系统是用来控制火箭发动机推力矢量的液压伺服系统,其根据控制系统指令调整飞行器的姿态,实现俯仰、偏航和滚动控制,并使飞行器按照预定轨道飞行。液压伺服系统产品生产调试过程中,由于检测项目多、周期长,影响了产品批生产的效率。为此,北京精密机电控制设备研究所针对需求任务开展了设计要求、工艺流程、生产布局、设备设施等方面的优化挖潜,在保证产品质量的前提下,从工艺和设计2个方面对测试项目和工艺流程进行优化调整,并制定相应措施,以减少产品实做工时,提高生产效率。

单个阿秒脉冲表征技术研究进展

自本世纪初超快科学进入阿秒领域以来,阿秒脉冲以其超宽频谱和超短时间分辨,为研究阿秒时间尺度的瞬态过程提供了有力工具,推动了人们对光与物质相互作用以及微观超快动力学机制的理解。基于高次谐波的单个阿秒脉冲产生技术已日臻成熟,通过发展多种时空选通门技术,阿秒脉冲脉宽不断缩短,已达到的最短纪录为43 as。相较于阿秒脉冲的产生,对其精确测量与表征是深入研究和应用的基础,目前主流表征方法是通过阿秒条纹相机技术测量获得条纹能谱,进而从中提取阿秒脉冲的时域信息。首先简要回顾了高次谐波产生、单个阿秒脉冲选通及测量的发展,然后介绍了阿秒条纹相机技术的原理,并重点阐述了基于阿秒条纹能谱的表征算法,对其主要优缺点进行分析,最后对阿秒脉冲表征的发展进行了总结和展望。

牵着“蜗牛”去散步

提起我们班的“蜗牛”,那可是说来话长……午休课的铃声在校园内回荡。大家都匆匆地走回自己的教室,而他却还慢悠悠地在走廊上“散步”。你看他,有时一步三回头,望望这望望那,不时还自个儿开心地笑一下。