Time domain identification and ranking of noise sources in a pneumatic nail gun

This paper investigates the noise sources in a pneumatic nail gun. The study combines two complementary experimental approaches. The first uses simultaneous data observation, with sound, acceleration and air pressure signals simultaneously recorded in conjunction with a nail gun motion high speed video. This strategy allows the identification of the physical processes involved in the operation of the machine at different time instants, as well as the associated noise generation mechanisms. However, since multiple noise sources radiate at the same time, this observation technique is not sufficient for noise source identification and ranking. Thus, a second approach introduces a selective wrapping procedure, and the strategy assures a reliable classification of the noise sources. The investigation considers the following noise origins: the air exhaust, the machine body and the workpiece/worktable.     

Dynamics of plasma channel in a parallel-plate plasma gun

Lumped parameter models for describing dynamics of the plasma channel in a parallel-plate plasma gun are compared with the experimental results obtained from two plasma guns with different rail geometries. Comparison between the experiments and the numerical calculations reveals that the lumped parameter models can be utilized to describe the dynamic motion of the plasma channel quite well. Parametric study shows that minimizing the line inductance and increasing the charging voltage on a capacitor as well as minimizing the gas injection time for reducing the mass of the plasma channel are the key factors to increase the flow velocity of the plasma jet ejected from the plasma gun.     

感应耦合等离子体中和枪的电子引出特性研究

给出了一种感应耦合等离子体源的设计,用于等离子体中和枪装置.通过实验方法研究等离子体源的电子引出特性,并结合理论分析了等离子体密度随射频功率的变化关系.研究结果表明等离子体源的电子引出特性与放电腔内气压有关联性,E?H模式转换中电子密度的变化与负载的电感值相关.研究成果对等离子体中和枪的发展有重要的参考价值.     

钨合金柱形弹超高速撞击水泥砂浆靶的侵彻深度研究

为探索钨合金柱形弹超高速撞击水泥砂浆靶的侵彻深度随撞击速度变化规律,利用二级轻气炮开展了?3.45 mm×10.5 mm的克级93 W钨合金柱形弹以1.82~3.66 km/s的速度撞击水泥砂浆靶的实验,利用CT图像诊断技术获得了侵彻深度和残余弹长随撞击速度的变化规律,对超高速撞击过程进行了数值模拟,结合数值模拟结果进一步分析了超高速撞击物理过程。结果表明:(1)超高速撞击条件下成坑是弹坑+弹洞型;(2)侵深-速度曲线呈现先增大后减小的现象,在弹速2.6 km/s附近存在侵彻深度极大值,约为8.5倍弹长,相对于中低速侵彻的深度并没有显著优势。(3)通过基于数值模拟得到的弹靶界面压力时程曲线将侵彻过程分为4个阶段,其中准定常侵彻阶段和第三侵彻阶段是决定总侵深的主要阶段。(4)随撞击速度增加,弹体侵蚀逐渐剧烈,此时准定常侵彻阶段的侵深变化不大,而第三侵彻阶段中的刚体侵彻部分大幅降低,导致总侵深大幅降低,使总侵深曲线呈现先增大后减小的现象。     

平衡炮实验弹丸膛内过载计算模型及应用

 针对平衡炮的具体结构特点,为了精确计算弹丸膛内过载变化过程,利用经典内弹道法对某口径的平衡炮进行了仿真计算,得出了内弹道诸元随时间的变化曲线,再根据膛压与过载的关系,推导出了过载随时间变化的曲线图,理论计算与实验结果相吻合,该计算方法可为此类火炮的内弹道参数评估和弹丸设计提供依据。     

8 mm二次谐波回旋速调管放大器双阳极磁控注入电子枪的设计

 计算了8 mm二次谐波回旋速调管双阳极电子枪的设计参数，根据这些参数，采用EGUN软件进行模拟和优化，设计出了一只双阳极磁控注入电子枪，该枪的电子束纵横速度比为1.45，速度零散为5.4%，并讨论了电极形状、磁场分布、电流、控制极电压和第二阳极电压对电子注性能的影响，结果发现电子注对这些影响因子非常敏感，设计中应对它们进行充分优化。     

用于短波长FEL的光阴极微波电子枪设计研究

高增益、短波长自由电子激光器需要发射度低、峰值电流高的短脉冲电子束流.采用发射度补偿技术,设计了一台S波段、一个半腔体的光阴极微波电子枪以用于建议中的SDUV-FEL装置.POISSON,SUPERFISH和PARMELA程序的计算表明:当微脉冲电量为2nC时,这种设计能产生ε_n,rms=2.3π·mm·mrad、E_k=4.8MeV的电子束流.报道了该枪的设计考虑和模拟结果.     

低反轰热阴极微波电子枪初步实验

 简述了紧凑型自由电子激光太赫兹源研制的系统设计方案,介绍了具有两路微波馈入的热阴极微波电子枪的研制与测试情况,利用束流传感器测试了束流强度,并利用CCD相机测试了束斑大小,给出了微波电子枪通过初步热测实验得到的结果。测得微波电子枪出口处束流强度超过500 mA,束斑约3 mm,采用双屏法测量束流发射度,得到归一化发射度约为13.5 π·mm·mrad,测试指标与理论设计值吻合较好。     

Bunch length measurement at Tsinghua Thomson scattering X-ray source

The length of electron beam from a photocathode RF gun is determined by a spectrometer, according to the relative energy spread induced by the bunch length during the acceleration in a linac. For a photocathode RF gun, different laser injected phase and beam charge are studied. The compression is changed for the different laser phases, as from 10° to 30°, and the bunch length is lengthened due to the strong longitudinal space charge force, caused by the increased charge.     

Emittance measurement & optimization for the photocathode RF gun with laser profile shaping

The Laser Undulator Compact X-ray source(LUCX) is a test bench for a compact high brightness X-ray generator,based on inverse Compton Scattering at KEK,which requires high intensity multi-bunch trains with low transverse emittance.A photocathode RF gun with emittance compensation solenoid is used as an electron source.Much endeavor has been made to increase the beam intensity in the multi-bunch trains.The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects,so that the field gradient on the cathode surface is relatively higher when the forward RF power into gun cavity is not high enough.A laser profile shaper is employed to convert the driving laser profile from Gaussian into uniform.In this research we seek to find the optimized operational conditions for the decrease of the transverse emittance.With the uniform driving laser and the unbalanced RF gun,the RMS transverse emittance of a 1 nC bunch has been improved effectively from 5.46 πmm.mrad to 3.66 πmm.mrad.