Soft X-ray point source based on a gas pinch

JETP Letters - The results of a study of a radiating Z-pinch with a profiled initial gas-density distribution over the z axis are presented. The gas distribution with the density maximum and...     

Hard X-ray source based on low-impedance rod pinch diode

The results of experiments on the formation of a low-impedance diode in a rod pinch diode configuration preliminarily short-circuited by a radial foil have been described. The low-impedance diode is formed as a result of detachment of the foil (accelerated by the current of a high-current generator) from the anode rod. It has been shown that, by changing the shape of the anode tip, the thickness of the aluminum foil, and its position relative to the anode tip as by reconnecting the current via the foil and rod plasma, it is possible to obtain from one to several sequential hard X-ray pulses.     

感应电压叠加器驱动阳极杆箍缩二极管型脉冲X射线源

介绍了自行研制的用于闪光照相且基于感应电压叠加器和阳极杆箍缩二极管的X射线源的组成、结构和主要参数。输出电压3 MV的Marx发生器给阻抗7.8 Ω水介质脉冲形成线充电,产生脉宽约70 ns,电压约1 MV的高功率脉冲,经过峰化开关和预脉冲开关后分成3路馈入三级感应电压叠加器感应腔进行电压叠加,感应电压叠加器次级采用真空绝缘传输线,阻抗从40 Ω变成60 Ω,驱动阳极杆箍缩二极管,二极管阴极为石墨,阳极为直径1.2 mm的钨杆,石墨阴极产生的电子束在电流自磁场作用下发生箍缩,轰击阳极,产生小焦斑脉冲Ｘ射线。该装置在Marx充电电压为±35 kV时,二极管电压约2.0 MV,二极管电流约为50 kA,半高宽约80 ns;X射线半高宽约为40 ns,剂量约为28 mGy,焦斑约为0.95 mm。利用该X射线源拍摄到了炸药爆炸产生的层裂碎片不同飞行时间的图像。     

感应电压叠加器驱动阳极杆箍缩二极管型脉冲X射线源

 介绍了自行研制的用于闪光照相且基于感应电压叠加器和阳极杆箍缩二极管的X射线源的组成、结构和主要参数。输出电压3 MV的Marx发生器给阻抗7.8 Ω水介质脉冲形成线充电,产生脉宽约70 ns,电压约1 MV的高功率脉冲,经过峰化开关和预脉冲开关后分成3路馈入三级感应电压叠加器感应腔进行电压叠加,感应电压叠加器次级采用真空绝缘传输线,阻抗从40 Ω变成60 Ω,驱动阳极杆箍缩二极管,二极管阴极为石墨,阳极为直径1.2 mm的钨杆,石墨阴极产生的电子束在电流自磁场作用下发生箍缩,轰击阳极,产生小焦斑脉冲Ｘ射线。该装置在Marx充电电压为±35 kV时,二极管电压约2.0 MV,二极管电流约为50 kA,半高宽约80 ns;X射线半高宽约为40 ns,剂量约为28 mGy,焦斑约为0.95 mm。利用该X射线源拍摄到了炸药爆炸产生的层裂碎片不同飞行时间的图像。     

基于传热窄点分析的跨临界CO2系统稳态性能研究

基于传热窄点研究了固定气体冷却器进出口水温时,高低不同的进水温度、不同的出水温度、排气压力、蒸发温度、过热度以及换热面积对于系统性能的影响。结果表明:随着进出口水温的升高和换热面积的减小,系统COP逐渐减小,并且最优高压压力逐渐升高;随着蒸发温度的升高,系统COP逐渐增加,最优高压压力逐渐升高;增加过热度只会在排气压力较低时提高系统的COP。当处于部分负荷工况时,冷端温差随负荷率的增加而减小;对于气冷器进出口水温温差大的工况,当负荷率小于1时传热窄点会位于换热器中间位置。在负荷率到达1时,传热窄点恰好移动到冷端。当负荷率大于1时,传热窄点一直稳定在冷端;对于气冷器进出口水温温差小的工况,当负荷率小于1时,传热窄点就已经到达冷端,并随着负荷率的增大一直稳定在冷端;部分负荷下的COP总是小于设计负荷下的COP,实际负荷偏离设计负荷越远,系统的COP越小。     

基于虚拟点探测器的虚拟点源效率刻度技术

主要针对尺寸为ϕ75 mm×25 mm的²⁴¹Am标准体源HPGe探测器探测效率展开研究,通过LabSOCS软件模拟及蒙卡计算研究发现,使用同一种结构类型的探测器测量特定形状的体源,其虚拟点探测器位置与虚拟点源位置满足线性、二次函数、指数等关系。针对确定的探测器,通过点源在对称轴线上不同高度位置实验就可以标定出虚拟点探测器位置,再结合它们的线性函数进一步计算出虚拟点源位置,最后将点源放置于虚拟点位置刻度即可得到体源的探测效率。因此,该技术方法首次提出通过虚拟点探测器位置找到了虚拟点源的位置,是一种全新的刻度方法,已达到实际应用的程度,可以大面积推广应用该技术成果。     

氢气放电源和X光机X射线源打靶谱的研究

用氢气放电源打靶的方法,测到了系列的谱线.为了鉴别这些谱线,进行了X光机X射线源打靶实验和两种源打靶的对比实验.实验结果表明:在X光机X射线源打靶谱中,除靶材料的特征X射线和两条源谱线外,还存在两种谱线:一种是能量变化的谱线,根据不同衍射角θ和测量角φ的实验结果,及打多晶体靶和非晶体靶的实验事实,表明这种能量变化的谱线是衍射线;另一种是能量恒定不变的谱线.氢气放电源和X光机X射线源打靶谱的对比实验结果表明:两种源打靶谱自洽.这说明和X光机X射线源打靶谱一样,氢气放电源打靶谱中那些能量变化的谱线是衍射线.但     

Strong temperature effect on X-ray photo-etching of polytetrafluoroethylene using a 10 Hz laser-plasma radiation source based on a gas puff target

The first results of experiments on direct photo-etching of heated PTFE using a 10 Hz X-ray source based on a laser-irradiated gas puff target are presented. X-ray radiation in the wavelength range from 6 to 20 nm was produced as a result of irradiation of a double-stream gas puff target with Nd:YAG laser pulses of energy 0.8 J and time duration 3 ns. The resulting X-ray pulses with energy of about 100–200 mJ were used to irradiate samples of PTFE to create microstructures by direct photo-etching. Strong enhancement of the photo-etching process was observed for samples heated up to 300 °C. PACS 52.38.Ph; 81.65.Cf; 61.82.Pv     

Efficient high-repetition-rate fs-laser based X-ray source

The generation of [_Fe]K line radiation has been studied on a compact, ultrashort, laser based hard X-ray source, particularly suited for high-repetition-rate laser systems (1 to >10 kHz). Sub-millijoule, 25 fs Ti:sapphire laser pulses are applied to generate hard X-ray radiation on a commercially available ferric audio cassette tape target. Spectroscopic investigations reveal strong iron K emission in addition to a weak bremsstrahlung continuum. Under single exposure and single pulse conditions the X-ray yield is low. Energy conversion efficiencies of about _K=2×10^-7 are observed. Prepulse and multiple shot exposure techniques, both successfully used with high energy/low repetition rate systems, are investigated for these low energy/high repetition rate conditions. Depending on the applied pulse energy and intensity, the X-ray yield can be enhanced by more than three orders of magnitude. Photon fluxes exceeding 2×10⁹Kphotons/s are generated with the presented tape target yielding conversion efficiencies of nearly _K=10^-5. PACS 42.65.-k; 52.38.Ph; 52.50.Jm     

X-ray source based on a compact electron linear accelerator with a thin anode

An experiment confirming the possibility of extracting a narrow energy band from a wide spectrum produced by a compact electron linear accelerator with a thin transmission anode is described. A flat crystal of pyrolytic graphite was used as a monochromator.     

基于X光微点源的半影成像技术

基于X光微点源装置,从实验角度验证了半影成像的原理。利用针孔成像,直接测量了微点源源区图像;给出了半影孔成像、半影锥成像和环孔成像原理,以及在微点源的半影成像结果和维纳滤波重建结果。从实验结果可知:半影锥成像具有与半影孔成像相同的诊断能力,两种方法的重建图像尺寸与源尺寸一致;环孔成像的诊断能力更好,重建图像的尺寸和形状更接近源图像。     

基于X光微点源的半影成像技术

基于X光微点源装置,从实验角度验证了半影成像的原理。利用针孔成像,直接测量了微点源源区图像;给出了半影孔成像、半影锥成像和环孔成像原理,以及在微点源的半影成像结果和维纳滤波重建结果。从实验结果可知：半影锥成像具有与半影孔成像相同的诊断能力,两种方法的重建图像尺寸与源尺寸一致;环孔成像的诊断能力更好,重建图像的尺寸和形状更接近源图像。     

高对比度飞秒激光与固体薄膜相互作用硬X射线源的研究

文章作者使用60 fs倍频高对比度激光脉冲聚焦到Cu膜上,发现与基频激光脉冲相比,从激光到KαX射线的能量转化效率(ηk)明显增强.ηk对激光脉冲非线性啁啾上升沿呈现出很强的依赖性,它在激光为100fs负啁啾脉冲时达到最大值.实验表明对超热电子有效的加热导致了ηk的增强.这说明由于能够驱动真空加热机制来增强超热电子的产生,高对比度激光已成为优化ηk的有效工具.这些结果发表在Phys.Rev.Lett.,2008,100:045004上.     

高对比度飞秒激光与固体薄膜相互作用硬X射线源的研究

文章作者使用60 fs倍频高对比度激光脉冲聚焦到Cu膜上,发现与基频激光脉冲相比,从激光到KαX射线的能量转化效率(ηk)明显增强.ηk 对激光脉冲非线性啁啾上升沿呈现出很强的依赖性,它在激光为100fs负啁啾脉冲时达到最大值.实验表明对超热电子有效的加热导致了ηk的增强.这说明由于能够驱动真空加热机制来增强超热电子的产生,高对比度激光已成为优化ηk的有效工具.这些结果发表在 Phys. Rev. Lett.,2008,100: 045004上.     

初始充气密度对毛细管放电泵浦的软X射线激光的影响

 利用哈尔滨工业大学的毛细管放电装置的放电参数，对放电过程中毛细管内初始氩气密度的变化对等离子体状态和类氖氩离子3p-3s跃迁线的增益系统的影响进行了全过程的理论模拟计算。给出了毛细管放电中等离子体状态和增益系数的空间分布的时间演变过程。理论计算表明能够出现增益的密度范围比较宽，这对于实验是有利的。现有放电参数下，选取初始氩气密度在气压为40~80 Pa情况对获取好的实现结果是比较理想的。     

基于空间应用的透射式微型微束调制X射线源

针对空间应用对X射线源的需求, 提出了一种透射式微型微束调制X射线源的设计方案, 建立了调制X射线源的理论模型. 相较传统的X射线源, 增加了栅极电压控制和多个聚焦极微束聚焦功能, 通过改变栅极电压实现X射线的幅度调制和脉冲调制. 利用带电粒子光学仿真软件SIMION, 模拟计算了不同管电压下透射式阳极靶的最佳靶厚, 仿真分析了不同栅极电压对电子束运动轨迹的影响, 最终得到了150 μm的微束焦斑直径. 完成了原理样机的加工镀膜和真空密封, 搭建了调制X射线源的测试装置, 实验报道了阳极钨靶的谱线特性, 分析了栅极电压影响出射X射线强度的原因, 讨论了栅极幅度调制的可能性, 完成了调制X射线源栅极脉冲调制的验证.     

Scalar radiation from a point source

We consider a classical scalar field, obeying the inhomogeneous Klein-Gordon equation, in the case of a single point source. We propose a definition for the radiated energy-momentum and give an expression for it in terms of the prescribed world line of the source where we assume that the acceleration vanishes outside a finite interval. We find that only the part of the world line with non-vanishing acceleration contributes to the radiation, which travels at all speeds less than but not equal to the speed of light. We briefly discuss the case with more than one point source.     

一台基于串级二极管技术的高强度脉冲硬X射线源

介绍了利用串级二极管产生高强度脉冲硬X射线的方法及其辐射场参数。以“闪光二号”加速器为平台,通过适应性改造,产生快前沿电压脉冲;研制了两级阻抗1 Ω串级二极管,通过串联分压降低二极管端电压、各级二极管电子束独立打靶在空间叠加形成高强度均匀辐射场。解决了悬浮电极绝缘支撑、二极管阴极均匀发射等技术难题,实现了串级二极管的稳定工作。在总电压约700 kV、电流约310 kA条件下,X射线平均能量87 keV,500 cm²上的平均能注量36 mJ/cm²,剂量均匀性（最大值比最小值）达到2∶1。     

XBIC using a laboratory X-ray source

Results from using the current method, in which a current is induced by a focused X-ray beam (XBIC = X-ray beam induced current) on a laboratory source are presented. It is shown that by reducing the X-ray probe sizes and improving the resolution, there is a gain in contrast increase for obtained images of grain boundaries in a crystal.