拉曼自由电子激光器

文章介绍了拉曼自由电子激光器的应用，概述了我们在拉曼自由电子激光器调谐、新型小周期波荡器、具有分布反馈谐振腔的拉曼自由电子激光振荡器和虚火花放电等方面的研究进展。     

超强自由电子激光器

德国汉堡ＤＥＳＹ (ＤｅｕｔｓｃｈｅｓＥｌｅｋｔｒｏｎｅｎ -Ｓｙｃｈｒｏ ｔｒｏｎ)研究中心的科学家们获得了一种比任何其他激光都要强得多的紫外激光 .该结果证实了“自由电子激光可以将光放大数千万倍”的预言 .由于这种紫外光所具有的特殊性质 ,它是目前一种最强大的研究工具 ,这也意味着朝超强Ｘ射线激光迈出了重要的一步 .超强Ｘ射线激光在物理、化学、生物和医学中都有着广泛的应用前景 ,这对于材料微区结构、微区化学组分与微区物性间的关系的研究 ,也是一大福音 .传统的激光是由电子在原子或分子中确定的能级间跃迁产生光发射实…     

About works on research of stationary and non-stationary waves of burning in the hydrogen-oxygen mix on the Novosibirsk Free Electron Laser

This work presents schemes, techniques of experiments and the first results on registration of burning front of hydrogen-oxygen mixture with the use of terahertz radiation. The problems of choice of absorption lines, on which registration is carried out, are discussed. The investigation of distribution of absorption at wavelength of 166.81 microns over the cross-section of stationary hydrogen-oxygen flame above the burner is carried out. In the dynamic experiment, the diagrams of flame propagating along the pipe obtained with both pyrodetector and Shottky detectors were compared.     

喇曼自由电子激光振荡器

本文报道喇曼自由电子激光振荡器的研究结果。脉冲加速器电子束能量０．４ＭｅＶ，束流８００Ａ。采用满足布喇格条件的分布反馈谐振腔，取代传统的激光器反射镜。理论上进行了分析和设计，采用正弦形波结构选择振荡模式。喇曼自由电子激光振荡器实验表明，输出光谱显著变窄。频率分布半高宽度，超辐射下范围为７．５ｍｍ～９．２ｍｍ，分布腔下范围为８．６ｍｍ～８．９ｍｍ。     

Phytoremediation of Lead in Soil: Recent Applications and Future Prospects

Abstract

Lead is a very serious contaminant in soil because of its widespread previous application in residential, agricultural, and industrial environments combined with its severe impacts upon human health, particularly upon children. Phytoremediation is a nontraditional approach to remediate contaminated soil involving the use of green plants. Phytostabilization involves the use of plants to stabilize contaminants to reduce human exposure. Phytoextraction involves the use of plants to accumulate contaminants in aboveground shoots, which can be harvested to recycle or discard. Recent phytomediation work has indicated the importance of determining the chemical forms of lead present at a site to develop the most appropriate remediation strategy. Lead phytoextraction typically involves the addition of a chelating agent in order to increase the bioavailability of this contaminant. Because concerns have been raised regarding the persistence of chelating agents in the environment, several research teams have investigated the use biodegradable compounds for this application. It is anticipated that phytoremediation will continue to be a low-cost approach for the remediation of lead in soil.     

Ultrafast Dynamics Using Free Electron Laser Sources

As avid readers of SRN know, free electron lasers have recently emerged as important synchrotron-radiation-based tools for a broad range of scientific studies. The combination of their short wavelength (from VUV to hard X-ray) with their exceedingly brief pulses (down to a few femtoseconds), high pulse energy, and coherence makes them particularly useful tools for studying ultrafast dynamics with chemical specificity and atomic-scale structural sensitivity.     

求解自由电子激光场的微扰方法

借助于固体理论中的ＬＬＰ变换研究自由电子激光场的光子统计性质，并发展了一种微扰方法予以求解。     

Relativistic Cloud-In-Cell Simulation of Free Electron Laser

We have developed one-and a half-dimensional (one space dimension and two velocity components) relativistic electromagnetic cloud-in-cell simulation (CIC-R) code which is suitable for simulating the free-electron laser process. Using CIC-R we have simulated the temporal evolution of the free-electron laser, and obtained the results on the linear growth rates of the unstable spectrum and the dispersion relation of the coupling between the electromagnetic waves and electrostatic waves which agree with the theory. Other results such as the time development of the electron distribution function, nonlinear saturation and the efficiency of energy conversion are also presented in detail.     

台式拉曼自由电子激光器建议

提出台式拉曼自由电子激光器的建议，新型台式拉曼自由电子激光器由马克斯发生器、虚火花放电电子束源和小周期波荡器等部分组成。外形尺寸将为传统的拉曼自由电子激光器的１／４至１／５。     

北京自由电子激光Wiggler中电子轨迹偏离的改进

提出了一种从实验上确定用于北京自由电子激光（ＢＦＥＬ）装置的Ｗｉｇｇｌｅｒ中ＮｄＦｅＢ矩形磁块的轨迹敏感系数β的方法．用β值来表征磁单块在Ｗｉｇｇｌｅｒ中对电子轨迹的贡献，并用此β值对磁块进行挑选，优化组合，可达到改进Ｗｉｇｇｌｅｒ对电子轨迹偏离的目的．     

The Rippled-Field Magnetron (Cross-Field Free Electron Laser)

Millimeter-wave emission from the rippled-field magnetron (cross-field free electron laser (FEL)) is investigated experimentally and theoretically. In this device, electrons move in quasi-circular orbits under the combined action of a radial electric field, a uniform axial magnetic field, and a radial azimuthally periodic wiggler magnetic field. In excess of 300 kW of RF power is observed in two narrow spectral lines whose frequency can be tuned continuously from ~25 to ~50 GHz by variation of the axial magnetic field. The observations are interpreted as a FEL type of instability, associated with a resonance in the particle motion of a layer of electrons embedded in the dense spacecharge cloud. The resonance is shown to occur when 2kw?0 ? (?>0/?0) ?1 -(?p/?0)2, where kw is the wiggler wavenumber, ?0 is the azimuthal electron velocity, ?0 is the relativistic cyclotron frequency in the axial magnetic field, wp is the relativistic plasma frequency, and ?0 = [1 - (?0/c)2]-1/2 of the resonant electron layer.     

康普顿型谐波自由电子激光器的增益与饱和特性

本文用微扰方法计算了电子分布函数，得到了康普顿型谐波自由电子激光器小信号增益及饱和增益的公式，最后对模型及结果进行了分析与讨论。     

FTIR法研究自由电子激光作用下邻氨基苯甲酸类分子的结构变化

自由电子激光（FEL）可以输出中红外激光（波长6-16μm，波数1660-630cm^-1），由于FEL提供的能量与分子的振动能级相当，所以可用于探讨与物质相互作用时的能量转换机理；其次FEL的波长在一定范围内能够连续调节，可以用来研究化学键的变化，即FEL诱导的分子结构变化，基于红外和拉曼光谱是分子结构变化的灵敏探针，我们比较了FEL照射前后苯甲酸及邻氨基苯甲酸的FTIR变化，发现N-H和C=O的伸缩振动峰经FEL照射后发生了位移，表明FEL诱导有机分子引发COOH和NH2之间氢键的重排，初步认为这是由于分子中存在稳态和亚稳态结构，进一步的解释将涉及到多光子传递以及非线性光学。     

远红外自由电子激光太赫兹光源研究

基于射频电子直线加速器的可调谐相干太赫兹(THZ)光源实现了出光，该光源为远红外自由电子激光，具有辐射波长可设计并可以实现大范围调谐特性．利用光栅谱仪测量了受激辐射谱，中心波长为115μm，谱宽约为1％．     

Proposal for Efficiency Enhancement of a Far Infrared Free Electron Laser

ＰｒｏｐｏｓａｌｆｏｒＥｆｆｉｃｉｅｎｃｙＥｎｈａｎｃｅｍｅｎｔｏｆａＦａｒＩｎｆｒａｒｅｄＦｒｅｅＥｌｅｃｔｒｏｎＬａｓｅｒ￥ＨＵＳｕｘｉｎｇ；ＦＵＥｎｓｈｅｎｇ；ＸＵＺｈｉｚｈａｎ（ＳｈａｎｇｈａｉＩｎｓｔｉｕｔｅｏｆＯｐｔｉｃｓａｎｄＦｉｎｅＭ...     

Effects of Background Plasma on Free Electron Laser with Planar Wiggler

Dispersion equation of planar-wiggler free-electron laser with background plasma is derived using linear fluid theory. The characteristic of this plasma FEL is analyzed in detail. It is shown that reasonable background plasma density tends to improve FEL growth rate. We also find there exits a critical plasma density for FEL operating. When the background plasma density is higher than critical density, the FEL can no longer be excited.