共查询到19条相似文献,搜索用时 93 毫秒
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考虑电子束自身场情况下,给出了反向导引磁场自由电子激光中平衡态电子运动的一种正则描述。证明了在可积极限下,不动点附近相轨道的稳定性;并采用美国麻省理工学院的反向导引场自由电子激光实验参数,计算了不同束流强度下的Poincaré截面。结果表明,即使自身场相当强(束流强度达到6000A),平衡态电子的相轨道仍保持其规则性,相空间没有出现混沌,这说明在自由电子激光器中,利用反向导引磁场可以获得比传统的采用正向导引磁场更好的电子束质量,从而改善器件的输出性能。
关键词: 相似文献
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拉曼型自由电子激光器作为一种兆瓦级高功率毫米波、太赫兹波辐射源, 其电子的运动稳定性对整体器件的性能至关重要.本文采用科尔莫戈罗夫熵方法, 以典型的麻省理工学院公布的实验数据为例, 比较研究拉曼型正向导引磁场和反向导引磁场两类自由电子激光器中相对论电子的运动稳定性. 结果表明:摇摆器绝热压缩磁场对电子运动的稳定性无实质性影响, 但对电子运动影响大; 电子束自身场在拉曼型正向导引磁场自由电子激光器中使电子运动稳定性变差, 而在拉曼型反向导引磁场自由电子激光器中则可改善电子运动稳定性.
关键词:
拉曼型自由电子激光器
相对论电子运动稳定性
科尔莫戈罗夫熵
电子束自身场 相似文献
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通过对层流平衡相对论电子的运动微分方程组进行数值求解,得到正则角动量在pθ=0,pθ=const.和pθ∝r2三种情况下,束流的传输特性.针对pθ=0的相对论实心电子束,利用数值求解得到了与解析方法一致的结果,从而验证了数值方法的合理性;针对无法用解析方法求解的pθ=0环行电子束、pθ=const.和pθ∝r2的情况,利用数值方法得到了束流和空间极限电流关于波导、电子束结构和二极管电压等参数的变化规律及对轴向导引磁场的要求.计算结果表明:当相对论电子束以层流平衡态传输时,环行束较实心束具有更高的空间极限电流和更低的轴向导引磁场,且当阴极发射面与导引磁场的磁场线垂直时,维持电子束层流平衡所需的轴向导引磁场最低;电子束在有限磁场导引下以层流平衡态传输时,空间极限电流明显大于无限大磁场导引下一维近似的情况.利用数值方法对层流平衡相对论电子束进行理论研究,更全面地揭示了电子束在正则角动量满足不同条件时的束流特性,为设计新型结构的高功率微波器件提供理论参考. 相似文献
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计算了广义球对称含荷黑洞视界上标量场的量子态数和自由能,得到了黑洞熵与视界面积成 正比的结论,表明黑洞熵就是其视界上的量子态的熵.考虑广义不确定原理对黑洞熵的影响 ,采用二维膜模型,克服了brick-wall模型中的发散困难,计算中无须任何截断,且brick- wall模型中的小质量近似也可以避免.对视界外二维膜上的量子场的熵做了级数展开讨论, 得到了一些值得探讨的结论.
关键词:
广义不确定原理
黑洞熵
视界
截断 相似文献
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利用改进后的薄膜brick-wall模型,计算了动态广义球对称含荷黑洞Dirac场的熵.按薄层模型的观点,在视界附近薄场上的熵就是黑洞的熵.计算结果表明所得到的黑洞熵与其视界面积成正比.
关键词:
黑洞
薄膜brick-wall模型
熵
Dirac场 相似文献
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利用薄层(改进的brick-wall模型),通过分别求解标量场方程和Dirac场方程,计算了环面黑洞事件视界附近的标量场和Dirac场的量子统计熵.按薄层模型的观点,在视界面附近薄层上的量子场的熵就是黑洞的熵.结果表明,黑洞熵正比于事件视界的面积,遵循Beken-stein-Hawking面积熵公式.
关键词:
熵
环面黑洞
薄层模型
量子场 相似文献
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Zheng-Biao Ouyang Shi-Chang Zhang Jian-Bo Jin Chun-Rong Qui Hui-Bo Zhang Li Hu Xiao-Ping Liang 《International Journal of Infrared and Millimeter Waves》2003,24(4):585-591
The free-electron laser (FEL) based on the self-amplified spontaneous emission (SASE) is an effective candidate of the coherent optical sources at wavelengths in ultraviolet and x-rays. It requires a relativistic electron beam with extremely high quality and extremely stable transmission. In this paper we analyze the dynamic behavior of the relativistic electron in that device by calculating the entropy-like quantity. Results show that if there is no adiabatic field of the wiggler, the electron beam may have great fluctuation in velocity space and diverge in configuration space. 相似文献
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Jacobi fields on statistical manifolds of negative curvature 总被引:3,自引:0,他引:3
Two entropic dynamical models are considered. The geometric structure of the statistical manifolds underlying these models is studied. It is found that in both cases, the resulting metric manifolds are negatively curved. Moreover, the geodesics on each manifold are described by hyperbolic trajectories. A detailed analysis based on the Jacobi equation for geodesic spread is used to show that the hyperbolicity of the manifolds leads to chaotic exponential instability. A comparison between the two models leads to a relation among statistical curvature, stability of geodesics and relative entropy-like quantities. Finally, the Jacobi vector field intensity and the entropy-like quantity are suggested as possible indicators of chaoticity in the ED models due to their similarity to the conventional chaos indicators based on the Riemannian geometric approach and the Zurek-Paz criterion of linear entropy growth, respectively. 相似文献
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We extend a generalized integral fluctuation relation in diffusion processes that we obtained previously to the situation with feedback control. The general relation not only covers existing results but also predicts other unnoticed fluctuation relations. In addition, we find that its explanation of time-reversal automatically emerges in the derivation. This interesting observation leads into an alternative inequality about the entropy-like quantity with an improved lower bound. Two feedback-controlled Brownian models are used to verify the result. 相似文献
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A. Goepfert F. Lison R. Schütze R. Wynands D. Haubrich D. Meschede 《Applied physics. B, Lasers and optics》1999,69(3):217-222
We have studied guidance and deflection of a beam of cesium atoms by a strong toroidal magnetic quadrupole field. The beam
guide is made from permanent magnets sustaining a radial field gradient of 2.8 T/cm. Atoms with moderate longitudinal velocities
ranging from 30 m/s to 70 m/s were inserted across the 10-mm-diameter aperture of a 24.5° arc with radius 300 mm. We have
measured transmission and beam divergence and find good agreement with ray-tracing calculations and analytical estimates.
The magnetic beam guide allows for 100% transmission of heavy atoms over large angles.
Received: 9 November 1998 / Revised version: 6 April 1999 / Published online: 30 July 1999 相似文献
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阐述了对国际上正在发展的高能激光系统核心特征量的理解。分析了影响这个核心特征量的若干要素:主激光器选择变化的历史轨迹及其原因;光束质量是高能激光系统的生命线,做好光束质量是一个多环节的科学工程;分析了这一技术链条上游、中游和下游的技术难点以及与其都有关系的全系统的稳定性问题。最后,把这些要素结合起来,可将核心特征量综合表达为目标上的激光亮度。 相似文献
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Adam Balkcum Richard Ellis Derek Boyd Samar Guharay 《International Journal of Infrared and Millimeter Waves》1992,13(9):1321-1340
Linearly polarized fundamental mode Gaussian beams were generated and coupled to a hollow circular oversized dielectric waveguide by placing the waist of the beam at the guide entrance. The transmission properties of the waveguide were characterized as a function of frequency for a variety of coupling conditions. These conditions included changes in the input beam waist radius, angle of incidence, and displacement perpendicular and parallel to the guide axis. It has been found that: 1.) power transmission is maximized when the waist of the input beam is centered at the guide input, injected normally, and has a radius of 0.43 times the waveguide radius, 2.) power transmission decreases rapidly with increasing angle of incidence and the rate of that loss increases with frequency, 3.) the waveguide preserves the linear polarization of the input beam, 4.) power transmission in the fundamental waveguide mode is not greatly affected by moderate displacements in the input beam position, and 5.) upon exit from the waveguide the launched EH11 mode propagates as a fundamental mode Gaussian beam in the quasi-far field. The results compare favorably to the transmission theory of Belland and Crenn and approximately to the near and far field mode pattern theory of Degnan. 相似文献
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给出了强流相对论电子束在磁透镜场中压缩传输系数的理论公式和计算结果,其结果说明能量传输效率随磁透镜比的增大而减小,随阴极处磁感应强度的增大而增大,对于一个特定的系统存在一个能通量密度的极限值。 相似文献