Self-amplified spontaneous emission FEL with energy-chirped electron beam and its application for generation of attosecond x-ray pulses
Self-amplified spontaneous emission FEL with energy-chirped electron beam and its application for generation of attosecond x-ray pulses
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DOI：
10.1103/physrevstab.9.050702
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发表时间：
2006-05-01
影响因子：
--
通讯作者：
Yurkov, M. V.
中科院分区：
文献类型：
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作者：
Saldin, E. L.;Schneidmiller, E. A.;Yurkov, M. V.
用一维模型解析和数值研究了电子束中的线性能量啁啾对自放大自发辐射(SASE)自由电子激光器(FEL)运转的影响。分析结果是基于Krinsky和Huang[Phys.圣·阿克塞尔牧师。梁6,050702(2003年)]。在小能量和大能量啁啾参数的限制下，得到了高增益线性范围内SASE自由电子激光器的格林函数和输出功率的显式表达式。数值计算了饱和长度和功率-能量啁啾参数。结果表明，线性能量啁啾对自由电子激光增益的影响等同于线性波荡器的锥化(或沿波动器的线性能量变化)。这一事实的结果是有可能通过与能量线性调频参数值无关的波荡器锥化来完美地补偿由能量线性调频引起的自由电子激光增益劣化。提出了这种效应在硬X射线自由电子激光器产生阿秒脉冲中的应用。通过放置在主波动器前面的短波动器中的几个周期的光激光脉冲，在电子束的短片内产生强烈的能量调制。该片内的增益降级通过适当的波动器锥度来补偿，而束的其余部分则受到该锥度的影响，并且不会激光。三维模拟预测，在Angstrom波长范围内，可以产生高对比度的短(200阿秒)高功率(高达100GW)脉冲。讨论了将脉冲宽度减小到100阿秒以下的可能性。
Influence of a linear energy chirp in the electron beam on a self-amplified spontaneous emission (SASE) Free Electron Laser (FEL) operation is studied analytically and numerically using a 1D model. Analytical results are based on the theoretical background developed by Krinsky and Huang [Phys. Rev. ST Accel. Beams 6, 050702 (2003)]. Explicit expressions for Green's functions and for output power of a SASE FEL are obtained for the high-gain linear regime in the limits of small and large energy chirp parameters. Saturation length and power versus energy chirp parameter are calculated numerically. It is shown that the effect of linear energy chirp on FEL gain is equivalent to the linear undulator tapering ( or linear energy variation along the undulator). A consequence of this fact is a possibility to perfectly compensate FEL gain degradation, caused by the energy chirp, by means of the undulator tapering independently of the value of the energy chirp parameter. An application of this effect for generation of attosecond pulses from a hard x-ray FEL is proposed. Strong energy modulation within a short slice of an electron bunch is produced by a few-cycle optical laser pulse in a short undulator, placed in front of the main undulator. Gain degradation within this slice is compensated by an appropriate undulator taper while the rest of the bunch suffers from this taper and does not lase. Three-dimensional simulations predict that short (200 attoseconds) high-power (up to 100 GW) pulses can be produced in Angstrom wavelength range with a high degree of contrast. A possibility to reduce pulse duration to sub-100 attosecond scale is discussed.