An application of laser-plasma acceleration: towards a free-electron laser amplification
An application of laser-plasma acceleration: towards a free-electron laser amplification
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DOI：
10.1088/0741-3335/58/3/034020
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发表时间：
2016-03-01
影响因子：
2.2
通讯作者：
Loulergue, A.
中科院分区：
文献类型：
--
作者：
Couprie, M. E.;Labat, M.;Loulergue, A.
激光等离子体加速器（LPA）目前提供具有几kA的典型电流、几fs的聚束长度、几百MeV到几GeV范围内的能量、典型地1 mrad的发散度、1%量级的能量扩展和π mm mrad量级的归一化发射度的电子束。第一批应用之一可能是使用这些光束产生辐射：已经观察到波荡器发射，但相当大的能量扩展（1%）和发散（1 mrad）阻止了直接的自由电子激光（FEL）放大。然后需要通过传输到波荡器的适当的束操纵。这里提出的关键概念依赖于朝向波荡器的传输中的创新电子束纵向和横向操纵：一个“分层”弯道根据电子的能量对电子进行分类，并将扩散从1%减少到千分之几的一部分，并且有效横向尺寸沿着波荡器沿着保持恒定通过电子束聚焦与光波的行进的适当同步来实现（超匹配）。目前正在准备一个演示用LPA进行自由电子激光放大的试验实验。电子束传输遵循不同的步骤，其中具有可变强度的永磁四极的强聚焦、具有常规偶极的分层弯道以及用于在波荡器中进一步聚焦的第二组四极。介绍了自由电子激光的模拟和实验准备的进展情况。
The laser-plasma accelerator (LPA) presently provides electron beams with a typical current of a few kA, a bunch length of a few fs, energy in the few hundred MeV to several GeV range, a divergence of typically 1 mrad, an energy spread of the order of 1%, and a normalized emittance of the order of pi.mm. mrad. One of the first applications could be to use these beams for the production of radiation: undulator emission has been observed but the rather large energy spread (1%) and divergence (1 mrad) prevent straightforward free-electron laser (FEL) amplification. An adequate beam manipulation through the transport to the undulator is then required. The key concept proposed here relies on an innovative electron beam longitudinal and transverse manipulation in the transport towards an undulator: a 'demixing' chicane sorts the electrons according to their energy and reduces the spread from 1% to one slice of a few parts per thousand and the effective transverse size is maintained constant along the undulator (supermatching) by a proper synchronization of the electron beam focusing with the progress of the optical wave. A test experiment for the demonstration of FEL amplification with an LPA is under preparation. Electron beam transport follows different steps with strong focusing with permanent magnet quadrupoles of variable strength, a demixing chicane with conventional dipoles, and a second set of quadrupoles for further focusing in the undulator. The FEL simulations and the progress of the preparation of the experiment are presented.