Toward a terahertz-driven electron gun.
Toward a terahertz-driven electron gun.
复制标题
朝着Terahertz驱动的电子枪。
DOI：
10.1038/srep14899
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发表时间：
2015-10-21
影响因子：
4.6
通讯作者：
Kärtner FX
中科院分区：
文献类型：
--
作者：
Huang WR;Nanni EA;Ravi K;Hong KH;Fallahi A;Wong LJ;Keathley PD;Zapata LE;Kärtner FX
凝聚态物理学家需要具有keV能量和eV能量扩展的飞秒电子束来解决碳纳米管，分子结构，有机盐和电荷密度波材料中的状态转换。这些半相对论电子源不仅对超快电子衍射感兴趣，而且对电子能量损失谱和作为X射线自由电子激光的种子也感兴趣。到目前为止，超快电子枪的输出能量扩展（因此脉冲持续时间）受到发射器表面处可实现的电场的限制，该电场对于DC枪为10 MV/m，对于RF枪为200 MV/m。单周期太赫兹电子枪提供了一个独特的机会，不仅实现GV/m表面电场，而且具有相对低的太赫兹脉冲能量，因为单周期变换限制波形是最有效的方式来实现强电场。在这里，电子束的50 fC从一个平面的铜光电阴极从休息加速到几十eV的微焦耳太赫兹脉冲与峰值电场为72 MV/m，在1 kHz的重复率。我们表明，缩放到容易获得的GV/m太赫兹场制度将转化为~100 keV的单能电子束。
Femtosecond electron bunches with keV energies and eV energy spread are needed by condensed matter physicists to resolve state transitions in carbon nanotubes, molecular structures, organic salts, and charge density wave materials. These semirelativistic electron sources are not only of interest for ultrafast electron diffraction, but also for electron energy-loss spectroscopy and as a seed for x-ray FELs. Thus far, the output energy spread (hence pulse duration) of ultrafast electron guns has been limited by the achievable electric field at the surface of the emitter, which is 10 MV/m for DC guns and 200 MV/m for RF guns. A single-cycle THz electron gun provides a unique opportunity to not only achieve GV/m surface electric fields but also with relatively low THz pulse energies, since a single-cycle transform-limited waveform is the most efficient way to achieve intense electric fields. Here, electron bunches of 50 fC from a flat copper photocathode are accelerated from rest to tens of eV by a microjoule THz pulse with peak electric field of 72 MV/m at 1 kHz repetition rate. We show that scaling to the readily-available GV/m THz field regime would translate to monoenergetic electron beams of ~100 keV.