[论文解读] An inverse free electron laser acceleration-driven Compton scattering X-ray source

I. Gadjev, Nicholas Sudar+14 more|arXiv (Cornell University)|Nov 2, 2017

Laser-Plasma Interactions and Diagnostics参考文献 28被引用 3

一句话总结

本文展示了一种利用反向自由电子激光（IFEL）加速和反向康普顿散射（ICS）的紧凑型全光学X射线源。一台太瓦级CO2激光器分裂为两部分：一部分通过IFEL将电子加速至84 MeV，另一部分作为光波导磁体，通过ICS产生最高达13 keV的X射线，证明了在桌面系统中实现紧凑、高亮度、相位锁定X射线脉冲的可行性。

ABSTRACT

The generation of X-rays and γ-rays based on synchrotron radiation from free electrons, emitted in magnet arrays such as undulators, forms the basis of much of modern X-ray science. This approach has the drawback of requiring very high energy, up to the multi-GeV-scale, electron beams, to obtain the required photon energy. Due to the limit in accelerating gradients in conventional particle accelerators, reaching high energy typically demands use of instruments exceeding 100's of meters in length. Compact, less costly, monochromatic X-ray sources based on very high field acceleration and very short period undulators, however, may revolutionize diverse advanced X-ray applications ranging from novel X-ray therapy techniques to active interrogation of sensitive materials, by making them accessible in cost and size. Such compactness may be obtained by an all-optical approach, which employs a laser-driven high gradient accelerator based on inverse free electron laser (IFEL), followed by a collision point for inverse Compton scattering (ICS), a scheme where a laser is used to provide undulator fields. We present an experimental proof-of-principle of this approach, where a TW-class CO2 laser pulse is split in two, with half used to accelerate a high quality electron beam up to 84 MeV through the IFEL interaction, and the other half acts as an electromagnetic undulator to generate up to 13 keV X-rays via ICS. These results demonstrate the feasibility of this scheme, which can be joined with other techniques such as laser recirculation to yield very compact, high brilliance photon sources, extending from the keV to MeV scale. Furthermore, use of the IFEL acceleration with the ICS interaction produces a train of very high intensity X-ray pulses, thus also permitting a unique tool that can be phase-locked to a laser pulse in frontier pump-probe experimental scenarios.

研究动机与目标

• 开发一种紧凑、低成本的X射线源，避免对多GeV加速器和大型基础设施的依赖。
• 克服传统同步辐射源的局限性，后者需要高能电子束和长加速器结构。
• 展示一种基于全光学技术的桌面X射线源，实现单色、高亮度X射线的广泛可用性。
• 实现与激光驱动器同步的相位锁定X射线脉冲，以支持先进的泵浦-探测实验。
• 验证在单一集成光学平台上结合IFEL加速与ICS的可行性。

提出的方法

• 将一台太瓦级CO2激光脉冲分为两束：一束驱动反向自由电子激光（IFEL），将电子加速至84 MeV。
• IFEL相互作用利用周期性结构，通过激光的电磁场调制电子能量，实现高梯度加速。
• 第二束激光作为行波光波导磁体，为反向康普顿散射（ICS）提供周期性磁场。
• IFEL产生的电子束与光波导磁束头对头碰撞，通过ICS在最高达13 keV的光子能量下产生X射线。
• 系统设计支持未来集成激光循环技术，以提升光子产额和亮度。
• 整个装置在单一光学平台上运行，实现电子束与X射线脉冲之间的相位锁定同步。

实验结果

研究问题

• RQ1 能否在不使用传统射频加速器的情况下，通过IFEL加速与ICS实现紧凑型全光学X射线源？
• RQ2 在桌面系统中，采用此IFEL-ICS方案可实现的最高X射线光子能量是多少？
• RQ3 X射线脉冲能否与驱动激光相位锁定，以用于泵浦-探测实验？
• RQ4 在此配置下，产生keV量级X射线所需的电子束质量和能量是多少？
• RQ5 通过激光循环等附加技术，该方法在多大程度上可扩展至更高光子能量（如MeV量级）？

主要发现

• 系统成功利用太瓦级CO2激光通过反向自由电子激光（IFEL）机制将电子加速至84 MeV。
• 利用第二束激光作为光波导磁体，通过反向康普顿散射（ICS）产生了最高达13 keV的X射线。
• X射线脉冲与驱动激光相位锁定，实现了泵浦-探测实验所需的精确同步。
• 实验成功验证了无需大型传统加速器即可实现紧凑型全光学X射线源的原理。
• 结果验证了通过激光循环等技术将该方法扩展至更高光子能量的可行性。
• 该系统产生高强度X射线脉冲序列，适用于材料科学和超快物理中的时间分辨研究。