Dataset for 'High gradient Terahertz-driven ultrafast photogun'

Terahertz (THz)-based electron acceleration has the potential as a technology for next-generation cost-efficient compact electron sources. Although proof-of-principle demonstrations have proven the feasibility of many THz-driven accelerator components, THz-driven photoguns with sufficient brightness, energy, and control for use in demanding ultrafast applications have yet to be achieved. Here, we present a novel millimeter scale waveguide-based THz-driven photogun that exploits field enhancement to boost the electron energy, a movable cathode to achieve precise control over the accelerating phase as well as a multifunction cavity for exquisite beam control. The short driving wavelength enables a peak acceleration gradient as high as ~3 GV/m. Using microjoule-level single-cycle THz pulses, we demonstrate electron beams with up to ~14 keV electron energy, 1% energy spread and ~0.02 mm mrad transverse emittance. With a highly integrated rebunching cavity the bunch is further compressed by about 10 times to 167 fs with ~10 fC charge. High-quality diffraction patterns of single crystal silicon and projection microscopy images of the copper mesh are achieved. We are able to reveal the transient radial electric field developed from the charged particles on a copper mesh after photoexcitation with high spatiotemporal resolution, providing a potential scheme for plasma-based beam manipulation. Overall, these results represent a new record in energy, field gradient, beam quality and control for a THz-driven electron gun, enabling for the first-time real applications in electron projection microscopy and diffraction. It is therefore a critical step and milestone in the development of all-optical THz-driven electron devices validating the maturity of the technology and its use in precision applications.基于太赫兹（Terahertz, THz）的电子加速技术，有望成为下一代高性价比紧凑型电子源的核心技术。尽管原理验证实验已证实诸多太赫兹驱动加速器组件的可行性，但具备足够亮度、能量与调控能力、可满足严苛超快应用场景需求的太赫兹驱动光电枪（photogun）仍尚未实现。本文报道一款新型毫米级波导型太赫兹驱动光电枪，其利用场增强效应提升电子能量，搭载可移动阴极以实现加速相位的精准调控，并集成多功能腔体实现精细束流操控。较短的驱动波长可实现高达约3吉伏每米（GV/m）的峰值加速梯度。研究团队采用微焦耳级单周期太赫兹脉冲，成功获得电子能量最高约14千电子伏（keV）、能量分散度1%、横向发射度约0.02 mm·mrad的电子束。借助高度集成的聚束腔体，束团可被进一步压缩约10倍至167飞秒（fs），电荷量约10飞库仑（fC）。实验成功获取单晶硅的高质量衍射图样，以及铜网的投影显微图像。本研究还以极高的时空分辨率观测到光激发后铜网上带电粒子产生的瞬态径向电场，为基于等离子体的束流操控提供了可行方案。综上，本研究成果在太赫兹驱动电子枪的能量、场梯度、束流质量与调控性能方面创下新纪录，首次实现了该技术在电子投影显微与衍射领域的实际应用。这是全光学太赫兹驱动电子器件发展历程中的关键一步与里程碑，验证了该技术的成熟度及其在精密应用场景中的应用潜力。