Terahertz-driven acceleration has recently emerged as a route for delivering ultrashort bright electron beams efficiently, reliably and in a compact set-up. Many working schemes and key technologies related to terahertz-driven acceleration have been successfully demonstrated and are being developeds^{1,2,3,4,5,6,7,8,9,10}. However, the achieved acceleration gradient and energy gain remain low, and the potential physics and technical challenges in the high-energy regime are still underexplored. Here we report whole-bunch acceleration of relativistic beams with an effective acceleration gradient of up to 85 MV m^–1 in a single-stage configuration and demonstrate a cascaded terahertz-driven acceleration scheme of relativistic beams with an energy gain of 204 keV. These proof-of-principle results represent a critical advance towards high-energy terahertz-driven acceleration of relativistic beams, are scalable and have great potential to provide high-quality beams, with implications for future terahertz-driven electron sources and related scientific discoveries.

太赫兹驱动的加速最近已成为一种有效、可靠且紧凑的装置提供超短明亮电子束的途径。许多与太赫兹驱动加速相关的工作方案和关键技术已成功论证并正在开发中^{1、2、3、4、5、6、7、8、9、10}。然而，实现的加速度梯度和能量增益仍然很低，高能状态下潜在的物理和技术挑战仍未得到充分探索。在这里，我们报告了相对论光束的整体加速度，有效加速度梯度高达 85 MV m ^–1在单级配置中，并展示了一个级联太赫兹驱动的相对论光束加速方案，能量增益为 204 keV。这些原理验证结果代表了向高能太赫兹驱动的相对论光束加速的关键进展，具有可扩展性并且具有提供高质量光束的巨大潜力，对未来的太赫兹驱动电子源和相关科学发现具有重要意义。