AI 中文总结
该研究通过实验演示拉盖尔-高斯激光驱动自生磁箍缩机制，实现了发散度降低三倍、有效密度提升近一个数量级的稠密相对论电子束，为克服横向膨胀、增强高通量粒子源相关相互作用提供了新途径。
AI 中文摘要
在多拍瓦激光等离子体加速器中，获得高密度相对论电子束通常伴随大横向发散，限制了实验室天体物理相关高通量相互作用 regime 所需的有效电子密度。本文报道自生磁箍缩（SMP）的实验演示，这是一种集体机制，利用相对论强度（约8×10^19 W/cm²）的拉盖尔-高斯激光与欠密等离子体相互作用，主动调控束的横向动力学。电子束从双瓣高电荷注入结构演变为压缩的高密度轮廓，与高斯驱动源相比，发散度降低三倍，有效束密度提升近一个数量级。粒子模拟与实验观察一致，揭示自生 azimuthal 磁场在SMP regime 内主导电子动力学，该 regime 的形成条件定义为S = 0.717 l a0 [ne(10^18 cm^-3)]^-3/4 = 1，其中l、a0和ne分别为拓扑电荷、激光振幅和等离子体密度。来自稠密内鞘电子群的瞬态 kick 驱动集体磁箍缩，将初始分离的电子分布转化为压缩且准直良好的束。对于更高功率激光系统，形成条件可扩展至更高等离子体密度和更大轨道角动量模式，有望实现电荷超过几纳库仑、有效密度高于10^19 cm^-3的电子束。该机制为克服横向膨胀、增强与高通量粒子源相关的稀有相互作用过程提供了途径。
英文摘要
In multi-petawatt laser plasma accelerators, achieving high-density relativistic electron beams is typically accompanied by large transverse divergence, limiting the attainable effective electron density needed for high-flux interaction regimes relevant to laboratory astrophysics. Here we report experimental demonstration of self-generated magnetic pinching (SMP), a collective mechanism that actively regulates transverse beam dynamics using a Laguerre-Gaussian laser at strong relativistic intensity (~8 x 10^19 W/cm^2) interacting with an underdense plasma. The electron beam evolves from a two-lobe high-charge injection structure into a compressed, high-density profile, yielding a threefold reduction in divergence and nearly an order-of-magnitude enhancement in effective beam density compared with a Gaussian driver. Particle-in-cell simulations agree with the experimental observations and reveal that a self-generated azimuthal magnetic field governs the electron dynamics within the SMP regime, which is defined by the forming condition S = 0.717 l a0 [ne(10^18 cm^-3)]^-3/4 = 1, where l, a0, and ne are topological charge, laser amplitude, and plasma density, respectively. A transient kick from a dense inner sheath electron population drives collective magnetic pinching, transforming an initially separated electron distribution into a compressed and well-collimated beam. For higher-power laser systems, the forming condition can be extended to higher plasma densities and larger orbital angular momentum modes, potentially enabling electron beams with charges exceeding several nC and effective densities above 10^19 cm^-3. This mechanism provides a route to overcoming transverse expansion and enhancing rare interaction processes relevant to high-flux particle sources.
