相对论飞秒激光驱动产生高品质正电子源研究

Positron sources have important applications in many fields, such as laboratory astrophysics, medical detection and material science. The novel promising scheme of laser-driven positron generation has been widely studied. However, the qualities of generated positron sources, such as yield, energy and density, still have great disparity with the requirements of practical applications. This project, based on our pioneering work, aims to study some new schemes of high-quality positron sources generation driven by relativistic femtosecond laser and the important issues existed. The topics include: 1) study and optimize the factors of laser-driven positron generation scheme based on high-density gas targets to generate high-quality positron sources, 2) theoretically analyze and experimentally explore the new scheme of laser-driven positron generation based on micro-channel targets, 3) study the propagation process of positron beams with electron beams together to propose a novel scheme of positron acceleration and quality-improving. The research on these subjects will not only contribute to perfecting the schemes of laser-driven positron generation, but also hopefully improve the qualities of positron sources and satisfy the requirements of practical applications in many fields, having great practical utility and potential economic benefits.

正电子源在实验室天体物理、医学检测以及材料科学等领域具有极其重要的应用，激光驱动产生正电子源作为具有广阔发展前景的新型方案获得了广泛研究，然而其产生正电子源的产额、能量、密度等品质与实际应用需求仍有较大差距。本项目将结合我们现有的工作基础，研究相对论飞秒激光驱动产生高品质正电子源的新方案与存在的重要问题。本项目研究内容有：1）研究激光、等离子体与高Z靶参数对正电子产生的影响，重点优化基于高密度气体靶的激光正电子产生方案得到的正电子品质；2）理论分析与实验探索基于微通道靶的激光正电子产生新方案；3）研究正负电子束一同传播过程，提出高密度电子束驱动的正电子加速与品质提升方案。开展这一方面的专门研究不仅有助于完善激光正电子产生方案，而且有望大幅改善正电子源品质，满足其在众多领域的应用需求，具有重大的实用价值和潜在的经济效益。

激光驱动产生的正电子源具有短脉冲、微尺寸、高密度等优点，在实验室天体物理、材料无损探测等方面具有广泛应用前景。本项目通过物理实验结合理论分析与数值模拟的方法，在相对论飞秒激光驱动产生高品质正电子源方向开展前沿性研究，着力优化正电子源的产额与密度、脉宽与发散、能量与能散等品质。主要工作包括：1）利用飞秒拍瓦激光装置，开展了基于超强激光与高密度气体靶相互作用产生正电子束的实验研究。通过优化激光峰值能量、气体电子密度等参数，实验上获得了电荷量超过15nC的高能电子束。在此基础上加入铜/铅等高Z靶获得正电子束，相较于前期结果两者均提高了近一个数量级。2）实验上初步开展了利用超强飞秒激光与微通道靶相互作用加速电子及进一步产生高密度正电子源的研究。为后续基于微通道靶产生高密度正电子源研究奠定了基础。3）提出了一种新颖的正电子加速机制，即基于相干渡越辐射的正电子加速新机制，开展了GeV量级正电子束加速的理论研究工作，同时在实验上也进行了初步探索并在继续优化完善相关实验方案。此外，我们还开展了基于超强激光的超快反质子束产生理论研究。