First, we put forward a novel method for producing ultrarelativistic high-density high-polarization positrons through a single-shot interaction of a strong laser with a tilted solid foil [1]. In our method, the driving laser ionizes the target, and the emitted electrons are accelerated and subsequently generate abundant gamma photons via the nonlinear Compton scattering, dominated by the laser. These gamma photons then generate polarized positrons via the nonlinear Breit-Wheeler process, dominated by a strong self-generated quasistatic magnetic field. Second, laser wakefield acceleration is paving the way for the next generation of electron accelerators, for their own sake and as radiation sources. Here we also put forward a controllable dual-wake injection scheme to generate an ultrashort triplet electron bunch with high brightness and high polarization, employing a radially polarized laser as a driver [2]. Third, vortex gamma photons with intrinsic orbital angular momenta possess a wealth of applications in various fields—e.g., strong-laser physics, nuclear physics, particle physics, and astrophysics—yet their generation remains unsettled. Here we investigate the generation of vortex gamma photons via nonlinear Compton scattering of ultrarelativistic electrons in a circularly polarized laser pulse [3]. Finally, traditional photonuclear reactions primarily excite giant dipole resonances, making the measurement of isovector giant resonances with higher multipolarities a great challenge. In this talk, we further introduce one of our recent works on the manipulation of collective excitations of different multipole transitions in even-even nuclei via vortex gamma photons [4].

[1] Kun Xue, Ting Sun, Ke-Jia Wei, Zhong-Peng Li, Qian Zhao, Feng Wan, Chong Lv, Yong-Tao Zhao, Zhong-Feng Xu, and Jian-Xing Li. Generation of high-density high-polarization positrons via single-shot strong laser-foil interaction. Phys. Rev. Lett. 131, 175101 (2023). Editors' Suggestion.
[2] Ting Sun, Qian Zhao, Feng Wan, Yousef I. Salamin, and Jian-Xing Li. Generation of ultrabrilliant polarized attosecond electron bunch via dual-wake injection. Phys. Rev. Lett. 132, 054001 (2024).
[3] Mamutjan Ababekri, Ren-Tong Guo, Feng Wan, B. Qiao, Zhongpeng Li, Chong Lv, Bo Zhang, Weimin Zhou, Yuqiu Gu, and Jian-Xing Li. Vortex γ photon generation via spin-to-orbital angular momentum transfer in nonlinear Compton scattering. Phys. Rev. D 109, 016005 (2024).
[4] Zhi-Wei Lu, Liang Guo, Zheng-Zheng Li, Mamutjan Ababekri, Fang-Qi Chen, Changbo Fu, Chong Lv, Ruirui Xu, Xiangjin Kong, Yi-Fei Niu, and Jian-Xing Li. Manipulation of Giant Multipole Resonances via Vortex γ Photons. Phys. Rev. Lett. 131, 202502 (2023).

strong-field QED,nonlinear Compton scattering,nonlinear BW,orbital angular momentum,Photonuclear reactions