| dc.description.abstract | Short-pulse X-rays find universal applications in science and biomedicine. Betatron radiation generated from laser wakefield acceleration (LWFA) offers a method for pro- ducing ultrashort-pulse X-rays. LWFA utilizes the interaction between short-pulse lasers and plasmas to accelerate electrons, achieving acceleration gradients approximately 1000 times higher than conventional radio frequency accelerators, thus decreasing the need for large-scale experimental facilities. In LWFA, strong transverse focusing forces cause the electron beam to oscillate during acceleration, similar to the motion of an Wiggler, producing ultrashort-pulse X-rays. We enhanced the electron beam oscillation by breaking the symmetry of the shock front and verified its feasibility using particle-in-cell (PIC) simulations. By tilting the shock front by 15◦, we successfully reproduced the 2D simulation results in [1] and achieved single-sided electron injection. Further studies show that by reducing ?0 and increasing the laser waist at a 15◦, complete one-side injection can be achieved. However, the laser evolution conditions in 2D and 3D simulations differ. To achieve similar laser intensity evolution in 2D simulations, ?0 needs to be divided by √2, leading to differences in laser waist evolution. This indicates that 2D simulations cannot fully capture more complex laser evolution phenomena. Therefore, we employed 3D PIC simulations to investigate the conditions of the tilted shock front. It was found that transverse injected electrons could not be completely one- side injected at a 15◦, and the total injected charge was not significantly different from that at a 0◦. To achieve one-side injection, we increased the tilt angle to 65◦, successfully generating a one-side electron beam. Similarly, for longitudinal injected electrons, only at a 65◦ did we achieve an 85 % one-side injection rate, indicating that both transverse and longitudinal injected electrons require a larger angle in 3D simulations to achieve a high one-side injection rate. To verify the collective motion of single-sided injected electron beams, we tracked and analyzed their behavior. Results show that both transverse and longitudinal injections exhibit stronger average oscillations at larger angles, but longitudinal injections lead to larger deviations in the other direction, reducing polarization. Flux analysis indicates that transverse injections yield higher polarization, reaching 62 % at 65◦, while longitudinal injections show no angular dependence. We found that transverse injections at 65◦ can produce attosecond-level X-rays with a brilliance of 1020. | en_US |