上海科技大学知识管理系统

["X-ray free-electron lasers (XFELs) with megahertz repetition rates enable X-ray photon correlation spectroscopy (XPCS) studies of fast dynamics on microsecond and submicrosecond time scales. Beam-induced sample heating is one of the central concerns in these studies, as the interval time is often insufficient for heat dissipation. Despite the great efforts devoted to this issue, few have evaluated the thermal effects of X-ray beam profiles. This work compares the effective dynamics of three common beam profiles using numerical methods. Results show that under the same fluence, the effective temperatures increase with the nonuniformity of the beam, such that the Gaussian beam profile yields a higher effective temperature than the donut-like and uniform profiles. Moreover, decreasing the beam sizes is found to reduce beam-induced thermal effects, in particular the effects of beam profiles.","(c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement"]