Lu H, Gauthier A, Hepting M, Tremsin A S, Reid A H, Kirchmann P S, Shen Z X, Devereaux T P, Shao Y C, Feng X, Coslovich G, Hussain Z, Dakovski G L, Chuang Y D, Lee W S
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, CA, 94025, USA.
Space Sciences Laboratory, University of California at Berkeley, Berkeley, CA, 94720, USA.
Sci Rep. 2020 Dec 17;10(1):22226. doi: 10.1038/s41598-020-79210-4.
Time-resolved resonant inelastic X-ray scattering (RIXS) is one of the developing techniques enabled by the advent of X-ray free electron laser (FEL). It is important to evaluate how the FEL jitter, which is inherent in the self-amplified spontaneous emission process, influences the RIXS measurement. Here, we use a microchannel plate (MCP) based Timepix soft X-ray detector to conduct a time-resolved RIXS measurement at the Ti L-edge on a charge-density-wave material TiSe. The fast parallel Timepix readout and single photon sensitivity enable pulse-by-pulse data acquisition and analysis. Due to the FEL jitter, low detection efficiency of spectrometer, and low quantum yield of RIXS process, we find that less than 2% of the X-ray FEL pulses produce signals, preventing acquiring sufficient data statistics while maintaining temporal and energy resolution in this measurement. These limitations can be mitigated by using future X-ray FELs with high repetition rates, approaching MHz such as the European XFEL in Germany and LCLS-II in the USA, as well as by utilizing advanced detectors, such as the prototype used in this study.
时间分辨共振非弹性X射线散射（RIXS）是随着X射线自由电子激光（FEL）的出现而发展起来的技术之一。评估自放大自发辐射过程中固有的FEL抖动如何影响RIXS测量非常重要。在这里，我们使用基于微通道板（MCP）的Timepix软X射线探测器，在电荷密度波材料TiSe的Ti L边进行时间分辨RIXS测量。快速并行的Timepix读出和单光子灵敏度实现了逐脉冲数据采集和分析。由于FEL抖动、光谱仪的低探测效率以及RIXS过程的低量子产率，我们发现不到2%的X射线FEL脉冲产生信号，这使得在该测量中保持时间和能量分辨率的同时无法获得足够的数据统计量。通过使用未来高重复率（接近MHz）的X射线FEL，如德国的欧洲XFEL和美国的LCLS-II，以及利用先进的探测器，如本研究中使用的原型，可以减轻这些限制。
