Evaluation of Pulse Duration of the Soft X-ray Free Electron Laser at SACLA BL1 with Single-Shot Spectrometry

We performed single-shot spectrometry to evaluate the pulse duration of the soft X-ray free electron laser (FEL) at BL1 of SPring-8 Angstrom Compact free electron LAser (SACLA). The soft X-ray FEL beam was focused with a Kirkpatrick-Baez (KB) focusing mirror system and single-shot spectra were measured with a grating and a two dimensional detector. The spike widths of the spectra, which are inversely proportional to the pulse duration, varied when we changed the operation conditions of the accelerator. By comparing the spike widths with a simulation, the pulse duration was evaluated to be less than 100 fs.