Femtosecond Optical Laser System with Spatiotemporal Stabilization for Pump-Probe Experiments at SACLA
, Shigeki Owada 1,2, Yuya Kubota 2, Keiichi Sueda 2, Tetsuo Katayama 1,2, Hiromitsu Tomizawa 1,2, Toshinori Yabuuchi 1,2, Kensuke Tono 1,2 and Makina Yabashi 1,2Round 1
Reviewer 1 Report
The paper submitted by Togashi et al. summarizes the available beam parameters and the performance of the femtosecond laser system developed for pump-probe experiments at the SPring-8 Angstrom Compact Free Electron Laser (SACLA). Important design goals were stabilization of the output power and pointing as well as minimization of the temporal jitter between the x-ray FEL pulses and the optical laser pulses. The successful commissioning of the system comprising laser amplification, beam transport, pulse compression, and frequency conversion is demonstrated by the observation of optically excited coherent phonon oscillations in prototypical time-resolved x-ray diffraction experiments on bismuth.
This is a rather technical paper describing the current status of the pump-probe laser at the SACLA facility. State-of-the art know-how and technology is applied and the resulting optical beam properties and numbers are reasonable and agree with the expectations according to similar systems installed at other FEL facilities. However, the paper may serve as a standard reference for future time-resolved experimental works at the facility and as such it qualifies for publication.
Author Response
We thank the reviewer for his/her accurate summary and positive comment.
We wrote this paper for introducing the current status of the optical laser system for the pump-probe experiments of the ultrafast X-ray spectroscopy in SACLA. We would be glad if the readers refer to our paper as one of the optical laser system standards in XFEL facilities.
Please let us know if the reviewer has suggestions to revise some confusing expressions or spelling errors.
Reviewer 2 Report
This is a descriptive paper of big interest to anyone actively pursuing experiments
at X-ray free electron lasers, or planning to do so. I can recommend publication
without revision.
However, should the authors agree with me, I think a short section where their
new laser system is compared in terms of performance with laser systems at
other, comparable facilities (listed in the Introduction) would be most interesting.
Author Response
We appreciate the effort of the reviewer and thank him/her for the positive comment.
As the introduction, we mentioned the high-repetition laser system's progress in the European XFEL and LCLS-II. It is hard to compare the laser systems in each facility because they are different due to the scientific area, the experimental methods, and the XFEL operation. We would be pleased if the readers to refer to the XFEL facilities' published papers regarding optical laser systems.
Please let us know if the reviewer has suggestions to revise some confusing expressions or spelling errors.
