Abstract
The SPring-8 Angstrom Compact free-electron LAser (SACLA) has been open for user experiments
since March 2012. SACLA is the world first compact XFEL facility aiming at a general-purpose
machine spread widely, which was designed to make the facility size compact as much as possible with
the state-of-the art technology. Success of SACLA actually stimulates lots of researchers who are eager
to utilize XFEL for their experiments to build their own XFEL facilities. Construction of compact
XFEL, which SACLA first showed how to realize, is now a hot topic all over the world and some of
them are being investigated for budgeting. This article aims at providing basic knowledge on a SACLA
system and toward which SACLA is going. For this purpose the article compares approaches to XFEL
among three leading XFEL projects, LCLS, European XFEL and SACLA and then, describes features of
SACLA in detail.
