The hard X-ray FEL has come of age. A free-electron laser is not like other lasers. It works by forcing a beam of electrons, travelling at nearly the speed of light, to oscillate in a long ...

Unlike conventional X-ray sources, XFELs generate X-rays through a process called self-amplified spontaneous emission (SASE). In this process, a beam of electrons is accelerated to nearly the speed of ...