X-Ray Laser Achieves Its Final, Colder-Than-Space Temperature . MENLO PARK, Calif., May 12, 2022 — The superconducting particle accelerator, an upgrade to the Linac Coherent Light Source (LCLS) x-ray free-electron laser at the U.S. Department of Energy’s SLAC National Accelerator Laboratory, has been cooled to a temperature of ?456 °F, or 2 K. At this temperature, the particle accelerator becomes superconducting and can boost electrons to high energies with nearly zero ene...