LCLS-II Cooldown (IMAGE) DOE/SLAC National Accelerator Laboratory Caption A half-mile-long stretch of tunnel in Menlo Park, California, is now colder than most of the universe. It houses a new superconducting particle accelerator, part of an upgrade project to the Linac Coherent Light Source (LCLS) X-ray free-electron laser. Credit Jim Gensheimer, Greg Stewart/SLAC National Accelerator Laboratory Usage Restrictions No restrictions. License Public Domain Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.