A particle accelerator is now colder than space to produce 1 million X-ray pulses a second

A view of the tunnel housing part of the upgraded Linac Coherent Light Source (LCLS) X-ray free-electron laser.
A view of the tunnel housing part of the upgraded Linac Coherent Light Source (LCLS) X-ray free-electron laser. (Image credit: Jim Gensheimer, Greg Stewart/SLAC National Accelerator Laboratory)

If you thought the coldest place on Earth is Antarctica, well, you just might be wrong about that. One of the coldest places on Earth is actually in Menlo Park, California — or more specifically, 30 feet (9 meters) below it.

An underground superconducting particle accelerator at the SLAC National Accelerator Laboratory has been cooled down to a mind-boggling minus 456 degrees Fahrenheit (minus 271 degrees Celsius or 2 kelvin). That's just a few degrees above the coldest possible temperature in the universe, absolute zero. The extreme cooling is part of an upgrade to the Linac Coherent Light Source (LCLS) X-ray free-electron laser — soon to be dubbed LCLS-II — which can accelerate electrons close to the speed of light. The apparatus is used to study rare chemical events, biological molecules, quantum mechanics and complex materials used in computing (an appropriate purpose, given the accelerator's location in Silicon Valley).

Once the upgrades are complete, LCLS-II will be able to produce X-ray pulses 10,000 times brighter than its predecessor, at a rate of up to one million pulses per second — something that's only possible under the extremely cold temperatures of the accelerator, according to a statement from the facility.

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In the former iteration of LCLS, which began work in 2009, electrons were accelerated through half a mile of copper pipes at ambient temperature, which only permitted a maximum of 120 X-ray pulses per second. 

Instead, the new system features 37 cryogenic accelerator modules lined with cavities made of the metal niobium, all surrounded by a host of cooling equipment. Once the niobium cavities reach minus 456 F, they become superconducting. That state eliminates electrical resistance so that the electrons can reach incredibly high speeds.

"In just a few hours, LCLS-II will produce more X-ray pulses than the current laser has generated in its entire lifetime," Mike Dunne, director of LCLS, said in the statement. "Data that once might have taken months to collect could be produced in minutes. It will take X-ray science to the next level, paving the way for a whole new range of studies and advancing our ability to develop revolutionary technologies to address some of the most profound challenges facing our society."

To develop LCLS-II, SLAC partnered with Argonne National Laboratory, Lawrence Berkeley National Laboratory (Berkeley Lab), Fermilab, the Thomas Jefferson National Accelerator Facility (Jefferson Lab), and Cornell University.

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Stefanie Waldek
Contributing writer

Space.com contributing writer Stefanie Waldek is a self-taught space nerd and aviation geek who is passionate about all things spaceflight and astronomy. With a background in travel and design journalism, as well as a Bachelor of Arts degree from New York University, she specializes in the budding space tourism industry and Earth-based astrotourism. In her free time, you can find her watching rocket launches or looking up at the stars, wondering what is out there. Learn more about her work at www.stefaniewaldek.com.