25/02/2023
A particle accelerator that slams electrons together here on Earth has achieved temperatures colder than those of outer space.
Using the X-ray free-electron laser at the Department of Energy's SLAC National Accelerator Laboratory – part of an upgrade project to the Linac Coherent Light Source (LCLS), called LCLS II – scientists chilled liquid helium to minus 456 degrees Fahrenheit (minus 271 degrees Celsius), or 2 kelvins.
That is just 2 kelvins above absolute zero, the coldest possible temperature at which all particle movement ceases.
That frosty environment is crucial for the accelerator, because at such low temperatures the machine becomes superconducting, meaning it can boost electrons through it with just about zero energy loss.
Even empty regions of space aren't this cold, as they are still filled with the cosmic microwave background radiation, a remnant from shortly after the Big Bang that has a uniform temperature of minus 454 F (minus 271 C), or 3 K.
"The next-generation superconducting accelerator of the LCLS-II X-ray free-electron laser has reached its operating temperature of 2 degrees above absolute zero," Andrew Burrill, director of the SLAC's Accelerator Directorate, told Live Science.
LCLS-II is now ready to begin accelerating electrons at 1 million pulses per second, which is a world record, he added.
"This is four orders of magnitude more pulses per second than its predecessor, LCLS, meaning that – in just a few hours – we will have sent more X-rays to users [who aim to utilize them in experiments] than LCLS has done in the past 10 years," Burrill said.
This is one of the last milestones that LCLS-II needs to achieve before it can go on to produce X-ray pulses that are on average 10,000 times brighter than those created by its predecessor.
This should help researchers to probe complex materials in unprecedented detail. The high-intensity, high-frequency laser pulses enable researchers to see how electrons and atoms in materials interact with unprecedented clarity.
This will have a number of applications, from helping to reveal "how natural and man-made molecular systems convert sunlight into fuels, and thus how to control these processes, to understanding the fundamental properties of materials that will enable quantum computing," Burill said.