[vemba_video vemba_id=”25086″ /]
VIDEO: The world’s most powerful laser at the SLAC National Accelerator Laboratory lets researchers examine matter at an atomic level, allowing them to study chemical interactions. CLICK HERE if you are having trouble viewing the video or photos on your mobile device.
MENLO PARK – A $1 billion project to create the world’s most powerful X-ray laser is quietly taking shape near Stanford University. Located 30 feet below ground, the giant X-ray laser is part of a quest to illuminate some of science’s great remaining mysteries.
The upgrade to the Department of Energy funded SLAC National Accelerator Laboratory in Menlo Park “will allow us to look at the world in a fundamentally new way,” said Mike Dunne, director of the X-ray laser at SLAC. Construction began last year, and two key pieces of the project were delivered and installed last month.
When the upgraded facility starts running experiments early next decade, it will catapult research into unexplored frontiers of the super-small and super-fast by producing an X-ray laser 10,000 times brighter and 8,000 times faster – firing a million pulses every second – than the existing system.
The project’s unprecedented resolution won’t be a mere academic exercise. This giant laser is poised to fire into the heart of some of humanity’s most central concerns: energy, health and technology.
Scientists say the brilliant X-ray beam could help us develop drugs with fewer side effects, better batteries, DNA-style data storage and new materials engineered down to the way their atoms fit together.
The LCLSII, the somewhat uncreatively named update to the Linac Coherent Light Source (LCLS), will use temperatures as cold as outer space to produce the most powerful X-ray laser beams in the world. When completed, the project will extend the length of the facility from two miles to three.
Scientists will be able to observe individual atoms in motion and freeze the action of events that were formerly too fast, too small or too rare to detect and study.
“Imagine looking at a city from above,” Dunne said. “If you only take two or three photos per day, you can understand quite a bit, but you can’t learn anything about traffic. If you take thousands of photos you’ll understand rush hour, traffic jams and how traffic moves.”
He said that’s the key to LCLS II’s innovation – its ability to slice events such as chemical reactions, proteins folding or electrons passing through material into slivers of time only one quadrillionth of a second thick. At this tiny scale, that’s the difference between seeing the traffic move and just knowing where the buildings are.
Researchers are particularly eager to turn the laser’s power to the inner-workings of photosynthesis. This seemingly simple chemical process in which plants use sunlight, carbon dioxide and water to make food has some mysterious intermediate steps.
“Currently, we are limited by how fast the X-ray fires. We can make molecular movies of photosynthesis but they are quite rough. With LCLS II we will be able to create an almost continuous movie that shows what happens between point A and point B,” said biophysicist Junko Yano of Lawrence Berkeley National Laboratory. “Understanding what nature does during photosynthesis can help us create renewable energy technologies like liquid fuels.”
Those million pulses of X-ray light per second will also allow researchers to gather more data in less time. LCLS II will be able to fire more X-ray pulses in a few hours than the current laser did in its entire lifetime.
That increased speed will have serious fringe benefits for researchers. “Right now my family dreads it when I have experiments using LCLS at SLAC. I’m gone four days at a time,” said biophysicist Peter Zwart of Lawrence Berkeley National Laboratory. “If I can complete an experiment in a day that makes a huge difference to me.”
On Jan. 19, the first piece of LCLS II, called a cryomodule, arrived after a journey from Fermi National Laboratory in Illinois. A few days later on Jan. 22 a brand new electron injector gun was delivered by Lawrence Berkeley National Laboratory.
When the project is finished, there will be 37 40-foot cryomodules – designed to fit together like interchangeable Legos. Each cryomodule contains what SLAC physicist Marc Ross likened to a series of connected metal balloons.
Each balloon is made of the element niobium, which becomes a superconductor when chilled to nearly absolute zero, which is defined as the temperature at which atoms sit completely still. “Electrical current then flows through the metal with no resistance,” said Ross.
When the vacuum cavities of the niobium balloons are charged up with electricity, they help slingshot the passing electrons to near the speed of light.
No electrical resistance means none of the electricity fed into the system is lost in the form of heat. “You charge the superconductor balloons and it can stay on indefinitely unlike LCLS, which built up heat,” said Ross.
This makes LCLS II more efficient, and without the need to shut down to cool off between experiments, so more experiments can be run each day.
To achieve these beyond-freezing temperatures, SLAC is building a giant refrigerator that will pump out liquid helium at a temperature of minus 456 degrees Fahrenheit – about as cold as outer space.
Electrons are the namesake of particle accelerators – they are the particles that are getting sped up. The second piece of LCLS II to arrive, the electron “gun,” will be supplying those particles.
The gun fires a laser beam of ultraviolet or visible light at a semiconductor surface known as a cathode. The end result is a blast of electrons from the cathode travelling down the length of the accelerator tube. The steady stream of electron bunches produced by the gun will help enable LCLS II’s rapid-fire 1 million pulses per second.
The fabrication of each piece of this next generation facility requires a level of cleanliness that would make even a neat freak blush. Even a fingerprint inside the niobium cavities of the cryomodules would pollute the pure vacuum technicians must achieve, Ross said.
For the most sensitive pieces of equipment, work could only be done within a clean-room nested inside another larger clean-room. To prepare components for assembly, Berkeley Lab technicians developed a technique of blasting parts clean with pellets of dry ice.
The remaining 36 cryomodules are now being built and are expected to arrive at SLAC over the next 18 months.
Because LCLS II is only one laser, getting what researchers call “beam time” is extremely competitive. Dunne is partly tasked with selecting the experiments that get that beam time. SLAC’s federal funding comes with a mandate that it advance scientific or technical knowledge. This means ensuring the investigations of the facility strike a balance between both basic and applied science.
“We’re not going into some esoteric world where people don’t care about what we’re doing,” he said. “This facility can answer fundamental scientific questions about systems that are of great societal importance.”
