Reaching 2 petawatts of energy, the NSF-funded ZEUS facility on the College of Michigan helps analysis with potential advantages for medication, nationwide safety, supplies science, and different fields.
The ZEUS laser facility on the College of Michigan has achieved its first official experiment at 2 petawatts (2 quadrillion watts), almost doubling the height energy of some other laser presently working in the US.
Exceeding the whole electrical energy produced worldwide by greater than 100 occasions, this immense burst of energy exists just for the extraordinarily quick span of a laser pulse, simply 25 quintillionths of a second.
“This milestone marks the start of experiments that transfer into unexplored territory for American excessive area science,” mentioned Karl Krushelnick, director of the Gérard Mourou Heart for Ultrafast Optical Science, which homes ZEUS.
Functions throughout science and society
Analysis at ZEUS may have purposes in medication, nationwide safety, supplies science and astrophysics, along with plasma science and quantum physics. Supported by the U.S. National Science Foundation, ZEUS is a user facility—meaning that research teams from all over the country and internationally can submit experiment proposals that go through an independent selection process.
“One of the great things about ZEUS is it’s not just one big laser hammer, but you can split the light into multiple beams,” said Franklin Dollar, professor of physics and astronomy at the University of California, Irvine, whose team is running the first user experiment at 2 petawatts. “Having a national resource like this, which awards time to users whose experimental concepts are most promising for advancing scientific priorities, is really bringing high-intensity laser science back to the U.S.”
Producing particle accelerator-level beams
Dollar’s team, working with the ZEUS facility, is aiming to generate electron beams with energies comparable to those produced in particle accelerators that stretch for hundreds of meters. These beams would carry 5 to 10 times more energy than any previously achieved at ZEUS.
“We aim to reach higher electron energies using two separate laser beams—one to form a guiding channel and the other to accelerate electrons through it,” said Anatoly Maksimchuk, U-M research scientist in electrical and computer engineering, who leads the development of the experimental areas.
Part of this effort involves a redesigned target. The team extended the gas cell that contains the helium into which the laser pulse is directed. When the pulse passes through, it strips electrons from the atoms, creating plasma—a mixture of free electrons and positively charged ions. The freed electrons are then pulled along in the wake of the laser pulse, much like surfers riding waves behind a speeding boat, in a process known as wakefield acceleration.
Because light travels more slowly through plasma, the electrons can catch up to the laser pulse. With a longer and less dense target, they can spend additional time accelerating before overtaking the pulse, allowing them to reach significantly higher speeds.
Toward zettawatt-scale experiments
This demonstration of ZEUS’s capabilities sets the stage for its landmark experiment, expected later this year, in which accelerated electrons will collide with counter-propagating laser pulses. From the perspective of the electrons, a 3-petawatt laser pulse will appear amplified to the scale of a zettawatt. This phenomenon is what gives ZEUS its full name: the “Zettawatt Equivalent Ultrashort laser pulse System.”
“The fundamental research done at the NSF ZEUS facility has many possible applications, including better imaging methods for soft tissues and advancing the technology used to treat cancer and other diseases,” said Vyacheslav Lukin, program director in the NSF Division of Physics, which oversees the ZEUS project. “Scientists using the unique capabilities of ZEUS will expand the frontiers of human knowledge in new ways and provide new opportunities for American innovation and economic growth.”
The ZEUS facility fits in a space similar in size to a school gymnasium. At one corner of the room, a laser produces the initial infrared pulse. Optical devices called diffraction gratings stretch it out in time so that when the pump lasers dump power into the pulse, it doesn’t get so intense that it starts tearing the air apart. At its biggest, the pulse is 12 inches across and a few feet long.
After four rounds of pump lasers adding energy, the pulse enters the vacuum chambers. Another set of gratings flattens it to a 12-inch disk that is just 8 microns thick—about 10 times thinner than a piece of printer paper. Even at 12 inches across, its intensity could turn the air into plasma, but then it is focused down to 0.8 microns wide to deliver maximum intensity to the experiments.
Animated fly-through of the ZEUS laser system. Credit score: College of Michigan
“As a midscale-sized facility, we are able to function extra nimbly than large-scale services like particle accelerators or the Nationwide Ignition Facility,” mentioned John Nees, U-M analysis scientist in electrical and pc engineering, who leads the ZEUS laser development. “This openness attracts new concepts from a broader neighborhood of scientists.”
Challenges in constructing to full energy
The street to 2 petawatts has been gradual and cautious. Simply getting the items they should assemble the system has been more durable than anticipated. The largest problem is a sapphire crystal, infused with titanium atoms. Virtually 7 inches in diameter, it’s the vital element of the ultimate amplifier of the system, which brings the laser pulse to full energy.
“The crystal that we’re going to get in the summertime will get us to three petawatts, and it took 4 and a half years to fabricate,” mentioned Franko Bayer, challenge supervisor for ZEUS. “The dimensions of the titanium sapphire crystal we have now, there are just a few on the planet.”
Within the meantime, leaping from the 300 terawatt energy of the earlier HERCULES laser to simply 1 petawatt on ZEUS resulted in worrying darkening of the gratings. First, they needed to decide the trigger: Have been they completely broken or simply darkened by carbon deposits from the highly effective beam tearing up molecules floating within the imperfect vacuum chamber?
When it turned out to be carbon deposits, Nees and the laser workforce had to determine what number of laser pictures may run safely between cleanings. If the gratings turned too darkish, they might distort the laser pulses in a manner that damages optics additional alongside the trail.
Lastly, the ZEUS workforce has already spent a complete of 15 months working consumer experiments because the grand opening in October 2023 as a result of there’s nonetheless loads of science that might be accomplished with a 1 petawatt laser. To date, it has welcomed 11 separate experiments with a complete of 58 experimenters from 22 establishments, together with worldwide researchers. Over the following yr, between consumer experiments, the ZEUS workforce will proceed upgrading the system towards its full potential.
Supported by the U.S. Nationwide Science Basis
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