Reaching 2 Petawatts of Power, the installation of ZEUS funded by the NSF at the University of Michigan supports research with potential advantages for medicine, national security, materials science and other areas.
The Zeus laser installation of the University of Michigan carried out its first official experience at 2 Petawatts (2 quadrillion Watts), almost doubling the advanced power of any other laser which currently works in the United States.
Going beyond the total electricity produced in the world of more than 100 times, this immense burst of power exists only for the extremely short duration of a laser impulse, only 25 quintillions of a second.
“This stage marks the start of experiences that move to an unexplored territory for high -level American sciences,” said Karl Krushelnick, director of Gérard Mourou Center for UltraFast Optical Science, which houses Zeus.
Applications through science and society
Research in Zeus will have applications in medicine, national security, material science and astrophysics, in addition to[{” attribute=”” tabindex=”0″ role=”link”>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.
https://www.youtube.com/watch?v=3Syblssqbze
Flight animation of the Zeus laser system. Credit: University of Michigan
“As a medium -sized installment, we can operate more agile than large -scale installations such as particle accelerators or the national ignition installation,” said John Nees, UM researcher in electrical and computer engineering, who directs the Zeus laser construction. “This opening attracts new ideas from a wider community of scientists.”
Challenges in full power construction
The road to 2 Petawatts was slow and cautious. The simple fact of obtaining the parts they need to assemble the system was more difficult than expected. The biggest challenge is a sapphire crystal, infused with titanium atoms. Almost 7 inches in diameter, it is the critical component of the final amplifier of the system, which carries the most laser power at full power.
“The crystal that we are going to get in summer will bring us to 3 petawatts, and it took four and a half years for manufacturing,” said Franko Bayer, project manager for Zeus. “The size of the titanium sapphire crystal that we have, there are only a few in the world.”
In the meantime, the jump of the 300 terawatt power from the previous Hercules laser to only 1 Petawatt on Zeus led to the darkening of the networks. First, they had to determine the cause: were they permanently damaged or simply darken by carbon deposits of the powerful beam heartworming floating molecules in the imperfect empty room?
When it turned out to be carbon deposits, Nees and the laser team had to understand how many laser blows could operate safely between cleaning. If the networks became too dark, they could distort the laser pulses in a way that damages the optics along the path.
Finally, the Zeus team has already spent a total of 15 months to direct user experiences since the big opening in October 2023 because there is still a lot of science that could be done with a laser 1 Petawatt. Until now, he has welcomed 11 distinct experiences with a total of 58 experimenters from 22 institutions, including international researchers. During the next year, between user experiences, the Zeus team will continue to upgrade the system to its full potential.
Supported by the US National Science Foundation
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