A sub-atomic undertaking

The United States is upgrading its laser capabilities with ZEUS, a new three-petawatt system to be built at the University of Michigan. Three petawatts is equal to three quadrillion watts, or a 3 followed by 15 zeros.

Funded with $16 million from the National Science Foundation, the facility will enable both basic and applied research. It will test a leading theory on how the universe operates at a subatomic level, and it could lead to advancements in medicine, materials science, and national security.

“This laser will have the highest peak power in the United States and will be among the world’s most powerful laser systems for the next decade,” says Karl Krushelnick, director of the Gérard Mourou Center for Ultrafast Optical Science at U-M, where the laser will be built.

The U.S. built the world’s first petawatt laser in 1996, but hasn’t kept pace with more ambitious systems under construction elsewhere in the world. This includes two 10-petawatt in Europe and a 5.3-petawatt laser in China, which also has plans to build a 100-petawatt laser.

Getting back into the game with a 3-petawatt laser for $16 million is a bargain. The cost savings come in part from the fact that some high-power laser components are now produced commercially, so they don’t need to be custom-built. In addition, ZEUS will be an upgrade of an existing 0.5-petawatt laser, known for roughly two decades as HERCULES.

Probing quantum electrodynmaics

ZEUS will be what is known as a “user facility,” providing access to extreme laser intensities to scientists and engineers across the country.

“The NSF-supported ZEUS user facility will reestablish the United States as a world leader in high-intensity laser science, as recently recommended by the National Academies,” says Slava Lukin, who directs the NSF plasma physics program. “More than that, it will help advance our understanding of the cosmos by re-creating some of the universe’s most energetic light and particle acceleration phenomena in a university laboratory setting.”

One of the signature experiments planned will shoot the laser at a high-energy electron beam going the opposite way. This way, researchers will be able to mimic a much more powerful zettawatt laser (that’s 1 quintillion watts, or a 1 followed by 21 zeros). With this capability, the U-M team is most excited about the possibility of probing quantum electrodynamics, the reigning explanation of how the universe operates at the subatomic level.

“Quantum electrodynamics is a very successful theory, which has been accurate every time it has been measured in the laboratory. We hope to explore the more extreme regimes, where there is much more uncertainty in the theoretical predictions,” says Krushelnick, professor of nuclear engineering and radiological sciences, electrical engineering and computer science, and physics.

For instance, quantum electrodynamics predicts how the high intensities generated with ZEUS could affect the vacuum — essentially the underlying fabric of spacetime. Rather than being simple nothingness, the vacuum does strange things when a very high electric field is concentrated in one location. The pulses from the laser, scattering from the electron beam, should be strong enough to make matter and antimatter—pairs of electrons and positrons—suddenly appear from nothing. This has been called “boiling the vacuum.”

Quantum electrodynamics also predicts that the electric field from the laser could become so strong that it makes the vacuum behave like a lens for light.

Imagine the possibilities

In addition to these very fundamental questions, ZEUS could help develop methods and technologies for use in medicine, defense, materials science, and astrophysics, such as:

• Making advanced cancer therapies more widely available to patients by shrinking the accelerators needed to generate proton beams and radioactive isotopes
• Improving detection nuclear weapons materials in shipping containers
• Exploring how materials change on very fast timescales
• Providing new insights into black holes by exploring the high energy electron-positron jets they are believed to emit

The funding for ZEUS is part of the NSF’s Mid-Scale Research Infrastructure program.

(Top image: Anatoly Maksimchuk, EECS research scientist, and John Nees, EECS associate research scientist, demonstrate use of the HERCULES 300 TW laser in the Carl A. Gerstacker Building in September 2017. Image: Joseph Xu.)