The US test fired its most powerful laser ever

A laser named after the most powerful god in ancient Greece is living up to its name. According to the University of Michigan, the first official experiment from the Zettawatt-Equivalent Ultrashort pulse laser System (ZEUS) yielded 2 petawatts (2 quadrillion watts) of power. For reference, that’s more than 100 times the electricity output across the entire planet—but you’ll likely miss it if you blink.

The school gym-sized ZEUS is the successor to the university’s HERCULES system, which topped out at 300 terawatts. ZEUS relied on a reconfigured target for its debut demonstration, which required firing a laser pulse at a cell containing helium. The subsequent interaction produced plasma as it tore electrons away from the helium atoms, resulting in a mixture of both positive ions and free electrons. The electrons started gaining speed behind the laser pulse in a phenomenon known as wakefield acceleration. Because light moves slower in plasma, the electrons can catch up to the laser beam. Those free electrons also get more time to speed up given the size of the target chamber and thereby hit higher speeds.

The recent demonstration is a prelude to the signature ZEUS experiment scheduled for later this year. In that test, the accelerating electrons will also smack into laser pulses coming from the opposite direction. This is where things get (even) more complicated—but to condense it down, the effect makes a 3-petawatt laser appear one million times more powerful, hence the “zettawatt-equivalent” in ZEUS’ name.

Accomplishing this and other experimental feats does require some safeguards. ZEUS includes optical devices known as diffraction gratings that stretch out the initial infrared pulse over time. This ensures the initial power doesn’t get so intense that it begins tearing apart the air around it.

Another goal is to ultimately create beams of electrons with energies similar to those found in particle accelerators hundreds of feet longer than ZEUS at a fraction of both its size and operating costs. At only $16 million to construct, the University of Michigan previously described the machine as a “bargain.”

Years of construction, calibration, and expertise is showcased in an astoundingly short amount of time. ZEUS’ 2 petawatt firing lasted just 25 quintillionths of a second. But future experiments will make the most of these moments. 

“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,” explained Vyacheslav Lukin, program director in the National Science d Division of Physics, which is responsible for the ZEUS project.

Meanwhile, ZEUS experiments could also help researchers explore the dynamics of positron jets that shoot out of black holes, or how gamma ray bursts operate. 

“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, a University of California professor of physics and astronomy who oversaw the 2 petawatt experiment. “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.”

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