If you walk across the open yard in front of the Physics, Math and Astronomy building at the University of Texas at Austin, you’ll see a 17-story tower and a huge L-shaped building. What you won’t see is what’s underneath you. Two floors below ground, behind heavy double doors stamped with a logo that most students have never noticed, sits one of the most powerful lasers in the United States.
I was the lead laser scientist on the Texas Petawatt, or TPW as we called it, from 2020 to 2024. Texas Petawatt, which is currently closed due to funding cuts, was a government-funded research center where scientists from across the country applied for time to use specialized equipment. It was part of LaserNetUS, a Department of Energy network of high-power laser labs.
This type of laser takes a tiny pulse of light, stretches it out so it doesn’t blast optics to pieces, and amplifies it until, for a brief instant, it carries more power than the entire U.S. electrical grid. Then it compresses the pulse back to a trillionth of a second to create a star in a vacuum chamber.
On a typical shot day, the target might be a piece of metal foil thinner than a human hair, a jet of gas or a tiny plastic pellet – each designed to answer a different scientific question.
Scientists from across the country applied for time on TPW to study everything from the physics of stellar interiors and fusion energy to new approaches for cancer treatment.
Most people hear about petawatt lasers and picture something out of a movie. A “shot day” is actually hours of quiet, repetitive work followed by about 10 seconds where nobody breathes.
I now work as a research scientist at the University of Texas-Austin, studying the interaction of lasers with different materials, but a typical shot day during my time running TPW would look like this:
7 a.m.
I arrive two hours before the first scheduled shot. I put on my gown, boots and hairnet and step into the cold clean room. The laser doesn’t just turn on. You coax it awake.
I start with the oscillator, a small box that generates the first seed of light. I write down the parameters that define how the laser will behave during the shot: energy, center frequency, vacuum pressure in the tubes, cooling water level and flow. At this stage, they are fixed regardless of the experiment. The laser must perform the same way every time before the science can begin. Then I fire up the pump laser that will amplify this tiny pulse from nanojoules to about half a joule.
The anatomy of a petawatt laser. A tiny pulse starts at the oscillator, gets stretched in time to avoid damaging the optics, is amplified through progressively larger stages, then is compressed back down to a trillionth of a second inside the vacuum chamber at right.
Ahmed Helal, Fourni par l’auteur
The system needs at least 30 minutes to stabilize. During that time, I check alignment through every pinhole and every…
