A team of scientists has successfully captured a high-definition “movie” of shockwaves moving through a microscopic water jet, revealing a hidden mechanism that could solve one of the greatest engineering hurdles in nuclear fusion.

The study details how researchers used a groundbreaking “multi-messenger” imaging technique to watch material compress in picosecond steps. 

The results provide an unprecedented look at the microphysics of Inertial Confinement Fusion (ICF), the process of recreating the sun’s power here on Earth.

“It was a challenging experiment, but with very fruitful results,” said Hai-En Tsai, a research scientist at Berkeley Lab’s Accelerator Technology & Applied Physics (ATAP) Division. 

Multi-messenger discovery

The most significant finding came from a dual-view perspective that uncovered something previous X-ray-only experiments had missed: a thin layer of water vapor surrounding the target.

This vapor layer unexpectedly acts as a cushion, ensuring the shockwave compresses the water symmetrically. 

This discovery is critical because “uniform compression” is the “holy grail” of fusion; even minor instabilities can prevent a fusion plasma from “burning” properly and generating power.

“These results can actually help verify the simulation models used for ICF,” added Tsai.

“We watched the interaction in picosecond [one trillionth of a second] steps, frame by frame, with micrometer imaging precision. These are unprecedented precision levels in inertial fusion energy.”

Combining two types of radiation pulses

To capture these ultra-fast events, the University of Michigan-led team combined two types of radiation pulses at the Berkeley Lab Laser Accelerator (BELLA) Center. 

This included ultrafast X-rays to capture the physical density and structure of the shockwave, as well as high-energy electron beams to detect how electric and magnetic fields evolved in real-time.

“We wanted to demonstrate that the X-rays produced by extremely intense lasers have unique properties that allow us to capture a ‘movie’ of the extremely fast motion of plasma,” explained Alec Thomas, a professor at the University of Michigan.

“There’s a lot of excitement surrounding recent breakthroughs in laser-driven fusion. Making further progress requires accurate diagnostics to capture the dynamics of hot plasma, especially unstable behavior that can prevent fusion plasmas from burning properly.”

By stitching these views together, researchers created a frame-by-frame visualization of plasma dynamics that were previously invisible to standard sensors or simulations.

Using flowing jet of water

The experiment utilized a unique target: a flowing jet of water roughly the thickness of a human hair. Unlike traditional solid targets—which are destroyed after one laser blast and must be manually replaced—the water jet automatically replaces itself.

This allowed the team to fire the laser once per second, significantly accelerating the pace of data collection. The months of engineering required to keep the water from freezing in the experiment’s vacuum paid off, allowing for high-repetition-rate tracking of the interaction.

While the experiment used water as an analog, the physics observed are directly applicable to actual fusion fuel capsules. 

Scientists believe that shrinking this laser-plasma accelerator (LPA) technology could eventually allow these diagnostic tools to be installed directly at large-scale fusion facilities.