Amy Sprague
December 4, 2024
In A&A's Plasmawise Lab, PhD student Daniel Alex is helping to unlock the future of clean energy through complex computer simulations of plasma physics. His research tackles one of fusion energy's greatest challenges: the unpredictable behavior of plasma itself.
Daniel Alex, A&A PhD student
"Most people don't realize that when they look up at the night sky, almost everything they see is plasma," Daniel says. "Stars, nebulae, even the space between galaxies – it's all plasma. And we're trying to harness that same state of matter right here on Earth."
As it turns out, plasma – that exotic fourth state of matter – is both everywhere and surprisingly elusive. Making up over 99% of the visible universe, plasma holds the key to potentially limitless clean energy through nuclear fusion. But first, researchers like Daniel need to solve some of the most complex puzzles in modern physics, including the vexing instabilities that make plasma so difficult to control.
Dancing with chaos
The challenge with plasma lies in its unpredictable nature. "It's a lot of chaotic situations," Daniel explains, pulling up a visualization on his computer screen. His work, under Professor Bhuvana Srinivasan's guidance, focuses on one of fusion's biggest hurdles: turbulence during the fusion process itself.
At the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, where Daniel collaborated this past summer, researchers compress tiny spherical pellets filled with hydrogen isotopes deuterium and tritium, hoping to achieve fusion. "When we fuse these isotopes, we get helium and energetic neutrons," Daniel explains. "If we can heat the plasma enough to achieve fusion, we can use the heat from those reactions to sustain additional fusion reactions. This process is called ignition."
An inertial fusion implosion; a Deuterium-Tritium capsule is compressed, forming a hot plasma and heating the center of the capsule to start a fusion reaction, heating and fusing the remaining mass surrounding the hotspot in a process called ignition.
One of the main villains in this story is something called the Rayleigh-Taylor instability – an effect of the mixing of fluids of different densities that can wreak havoc in fusion experiments. "It's like a buoyancy-driven activity," Daniel explains. "Similar to what happens if you pour water into a glass of oil – you get chaotic mixing."
The National Ignition Facility: Big Science for Fusion
The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory serves as a crucial testing ground for fusion research. Using 192 high-energy lasers, the facility compresses and heats tiny capsules of fusion fuel to star-like conditions. Researchers like Daniel use data from these experiments to refine their models and deepen our understanding of plasma physics, bringing us one step closer to practical fusion energy.
Magnetic mysteries
Perhaps the most fascinating aspect of Daniel's research involves magnetic fields that seem to appear out of nowhere. "There are certain situations where a plasma can generate its own magnetic fields without anything being externally imposed," he says. These self-generated fields are incredibly powerful – Daniel's simulations show fields reaching 11,000 Tesla. "For comparison, MRI scanners can only do about one to two Tesla, and ITER, which will be the largest fusion experiment in the world, is expected to generate 13 Tesla."
Magnetic fields produced during mixing; dense fluid falls downward, mixing with the hotter, less dense fluid (left), producing localized high-strength magnetic fluxes (right).
These magnetic fields aren't just scientific curiosities – they appear to be making the turbulence worse. "Along the interface between high and low densities, we see a cold region where the magnetic field is cooling the plasma, with some heating in adjacent regions," Daniel explains. "We believe this cooling creates a low-pressure region that accelerates mixing."
Daniel's insights into turbulence and magnetic field generation aren't just theoretical advances. They could help solve some of the major roadblocks in fusion energy research. It's exactly the kind of innovative thinking we need in this field.”
Daniel's focused approach is helping crack this crucial piece of the puzzle with simulations. "Often, the design of fusion experiments do not incorporate magnetic effects, but many researchers have come to recognize that magnetic fields can play a significant role,” he notes.
Srinivasan, whose NSF CAREER award supports Daniel's research, emphasizes the deeper scientific significance of these investigations. "What's truly remarkable is how the fundamental physics of plasma instabilities transcend boundaries," she explains. "The same complex mixing and transport phenomena we study occur both in the extreme environments of distant stars and in our most advanced fusion experiments."
This research, funded specifically to explore instabilities in astrophysical plasmas, reveals the synergy between cosmic and laboratory physics—showing how understanding one realm can provide crucial insights into another.
What is a Tesla?
A Tesla (T) is the international standard unit for measuring magnetic field strength. To put the magnitude of a Tesla in perspective: Earth's protective magnetic field is a mere 25-65 millionths of a Tesla at the surface. Hospital MRI machines, which use magnetic fields to create detailed body images, typically operate at around 2 Tesla – strong enough to lift a car. Even ITER, the largest fusion experiment on Earth, is only expected to produce 13 Tesla when up and running. But these pale in comparison to the extreme magnetic fields in plasma physics: self-generated fields around plasma can surge beyond 10,000 Tesla, creating immense challenges for scientists working to harness fusion energy. Managing these intense fields, which could instantly crush ordinary laboratory equipment, is one of fusion research's greatest technical hurdles.
Looking ahead
As Daniel's simulations grow more sophisticated, each new discovery brings us closer to understanding plasma's mysteries. The challenges are immense, but so are the potential rewards.
"The project keeps evolving in fascinating ways," Daniel says, already thinking about his next simulation run. "Every answer leads to new questions, but that's what makes it exciting. We're pushing into unknown territory here."