illustration of a plasma particle
The fusion reaction is created using a shrinking plasma shell, called the liner, to compress a high-density magnetized plasma target in the center of a spherical vacuum chamber. The plasma liner is generated by dozens of high velocity plasma jets produced from plasma guns mounted around the chamber.
Courtesy LANL

Mechanical and aerospace engineering faculty at The University of Alabama in Huntsville (UAH) have won a pair of research awards totaling $750,000 to collaborate with the Los Alamos National Laboratory (LANL) on research to advance knowledge toward one of the most sought-after goals of plasma physics, plasma fusion energy. This project marks the first experimental collaboration between the university and the LANL, helping to bring fusion and high energy density (HED) plasma research to UAH, a part of The University of Alabama System.

Dr. Gabriel Xu, associate professor, and Dr. Jason Cassibry, a professor affiliated with the UAH Propulsion Research Center, will be studying magnetized high-energy density plasma interactions to advance plasma-jet magneto inertial fusion, or PJMIF, a key component to achieving breakeven fusion, which could one day lead to abundant clean energy.

“I am very much looking forward to doing research that can contribute in some small way to fusion research at UAH,” Dr. Xu says. “Plasma fusion is one of the holy grails in our field of plasma physics and important for the world.”

The two awards are separately funded by the Department of Energy (DOE) Established Program to Stimulate Competitive Research, which is a state and national laboratory partnerships program that works to facilitate collaborations with national laboratories like the LANL.

How fusion occurs

Plasma is one of four fundamental states of matter and the most abundant form found in the universe. It’s mostly associated with stars, which generate energy through nuclear fusion when protons of hydrogen atoms in their cores violently collide to fuse and form helium atoms. Producing accurate simulations of fusion plasma conditions at peak compression in the laboratory is crucial to guiding experiments that could ultimately lead to the development of a viable fusion reactor. “Breakeven fusion” describes the moment when plasmas in a fusion device release at least as much energy as is required to heat them.

Nuclear fusion has been a goal of scientists around the world since the 1950s. Unlike solar and wind power, the energy it produces is virtually limitless, and – unlike electricity generated by fission reactors, coal, oil, or natural gas – fusion energy requires no fossil fuels and leaves behind zero hazardous waste.

Michael Mercier | UAH

“The focus of our project is to look at the next step in the PJMIF approach, namely the interaction of the plasma liner with the magnetized target plasma,” Dr. Xu says. “For fusion to occur, the liner has to compression the target and convert its kinetic energy into thermal energy and heat the plasma to fusion conditions. So, our small-scale test will be one step towards understanding the plasma interactions and energy conversion process that can inform the larger scale efforts of PJMIF.”

Magneto-inertial fusion (MIF) describes a class of fusion devices that use magnetic fields to confine an initial warm, low-density plasma, which it then compresses to fusion conditions. Though the scale and energies of this experiment will not reach actual fusion levels, the new research aims to provide insight into how to achieve this goal.

“The PJMIF concept creates a fusion reaction by using a shrinking plasma shell, called the liner, to compress a high-density magnetized plasma target in the center of a spherical vacuum chamber,” explains Dr. Xu. “The plasma liner is generated by dozens of high velocity plasma jets produced from coaxial plasma guns mounted around the chamber. As the plasma jets move towards the target in the center, they would merge into the shell/liner.

“At this point, LANL’s research is focused on studying this merging behavior and formation of the liner. Our project seeks to take a step forward in the process and study the interaction between the magnetized plasma target and a high velocity plasma jet. So, you could imagine taking a slice of the PJMIF sphere, and that’s what we’re looking at. Understanding how the two plasma interact and how to convert the kinetic energy of the jet to thermal energy that can heat and compress the target will help PJMIF and other related concepts towards breakeven.”

History in the making

Advancing concepts on magnetized high-energy density plasma interactions has been a long-term goal for North Alabama researchers, Dr. Xu notes.

“This work started at NASA’s Marshall Space Flight Center with Francis Thio and Richard Eskridge as a propulsion program back in 1998. Dr. Cassibry joined this team as a graduate student and conducted dissertation work on coaxial plasma guns, which could produce the jets. Subsequently, several DOE, Advanced Research Projects Agency–Energy (ARPA-E) and NASA grants have supported the work, including the most recent ARPA-E Breakthroughs Enabling THermonuclear-fusion Energy (BETHE) program.”

“Dr. Xu’s expertise in experimental plasmas, along with his recent work in studying interactions of plasma jets with magnetic fields, seemed to facilitate a perfect collaboration for the DOE opportunity,” says Dr. Cassibry.

“Both Dr. Cassibry and I have been interested in fusion research for a while now, and we had been working at it from different angles with different projects in plasma sciences and engineering,” Dr. Xu says. “While Dr. Cassibry had worked with LANL before in computational modeling, UAH and I had never done experimental fusion-related research. This project idea came about in discussion with a colleague at LANL whom both Dr. Cassibry and I knew from prior interactions. He helped us formulate the project idea based on our interests and capabilities, and what would benefit LANL. So, it's a win for everyone!”

One of the main objectives here at UAH is to develop the staged plasma guns required to produce high velocity plasma jets, which will in turn lead to large-scale plasma gun development at LANL.

“To get high compression, you want high velocity kinetic energy in the jets,” Dr. Xu says. “You could try and make a single coaxial plasma gun longer or more powerful to get faster jets, but that has problems like parasitic plasma formation, because electrical power always wants to find the path of least resistance. So, another method is to create separate acceleration stages that have independent power systems. We have recently successfully fired a single stage coaxial plasma gun (CPG) in the lab. So that was the first step in the project and arguably the most important. Next, we’ll start designing secondary acceleration stages and learn how to couple them physically and electrically. It will not be easy, as the coaxial configuration make electrical connections challenging, but we’re excited to try.”

Just how integral is the PJMIF concept to achieving clean energy? “It’s hard to predict what’s the best way to achieve breakeven fusion,” Dr. Xu says. “Progress on inertial and magnetic concepts suggest a working fusion pilot plant is achievable in about 15 to 20 years. The National Ignition Facility achieved ignition for the first time last year. That’s not breakeven, but it’s a step towards it. The PJMIF concept is an effort to move towards an economical power production device design. It’s likely not the device that will achieve breakeven at the end of the day, but the science we learn from our project and PJMIF will inform future pulsed fusion concepts and designs that can finally give us breakeven fusion and clean energy.”