Arunav Kumar is a postdoctoral researcher at Massachusetts Institute of Technology (MIT) developing advanced models to ensure the stability of nuclear fusion plasmas, bridging first-principles physics with real-time surrogate models to enable practical, power-plant-scale fusion energy solutions. In this Postdoc Portrait interview, he shares key challenges in maintaining control in nuclear fusion devices and how his experiences have shaped the way he approaches scientific problems.
Advancing Plasma Control and Stability
Q | What drew you to plasma physics?
I was always drawn to problems that didn’t have obvious answers and systems where many things interact at once. Physics appealed to me because it forces you to be precise while still leaving room for creativity.
During my early training, I became fascinated by plasmas because they sit at the intersection of mathematics, computation, and real physical machines. Fusion research, in particular, felt uniquely motivating. It is intellectually demanding, experimentally grounded, and tied to a clear long-term goal that matters beyond academia.
What really pulled me in was working with complex simulation tools and seeing how abstract equations translate into the behavior of real devices. Over time, I became especially interested in stability and control—understanding not just how plasmas behave, but how we can actively shape and regulate them. That focus naturally led me to combine traditional plasma physics with machine learning, where fast models can help bridge the gap between theory, simulation, and real-time operation.
Q | What scientific problem are you trying to solve?
One of my favorite research projects focuses on building robust operating scenarios to avoid plasma disruptions in high-performance fusion devices like tokamaks. These disruptions often arise not from a single instability, but from limited controllability under realistic conditions, including passive structures, actuator constraints, and reduced diagnostic information.
My work examines vertical instability using reduced-order magnetohydrodynamic models that capture plasma-wall coupling and eddy current effects. I use these models to quantify stability margins and control authority across reactor-relevant scenarios for the Affordable, Robust, and Compact (ARC) and Smallest Possible ARC (SPARC) tokamaks. To extend this analysis beyond individual simulations, I develop physics-informed surrogate models that can rapidly scan operating space and identify regimes where robust control is achievable.
The key lesson from this project is that disruption avoidance is as much a control and design problem as it is a physics problem. By linking first-principles modeling with fast predictive tools, this work helps translate detailed stability analysis into practical guidance for scenario design and real-time plasma control.
Bridging Theory and Practical Fusion Energy
Q | What has been the most rewarding part of your research journey?
The most exciting part of my scientific journey has been working at a moment when fusion research is shifting from proof-of-principle experiments to devices designed with power-plant relevance in mind. Being involved in the SPARC and ARC programs has meant thinking not only about plasma physics in isolation, but about how theory, modeling, engineering, and control come together in real machines.
At MIT’s Plasma Science and Fusion Center, I’ve had the opportunity to work alongside colleagues who approach problems from very different angles—experimentalists, theorists, control engineers, and industry partners—yet are all focused on the same goal. That environment has shaped how I think about research: ideas are tested against hardware constraints early, and models are expected to be useful, not just elegant.
What has been especially rewarding is seeing tools I help develop move from analysis and simulation toward influencing design choices and control strategies for next-generation, high-field tokamaks. Contributing to work that sits so close to the path toward practical fusion energy has made this stage of my career uniquely motivating.
Q | If you could be a laboratory instrument, which one would you be and why?
I would be a magnetic control system, because there’s real beauty to it. At 100 million degrees Celsius, plasma behaves unpredictably, yet the right model or control law can steer that chaos into something useful. And every small advance in control isn’t just an academic gain; it’s a step toward making a reactor that actually produces net fusion energy.
Responses have been edited for length and clarity.
Are you a researcher who would like to be featured in the “Postdoc Portraits” series? Send in your application here.
