Research Projects

Currently I am working towards developing a bayesian optimization workflow to optimize fusion reactor scenarios, as well as collaborating with experimental teams at the ASDEX Upgrade and JET tokamaks for the validation of transport models in regards to fluctuation measurements and isotope effects. I am also involved in the development of the SPARC physics basis and research program through scenario modeling techniques.

Over the years I have worked on several projects in physics and engineering, with a strong focus on optimization, modeling and experimental validation. A non-extensive list of the projects I have been involved with is:

Integrated Modeling of SPARC Burning Plasmas

As a postdoctoral researcher at the Plasma Science and Fusion Center, I have been collaborating with the company Commonwealth Fusion Systems on the design of SPARC, a new tokamak that will start operations in 2025. Thanks to innovative superconductor technology, SPARC will be the first device to generate net energy (Q>1), a very important milestone in the quest for fusion energy.

Integrated modeling simulations allow us to dive into the physics of SPARC plasmas, to have an early look into what regimes to expect and what performance SPARC will be able to achieve. My role in the project has been to lead the integrated modeling efforts to inform the design of this unique machine, and provide predictions of kinetic profiles and other plasma quantities to use in further physics studies.

This work has been critical for the development and publication of the SPARC physics basis, and the main results have been featured in The New York Times.

Cutaway of SPARC engineering design (2020). Image courtesy CFS/MIT-PSFC, Rendering by T. Henderson.

Main papers associated with this work:
P. Rodriguez-Fernandez et al 2020 Journal of Plasma Physics 86(5) 865860503
J.W. Hughes et al 2020 Journal of Plasma Physics 86(5), 865860504

Want to know more about the SPARC project?

Status of the SPARC physics basis

Release of the SPARC Physics Basis in the Journal of Plasma Physics and associated press releases.

Perturbative Transport in Tokamaks

During my years as a doctoral student at MIT under the supervision of Prof. White, I worked on unveiling one of the most prominent mysteries in core plasma transport physics: Why does the temperature at the center of the tokamak increases when the edge is cooled down?

As a result of three and a half years of work, and thanks to fruitful collaborations with scientists at MIT, General Atomics, Princeton and Max Planck Institute, we provided an explanation to this 20-year-old problem. We published five peer-reviewed journal papers, including an article in Physical Review Letters, and the work has been featured in about a dozen talks at international conferences and workshops. Our work includes experiments in three world-class devices (Alcator C-Mod, DIII-D and ASDEX Upgrade) and simulations with two of the leading transport solvers in our community (TRANSP and ASTRA).

C. Angioni et al 2019 Nucl. Fusion 59 106007
P. Rodriguez-Fernandez et al 2019 Phys. Plasmas 26 062503
P. Rodriguez-Fernandez et al 2019 Nucl. Fusion 59 066017
P. Rodriguez-Fernandez et al 2018 Phys. Rev. Lett. 120 075001
P. Rodriguez-Fernandez et al 2017 Nucl. Fusion 57 074001

Ph.D. Thesis:
P. Rodriguez-Fernandez 2019 Ph.D. Thesis, MIT

News articles:
MIT News 2019: “Heating by Cooling
MIT News 2018: “Integrated simulations answer 20-year-old question in fusion research“

Time-dependent simulation results following injection of impurities at the plasma edge. Figure from P. Rodriguez-Fernandez et al 2019 Nucl. Fusion 59 066017

Surrogate Techniques for Model Validation

As a side project during my Ph.D., I developed a technique to efficiently explore the vast parameter space required for the validation of plasma transport models. The tool was named VITALS (Validation via Iterative Training of Active Learning Surrogates), and it makes use of the same genetic algorithms aided by surrogate modeling that I developed for turbine optimization.

P. Rodriguez- Fernandez et al 2018 Fusion Technol. 74:1-2, 65-76

Publications using VITALS:
A. J. Creely et al 2019 Plasma Phys. Control. Fusion 61 085022
A. J. Creely 2019 Ph.D. Thesis, MIT

VITALS example (by Prof. White):

Turbine Optimization via Evolutionary Algorithms

For my Master’s thesis project, I had the pleasure to work at the Laboratorio di Fluidodinamica delle Macchine from the Politecnico di Milano, Italy. I worked alongside Prof. Persico on the development of optimization techniques for the shape of turbomachinery blades, particularly those used in Organic Rankine Cycles (ORC). We employed genetic algorithms for multi-objective, constrained optimization problems, and gaussian process regression models to reduce the number of Computational Fluid Dynamics (CFD) simulations required.

We demonstrated the benefit of using this technique on a ORC benchmark case. With respect to the baseline design, our workflow reduced single-blade pressure losses by half, an improvement of 20% with respect to previous gradient-based methods.

G. Persico et al 2019 J. Turbomach. 141(8): 081010
P. Rodriguez-Fernandez 2015 Master Thesis, UPM
P. Rodriguez-Fernandez and G. Persico 2015 ASME ORC

CAD representation of ORC turbine blades and flow pressure contours from a CFD simulation. Figure from P. Rodriguez-Fernandez 2015 Master Thesis, UPM