Spanish physicist at CIEMAT who made foundational contributions to stellarator optimization and became a driving force behind the IFMIF-DONES neutron irradiation facility — essential infrastructure for qualifying fusion materials.
Carlos Alejaldre Branas (commonly published as Carlos Branas or Carlos Alejaldre) has been a leading figure at CIEMAT (Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas), Spain's national energy research center in Madrid. His career has spanned stellarator physics, fusion technology development, and major international facility leadership roles.[1]
At CIEMAT, Branas contributed to the TJ-II flexible heliac stellarator program, one of Europe's key stellarator experiments. His work addressed plasma heating, confinement optimization, and the fundamental physics of three-dimensional magnetic configurations. The TJ-II device, with its uniquely flexible magnetic geometry, served as a testbed for understanding how stellarator plasmas behave under varied configuration parameters.[2]
Perhaps Branas's most consequential contribution has been his leadership role in the development of IFMIF-DONES (International Fusion Materials Irradiation Facility — Demo Oriented Neutron Source). This accelerator-based neutron source is designed to produce a fusion-relevant neutron spectrum at sufficient intensity to qualify structural materials for use in demonstration fusion power plants.[1]
The facility uses a high-energy deuteron beam striking a liquid lithium target to generate neutrons with an energy spectrum closely matching that of D-T fusion reactions. Branas helped shepherd the project through its engineering design phases and advocated for its construction in Granada, Spain, where it is now planned as a European priority infrastructure.[3]
Branas recognized early that materials qualification represented a potential bottleneck on the path to fusion power. Structural materials in a fusion reactor must withstand unprecedented combinations of neutron damage (measured in displacements per atom), helium and hydrogen transmutation production, and high operating temperatures. Accelerated testing under realistic neutron spectra is essential to validate material performance predictions and satisfy regulatory requirements.[2]
His technical contributions included the design of irradiation test modules, neutronics optimization of the lithium target system, and development of the scientific case linking IFMIF-DONES experimental capabilities to DEMO reactor material needs.[3]
Through his work on IFMIF-DONES and stellarator physics, Branas has been deeply embedded in European fusion strategy discussions. He contributed to roadmap exercises defining the technology development path from ITER through DEMO to commercial fusion power, consistently emphasizing that enabling technologies — not just plasma physics milestones — would determine the timeline to fusion electricity.[1]