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Carlos Alejaldre

Spanish fusion physicist who served as ITER Deputy Director-General for Safety and Security — and directed the TJ-II stellarator programme, Spain’s flagship fusion experiment.

Reviewed Last reviewed: 9 Aug 2026 · Category: Scientists & Pioneers

Career

Carlos Alejaldre is a Spanish plasma physicist who directed the National Fusion Laboratory at CIEMAT (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas) in Madrid, where he led the TJ-II flexible heliac stellarator programme. He subsequently served as ITER Deputy Director-General for Safety, Quality, and Security from 2006 to 2014.[1]

TJ-II: The TJ-II is a four-period heliac stellarator with remarkable magnetic configuration flexibility. Under Alejaldre’s leadership, it became a world-leading facility for studying the effect of magnetic configuration on plasma properties, contributing uniquely to stellarator optimisation physics.

ITER Safety

At ITER, Alejaldre was responsible for establishing the safety framework for the world’s largest fusion experiment. He led the development of ITER’s safety case, demonstrating that fusion’s inherent safety characteristics (no chain reaction, limited radioactive inventory, no meltdown mechanism) justified a regulatory approach fundamentally different from fission.[2]

Recognition

Alejaldre has been a key figure in building Spain’s fusion programme and in the international stellarator community. He has served on numerous IAEA and European advisory committees.[3]

Sources

  1. Alejaldre, C. et al. "First plasmas in the TJ-II flexible heliac." Plasma Physics and Controlled Fusion, 41, A539, 1999.
  2. ITER Organization. "ITER Safety." iter.org.
  3. CIEMAT. "National Fusion Laboratory." fusionlab.ciemat.es.

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