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The Untold Story of Building the First Megaton Thermonuclear Fusion Device: The Simple Element and IVY Mike

Jonathan E. Morgan

Fusion Science and Technology / Volume 82 / Number 3 / April 2026 / Pages 487-550

Research Article / dx.doi.org/10.1080/15361055.2025.2503035

Received:December 4, 2024
Accepted:April 28, 2025
Published:March 3, 2026

This report is a research and development engineer’s perspective on the fascinating story of the world’s first megaton-class thermonuclear device, IVY Mike (10.4 Mt). Few modern scientific endeavors have matched the complexity and breadth of scientific achievement in such a short amount of time as IVY Mike. This paper will take a look at the design, engineering, fielding, and execution of the world’s first megaton-class physics experiment by Los Alamos Scientific Laboratory and the birth of industrial liquid hydrogen use spawned by the Cold War effort. Although others have written on aspects of this technical history, they have not benefited from access to the original classified documents used by the present author. The present paper must necessarily omit some technical details that remain classified but represents the most comprehensive summary of the engineering and fabrication of the IVY Mike device in the open literature.