 Livermore started its laser fusion program in 1962-63 and began to greatly expand its inertial fusion program in the early 1970s as the first high-power lasers became available.In 1975, Nuckolls was promoted to become the Associate Leader of the Laser Fusion Program, as well as the Divisional Leader of the "X-group" that designed the fuel "targets".In 1983 he was promoted to become the Associate Director of the entire Physics branch.