In the mid-1950s Willibald Jentschke was Director of the Hamburg Institute for Physics and was nominated to lead a new project to build a world-class electron machine, now known as DESY (Deutsches Elektronen Synchrotron).

From 1964-1967 he was the Federal Republic of Germany's delegate to Council and a member of the Scientific Policy Committee. In 1968 he remained at CERN one year as a Guest Professor. In 1969, during Bernard Gregory's years as Director-General of CERN, Willibald Jentschke was appointed Chairman of the ISR Committee.

In the early 1970s, two CERN Laboratories existed side by side at Meyrin and Prévessin. The Prévessin (France) site, where the Super Proton Synchrotron was located, remained under the leadership of John Adams as Dir ector-General of CERN Laboratory II. Willibald Jentschke became Director-General of CERN Laboratory I (Meyrin, Switzerland) in January 1971 - December 1975.