Director-Generalde: janvier 1971 à: décembre 1975
In the mid-50s Willibald Jentschke was director of the Hamburg Institute for Physics and was nominated to lead a project to build DESY (Deutsches Elektronen Synchrotron), a world-class electron machine.
From 1964 to 1967 he was the Federal Republic of Germany's delegate to the CERN council and a member of the Scientific Policy Committee. He stayed at CERN in 1968 as a guest professor. In 1969, during Bernard Gregory's years as CERN Director-General, 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 site in France, where the Super Proton Synchrotron was located, remained under the leadership of John Adams as Director-General of CERN Laboratory II. In January 1971 Jentschke was appointed Director-General of CERN Laboratory I in Meyrin, Switzerland. He held the post until December 1975.