In 1971, Jentschke accepted the post as Director General of CERN Laboratory I (the Meyrin site); John Adams was Director General of the neighboring CERN Laboratory II (Prévessin), where the new SPS proton synchrotron was being constructed.
In 1971, Jentschke took charge of CERN Laboratory I (Meyrin) and John Adams managed the adjacent CERN Laboratory II (Prévessin), which was building a new SPS proton accelerator.