In 1956, he became a professor of physics at the University of Hamburg and spearheaded the effort to build the 7.5 GeV electron synchrotron DESY, the foundation of which was in December 1959.

This work was done under the German nuclear energy project, also known as the Uranverein (Uranium Club); see, for example, the publications cited below under Internal Reports.

This was borne out by the work of Eugene T. Booth, John R. Dunning, A. V. Grosse, and Alfred O. C. Nier, which was submitted for publication in the spring of 1940.

[2] Near the close and after the end of World War II in Europe, the Russians and the Western powers had programs to foster technology transfer and exploit German technical specialists.

This was rectified with a decree in late 1944 and the formation of specialize exploitation teams in early 1945 under the Russian Alsos, which had broader objectives, which included wholesale relocation of scientific facilities to the Soviet Union.

On his way to the United States, Jentschke wrote to Walther Bothe that his reasons for going there was to do real scientific work, which then not possible in Austria and Germany.

Other members of the Nuclear Physics Working Group in both 1956 and 1957 were: Werner Heisenberg (chairman), Hans Kopfermann (vice-chairman), Fritz Bopp, Walther Bothe, Wolfgang Gentner, Otto Haxel, Heinz Maier-Leibnitz, Josef Mattauch, Wolfgang Riezler [de], Wilhelm Walcher, and Carl Friedrich von Weizsäcker.

While at DESY, Jentschke endorsed the electron-positron storage ring scheme for the DORIS accelerator, and promoted the use of synchrotron radiation for research purposes.

While Director General, Jentschke oversaw the exploitation of the new research tool, the Intersecting Storage Rings, which began operation in 1971.

The reports were confiscated under the Allied Operation Alsos and sent to the United States Atomic Energy Commission for evaluation.