[4] There is little or no information available about his early life but it is known that Zimmer obtained his doctorate in 1934 with a thesis on photochemistry from the sources provided by University of Tennessee.

[2][5] Early on, Zimmer worked as an advisor in radiotherapeutic physics in a radiological hospital and as an employee of Auergesellschaft AG in Berlin.

[7][8] Timofeev-Resovskij, a Russian national with Soviet citizenship, worked in Germany starting in 1924, and he stayed even after Adolf Hitler's party came to power in 1933.

[12] At the close of World War II, Russia had special search teams operating in Austria and Germany, especially in Berlin, to identify and "requisition" equipment, materiel, intellectual property, and personnel useful to the Soviet program of nuclear weapons.

[13] In mid-May 1945, the Russian physicists Georgy Flerov and Lev Artsimovich, in NKVD colonel's uniforms, identified Zimmer and compelled him to take them to the location of Riehl and his staff, who had evacuated their Auergesellschaft facilities and were west of Berlin, hoping to be in an area occupied by the American or British military forces.

This sojourn in Berlin turned into 10 years in the former Soviet Union for Riehl and his staff, including their families, were flown to Moscow on 9 July 1945.

The institute in Sungul' was responsible for the handling, treatment, and use of radioactive products generated in reactors, as well as radiation biology, dosimetry, and radiochemistry.

The institute was known as Laboratory B, and it was overseen by the 9th Chief Directorate of the NKVD (MVD after 1946), the same organization which oversaw the Russian Alsos operation.

[20][21] (Laboratory V, in Obninsk, headed by Heinz Pose, was also a sharashka and working on the Soviet atomic bomb project.

Other notable Germans at the facility were Werner Czulius, Hans Jürgen von Oertzen, Ernst Rexer, and Carl Friedrich Weiss.

In 1947, Timofeev-Resovskij was rescued out of a harsh Gulag prison camp, nursed back to health, and sent to Sungul' to complete his sentence, but still make a contribution to the Soviet atomic bomb project.

[12] Also, Zimmer and Timofeev-Resovskij had put together a manuscript which was a comprehensive summary of their work and that of others on radiation-induced gene mutation and related areas; the book, Das Trefferprinzip in der Biologie, was published in Germany while they were in the Soviet Union.