Georg Robert Döpel (3 December 1895 – 2 December 1982) was a Germany experimental nuclear physicist. He was a participant in a group known as the "first Uranverein", which was spawned by a meeting conducted by the Reichserziehungsministerium, in April 1939, to discuss the potential of a sustained nuclear reaction. He worked under Werner Heisenberg at the University of Leipzig, and he conducted experiments on spherical layers of uranium oxide surrounded by heavy water. He was a contributor to the German nuclear weapon project (Uranprojekt). In 1945, he was sent to Russia to work on the Soviet atomic bomb project. He returned to Germany in 1957, and he became professor of applied physics and director of the Institut für Angewandte Physik at the Hochschule für Elektrotechnik, now Technische Universität, in Ilmenau (Thuringia).
Döpel was born in Neustadt. From 1919 to 1924, he attended the University of Leipzig, the Friedrich Schiller University Jena, and the Ludwig Maximilian University of Munich (LMU). He received his doctorate, in 1924, under the Physics Nobel Laureate Wilhelm Wien at LMU.
After receipt of his doctorate, Döpel became Robert W. Pohl's teaching assistant at the University of Göttingen. He also worked with the Physics Nobel Laureate Johannes Stark on canal rays, at the private laboratory of Rudolf Freihern von Hirsch zu Planegg, just west of Munich.
In 1929, Döpel became a teaching assistant at the Julius-Maximilians-Universität Würzburg, and in 1932 he became a privatdozent there.
In 1939, Döpel became an extraordinarius professor at the University of Leipzig, where he was a colleague of Werner Heisenberg. At some point, Döpel succeeded Fritz Kirchner as professor of radiation physics.
On 22 April 1939, after hearing a paper by Wilhelm Hanle on the use of uranium fission in a uranmaschine (uranium machine, i.e., nuclear reactor), Georg Joos, along with Hanle, notified Wilhelm Dames, at the Reichserziehungsministerium (REM, Reich Ministry of Education), of potential military applications of nuclear energy. Just seven days later, a group, organized by Dames, met at the REM to discuss the potential of a sustained nuclear chain reaction. Their Arbeitsgemeinschaft für Kernphysik was known informally as the first Uranverein (Uranium Club) and included the physicists Walther Bothe, Wilhelm Hanle, his friend Robert Döpel, Hans Geiger, Wolfgang Gentner, Gerhard Hoffmann, and Joos. Informal work began at the University of Göttingen by Joos, Hanle, and their colleague Reinhold Mannkopff. Their work was discontinued in August 1939, when the three were called to military training.
The second Uranverein began after the Heereswaffenamt (Army Ordnance Office) squeezed out the Reichsforschungsrat (Reich Research Council) of the Reichserziehungsministerium and started the formal German nuclear weapon project. The first meeting was held on 16 September 1939. A second meeting soon thereafter included Klaus Clusius, Carl Friedrich von Weizsäcker, Werner Heisenberg and Robert Döpel, his counterpart as an experimental physicist at the University of Leipzig. Here, Heisenberg was the director of the Department of Theoretical Physics until 1942.
In August 1940, Döpel showed the utility of using heavy water as a moderator in a research nuclear reactor (uranmaschine) together with his wife Klara. She had studied law and worked as a lawyer until 1933, when the Nazi regime prevailed. In 1934, she married Robert Döpel and changed her area of studies to physics, and she worked with him in Leipzig without wages. They conducted experiments with a spherical geometry (hollow spheres) of uranium surrounded by heavy water. Trial L-I was done in August 1940, and L-II was conducted six months later. Results from trial L-IV, in the first half of 1942, indicated that the spherical geometry, with five metric tons of heavy water and 10 metric tons of metallic uranium, could sustain a fission reaction. So, "the Germans were the first physicists in the world, with their Leipzig pile L-IV, to achieve positive neutron production." The results were set forth in an article by Döpel, Döpel's wife, and W. Heisenberg. The article was published at first in the Kernphysikalische Forschungsberichte (Research Reports in Nuclear Physics), a classified internal reporting vehicle of the Uranverein. 1942 was the year in which supervision of the Uranverein was transferred from the Heereswaffenamt to the Reichsforschungsrat.
In June 1942, Döpel's uranmaschine was destroyed by a low-speed detonation induced by hydrogen formation. This was the first in a series of accidents that destroyed nuclear energy assemblies due to wrong hydrogen handling. Already afore, a shift of the main works of Heisenberg towards the Kaiser-Wilhelm-Institut für Physik (after World War II the Max Planck Institute for Physics) in Berlin was decided. The Döpels didn't follow him despite his wishes, and they retired thereby from the uranium project. This finished the work on this topic at Leipzig.
In a letter written in December 1943, Döpel recounted that air raids had destroyed 75% of Leipzig, including his institute. Air raids during that year had also burned down Döpel's institute apartment and Heisenberg's house in Leipzig. Sixteen months later, on April 6, 1945, just 32 days before the surrender of Germany, Klara was killed in an air raid, while she was working in the physics building.
Near the close of World War II, the Soviet Union sent special search teams into Germany to locate and deport German nuclear scientists or any others who could be of use to the Soviet atomic bomb project. The Russian Alsos teams were headed by NKVD Colonel General A. P. Zavenyagin and staffed with numerous scientists, from their only nuclear laboratory, attired in NKVD officer's uniforms. The main search team, headed by Colonel General Zavenyagin, arrived in Berlin on 3 May, the day after Russia announced the fall of Berlin to their military forces; it included Colonel General V. A. Makhnjov, and nuclear physicists Yulij Borisovich Khariton, Isaak Konstantinovich Kikoin, and Lev Andreevich Artsimovich. Döpel was sent to the Soviet Union to work on their atomic bomb effort. At first, he worked at the Nauchno-Issledovatel'skij Institut-9 (NII-9, Scientific Research Institute No. 9), in Moscow. There, he worked with Max Volmer on the production of heavy water. In 1952, he became a regular professor of experimental physics at the university of Woronesh. In 1954, he married the Ukrainian Sinaida Fedorowna Trunowna, widow of a Soviet officer that had died in World War II.
Döpel returned to East Germany in 1957, together with his wife. He became professor of applied physics and director of the Institut für Angewandte Physik (Institute for Applied Physics) at the Hochschule für Elektrotechnik (today the Technische Universität) Ilmenau. There, he conducted spectral analysis of the mechanism of electric discharges in gases.
Later on, he was engaged in energetics in connection with waste heat and global warming problems. With his zero-dimensional climate model, he estimated global warming contributions from waste heat for coming centuries which have been confirmed meanwhile by more refined model calculations. He died in Ilmenau in 1982. In honour of his 100th birthday in 1995, there were solemn colloquia at the Universities of Ilmenau and of Leipzig.
The following reports were published in Kernphysikalische Forschungsberichte (Research Reports in Nuclear Physics), an internal publication of the German Uranverein. The reports were classified top secret, they had very limited distribution, and the authors were not allowed to keep copies. The reports were confiscated under the Allied Operation Alsos and sent to the United States Atomic Energy Commission for evaluation. In 1971, the reports were declassified and returned to Germany. The reports are available at the Karlsruhe Nuclear Research Center and the American Institute of Physics.