Gerhard Hoffmann

For the pilot, see Gerhard Hoffmann (pilot).

Gerhard Hoffmann (4 August 1880 – 18 June 1945) was a German nuclear physicist. During World War II, he contributed to the German nuclear energy project, also known as the Uranium Club.

Education

Hoffmann studied at the Georg-August-Universität Göttingen, the Universität Leipzig, and the Rheinische Friedrich-Wilhelms-Universität Bonn. He received his doctorate at Bonn, in 1906, under Walter Kaufmann. In 1908, he became Kaufmann’s teaching assistant at the Albertus-Universität Königsberg, where he completed his Habilitation in pure and applied physics in 1911.[1]

Career

In 1917, Hoffmann became an ausserordentlicher Professor (extraordinarius professor) and worked on precision measurement of radioactivity and research in cosmic rays. From 1928-1937, as successor to Gustav Hertz, he was ordentlicher Professor (ordinarius professor) at the Martin-Luther-Universität Halle-Wittenberg. In 1937 he succeeded Peter Debye and became ordinarius professor of experimental physics at the University of Leipzig, a position he held until his death in 1945.[2]

In December 1938, the German chemists Otto Hahn and Fritz Strassmann sent a manuscript to Naturwissenschaften reporting they had detected the element barium after bombarding uranium with neutrons;[3] simultaneously, they communicated these results to Lise Meitner, who had in July of that year fled to The Netherlands and then went to Sweden.[4] Meitner, and her nephew Otto Robert Frisch, correctly interpreted these results as being nuclear fission.[5] Frisch confirmed this experimentally on 13 January 1939.[6]

Paul Harteck was director of the physical chemistry department at the University of Hamburg and an advisor to the Heereswaffenamt (HWA, Army Ordnance Office). On 24 April 1939, along with his teaching assistant Wilhelm Groth, Harteck made contact with the Reichskriegsministerium (RKM, Reich Ministry of War) to alert them to the potential of military applications of nuclear chain reactions. Two days earlier, on 22 April 1939, after hearing a colloquium 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. The communication was given to Abraham Esau, head of the physics section of the Reichsforschungsrat (RFR, Reich Research Council) at the REM. On 29 April, a group, organized by Esau, met at the REM to discuss the potential of a sustained nuclear chain reaction. The group included the physicists Walther Bothe, Robert Döpel, Hans Geiger, Wolfgang Gentner (probably sent by Walther Bothe), Wilhelm Hanle, Gerhard Hoffmann, and Georg Joos; Peter Debye was invited, but he did not attend. After this, informal work began at Göttingen by Joos, Hanle, and their colleague Reinhold Mannfopff; the group of physicists was known informally as the first Uranverein (Uranium Club) and formally as Arbeitsgemeinschaft für Kernphysik. The group’s work was discontinued in August 1939, when the three were called to military training.[7][8][9][10]

The second Uranverein began after the HWA squeezed out the RFR of the REM and started the formal German nuclear energy project under military auspices. The second Uranverein was formed on 1 September 1939, the day World War II began, and it had its first meeting on 16 September 1939. The meeting was organized by Kurt Diebner, former student of Hoffmann at the University of Halle and advisor to the HWA, and held in Berlin. The invitees included Walther Bothe, Siegfried Flügge, Hans Geiger, Otto Hahn, Paul Harteck, Gerhard Hoffmann, Josef Mattauch, and Georg Stetter. A second meeting was held soon thereafter and included Klaus Clusius, Robert Döpel, Werner Heisenberg, and Carl Friedrich von Weizsäcker. Also at this time, the Kaiser-Wilhelm Institut für Physik (KWIP, Kaiser Wilhelm Institute for Physics, after World War II the Max Planck Institute for Physics), in Berlin-Dahlem, was placed under HWA authority, with Diebner as the administrative director, and the military control of the nuclear research commenced.[11][12][13][14]

Hoffmann made contributions to the Uranverein in the area of cyclotrons as a nuclear research tool. He was among the first in Germany to propose and arrange financing for the construction of a cyclotron. His arrangements in 1937 were through the Reichsforschungsrat; the cyclotron would eventually be installed at the University of Leipzig. Hoffmann had gone to Siemens und Halske AG with a proposal on the design of a cyclotron; the project was appealing to Desiderius Flir and Gustav Hertz at Siemens. Walther Bothe, Director of the Institut für Physik at the Kaiser-Wilhelm Institut für medizinische Forschung (Kaiser Wilhelm Institute for Medical Research; today, the Max-Planck Institut für medizinische Forschung), in Heidelberg, was concurrently a competitor for support and took a different design to Siemens. The construction of their cyclotron at Heidelberg was overseen by Wolfgang Gentner.[15][16][17]

Bibliography

Notes

  1. ↑ Hentschel and Hentschel, 1996, Appendix F; see entry for Hoffmann.
  2. ↑ Hentschel and Hentschel, 1996, Appendix F; see entry for Hoffmann.
  3. ↑ O. Hahn and F. Strassmann Über den Nachweis und das Verhalten der bei der Bestrahlung des Urans mittels Neutronen entstehenden Erdalkalimetalle (On the detection and characteristics of the alkaline earth metals formed by irradiation of uranium with neutrons), Naturwissenschaften Volume 27, Number 1, 11-15 (1939). The authors were identified as being at the Kaiser-Wilhelm-Institut für Chemie, Berlin-Dahlem. Received 22 December 1938.
  4. ↑ Ruth Lewin Sime Lise Meitner’s Escape from Germany, American Journal of Physics Volume 58, Number 3, 263- 267 (1990).
  5. ↑ Lise Meitner and O. R. Frisch Disintegration of Uranium by Neutrons: a New Type of Nuclear Reaction, Nature, Volume 143, Number 3615, 239-240 (11 February 1939). The paper is dated 16 January 1939. Meitner is identified as being at the Physical Institute, Academy of Sciences, Stockholm. Frisch is identified as being at the Institute of Theoretical Physics, University of Copenhagen.
  6. ↑ O. R. Frisch Physical Evidence for the Division of Heavy Nuclei under Neutron Bombardment, Nature, Volume 143, Number 3616, 276-276 (18 February 1939). The paper is dated 17 January 1939. [The experiment for this letter to the editor was conducted on 13 January 1939; see Richard Rhodes The Making of the Atomic Bomb 263 and 268 (Simon and Schuster, 1986).]
  7. ↑ Kant, 2002, Reference 8 on p. 3.
  8. ↑ Hentschel and Hentschel, 1996, 363-364 and Appendix F; see the entries for Esau, Harteck and Joos. See also the entry for the KWIP in Appendix A and the entry for the HWA in Appendix B.
  9. ↑ Macrakis, Kristie Surviving the Swastika: Scientific Research in Nazi Germany (Oxford, 1993) 164-169.
  10. ↑ Jagdish Mehra and Helmut Rechenberg The Historical Development of Quantum Theory. Volume 6. The Completion of Quantum Mechanics 1926-1941. Part 2. The Conceptual Completion and Extension of Quantum Mechanics 1932-1941. Epilogue: Aspects of the Further Development of Quantum Theory 1942-1999. (Springer, 2001) 1010-1011.
  11. ↑ Hentschel and Hentschel, 1996, 363-364 and Appendix F; see the entries for Diebner and Döpel. See also the entry for the KWIP in Appendix A and the entry for the HWA in Appendix B.
  12. ↑ Macrakis, Kristie Surviving the Swastika: Scientific Research in Nazi Germany (Oxford, 1993) 164-169.
  13. ↑ Jagdish Mehra and Helmut Rechenberg The Historical Development of Quantum Theory. Volume 6. The Completion of Quantum Mechanics 1926-1941. Part 2. The Conceptual Completion and Extension of Quantum Mechanics 1932-1941. Epilogue: Aspects of the Further Development of Quantum Theory 1942-1999. (Springer, 2001) 1010-1011.
  14. ↑ Kant, 2002, 3n13.
  15. ↑ Maria Osietzki, Maria The ideology of early particle accelerators: an association between knowledge and power pp. 262 and 264-265, in Monika Rennenberg and Mark Walker (editors) Science, Technology and National Socialism (Cambridge, 2002, first paperback edition) pp. 255-270.
  16. ↑ Ulrich Schmidt-Rohr Wolfgang Gentner: 1906-1980 (Universität Heidelberg).
  17. ↑ J. L. Heilbron and Robert W. Seidel Lawrence and His Laboratory: A History of the Lawrence Berkeley Laboratory, Volume I. (University of California Press, 1989 321 and 347-348.
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