GAEDE, WOLFGANG

(b. arb. Lehe, near Bremerhaven, Germany, 25 May 1878; d. Munich, Germany, 24 June 1945)

physics.

Gaede, the founder of high-vacuum technology, through his invention of the mercury rotary pump (1905), the molecular pump (1912), and the diffusion pump (1915), made possible numerous new applications in technology and physicsm-semiconductor technology and nuclear physics, to mention only two.

The son of Karl Wilhelm Gaede, a Prussian army captain, and of Amalie Ruef, Gaede spent his youth in Freiburg im Breisgau, his mother’s native city. There he attended the university. From childhood he had shown a remarkable ability to visualize and analyze complicated moving systems, a skill ob viously of invaluable help in his later inventions. He gave his technicians little more than a rough sketch, since he told them every detail of the pump under construction from memory.

At the University of Freiburg. Gaede first studied medicine but soon changed to physics. He received the Ph.D. in 1901 with a dissertation titled “Umlber die Aumlnderung der spezifischen Waumlrme der Metalle mit der Temperatur.” He remained at Freiburg, as assistant to Franz Himstedt, until 1908. Continuing the work of his dissertation with experiments on

a housing

b porcelain drum

c mercury pool

d1, d2 chambers

e intake port

f1, f2 exhaust channels

h stopcock.

the Volta effect in a vacuum, Gaede was led to his first invention, the mercury rotary pump. It was the first continuously working air pump and had a much higher pumping speed than previous pumps-about 0.2 cubic decimeters per second.

Gaede presented the pump to the scientific world in 1905, at the Naturforscherversammlung in Meran. The efficient pump immediately was in great demand, and Gaede commissioned the small firm E. Leybolds Nachfolger to produce it. Gaede maintained a close connection with this establishment, which became a leader in vacuum technology.

Between 1905 and 1909 Gaede spent much of his time investigating the external friction of gases and its possible usefulness for a new method of creating a high vacuum. He qualified to teach at the University of Freiburg with the Habilitationsschrift “Die aumlseere Reibung der Gase” (1911.)

a housing

b> rotating cylinder

c slot

d hose

e manometer.

One consequence of Gaede”s work on external friction of gases was the construction of the molecular pump in 1911. It was the first pump to be based on a method different in principle from that used by Otto Von Guericke. The gas molecules adhere to a fast-rotating surface, thus gaining additional mo mentum away from the vessel to be exhausted. The pumping speed was about 2 cubic deciliters per second, ten times greater than the mercury rotary pump. The ultimate vacuum presure was less than 10–6 millieters of mercury. In 1913 this invention brought Gaede an associate professorship at Freiburg and the Elliot cresson gold medal of the Franklin Institute.

Another new pumping principle discussed in Gaede”s Hanbilitationssschrift was that of the diffussion pump. In it the gas molecules diffuse into a rapidly moving vapor jet and thus move away from the evacuted space and toward the backing pump. With this apparatus Gaede obtained a new record low pressure. The prototype had a pumping speed of 0.2 cubic deciliters per second. In 1923 the efficiency

a mercury pool

b vapor compartment

c conduit for mercury vapor

d distributor

e nozzles

f slit

g cooling water intake and outlet, respectively

h return pipe for liquid mercury

i vacuum pump connection.

was improved to 150 cubic deciliters per second and in 1944 to 1.500 cubic deciliters per second.

In 1917 Gaede was offered a professorship at the declined because of the political instability in that city. In 1919 he decided to go to the Technical University of Karlsruhe, where he accepted the professorship once held by Heinrich Hertz. The Physical Society of London awarded Gaede the Dudell medal in 1933; in the same year he was de nounced by some of his assistants as being “polit ically unreliable.‘ and the medal made him an object of persecution by the Nazi regime. Although he was not Jewish. Gaede was dismissed from his pro fessorship at the end of 1933. However, the Siemens

a housing

b rotor with dampers

c gas ballast valve

d oil trap

e intake port

f dirt trap.

Ring Foundation voted to give him the Siemens Ring, the highest award a German inventor could receive. He transferred his work to a private lab oratory in Karlsruhe that was equipped and spon sored by Leybold.

In 1935 Gaede invented the gas ballast device that he applied to an oil-filled rotary vane pump (gas ballast pump). This device, which prevents pumped vapors from being condensed in the pump during the compression phase, injects a permanent gas, usually air, into the compression ratio of the vapor is reduced when the exhaust valve of the pump opens, and thus no condensation occurs.

In 1939 Gaede went to Munich, where he estab lished a private laboratory. In his contact with Arnold Sommerfeld and his co-workers he found an ac knowledgement he had not earlier enjoyed. The laboratory was destroyed during an air raid in 1944. A year later Gaede contracted a fatal case of diphtheria.

Throughout his life Gaede was an outsider. He could afford to be. Since he had no financial problems after the invention of the mercury rotary pump. He never married, and his sister Hannah always took care of him. Contacts with his colleagues were rare, and his students testified that he was a bad teacher. He seems to have been an amiable, eccentric man, asingenious inventors are sometimes said to be.

BIBLIOGRAPHY

1. Original Works. “Uuml die Aumlnderung der spezi fischen Waumlrme der Metalle mit der Temperatur” (Ph.D. Dissertation, Freiburg im Breisgau, 1902); “Demonstration einer rotierenden Quecksilberluftpumpe,” in Physikalische Zeitschrift, 6 (1905), 758–760; “Demonstaration einer neuen Verbesserung an der rotierende Quechsilberluftpumpe.” ibid., 8 (1907). 852–853; “Die aumlussere Reibung der Gase,” in Berichte der Naturforschenden Gesellschaft Zu Freiburg im Breisgau, 18 . no.2 (1911), 133–197, his Habilita tionsschrift; “Die aumlssere Reibung der Gase und ein neues Prinzip fuumlr Luiftpumpen: Die Molekularluftpumpe,” in Physikalische Zeitschrift, 13 (1912) 864–870, and in An nalen der Physik, 41 (1913), 289–336; “Die Molekular-Iuftpumpe,” in Annalen der Physik, 41 (1913), 337–380; “Die Diffusion der Gase durch Quecksilberdampf bei niederen Drucken und die Diffusionsluftpumpe,” ibid., 46 (1915), 357–392; “Die Entwicklung der Diffusions pumpe,” in Zeitschrift fuumlr technische Physick, 4 (1923), 337–369; “Die Ældiffusionspumpe,” ibid., 13 (1932), 210–212; and “Gasballastpumpen,” in Zeitschrift für Naturforschung, 2A (1947), 233–238.

Gaede wrote articles on pumps and vacuum technology for Felix Auerbach and W. Hort, eds., Handbuch der Physikalischen und technischen Mechanik, VI (Leipzig, 1928), 90–121; and Wilhelm Wien and F, harms, eds., Handbuch der Experimentalphysik, IV, pt.3 (Leipzig, 1930), 413–461.

II. Secondary Literature. Tributes are E. Justi, in Elektrotechnische Zeitschrift, 64 (1943), 285–287; K. May, in Zeitschrift fuuml technische Physik, 24 (1943), 65; and W. Molthan, ibid., 19 153–154.

Obituaries include Arnold Sommerfeld, “In Memoriam. Wolfgang Gaede,” in Zeitschrift fuumlr Naturforschung, 2A (1947), 240; and Franz Wolf, in Physikalische Blätter, 3 (1947), 384–386.

Biographical material is in Manfred Dunkel, Geschichte der Firma E. Leybolds Nachfolger: 1850–1966 (Cologne, 1963); Hannah Gaede, Wolfgang Gaede, der Schoumlpfer des Hochvakuums (Karlsruhe, 1954); Poggendorff, V (1926), 407, and VIIa, pt. 2 (1958), 154; and Franz Wolf, in Karlsruher akademische Reden, n.s. 3 (1947), and Neue deutsche Biographie, VI (1964), 16–17.

A. Branchner