The physicist who built an atomic accelerator amid wartime siege
“We flew to Khvoynaya, waited for darkness, then flew low over Lake Ladoga.”
Leonid Nemenov was a Soviet physicist who worked on nuclear physics and accelerator technology. At Kurchatov’s direction, he entered besieged Leningrad to recover vital parts of the Fiztekh cyclotron and led construction of the cyclotron brought into operation at Laboratory No. 2 in 1944. The machine provided the necessary basis for obtaining the first trace quantities of plutonium for chemical analysis.
Activities and affiliations
Career Timeline
- 1929Graduated from Leningrad State University
- 1929–1939Researcher at the Leningrad Physico-Technical Institute
- 1939–1944Worked on designing and building a large cyclotron
- 1943–1944Led construction of the Laboratory No. 2 cyclotron
- 1949Received a Doctor of Technical Sciences degree
- 1962Became a professor and full member of the Academy of Sciences of the Kazakh SSR
- 1968–1980Head of the All-Union Research Institute of Physico-Technical and Radio-Technical Accelerator Measurements
- 1980Died in Moscow
Related historical events
- 1941–1944Siege of LeningradRecovered cyclotron parts in besieged LeningradAt Kurchatov’s direction, he entered besieged Leningrad and recovered cyclotron parts.
- 1943–1949The Soviet Atomic ProjectCyclotron construction chiefSent by Kurchatov into besieged Leningrad to recover Fiztekh cyclotron parts, he built the first cyclotron for Laboratory No. 2, critical for producing the first micrograms of plutonium.
Pioneer of accelerator technology: from mass defect to the isochronous cyclotron
Nemenov’s scientific contribution extended far beyond a single episode of the bomb project and ran through an entire era of Soviet accelerator physics. From 1935 to 1937 he built the Soviet Union’s first precision mass spectrometer for measuring mass defect, carried out the first such measurements, and also studied secondary emission from metals under fast-ion bombardment. In 1937, together with Abram Alikhanov, Igor Kurchatov, and Yakov Khurgin, he designed what was then Europe’s largest cyclotron, with a pole diameter of 1,200 millimetres. Meant to go into operation in January 1942, it was halted by the Great Patriotic War, and later the parts he recovered from besieged Leningrad fed into the first cyclotron of Laboratory No. 2.
During the war Nemenov kept innovating under severe conditions. The M-1 cyclotron, brought up from Leningrad and put into operation in August 1944, had a pole diameter of 730 millimetres and a 25-ton magnet, and on 25 September 1944 it extracted a deuteron beam, the first in the Soviet Union. On the later 1.5-metre cyclotron (commissioned in 1947) he applied a one-metre layer of water with a boron absorber as radiation shielding, the first fully reliable biological protection of this kind anywhere, and also introduced fully remote control from a central panel for the first time.
After the war he led the mass production and international spread of cyclotrons. At Kurchatov’s direction he took scientific charge of the standard U-120 cyclotron supplied to CMEA member states, delivering machines to research centres in Romania, East Germany, Poland, Czechoslovakia, and China. After moving to Alma-Ata in 1960 he directed construction of the 1.5-metre cyclotron at the Institute of Nuclear Physics of the Kazakh SSR Academy of Sciences, commissioned in 1965, and then rebuilt it into the Soviet Union’s first isochronous cyclotron with adjustable ion energy. He published around a hundred papers over his lifetime, spanning dielectric and semiconductor physics, nuclear physics, and accelerator technology.