Konstantin Petrzhak

Konstantin Antonovich Petrzhak (alternatively Pietrzak; , ; 4 September 1907 – 10 October 1998), , was a Russian physicist of Polish origin, and a professor of physics at the Saint Petersburg State University.

Receiving credit with Georgy Flyorov, a physicist, for the fundamental discovery of spontaneous fission of uranium in 1940, Petrzhak's career in physics was then spent mostly in the former Soviet program of nuclear weapons. Konstantin Petrzhak was among of Soviet pioneers in nuclear physics research. Other Russian documented sources noted his birthplace in Dombrovo in Kaliningrad with same birth date. Later, he used his talent in painting when he covered the plates of ionization chamber with uranium which later led to discovery of spontaneous fission. In November 1936, Pertzhak eventually earned his diploma certified under Igor Kurchatov from the Leningrad State University.

Soviet program of nuclear weapons and academia In 1939, Kurchatov was assigned research under Georgy Flyorov and Petrzhak to conduct investigation on uranium fission induced by neutrons of different energy levels, following Yakov Frenkel's theory of fission. Earlier, Flyorov and his assistant Tatiana I. Nikitinskaya had already made an ionization chamber to detect heavy particles, and were directed to increase the sensitivity of the ionization chamber. The team created a multilayer ionization chamber to detect decay products originating from the fission of uranium.

The ionization chamber utilized electrodes with a total surface area of about 1000 cm2. The chamber's 15 plates were covered with uranium oxide with approximate surface density of 10–20 mg/cm2. The detector compared particle activity to a background level control. When the source of neutrons was taken away, the detector still found particles. The team made three ionization chambers to prove that the effect was not an error, including a more sensitive chamber with a surface area of 6000 cm2. Despite the instrument's high sensitivity, cosmic rays were still a possible source of particle activity. The team moved to an underground lab in the Dinamo station of Moscow Metro (about 50 m below the earth surface) in an attempt to rule out the effects of cosmic rays. In May 1940, they were confident that they had discovered spontaneous fission. The certificate of discovery stated, "the new type of radioactivity with mother nucleus decays into two nuclei, that have kinetic energy of about 160 MeV". Later, the discovery of spontaneous fission was confirmed by Otto Robert Frisch.

In 1940, Petrzhak was recommended for the top team in the Soviet atomic bomb project. He is rumored to have participated in the said project.

When the Soviet Union entered World War II, Petrzhak was eligible to serve in the Red Army. Winning the Stalin Prize would exempt him from front line service. In the early 1940s, the Academy of Sciences of the Soviet Union nominated him for the award, which he did not receive. Sources disagree on whether Petrzhak volunteered, into the army.

Petrzhak served in the military intelligence company of a CIWS regiment first as a junior lieutenant, and later as a senior lieutenant. On 28 June 1941, he participated in the battle of Karelian Isthmus. Later, he fought in Volkhov Front. He was one of the founders of the Engineering faculty of the Saint Petersburg State Institute of Technology. Petrzhak founded the Saint Petersburg State Institute of Technology department of nuclear physics in 1949, Hundreds of graduates of Engineering faculty studied under his supervision, he was also a scientific supervisor of dozens of Candidates of Science and Doktors of Science. In 1960s jointly with the colleagues Petrzhak performed a series of precision absolute measurements of induced fission, caused by neutrons, which have monoenergy as well as fission-spectrum neutrons. From 1973 through 1984, he took part in measuring induced fission cross-sections of U-238, U-235 and Pu-239 when irradiated by monoenergy neutrons In 1978, Konstantin Petrzhak co-authored a paper (with Yuri Oganessian and others) about synthesis of hassium performed in Joint Institute for Nuclear Research.

Petrzhak was awarded Doctor of Sciences in 1948 and a professor. He was never elected an academician or the corresponding member of any academy, but Petrzhak was a member of Nuclear Physics Department of Russian Academy of Sciences. Konstantin Petrzhak published articles on fission products from nuclear reactors until his death in 1998. He died on October 10, 1998, and was buried at Serafimovskoe Cemetery in Saint Petersburg.

Personal life Konstantin Petrzhak studied painting. He created paintings throughout his life. He used his skills in painting when he covered the plates of ionization chamber with uranium which later led to discovery of spontaneous fission. He was also an amateur violin and guitar player. ) 1950 Council of Ministers Prize (for work on fulfillment of governmental tasks) 1953 Stalin Prize (for work on soviet atomic project) 1953 Order of the Red Banner of Labour (for work on soviet atomic project) 1957 Presidium of Academy of Sciences of the Soviet Union Prize

Selected works