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Konstantin Petrzhak (alternatively Pietrzak; ; 1907-1998) was a Soviet–Russian nuclear physicist and university professor of Polish origin. He discovered spontaneous fission of uranium jointly with Georgy Flyorov in 1940; in addition, he also aided in Soviet Union's atomic bomb project . == Biography == Konstantin Petrzhak was born on 4 September 1907 in Łuków (Congress Poland, Russian Empire, now in Poland; another source also states he was born in Dombrovo, now Kaliningrad oblast). Antoni Petrzhak was his father. When Konstantin was 12 years old, he started working as a painter at a glass-making factory in Malaya Vishera (Russia). In 1928 he went to Saint-Petersburg to study at rabfak of Saint Petersburg State University (which was then called Leningrad State University). In 1931 he started studying in radiology group there. In November 1936 Konstantin Petrzhak completed his diploma work under supervision of Igor Kurchatov and graduated from Saint Petersburg State University. In 1934 he started working at Khlopin Radium Institute in Saint Petersburg (which was named First Radium Institute at that time). He worked there till the last days of his life.〔(Konstantin Petrzhak obituary )〕 Igor Kurchatov was the head of laboratory where he started working. There Konstantin Petrzhak wrote thesis "study of thorium and samarium radioactivity" to get the Candidate of Sciences degree (equivalent to Ph.D.). Vitaly Khlopin and Igor Kurchatov were his scientific supervisors. Konstantin Petrzhak participated in seminar on nuclear physics in Ioffe Institute. In 1939 Igor Kurchatov asked him and Georgy Flyorov to study uranium fission induced by neutrons of different energies. Earlier Georgy Flyorov and Tatiana Nikitinskaya made a highly sensitive ionization chamber to detect heavy particles. They decided to use it in this new experiment. Kurchatov asked Georgy Flyorov, Nikitinskaya and Petrzhak to make the sensitivity of the chamber even higher. In 1939 the experiments were carried out in Saint Petersburg. The team created a highly sensitive multilayer ionization chamber to detect decay products which originate from fission of uranium. The ionization chamber had electrodes in it with the total area of about 1000 cm2. The plates of the chamber were covered with uranium oxide with approximate surface density of 10–20 mg/cm2. The chamber consisted of 15 plates. The detector was checked while measuring background. When the source of neutrons was taken away, the detector still detected particles. They made three ionization chambers to prove that the effect was not connected to the first one. More than that they made even more sensitive chamber with the surface of 6000 cm2. Cosmic rays were one of possible sources of background counts. In 1940 to reduce the effect of cosmic rays measurements were made in an underground lab in Dinamo station of Moscow Metro (about 50 m below the earth surface). In May 1940 they assumed that spontaneous fission was discovered. 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".〔(【引用サイトリンク】trans-title=Discovery of spontaneous fission in uranium )〕 Their discovery was derived from the theory of fission by Yakov Frenkel. Later the discovery of spontaneous fission was confirmed by Otto Robert Frisch. In 1940 Konstantin Petrzhak was suggested to enter the leading team of soviet atomic bomb project. He is rumoured to participate in soviet atomic project. When Soviet Union entered the World War II, Petrzhak was eligible for serving in Red Army. If he was awarded the Stalin Prize, he could avoid entering the regular army. The Academy of Sciences of USSR nominated him to receive this prize in the early 1940s. But he didn't receive the prize. So during World War II Petrzhak volunteered〔 (other sources state he was commandeered). He served in military intelligence of a CIWS regiment first as a junior lieutenant and later as a senior lieutenant. Since 28 June 1941 he participated in battle on Karelian Isthmus. Later he fought in Volkhov Front.〔 In March 1942 he was ordered to leave the army〔 and work on atomic problems in Kazan where Radium Institute was evacuated. In 1943 he studied neutron induced fission of uranium under supervision of professor Piotr Lukirsky. In 1944 Konstantin Petrzhak proposed a method to determine the number of neutron, that are radiated by neutron sources based on the number of protons from nuclear reaction in chamber, filled with heavy hydrogen. He also made necessary calculations. He participated in development of technology of extraction of plutonium from irradiated uranium blocks. Jointly with M. Yakunin he developed methods of radiochemical determination of plutonium and found the mean free path of Pu-239 alpha particles. Konstantin Petrzhak founded a laboratory of neutron physics and nuclear fission in Khlopin Radium Institute in 1947 and was the head of this laboratory until 1986,〔 since 1986 he was a part-time contractor. As of 1949 Konstantin Petrzhak was a member of Uranium commission of USSR Academy of Sciences. He continued to study spontaneous fission. He was one of the founders of Engineering faculty of Saint Petersburg State Institute of Technology. Konstantin Petrzhak founded there a department of nuclear physics in 1949〔 and was the head of it for 22 years. In 1958 he was a scientific supervisor of Vladimir Georgievich Korsakov's diploma work. In 1961 he founded a laboratory of nuclear energy there. Konstantin Petrzhak created an express method of detection of plutonium and associated radioisotopes in samples of irradiated uranium.〔 Since at least 1963 to 1976 he published a series of articles on measurements of photofission. In 1973-1984 he also took part in setting up the measurements of induced fission cross-sections of U-238, U-235 and Pu-239 when irradiated by monoenergy neutrons which were performed in Khlopin Radium institute. In 1978 Konstantin Petrzhak was listed as one of the co-authors (with Yuri Oganessian and others) of a paper about synthesis of hassium performed in JINR. Right till the year of his death Konstantin Petrzhak published articles on study of fission products from Nuclear reactors. Konstantin Petrzhak was doktor nauk (since 1948) and a professor. He was never elected an academician of corresponding member of any academy, however Konstantin Petrzhak was a member of Nuclear Physics Department of Russian Academy of Sciences.〔(【引用サイトリンク】title=Members of Nuclear Physics Division of Physical Sciences Department of Russian Academy of Sciences )〕 He died on October 10, 1998 and was buried in Saint Petersburg. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Konstantin Petrzhak」の詳細全文を読む スポンサード リンク
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