Sir James Chadwick (photo posted in the article) is an English physicist, Nobel Prize winner, who became famous after the discovery of the neutron. This radically changed the physics of that time and allowed scientists to create new elements, and also led to the discovery of nuclear fission and its use for military and civilian purposes. Chadwick was part of a group of British scientists who helped the US develop the atomic bomb during World War II.
James Chadwick: short biography
Chadwick was born in Bollington, Cheshire, England on October 20, 1891, to John Joseph and Ann Mary Knowles. He studied at the local primary and Manchester municipal high schools. At sixteen he received a scholarship from the University of Manchester. James intended to study mathematics, but mistakenly attended introductory lectures in physics and enrolled in this speci alty. At first, he had misgivings about his decision, but after his first year, he found the course more interesting. Chadwick was enrolled in the classErnest Rutherford, where he studied electricity and magnetism, and later a teacher assigned James a research project on the radioactive element radium.
Early Research
James Chadwick graduated in 1911 and continued to work with Rutherford on gamma absorption, earning a master's degree in 1913. The supervisor facilitated a research fellowship that required him to work elsewhere. He decided to study in Berlin with Hans Geiger, who was visiting Manchester at the time James was completing his master's degree. During this period, Chadwick established the existence of a continuous spectrum of beta radiation, which discouraged researchers and led to the discovery of neutrinos.
Travel to the camp
Shortly before the First World War, when hostilities became inevitable, Geiger warned Chadwick to return to England as soon as possible. James was bewildered by the travel company's advice and remained in a German POW camp until the end of the war. During the five years of his imprisonment, Chadwick managed to negotiate with the guards and conduct elementary studies of fluorescence.
Working at the Cavendish Laboratory
James Chadwick, whose biography in physics had every chance of ending in 1918, thanks to the efforts of Rutherford, returned to science again and confirmed that the charge of the nucleus was equal to the atomic number. In 1921 he was awarded a research fellowship at Gonville College, Cambridge.and Keyes, and the following year became Rutherford's assistant at the Cavendish Laboratory.
Working every day, he still found time to conduct research, the direction of which was generally suggested by Rutherford. Chadwick and fellow prisoner Charles D. Ellis then went on to study at Trinity College and with Rutherford, researching the transmutation of elements by bombardment with alpha particles (helium nuclei). A research team in Vienna reported results that were inconsistent with the data obtained by the Cavendish Laboratory, the correctness of which was skillfully defended by further experiments by Chadwick and his colleagues.
In 1925, James married Eileen Stuart-Brown. The couple had twin daughters.
In the mid-1920s, James Chadwick conducted experiments to scatter alpha particles fired at targets made of metals, including gold and uranium, and then helium itself, the nucleus of which has the same mass as alpha particles. The scattering turned out to be asymmetric, and Chadwick explained it in 1930 as a quantum phenomenon.
Discovery of the neutron
As far back as 1920, Rutherford proposed the existence of an electrically neutral particle called the neutron to explain the existence of hydrogen isotopes. It was believed that this particle consisted of an electron and a proton, but the emission of such a composition was not detected.
In 1930, it was found that when light nuclei were bombarded with alpha rays emitted by polonium, penetrating radiation without an electric charge arose. It was supposed to be gamma rays. However, when using a beryllium target, the rays turned out to be many times more penetrating than when using other materials. In 1931, Chadwick and his colleague Webster suggested that neutral rays were in fact evidence of the existence of the neutron.
In 1932, researcher couple Irene Curie and Frédéric Joliot showed that the radiation from beryllium was more penetrating than reported by previous researchers, but they also called it gamma rays. James Chadwick read the report and immediately set to work on calculating the mass of the neutral particle, which could explain the latest results. He used beryllium radiation to bombard various elements and found that the results were consistent with the action of a neutral particle with a mass almost identical to that of a proton. This became experimental confirmation of the existence of the neutron. In 1925, Chadwick received the Nobel Prize in Physics for this achievement.
From neutron to nuclear reaction
The neutron quickly became a tool for physicists, who used it to penetrate the atoms of elements and transform them, so positively charged nuclei did not repel it. Thus, Chadwick prepared the way for the fission of uranium-235 and the creation of nuclear weapons. In 1932, for this important discovery, he was awarded the Hughes Medal and in 1935 the Nobel Prize. Then he learned that Hans Falkenhagen discovered the neutron at the same time as him, but was afraid to publish his results. German scientist modestlyrefused an offer to share the Nobel Prize, which made him James Chadwick.
The discovery of the neutron made it possible to create transuranium elements in laboratories. This was the impetus for the discovery by Nobel laureate Enrico Fermi of nuclear reactions caused by slow neutrons, and the discovery by German chemists Otto Hahn and Strassmann of nuclear fission, which led to the creation of nuclear weapons.
Working on the atomic bomb
In 1935, James Chadwick became professor of physics at the University of Liverpool. As a result of the 1940 Frisch-Peierls memorandum on the advisability of building a nuclear bomb, he was appointed to the MAUD committee, which investigated this issue in more detail. In 1940 he visited North America on the Tizard mission to establish cooperation in nuclear research. After returning to the UK, he decided that nothing would work until the war was over.
In December of that year, Francis Simon, who worked at MAUD, found a way to separate the uranium-235 isotope. In his report, he outlined the cost estimate and technical specification for the creation of a large enterprise for uranium enrichment. Chadwick later wrote that only then did he realize that a nuclear bomb was not only possible but inevitable. From that moment on, he had to start taking sleeping pills. James and his group generally supported the U-235 bomb and approved its isolation by diffusion from the U-238 isotope.
The result of life
Soon he wentto Los Alamos, the headquarters of the Manhattan Project, and, along with Niels Bohr, gave valuable advice to the developers of the atomic bombs dropped on Hiroshima and Nagasaki. Chadwick James, whose discoveries dramatically changed the course of human history, was knighted in 1945.
At the end of World War II, he returned to his post in Liverpool. Chadwick retired in 1958. After spending ten years in North Wales, he returned to Cambridge in 1969, where he died on 24 July 1974.
