Sir James Chadwick (photo posted in the article) is an English physicist, Nobel Prize laureate, who became famous after the discovery of the neutron. This fundamentally changed the physics of that time and allowed scientists to create new elements, and also led to the discovery of the fission of the nucleus and its use for military and peaceful purposes. Chadwick was part of a group of British scientists who during the Second World War helped the United States develop an atomic bomb.
James Chadwick: A Short Biography
Chadwick was born in Bollington, Cheshire, England on October 20, 1891, in the family of John Joseph and Ann Mary Knowles. He studied at the local primary and Manchester municipal secondary schools. At sixteen he received a scholarship from the University of Manchester. James intended to study mathematics, but mistakenly attended introductory lectures on physics and entered this specialty. At first, he had concerns about his decision, but after the first year of training, he found the course more interesting. Chadwick was enrolled in the class of Ernest Rutherford, where he studied electricity and magnetism, and later the teacher assigned James a research project on the radioactive element of radiation.
Early research
James Chadwick graduated from the University in 1911 and continued to work with Rutherford on the absorption of gamma radiation, receiving a master's degree in 1913. The supervisor contributed to the appointment of a research scholarship that required work elsewhere. He decided to study in Berlin with Hans Geiger, who visited Manchester at the time when James received a 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.
Camp voucher
Shortly before World War I, when hostilities became inevitable, Geiger warned Chadwick to return to England as soon as possible. James was bewildered by the advice of a travel company and stayed in a German prisoner of war camp until the end of the war. Over the five years of his imprisonment, Chadwick managed to negotiate with the guards and conduct elementary fluorescence studies.
Work in the Cavendish Laboratory
James Chadwick, whose biography in physics had every chance to end in 1918, thanks to the efforts of Rutherford returned to science and confirmed that the charge of the nucleus was equal to the atomic number. In 1921, he was awarded a research internship at the Cambridge College of Gonville and Keyes, and the following year became Rutherford's assistant at the Cavendish Laboratory.
Working every day, he still found time for research, the direction of which was generally proposed by Rutherford. Chadwick and his fellow prisoner Charles D. Ellis then continued their studies at Trinity College and at Rutherford, exploring the transmutation of elements bombarded 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 on the scattering of alpha particles fired at targets from metals, including gold and uranium, and then helium itself, whose core has the same mass as alpha particles. Scattering turned out to be asymmetric, and Chadwick explained this in 1930 as a quantum phenomenon.
Neutron discovery
As early as 1920, Rutherford suggested the existence of an electrically neutral particle called a 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 during the bombardment of light nuclei with alpha rays emitted by polonium, penetrating radiation without electric charge occurred. It was assumed that these are 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 actually indicated the existence of a neutron.
In 1932, a couple of researchers Irene Curie and Frederic Joliot showed that the radiation of beryllium was more penetrating than that 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 a neutral particle, which could explain the latest results. He used the radiation of beryllium to bombard various elements and found that the results are consistent with the effect of a neutral particle with a mass almost identical to the mass of the proton. This became an experimental confirmation of the existence of a neutron. In 1925, Chadwick received the Nobel Prize in Physics for this achievement.
From neutron to nuclear reaction
The neutron quickly became the tool of 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 found out that Hans Falkenhagen discovered the neutron simultaneously with him, but was afraid to print his results. The German scientist modestly refused the offer to share the Nobel Prize, which James Chadwick made to him.
The discovery of the neutron allowed the creation of transuranic elements in laboratories. This was the impetus for the discovery by the Nobel Prize winner Enrico Fermi of nuclear reactions caused by delayed neutrons, and the discovery by the German chemists Otto Hahn and Strassmann of nuclear fission, which resulted in the creation of nuclear weapons.
Work on the atomic bomb
In 1935, James Chadwick became a professor of physics at the University of Liverpool. Following the results of the 1940 Frisch-Peierls memorandum on the feasibility of creating a nuclear bomb, he was appointed to the MAUD committee, which investigated this issue in more detail. In 1940, he visited North America with the Tizard mission to establish cooperation in nuclear research. After returning to the UK, he decided that nothing would come of it until the war was over.
In December of that year, Francis Simon, who worked at MAUD, found the opportunity to separate the uranium-235 isotope. In his report, he outlined the cost estimate and technical specifications 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 he had to start taking sleeping pills. James and his group generally supported the bomb from U-235 and approved its separation by diffusion from the isotope U-238.
Life summary
Soon he went to Los Alamos, the headquarters of the Manhattan Project, and along with Niels Bohr gave valuable advice to the developers of atomic bombs dropped on Hiroshima and Nagasaki. Chadwick James, whose discoveries radically 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 resigned in 1958. After spending ten years in North Wales, he returned to Cambridge in 1969, where he died on July 24, 1974.