James Chadwick: biography, photos, discoveries

Sir James Chadwick (photo posted in the article) is an English physicist, Nobel laureate, who became known 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 peaceful purposes. Chadwick was a member of a group of British scientists who helped the US develop an atomic bomb during World War II.

James Chadwick: A Short Biography

Chadwick was born in Bellington, Cheshire, England on October 20, 1891, in the family of John Joseph and Ann Mary Knowles. He studied at the local elementary and Manchester municipal secondary schools. At sixteen received a scholarship from the University of Manchester. James intended to study mathematics, but mistakenly attended lectures on physics and entered this specialty. At first, he had fears 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 instructor appointed James a research project on the radioactive element radium.

Early research

James Chadwick graduated from the university in 1911 and continued to work at Rutherford over the absorption of gamma radiation, obtaining a master's degree in 1913. The supervisor promoted 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 permit

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 advice of a travel company and remained in the German prison camp until the end of the war. During five years of his imprisonment, Chadwick managed to negotiate with the guards and conduct elementary studies of fluorescence.

Work in the Cavendish Laboratory

James Chadwick, whose biography in physics could end in 1918, thanks to the efforts of Rutherford again returned to science and confirmed that the charge of the nucleus was equal to the atomic number. In 1921, he was awarded a research fellowship at Cambridge College of Gonville and Keith, and the following year became assistant to Rutherford in the Cavendish Laboratory.

Working every day, he still found time to conduct research, the direction of which in general was suggested by Rutherford. Chadwick and his fellow prisoner Charles D. Ellis then continued their studies at Trinity College and Rutherford, exploring transmutations of the elements when bombarded with alpha particles (helium nuclei). The research team in Vienna reported results that were not consistent with the data obtained by the Cavendish Laboratory, the correctness of which was skillfully protected by further experiments of Chadwick and his colleagues.

In 1925, James married Eileen Stewart-Brown. The couple had twin daughters.

In the mid-1920s, James Chadwick conducted experiments to scatter alpha particles fired at a metal target, including gold and uranium, and then helium itself, whose core has the same mass as the alpha particles. The scattering turned out to be asymmetric, and Chadwick explained this in 1930 as a quantum phenomenon.

The discovery of a neutron

Back in 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 when light nuclei were bombarded with alpha rays emitted by polonium, penetrating radiation appeared without electric charge. It was supposed that this is gamma rays. However, when using a beryllium target, the rays were many times more penetrating than with other materials. In 1931 Chadwick and his colleague Webster suggested that the neutral rays actually indicated the existence of a neutron.

In 1932, a married couple of researchers Irene Curie and Frederic Joliot showed that the radiation of beryllium was more penetrating than reported by previous researchers, but they also called it gamma rays. James Chadwick read the report and immediately proceeded to work on the calculation of 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 are consistent with the action of a neutral particle with a mass almost identical to that of the proton. This became an experimental confirmation of the existence of a neutron. In 1925, for this achievement, Chadwick received the Nobel Prize in Physics.

From neutron to nuclear reaction

The neutron quickly became an instrument of physicists who used it to penetrate the atoms of elements and transform them, so the positively charged nuclei did not repel it. Thus, Chadwick prepared the way for the division 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 had discovered the neutron at the same time as him, but was afraid to print his results. The German scientist modestly refused the offer to share the Nobel Prize, which was made to him by James Chadwick.

The discovery of a neutron made it possible to create transuranium elements in laboratories. This triggered the discovery of nuclear reactions by the Laureate of the Nobel Prize of Enrico Fermi, caused by delayed neutrons, and the discovery by German chemists of Otto Gan 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 Liverpool University. Following the results of the Frish-Peierls Memorandum of 1940 on the expediency 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 mission of Tizard to establish cooperation in the conduct of nuclear research. After returning to the UK, he decided that nothing will happen until the war is over.

In December of the same year, Francis Simon, who worked at MAUD, found it possible to separate the uranium-235 isotope. In his report, he outlined the valuation and technical specification for the creation of a large enterprise for uranium enrichment. Later Chadwick wrote that only then did he realize that the nuclear bomb was not only possible, but also 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 isolation by diffusion from the isotope U-238.

The result of life

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.

After the Second World War, 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.