Lawrence (Lawrence), Ernest O.( The American physicist, Nobel Prize in Physics, 1939)
Comments for Lawrence (Lawrence), Ernest O.
Biography Lawrence (Lawrence), Ernest O.
August 8, 1901, Mr.. - August 27, 1958
American physicist Ernest Orlando Lawrence was born in Canton (South Dakota). He was the eldest son of Carl Gustaf and Gundi (Jacobson), Lawrence, Parents L. emigrated to the United States from Norway. My father was the manager of a local school, and then the formation of a statewide teacher and president of several colleges, and his mother also worked in the education system. L. studied in urban schools and Pierre Cantona. In his spare time, he and his best friend and neighbor Merle Tyuv, also became a prominent physicist, built gliders and created their own system of wireless telegraphy.
When one of his cousins died from leukemia, L. decided to become a doctor. After receiving a scholarship, it is 1918. enrolled in the College of St.. Olaf in Nortfield (Minnesota), but a year later moved to the University of South Dakota. There, a professor of electrical Lewis E. Eykeli drew L. to in-depth studies in physics. After receiving in 1922, Mr.. Bachelor of Science with honors from L. enrolled in the graduate school of the University of Minnesota to U.F. G. During graduate school he was involved in a pilot study of electric induction in 1923. received his Master of Science degree.
A year later. with their teacher Swann joined the University of Chicago. There his interest in physics had increased further after meeting with Niels Bohr, Arthur Compton, Albert A. Michelson, X. A. Wilson and other prominent physicists. A year after the transition in the autumn 1924. at Yale University A. received his doctorate. His thesis on the photoelectric effect in potassium vapor was the first of his major works in this field of physics. The next two years he worked at Yale as a fellow of the National Council for Scientific Research and in 1927. was appointed assistant professor of physics. But in 1928. L. left Yale University and became an adjunct professor at the University of California at Berkeley.
California L. first begun by research in areas such as Photovoltaics and the measurement of very short periods of time. Among his other achievements include the time and experimental demonstration of the uncertainty principle of Werner Heisenberg. This principle predicts that the measurement of energy, for example, a photon of light (a photon is a portion, or particle of electromagnetic energy), it is so uncertain, the shorter the measurement time. Since the photon energy is proportional to the frequency of light, the uncertainty in energy is reduced to the uncertainty in the frequency of. The line in the optical spectrum is actually a narrow (ie. clear or well-defined) band of light frequencies. Including and quickly turning off the light during the measurement of the spectral lines, L. and his colleagues showed that the line extends. The light source did not undergo any changes, although its frequency became less certain, as it should from the Heisenberg uncertainty principle.
Then L. turned to nuclear physics, which then rapidly. In 1919, Mr.. Ernest Rutherford split the nucleus by bombarding it with alpha particles emitted by radium. Rutherford found that among the fragments that arise after the collision, there are atoms with smaller atomic weight than the original. Some of these fragments were isotopes of known elements, ie. have the same chemical properties, such as the nuclear charge, but had a different weight.
. In Rutherford's methods had serious drawbacks: radium was a rare element, alpha-particles ejected from the source in all directions, the number of observed collisions were extremely small, and the whole procedure is laborious observations
. Sci dire need of an abundant source of controlled high-energy particles. Since both the bombarding particles, . and the target nucleus are positively charged (electrons have played a very minor role in the collisions), . incoming particles must have been sufficiently high energy, . to overcome not only the electric repulsion, . but the binding energy, . ensure the integrity of the kernel,
. John Cockcroft and Ernest Walton built a linear particle accelerator, working at very high voltages. In these devices, positively charged particles are dispersed in a straight line in the direction of attracting them to the negative electrode and the purchased energy is proportional to the applied voltage.
. Linear accelerators are not like LA, because in them from time to time is the breakdown of insulation and high-level arose, reminiscent of the type of lightning
. In 1929, Mr.. L. saw a paper on the German origin of the Norwegian engineer Rolf Veeder, in which the scheme was considered a particle accelerator, proposed earlier by the Swedish physicist, Gustav A. Ising. Although L. not mastered the German language to understand all the subtleties, the basic idea was it clear from the illustrations to the article: the particles can be accelerated by increasing the voltage gradually, rather than creating one large 'hump'. L. realized that the straightforward way you can bend into a circle. Having done the necessary calculations, he, along with several staff members began designing and building the first cyclotron. With his creation a name usually associated L.
The basic idea of L. consisted in the fact that charged particles moving in a uniform magnetic field in circles. This is because a moving charge constitutes an electric current, which, like the current in the windings of the electromagnet, a magnetic field. Like two magnets, . presents made close to each other, . particle and the external magnet affect each other with a certain force, . but can only move a particle (in the case of the approaching of the two magnets that corresponds to, . that one magnet is rigidly fixed, . the other can move),
. The direction of force must always form right angles with the direction of the magnetic field and the direction of the particle. Since the direction of the particle is constantly changing, the particle moves in a circle. An important feature of the particle motion is that it always describes a full circle for one and the same time, regardless of the speed (kinetic energy) of the particle. But the diameter of the circle is greater, the greater the velocity of a particle. These features of particle motion and used the LA, designing a cyclotron.
. The heart of the cyclotron - a huge round hollow disk, divided by the diameter into two halves, resembling the letters D (these are called half dees)
. The disc is placed between the poles of a large flat magnet. Between the dees connected electric generator that creates alternating current in the gap between them. When a charged particle, such as proton falls into the gap, she is attracted to that of the dees, which at this moment has a negative voltage, and picks up speed. Once inside the dees, the particle describes a semicircle and out of it at a point diametrically opposite the entrance. The frequency generator is configured so that by that time the sign of the voltage changes, and proton rushes to another dees, which is now negative, is attracted to them and accelerating voltage applied to the gap. In the second proton dees falls, with greater speed, and therefore inside moves through the arc of a circle of radius greater than before.
. By the time the proton from the dees voltage again changes sign, the proton is again accelerated, and, entering the first dees with greater speed, moving inside the arc of a circle is the larger radius
. Since the proton gets 'recharge' (as it would 'push') every time it goes through the gap between the dees, and moves with increasing speed along arcs increasing radius until, until it reaches the perimeter of the disc. Then flies out of the proton cyclotron, and he was sent to the selected target. Disks large diameter allows to disperse the particles to high velocities, but require a larger and therefore more expensive magnets. Dees should be made of nonmagnetic material, which is not screened by the magnetic field, and that the particles do not lose energy in collisions with gas molecules in the cell must be deep vacuum.
. After the first, a rather imperfect cyclotron, built in 1930, L
. and his colleagues at Berkeley have created rapidly one after another, larger model. Using a 80-ton magnet is given to the Federal Telegraph Company, L. accelerate particles to energies in the record-breaking multi-million electron-volts. Cyclotrons were ideal experimental devices. In contrast to the particles emitted by nuclei during radioactive decay, particle beam, derived from the cyclotron, was unidirectional, their energy can be controlled, and flow rate was much higher than that of any radioactive source.
. High energy achieved L
. and his staff, the physicists have opened a vast new field for research. Bombing the atoms of many elements has allowed them to split the nucleus into fragments, which were isotopes of the radioactive. Sometimes the accelerated particles 'stick' to the nuclei-targets or cause nuclear reactions among the products which met the new elements that do not exist on Earth in the wild. The results showed that if the particles can be accelerated to sufficiently high energies, then using the cyclotron could be implemented almost any nuclear reaction. Cyclotron was used to measure the binding energies of many nuclei, and (by comparing the mass difference before and after the nuclear reaction) to verify the relationship between Albert Einstein's mass and energy.
. Cyclotron allowed to create radioactive isotopes for medical purposes
. Above the biomedical applications of nuclear physics A. worked with his younger brother John, a physician and director of the Biophysical Laboratory in Berkeley. John Lawrence has successfully used the isotopes to treat cancer patients, including his mother, who had a case of inoperable cancer. After treatment, she lived another 20 years.
L. was awarded the Nobel Prize in Physics 1939. 'for the invention and the creation of the cyclotron, for the progress of its results, especially the production of artificial radioactive elements ". Due to the outbreak of the Second World War Prize award ceremony was canceled. About the work of L. Manne Sigbann of the Royal Swedish Academy of Sciences said that the invention of the cyclotron has caused 'an explosion in the development of nuclear research ... In the history of experimental physics ... cyclotron is an exceptional place. Undoubtedly, the cyclotron is the largest and most complex of all ever built scientific instruments'. The Nobel Prize was awarded to L. in 1941. at the celebrations held in Berkeley. His Nobel lecture he gave in Stockholm in 1951
In 1940. L. participated in the creation of Radiation Laboratory at the Massachusetts Institute of Technology. At the insistence of L. many of his former students have become its members. The purpose of the laboratory was to improve radar technology, created the first time in England during the Second World War for the electronic detection of enemy aircraft. In 1941, Mr.. L. scored state underwater acoustics laboratory in San Diego, dedicated to the development of antisubmarine systems to combat German submarines lay in wait for the convoys with military supplies destined for the United States to the UK. L. Then, retaining only informal relationships with these laboratories engaged in the transformation of Berkeley 37-inch cyclotron in the mass spectrometer for separation of fissile uranium-235 and normal uranium-238. In the mass spectrometer, as in a cyclotron, uses a combination of electric and magnetic fields, but not for particle acceleration, and for the spatial separation of them - the direction in different trajectories depending on the masses and electric charges. Since the masses of isotopes are slightly different, the isotopes move in close, though divergent paths, and therefore can be separated, although the method of their separation is not very efficient.
. The success achieved by LS, was impressive enough to make all the work on isotope separation was assigned to his laboratory
. Oak Ridge (Tennessee) in the Manhattan Project (a secret plan for a U.S. atomic bomb) were built hundreds of mass spectrometers in the image and likeness of the cyclotron at Berkeley with a 184-inch magnet. Almost all the uranium in the bomb dropped in August 1945. on Hiroshima, was obtained by L. and his colleagues at Berkeley. Subsequently, the Oak Ridge plant for the separation of isotopes using mass spectrometers has been closed since gas diffusion method proved more effective.
At the end of the war L. and his staff returned to basic research. However, L. still involved in the creation of nuclear weapons. He was allocated funds for deployment in Livermore (near Berkeley), a second research laboratory for the needs of the military industry. It was independent from the Los Alamos National Laboratory, created under the Manhattan Project. Later received the name of the Lawrence Livermore Laboratory, a research institution has been the main center where the work was conducted to develop the hydrogen bomb.
At Berkeley, L. supervised the construction of accelerators that can disperse the particles to energies of billions of electron volts. At one of these accelerators, . to be known Bevatron, . Emilio Segre, and other researchers are the properties of mesons (elementary particles with masses, . intermediate between the masses of the electron and proton) have opened an antiproton (a proton with a double negative charge).,
. was invited by President Dwight D. Eisenhower as Adviser to the Government to examine the possibility determining violations of the nuclear test ban, which was seen at the Geneva Conference 1958. Upon returning home, L. was operated on for acute ulcer and died in hospital Palo Alto (Calif.) August 27, 1958
In 1932, Mr.. Lawrence married Mary Kimberly Blumer, daughter of the dean of the medical school at Yale University. In Lawrence was born six children.
In addition to his numerous works in nuclear physics A. invented the original construction of the television tube - hromatron Lawrence, produced on an industrial scale in Japan and the United States. Linger long at work on weekdays and weekends, L. however, he loved boating, play tennis, skating and listening to music. 'Important components of his success - I thought Louis. Alvarez - was a natural wit and soundness of scientific reasoning, great stamina, enthusiastic eccentric personality and dominant over all sense of integrity '.
. Among the numerous awards and honors, which was awarded the AL, Elliott Cresson Medal Franklinovskogo Institute (1937), the Hughes Medal of the Royal Society of London (1940) and Holley Medal, American Society of Mechanical Engineers (1942)
. He was an honorary doctorate by the University of South Dakota, Pennsylvania, British Columbia, Southern California and Glasgow, as well as Yale, Harvard, and McGill Rutdersa. L. was elected a member of the National Academy of Sciences of the USA, the American Philosophical Society and the Japan Physical Society, and was an honorary member of many foreign scientific societies.