crème de la crème

Jai Ganesh · 2024-09-26 15:31:58

2063) Raymond Davis Jr.

Gist:

Work

In certain nuclear reactions (such as when protons combine to form helium nuclei) elusive particles called neutrinos are created. Raymond Davies wanted to detect neutrinos in radiation from space to confirm the theory that this kind of nuclear reaction is the source of the sun’s energy. Beginning in the 1960s, he placed a large tank containing a chlorine-rich liquid inside a mine. In rare cases, a neutrino interacted with a chlorine atom to form an argon atom. By counting these argon atoms, neutrinos from space could be detected.

Summary

Raymond Davis, Jr. (born October 14, 1914, Washington, D.C., U.S.—died May 31, 2006, Blue Point, New York) was an American physicist who, with Koshiba Masatoshi, won the Nobel Prize for Physics in 2002 for detecting neutrinos. Riccardo Giacconi also won a share of the award for his work on X-rays.

Davis received a Ph.D. from Yale University in 1942. After military service during World War II, he joined Brookhaven National Laboratory in Upton, New York, in 1948. He remained there until his retirement in 1984. In 1985 Davis took a post as a research professor with the University of Pennsylvania.

Davis’s prizewinning work focused on neutrinos, subatomic particles that had long baffled scientists. Since the 1920s it had been suspected that the Sun shines because of nuclear fusion reactions that transform hydrogen into helium and release energy. Later, theoretical calculations indicated that countless neutrinos must be released in those reactions and, consequently, that Earth must be exposed to a constant flood of solar neutrinos. Because neutrinos interact weakly with matter, however, only one in every trillion is stopped on its way to Earth. Neutrinos thus developed a reputation for being undetectable.

Some of Davis’s contemporaries had speculated that one type of nuclear reaction might produce neutrinos with enough energy to make them detectable. If such a neutrino collided with a chlorine atom, it should form a radioactive argon nucleus. In the 1960s, in a gold mine in South Dakota, Davis built an underground neutrino detector, a huge tank filled with more than 600 tons of the cleaning fluid tetrachloroethylene. He calculated that high-energy neutrinos passing through the tank should form 20 argon atoms a month on average, and he developed a way to count those exceedingly rare atoms. Monitoring the tank for more than 25 years, he was able to confirm that the Sun produces neutrinos, but he consistently found fewer neutrinos than predicted. This deficit became known as the solar neutrino problem. Davis’s results were later confirmed by Koshiba, who also found evidence that neutrinos change from one type to another in flight. Because Davis’s detector was sensitive to only one type, those that had switched identity eluded detection.

Details

Raymond Davis Jr. (October 14, 1914 – May 31, 2006) was an American chemist and physicist. He is best known as the leader of the Homestake experiment in the 1960s-1980s, which was the first experiment to detect neutrinos emitted from the Sun; for this he shared the 2002 Nobel Prize in Physics.

Early life and education

Davis was born in Washington, D.C., where his father was a photographer for the National Bureau of Standards. He spent several years as a choirboy to please his mother, although he could not carry a tune. He enjoyed attending the concerts at the Watergate before air traffic was loud enough to drown out the music. His brother Warren, 14 months younger than he, was his constant companion in boyhood. He received his B.S. from the University of Maryland in 1938 in chemistry, which is part of the University of Maryland College of Computer, Mathematical, and Natural Sciences. He also received a master's degree from that school and a Ph.D. from Yale University in physical chemistry in 1942.[2]

Career

Davis spent most of the war years at Dugway Proving Ground, Utah observing the results of chemical weapons tests and exploring the Great Salt Lake basin for evidence of its predecessor, Lake Bonneville.

After his discharge from the army in 1945, Davis went to work at Monsanto's Mound Laboratory, in Miamisburg, Ohio, doing applied radiochemistry of interest to the United States Atomic Energy Commission. In 1948, he joined Brookhaven National Laboratory, which was attempting to find peaceful uses for nuclear power.

Davis reports that he was asked "to find something interesting to work on," and dedicated his career to the study of neutrinos, particles which had been predicted to explain the process of beta decay, but whose separate existence had not been confirmed. Davis investigated the detection of neutrinos by beta decay, the process by which a neutrino brings enough energy to a nucleus to make certain stable isotopes into radioactive ones. Since the rate for this process is very low, the number of radioactive atoms created in neutrino experiments is very small, and Davis began investigating the rates of processes other than beta decay that would mimic the signal of neutrinos. Using barrels and tanks of carbon tetrachloride as detectors, Davis characterized the rate of the production of argon-37 as a function of altitude and as a function of depth underground. He deployed a detector containing chlorine atoms at the Brookhaven Reactor in 1954 and later one of the reactors at Savannah River. These experiments failed to detect a surplus of radioactive argon when the reactors were operating over when the reactors were shut down, and this was taken as the first experimental evidence that neutrinos causing the chlorine reaction, and antineutrinos produced in reactors, were distinct. Detecting neutrinos proved considerably more difficult than not detecting antineutrinos. Davis was the lead scientist behind the Homestake Experiment, the large-scale radiochemical neutrino detector which first detected evidence of neutrinos from the sun.

Davis shared the Nobel Prize in Physics in 2002 with Japanese physicist Masatoshi Koshiba and Italian Riccardo Giacconi for pioneering contributions to astrophysics, Davis was recognized for his work on the detection of cosmic neutrinos, looking at the solar neutrino problem in the Homestake Experiment. He was 88 years old when awarded the prize.

Personal life

Davis met his wife Anna Torrey at Brookhaven and together they built a 21-foot wooden sailboat, the Halcyon. They had five children and lived in the same house in Blue Point, New York for over 50 years. On May 31, 2006, he died in Blue Point, New York, from complications of Alzheimer's disease.

Jai Ganesh · Yesterday 16:16:06

2064) Masatoshi Koshiba

Gist:

Life

Masatoshi Koshiba was born in Toyohashi, Aichi Prefecture in Japan. After first studying at Tokyo University he later earned his PhD from the University of Rochester in New York in 1955. After several years spent working at the University of Chicago, Koshiba returned to Tokyo, where he continues to work and where he conducted his Nobel Prize-winning research. Masatoshi Koshiba married Kyoko Kato in 1959.

Work

Certain nuclear reactions, including those where hydrogen atoms combine with helium, form elusive particles called neutrinos. By proving the existence of neutrinos in cosmic radiation, Raymond Davis showed that the sun's energy originates from such nuclear reactions. From 1980, Masatoshi Koshiba provided further proof of this through measurements taken inside an enormous water tank within a mine. In rare cases, neutrinos react with atomic nuclei in water, creating an electron and thus a flash of light that can be detected.

Summary

Koshiba Masatoshi (born September 19, 1926, Toyohashi, Japan—died November 12, 2020, Tokyo) was a Japanese physicist who, with Raymond Davis, Jr., won the Nobel Prize for Physics in 2002 for their detection of neutrinos. Riccardo Giacconi also won a share of the award for his work on the cosmic sources of X rays.

Koshiba earned a Ph.D. from the University of Rochester in New York in 1955. He then joined the University of Tokyo, where he became professor in 1960 and emeritus professor in 1987. From 1987 to 1997 Koshiba taught at Tokai University.

Koshiba’s award-winning work centred on neutrinos, subatomic particles that had long perplexed scientists. Since the 1920s it had been suspected that the Sun shines because of nuclear fusion reactions that transform hydrogen into helium and release energy. Later, theoretical calculations indicated that countless neutrinos must be released in these reactions and, consequently, that Earth must be exposed to a constant flood of solar neutrinos. Because neutrinos interact weakly with matter, however, only one in a trillion is stopped on its way to Earth. Neutrinos thus developed a reputation as being undetectable.

In the 1980s Koshiba, drawing on the work done by Davis, constructed an underground neutrino detector in a zinc mine in Japan. Called Kamiokande II, it was an enormous water tank surrounded by electronic detectors to sense flashes of light produced when neutrinos interacted with atomic nuclei in water molecules. Koshiba was able to confirm Davis’s results—that the Sun produces neutrinos and that fewer neutrinos were found than had been expected (a deficit that became known as the solar neutrino problem). In 1987 Kamiokande also detected neutrinos from a supernova explosion outside the Milky Way. After building a larger, more sensitive detector named Super-Kamiokande, which became operational in 1996, Koshiba found strong evidence for what scientists had already suspected—that neutrinos, of which three types are known, change from one type into another in flight.

Details

Masatoshi Koshiba (Koshiba Masatoshi, 19 September 1926 – 12 November 2020) was a Japanese physicist and one of the founders of neutrino astronomy. His work with the neutrino detectors Kamiokande and Super-Kamiokande was instrumental in detecting solar neutrinos, providing experimental evidence for the solar neutrino problem.

Koshiba won the Nobel Prize in Physics in 2002, jointly with Raymond Davis Jr., "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos".

He was a senior counselor at the International Center for Elementary Particle Physics (ICEPP) and professor at the University of Tokyo.

Early life

Koshiba was born in Toyohashi in central Japan on September 19, 1926, to Toshio and Hayako Koshiba. His father was a military officer. His mother died when he was three, leading to his father marrying his wife's elder sister. He grew up in Yokosuka, and completed his high school in Tokyo. It is mentioned that his initial interest was in studying German literature, but, ended up studying physics, spurred by a teacher's denigrating comments.

He graduated from the University of Tokyo in 1951 and received a PhD in physics from the University of Rochester, New York, in 1955.

Career and research

Koshiba started his career as a research associate at the Department of Physics, University of Chicago from July 1955 to February 1958, and was an associate professor at Institute of Nuclear Study, University of Tokyo from March 1958 to October 1963. While on leave from November 1959 to August 1962 he served as the acting director, Laboratory of High Energy Physics and Cosmic Radiation, Department of Physics, University of Chicago.

At the University of Tokyo he became associate professor in March 1963 and then professor in March 1970 in the Department of Physics, Faculty of Science, and emeritus professor there in 1987. From 1987 to 1997, Koshiba taught at Tokai University.

In 2002, he jointly won the Nobel Prize in Physics for "pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos". (The other shares of that year's Prize were awarded to Raymond Davis Jr. and Riccardo Giacconi of the U.S.A.).

Koshiba's initial research was in cosmic rays. In 1969, he shifted into electron-positron collider physics, and was involved with the JADE detector in Germany, which helped confirm the Standard Model. Along with Masayuki Nakahata and Atsuto Suzuki, Koshiba designed the Kamiokande experiment to detect proton decay, a prediction of grand unified theories. No proton decay was detected, but Koshiba realized the detector could be made to detect neutrinos, and adapted the project accordingly, following the pioneering U.S. work of Davis.

In the early 1970s, Koshiba collaborated with Gersh Budker (1918-1977), the particle-accelerator electron cooling pioneer in the Soviet Union. This collaboration was cut short for unknown reasons but Budker died of heart attack a few years later.

Through this experiment, he (and Davis in the U.S.) were able to confirm the prediction that neutrinos are generated during the nuclear fusion reaction in the sun. However, these experiments detected fewer neutrinos than had been expected. This deficit was called the solar neutrino problem. The deficit would be eventually explained by "neutrino oscillations", whose existence was confirmed by an enlarged version of Kamiokande, known as Super-Kamiokande, run under the direction of Koshiba's student Takaaki Kajita.

In 1987, the Kamiokande experimental detector detected neutrinos from the supernova explosion (designated SN 1987A) outside the Milky Way, the Large Magellanic Cloud. His research was pioneering in the establishment of neutrino astronomy as a field of study.

In 1996, with the promising results from Kamiokande, the team operationalized a larger and more sensitive detector called Super-Kamiokande. With this detector, scientists were able to demonstrate strong evidence to prove that neutrinos changed from one type to another of three types during flight. This demonstration resolved the solar neutrino problem with the reasoning being that the early detectors could detect one type of neutrino rather than all three types.

Koshiba was a member of the Board of Sponsors of the Bulletin of the Atomic Scientists, and also a foreign fellow of Bangladesh Academy of Sciences. He was a founding member of the Edogawa NICHE Prize Steering committee.

Personal life

Koshiba married Kyoto Kato, an art museum curator, when he returned to Japan in the late 1950s. The couple had a son and a daughter.

He died on November 12, 2020, at the Edogawa Hospital in Tokyo at the age of 94.

Math Is Fun Forum

#1601 2024-09-26 15:31:58

Re: crème de la crème

#1602 Yesterday 16:16:06

Re: crème de la crème

Board footer