SAGE (Soviet-American Gallium Experiment)
Encyclopedia
SAGE is a collaborative experiment devised by several prominent physicists to measure the solar neutrino
flux
.
, 71Ga
71Ge. The target for the reaction was 50-57 tonnes of liquid gallium
metal stored deep underground at the Baksan Neutrino Observatory
in the Caucasus mountains
in Russia
. About once a month, the neutrino induced Ge
is extracted from the Ga
. 71Ge is unstable with respect to electron capture
(
days) and, therefore, the amount of extracted germanium
can be determined from its activity as measured in small proportional counter
s.
The experiment had begun to measure the solar neutrino capture rate with a target of gallium metal in December 1989 and is running up to now with only a few brief interruptions. The experiment has measured the solar neutrino flux in 168 extractions between January 1990 and December 2007. The current result of the experiment based on the whole 1990-2007 set of data is 65.4 +3.1/-3.0 (statistical) +2.6/-2.8 (systematic
) SNU
. This represents only 56%-60% of the capture rate predicted by different Standard Solar Model
s, which predict 138 SNU.
The collaboration has used a 518 kCi
51Cr neutrino source to test the experimental operation. The energy of these neutrinos is similar to the solar 7Be neutrinos and thus makes an ideal check on the experimental procedure. The extractions for the Cr
experiment took place between January and May 1995 and the counting of the samples lasted until fall. The result, expressed in terms of a ratio of the measured production rate to the expected production rate, is 1.0±0.15. This indicates that the discrepancy between the solar model predictions and the SAGE flux measurement cannot be an experimental artifact. Also calibrations with a 37Ar neutrino source had been performed.
Solar neutrino
Electron neutrinos are produced in the Sun as a product of nuclear fusion. By far the largest fraction of neutrinos passing through the Earth are Solar neutrinos....
flux
Flux
In the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks.* In the study of transport phenomena , flux is defined as flow per unit area, where flow is the movement of some quantity per time...
.
The Experiment
SAGE was devised to measure the radio-chemical solar neutrino flux based on the inverse beta decay reactionReaction
Reaction may refer to:Response to another event*Adverse drug reaction*Chemical reaction*Emotional reaction*Light reaction*Nuclear reaction*TNA Reaction, a documentary show of TNA behind scenes.*Reaction , as defined by Newton's third law...
, 71Ga
71Ge. The target for the reaction was 50-57 tonnes of liquid galliumGallium
Gallium is a chemical element that has the symbol Ga and atomic number 31. Elemental gallium does not occur in nature, but as the gallium salt in trace amounts in bauxite and zinc ores. A soft silvery metallic poor metal, elemental gallium is a brittle solid at low temperatures. As it liquefies...
metal stored deep underground at the Baksan Neutrino Observatory
Baksan Neutrino Observatory
The Baksan Neutrino Observatory is a scientific laboratory of INR RAS located in the Baksan gorge in the Caucasus mountains in Russia. It started operations in 1977, becoming the first such observatory in the USSR...
in the Caucasus mountains
Caucasus Mountains
The Caucasus Mountains is a mountain system in Eurasia between the Black Sea and the Caspian Sea in the Caucasus region .The Caucasus Mountains includes:* the Greater Caucasus Mountain Range and* the Lesser Caucasus Mountains....
in Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. About once a month, the neutrino induced Ge
Gê
Gê are the people who spoke Ge languages of the northern South American Caribbean coast and Brazil. In Brazil the Gê were found in Rio de Janeiro, Minas Gerais, Bahia, Piaui, Mato Grosso, Goias, Tocantins, Maranhão, and as far south as Paraguay....
is extracted from the Ga
Gallium
Gallium is a chemical element that has the symbol Ga and atomic number 31. Elemental gallium does not occur in nature, but as the gallium salt in trace amounts in bauxite and zinc ores. A soft silvery metallic poor metal, elemental gallium is a brittle solid at low temperatures. As it liquefies...
. 71Ge is unstable with respect to electron capture
Electron capture
Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...
(
days) and, therefore, the amount of extracted germaniumGermanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....
can be determined from its activity as measured in small proportional counter
Proportional counter
A proportional counter is a measurement device to count particles of ionizing radiation and measure their energy.A proportional counter is a type of gaseous ionization detector. Its operation is similar to that of a Geiger-Müller counter, but uses a lower operating voltage. An inert gas is used to...
s.
The experiment had begun to measure the solar neutrino capture rate with a target of gallium metal in December 1989 and is running up to now with only a few brief interruptions. The experiment has measured the solar neutrino flux in 168 extractions between January 1990 and December 2007. The current result of the experiment based on the whole 1990-2007 set of data is 65.4 +3.1/-3.0 (statistical) +2.6/-2.8 (systematic
Systematic
Systematic is an American hard rock band from Oakland, California. They were one of the first signings to Metallica drummer Lars Ulrich's record label, The Music Company, via Elektra Records. The band released two studio albums before disbanding in 2004....
) SNU
Solar neutrino unit
Solar neutrino unit is a new unit defined for convenience, which is more suitable for very low event rates.In principle there are two ways of detecting solar neutrinos: radiochemical and real time experiments...
. This represents only 56%-60% of the capture rate predicted by different Standard Solar Model
Standard Solar Model
The Standard Solar Model refers to a mathematical treatment of the Sun as a spherical ball of gas...
s, which predict 138 SNU.
The collaboration has used a 518 kCi
CI
CI or Ci may refer to:-Criminology and military:* Counter-intelligence* Confidential Informant* Confidential Information* Crazy Ivan, a U.S...
51Cr neutrino source to test the experimental operation. The energy of these neutrinos is similar to the solar 7Be neutrinos and thus makes an ideal check on the experimental procedure. The extractions for the Cr
CR
-Other political places:* Castle Rock * Cedar Rapids, Iowa* Crawford County, Kansas* Province of Cremona in Northern Italy-Other places:* College of the Redwoods* public toilet, washroom, or comfort room...
experiment took place between January and May 1995 and the counting of the samples lasted until fall. The result, expressed in terms of a ratio of the measured production rate to the expected production rate, is 1.0±0.15. This indicates that the discrepancy between the solar model predictions and the SAGE flux measurement cannot be an experimental artifact. Also calibrations with a 37Ar neutrino source had been performed.
Members of SAGE
SAGE is led by the following physicists:- Vladimir Gavrin
- Georgiy ZatsepinGeorgiy ZatsepinGeorgiy Timofeyevich Zatsepin was a Soviet/Russian astrophysicist known for his works in cosmic rays physics and neutrino astrophysics. He was born in Moscow....
(Joint Institute for Nuclear ResearchJoint Institute for Nuclear ResearchThe Joint Institute for Nuclear Research, JINR , in Dubna, Moscow Oblast , Russia, is an international research centre for nuclear sciences, with 5500 staff members, 1200 researchers including 1000 Ph.D.s from eighteen member states The Joint Institute for Nuclear Research, JINR , in Dubna, Moscow...
, Russia) - Tom BowlesTom BowlesTom Bowles is a leading Nuclear Physicist working at the Los Alamos National Laboratory.Bowles received his B.Sc. degree at the University of Colorado in 1973 and his Ph.D. at Princeton University in 1978. He was awarded the M. A. Markov Prize from the Russian Academy of Sciences' Institute for...
(Los AlamosLos Alamos National LaboratoryLos Alamos National Laboratory is a United States Department of Energy national laboratory, managed and operated by Los Alamos National Security , located in Los Alamos, New Mexico...
)
See also
- GALLEXGALLEXGALLEX or Gallium Experiment was a radiochemical neutrino detection experiment that ran between 1991 and 1997 at the Laboratori Nazionali del Gran Sasso...
/GNO was the second (of two) large gallium-germanium radiochemical experiment. It was running in 1991-2003. - Hans BetheHans BetheHans Albrecht Bethe was a German-American nuclear physicist, and Nobel laureate in physics for his work on the theory of stellar nucleosynthesis. A versatile theoretical physicist, Bethe also made important contributions to quantum electrodynamics, nuclear physics, solid-state physics and...
was the architect of the theoryTheoryThe English word theory was derived from a technical term in Ancient Greek philosophy. The word theoria, , meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action...
of nuclear fusionNuclear fusionNuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
reactions in starStarA star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s. - The University of WashingtonUniversity of WashingtonUniversity of Washington is a public research university, founded in 1861 in Seattle, Washington, United States. The UW is the largest university in the Northwest and the oldest public university on the West Coast. The university has three campuses, with its largest campus in the University...
is playing a major role in the statistical analysis of the SAGE data and in the determination of systematic uncertainties. They are very active in the remaining analysis of the Cr experiment data as well as the solar neutrino data.
Literature
- SAGE Collaboration. Measurement of the solar neutrino capture rate with gallium metal. III: Results for the 2002--2007 data-taking period. Phys.Rev. C80:015807, 2009. See also arXiv:0901.2200
External links
- The web page of the experiment in the University of WashingtonUniversity of WashingtonUniversity of Washington is a public research university, founded in 1861 in Seattle, Washington, United States. The UW is the largest university in the Northwest and the oldest public university on the West Coast. The university has three campuses, with its largest campus in the University...
- Old page (1994) with results of the experiments
- Some results (2001)
- Hans Bethe talking about SAGE (video)