Kamioka Observatory
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The is a
neutrino A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass ...
and
gravitational waves Gravitational waves are waves of the intensity of gravity generated by the accelerated masses of an orbital binary system that Wave propagation, propagate as waves outward from their source at the speed of light. They were first proposed by Oliv ...
laboratory located underground in the Mozumi mine of the
Kamioka Mining and Smelting Co. is a Cities of Japan, city located in Gifu Prefecture, Gifu, Japan. , the city had an estimated population of 24,726, and a population density of 31 persons per km2, in 8,905 households. The total area of the city was . The official ''kanji'' f ...
near the Kamioka section of the city of Hida in
Gifu Prefecture is a prefecture of Japan located in the Chūbu region of Honshu. Gifu Prefecture has a population of 1,991,390 () and has a geographic area of . Gifu Prefecture borders Toyama Prefecture to the north; Ishikawa Prefecture to the northwest, F ...
,
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
. A set of groundbreaking neutrino experiments have taken place at the observatory over the past two
decades A decade () is a period of ten years. Decades may describe any ten-year period, such as those of a person's life, or refer to specific groupings of calendar years. Usage Any period of ten years is a "decade". For example, the statement that "du ...
. All of the experiments have been very large and have contributed substantially to the advancement of
particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...
, in particular to the study of
neutrino astronomy Neutrino astronomy is the branch of astronomy that observes astronomical objects with neutrino detectors in special observatories. Neutrinos are created as a result of certain types of radioactive decay, nuclear reactions such as those that take ...
and neutrino oscillation.


The mine

The Mozumi mine is one of two adjacent mines owned by the Kamioka Mining and Smelting Co. (a subsidiary of the
Mitsui is one of the largest '' keiretsu'' in Japan and one of the largest corporate groups in the world. The major companies of the group include Mitsui & Co. ( general trading company), Sumitomo Mitsui Banking Corporation, Nippon Paper Industri ...
Mining and Smelting Co.
Mitsui Kinzoku
'). The mine is famous as the site of one of the greatest mass-poisonings in Japanese history. From 1910 to 1945, the mine operators released cadmium from the processing plant into the local water. This cadmium caused what the locals called
itai-itai disease was the name given to the mass cadmium poisoning of Toyama Prefecture, Japan, starting around 1912. The term "''itai-itai'' disease" was coined by localsICETT Itai-itai disease (1998) for the severe pains (Japanese: 痛い ''itai'') people with t ...
. The disease caused weakening of the bones and extreme pain. Although mining operations have ceased, the smelting plant continues to process
zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
,
lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
and
silver Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
from other mines and recycling. While current experiments are all located in the northern Mozumi mine, the Tochibora mine 10 km south is also available. It is not quite as deep, but has stronger rock and is the planned site for the very large Hyper-Kamiokande caverns.


Past experiments


KamiokaNDE

The first of the Kamioka experiments was named KamiokaNDE for
Kamioka is a Cities of Japan, city located in Gifu Prefecture, Gifu, Japan. , the city had an estimated population of 24,726, and a population density of 31 persons per km2, in 8,905 households. The total area of the city was . The official ''kanji'' f ...
Nucleon Decay Experiment. It was a large
water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
Čerenkov detector A Cherenkov detector (pronunciation: /tʃɛrɛnˈkɔv/; Russian: Черенко́в) is a particle detector using the speed threshold for light production, the speed-dependent light output or the speed-dependent light direction of Cherenkov radi ...
designed to search for
proton decay In particle physics, proton decay is a hypothetical form of particle decay in which the proton decays into lighter subatomic particles, such as a neutral pion and a positron. The proton decay hypothesis was first formulated by Andrei Sakharov ...
. To observe the
decay Decay may refer to: Science and technology * Bit decay, in computing * Software decay, in computing * Distance decay, in geography * Decay time (fall time), in electronics Biology * Decomposition of organic matter * Tooth decay (dental caries ...
of a particle with a lifetime as long as a proton an experiment must run for a long time and observe an enormous number of protons. This can be done most cost effectively if the target (the source of the protons) and the detector itself are made of the same material. Water is an ideal candidate because it is inexpensive, easy to purify,
stable A stable is a building in which livestock, especially horses, are kept. It most commonly means a building that is divided into separate stalls for individual animals and livestock. There are many different types of stables in use today; the ...
, and can detect relativistic charged particles through their production of Čerenkov radiation. A proton decay detector must be buried deep underground or in a
mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited Summit (topography), summit area, and ...
because the background from
cosmic ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
muons A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of , but with a much greater mass. It is classified as a lepton. As wi ...
in such a large detector located on the surface of the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
would be far too large. The muon rate in the KamiokaNDE experiment was about 0.4 events per second, roughly five
orders of magnitude An order of magnitude is an approximation of the logarithm of a value relative to some contextually understood reference value, usually 10, interpreted as the base of the logarithm and the representative of values of magnitude one. Logarithmic dis ...
smaller than what it would have been if the detector had been located at the surface. The distinct pattern produced by Čerenkov radiation allows for
particle identification Particle identification is the process of using information left by a particle passing through a particle detector to identify the type of particle. Particle identification reduces backgrounds and improves measurement resolutions, and is essential ...
, an important tool both understanding the potential proton decay signal and for rejecting backgrounds. The ID is possible because the sharpness of the edge of the ring depends on the particle producing the radiation.
Electrons The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...
(and therefore also
gamma rays A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
) produce fuzzy rings due to the
multiple scattering Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including ...
of the low mass electrons. Minimum
ionizing Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...
muons A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of , but with a much greater mass. It is classified as a lepton. As wi ...
, in contrast produce very sharp rings as their heavier mass allows them to propagate directly. Construction of Kamioka Underground Observatory (the predecessor of the present Kamioka Observatory, Institute for Cosmic Ray Research,
University of Tokyo , abbreviated as or UTokyo, is a public research university located in Bunkyō, Tokyo, Japan. Established in 1877, the university was the first Imperial University and is currently a Top Type university of the Top Global University Project by ...
) began in 1982 and was completed in April, 1983. The detector was a
cylindrical A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infini ...
tank A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and good battlefield mobility provided by tracks and a powerful engin ...
which contained 3,000 tons of pure water and had about 1,000 50 cm diameter
photomultiplier A photomultiplier is a device that converts incident photons into an electrical signal. Kinds of photomultiplier include: * Photomultiplier tube, a vacuum tube converting incident photons into an electric signal. Photomultiplier tubes (PMTs for sho ...
tubes (PMTs) attached to the inner surface. The size of the outer detector was 16.0 m in height and 15.6 m in diameter. The detector failed to observe proton decay, but set what was then the world's best limit on the lifetime of the proton. Kamiokande-I operated 1983–1985.


Kamiokande-II

The Kamiokande-II experiment was a major step forward from KamiokaNDE, and made a significant number of important observations. Kamiokande-II operated 1985–1990.


Solar Neutrinos

In the 1930s,
Hans Bethe Hans Albrecht Bethe (; July 2, 1906 – March 6, 2005) was a German-American theoretical physicist who made major contributions to nuclear physics, astrophysics, quantum electrodynamics, and solid-state physics, and who won the 1967 Nobel Prize ...
and
Carl Friedrich von Weizsäcker Carl Friedrich Freiherr von Weizsäcker (; 28 June 1912 – 28 April 2007) was a German physicist and philosopher. He was the longest-living member of the team which performed nuclear research in Germany during the Second World War, under ...
had hypothesized that the source of the sun's energy was
fusion Fusion, or synthesis, is the process of combining two or more distinct entities into a new whole. Fusion may also refer to: Science and technology Physics *Nuclear fusion, multiple atomic nuclei combining to form one or more different atomic nucl ...
reactions in its core. While this hypothesis was widely accepted for decades there was no way of observing the sun's core and directly testing the
hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...
. Ray Davis's Homestake Experiment was the first to detect
solar neutrinos A solar neutrino is a neutrino originating from nuclear fusion in the Sun's core, and is the most common type of neutrino passing through any source observed on Earth at any particular moment. Neutrinos are elementary particles with extremely smal ...
, strong evidence that the nuclear theory of the sun was correct. Over a period of decades the Davis experiment consistently observed only about 1/3 the number of neutrinos predicted by the Standard Solar Models of his colleague and close
friend Friendship is a relationship of mutual affection between people. It is a stronger form of interpersonal bond than an "acquaintance" or an "association", such as a classmate, neighbor, coworker, or colleague. In some cultures, the concept of ...
John Bahcall John Norris Bahcall (December 30, 1934 – August 17, 2005) was an American astrophysicist, best known for his contributions to the solar neutrino problem, the development of the Hubble Space Telescope and for his leadership and development of th ...
. Because of the great technical difficulty of the experiment and its reliance on radiochemical techniques rather than real time direct detection many
physicists A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate caus ...
were suspicious of his result. It was realized that a large water Čerenkov detector could be an ideal neutrino detector, for several reasons. First, the enormous volume possible in a water Čerenkov detector can overcome the problem of the very small
cross section Cross section may refer to: * Cross section (geometry) ** Cross-sectional views in architecture & engineering 3D *Cross section (geology) * Cross section (electronics) * Radar cross section, measure of detectability * Cross section (physics) **Abs ...
of the 5-15
MeV In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacu ...
solar neutrinos. Second, water Čerenkov detectors offer real time event detection. This meant that Individual neutrino-
electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...
interaction candidate events could be studied on an event-by-event basis, starkly different from the month-to-month observation required in radiochemical experiments. Third, in the neutrino-
electron scattering Electron scattering occurs when electrons are deviated from their original trajectory. This is due to the electrostatic forces within matter interaction or, if an external magnetic field is present, the electron may be deflected by the Lorentz f ...
interaction the electron recoils in roughly the direction that the neutrino was travelling (similar to the motion of billiard balls), so the electrons "point back" to the sun. Fourth, neutrino-electron scattering is an
elastic Elastic is a word often used to describe or identify certain types of elastomer, elastic used in garments or stretchable fabrics. Elastic may also refer to: Alternative name * Rubber band, ring-shaped band of rubber used to hold objects togeth ...
process, so the energy
distribution Distribution may refer to: Mathematics *Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations * Probability distribution, the probability of a particular value or value range of a vari ...
of the neutrinos can be studied, further testing the solar model. Fifth, the characteristic "ring" produced by Čerenkov radiation allows discrimination of the signal against backgrounds. Finally, since a water Čerenkov experiment would use a different target, interaction process, detector technology, and location it would be a very complementary test of Davis's results. It was clear that KamiokaNDE could be used to perform a fantastic and novel experiment, but a serious problem needed to be overcome first. The presence of
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
backgrounds in KamiokaNDE meant that the detector had an
energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
threshold of tens of
MeV In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacu ...
. The signals produced by proton decay and atmospheric neutrino interactions are considerably larger than this, so the original KamiokaNDE detector had not needed to be particularly aggressive about its energy threshold or
resolution Resolution(s) may refer to: Common meanings * Resolution (debate), the statement which is debated in policy debate * Resolution (law), a written motion adopted by a deliberative body * New Year's resolution, a commitment that an individual mak ...
. The problem was attacked in two ways. The participants of the KamiokaNDE experiment designed and built new purification systems for the water to reduce the
radon Radon is a chemical element with the symbol Rn and atomic number 86. It is a radioactive, colourless, odourless, tasteless noble gas. It occurs naturally in minute quantities as an intermediate step in the normal radioactive decay chains through ...
background, and instead of constantly cycling the detector with "fresh" mine water they kept the water in the tank allowing the radon to decay away. A group from the
University of Pennsylvania The University of Pennsylvania (also known as Penn or UPenn) is a private research university in Philadelphia. It is the fourth-oldest institution of higher education in the United States and is ranked among the highest-regarded universitie ...
joined the
collaboration Collaboration (from Latin ''com-'' "with" + ''laborare'' "to labor", "to work") is the process of two or more people, entities or organizations working together to complete a task or achieve a goal. Collaboration is similar to cooperation. Most ...
and supplied new
electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
with greatly superior timing capabilities. The extra information provided by the electronics further improved the ability to distinguish the neutrino signal from radioactive backgrounds. One further improvement was the expansion of the cavity, and the installation of an instrumented "outer detector". The extra water provided shielding from gamma rays from the surrounding
rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...
, and the outer detector provided a
veto A veto is a legal power to unilaterally stop an official action. In the most typical case, a president or monarch vetoes a bill to stop it from becoming law. In many countries, veto powers are established in the country's constitution. Veto ...
for cosmic ray muons. With the
upgrade Upgrading is the process of replacing a product with a newer version of the same product. In computing and consumer electronics an upgrade is generally a replacement of hardware, software or firmware with a newer or better version, in order to ...
s completed the experiment was renamed Kamiokande-II, and started data taking in 1985. The experiment spent several years fighting the radon problem, and started taking "production data" in 1987. Once 450 days of data had been accumulated the experiment was able to see a clear enhancement in the number of events which pointed away from sun over random directions. The directional information was the
smoking gun The term "smoking gun" is a reference to an object or fact that serves as conclusive evidence of a crime or similar act, just short of being caught ''in flagrante delicto''. "Smoking gun" refers to the strongest kind of circumstantial evidence ...
signature of solar neutrinos, demonstrating directly for the first time that the sun is a source of neutrinos. The experiment continued to take data for many years and eventually found the solar neutrino flux to be about 1/2 that predicted by solar models. This was in conflict with both the solar models and Davis's experiment, which was ongoing at the time and continued to observe only 1/3 of the predicted signal. This conflict between the flux predicted by solar
theory A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may be s ...
and the radiochemical and water Čerenkov detectors became known as the
solar neutrino problem The solar neutrino problem concerned a large discrepancy between the flux of solar neutrinos as predicted from the Sun's luminosity and as measured directly. The discrepancy was first observed in the mid-1960s and was resolved around 2002. The fl ...
.


Atmospheric neutrinos

The flux of atmospheric neutrinos is considerably smaller than that of the solar neutrinos, but because the reaction cross sections increase with energy they are detectable in a detector of Kamiokande-II's size. The experiment used a "ratio of ratios" to compare the
ratio In mathematics, a ratio shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ...
of electron to muon flavor neutrinos to the ratio predicted by theory (this technique is used because many
systematic error Observational error (or measurement error) is the difference between a measured value of a quantity and its true value.Dodge, Y. (2003) ''The Oxford Dictionary of Statistical Terms'', OUP. In statistics, an error is not necessarily a " mistak ...
s cancel each other out). This ratio indicated a deficit of muon neutrinos, but the detector was not large enough to obtain the statistics necessary to call the result a
discovery Discovery may refer to: * Discovery (observation), observing or finding something unknown * Discovery (fiction), a character's learning something unknown * Discovery (law), a process in courts of law relating to evidence Discovery, The Discovery ...
. This result came to be known as the atmospheric neutrino deficit.


Supernova 1987A

The Kamiokande-II experiment happened to be running at a particularly fortuitous time, as a
supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...
took place while the detector was online and taking
data In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted ...
. With the upgrades that had taken place the detector was sensitive enough to observe the thermal
neutrinos A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is ...
produced by Supernova 1987A, which took place roughly 160,000
light years A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...
away in the
Large Magellanic Cloud The Large Magellanic Cloud (LMC), or Nubecula Major, is a satellite galaxy of the Milky Way. At a distance of around 50 kiloparsecs (≈160,000  light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the ...
. The neutrinos arrived at
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
in February 1987, and the Kamiokande-II detector observed 11 events.


Nucleon decay

Kamiokande-II continued KamiokaNDE's search for proton decay and again failed to observe it. The experiment once again set a lower-bound on the half-life of the proton.


Kamiokande-III

The final upgrade to the detector, Kamiokande-III operated 1990–1995.


Nobel Prize

For his work directing the Kamioka experiments, and in particular for the first-ever detection of astrophysical neutrinos
Masatoshi Koshiba 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 ...
was awarded the
Nobel Prize in Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...
in 2002.
Raymond Davis Jr. 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; ...
and
Riccardo Giacconi Riccardo Giacconi ( , ; October 6, 1931 – December 9, 2018) was an Italian-American Nobel Prize-winning astrophysicist who laid down the foundations of X-ray astronomy. He was a professor at the Johns Hopkins University. Biography Born in ...
were co-winners of the prize.


K2K

The KEK To Kamioka experiment used accelerator neutrinos to verify the oscillations observed in the atmospheric neutrino signal with a well controlled and understood beam. A neutrino beam was directed from the KEK accelerator to Super Kamiokande. The experiment found oscillation parameters which were consistent with those measured by Super-K.


Current experiments


Super Kamiokande

By the 1990s particle physicists were starting to suspect that the solar neutrino problem and atmospheric neutrino deficit had something to do with neutrino oscillation. The Super Kamiokande detector was designed to test the oscillation hypothesis for both solar and atmospheric neutrinos. The Super-Kamiokande detector is massive, even by particle physics standards. It consists of 50,000 tons of pure water surrounded by about 11,200 photomultiplier tubes. The detector was again designed as a cylindrical structure, this time tall and across. The detector was surrounded with a considerably more sophisticated outer detector which could not only act as a veto for cosmic muons but actually help in their reconstruction. Super-Kamiokande started data taking in 1996 and has made several important measurements. These include precision measurement of the solar neutrino flux using the elastic scattering interaction, the first very strong evidence for atmospheric neutrino oscillation, and a considerably more stringent limit on proton decay.


Nobel prize

For his work with Super Kamiokande,
Takaaki Kajita is a Japanese physicist, known for neutrino experiments at the Kamioka Observatory – Kamiokande and its successor, Super-Kamiokande. In 2015, he was awarded the Nobel Prize in Physics jointly with Canadian physicist Arthur B. McDonald. On 1 ...
shared the 2015 Nobel prize with
Arthur McDonald Air Marshal Sir Arthur William Baynes McDonald, (14 June 1903 – 26 July 1996) was a senior Royal Air Force officer. He served as Commander-in-Chief of the Royal Pakistan Air Force from 1955 to 1957. Early life McDonald was born on 14 June ...
.


Super Kamiokande-II

On November 12, 2001, several thousand photomultiplier tubes in the Super-Kamiokande detector imploded, apparently in a
chain reaction A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. In a chain reaction, positive feedback leads to a self-amplifying chain of events. Chain reactions are one way that syst ...
as the
shock wave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a med ...
from the concussion of each imploding tube cracked its neighbours. The detector was partially restored by redistributing the photomultiplier tubes which did not implode, and by adding protective
acrylic Acrylic may refer to: Chemicals and materials * Acrylic acid, the simplest acrylic compound * Acrylate polymer, a group of polymers (plastics) noted for transparency and elasticity * Acrylic resin, a group of related thermoplastic or thermosett ...
shells that it was hoped would prevent another chain reaction from recurring. The data taken after the implosion is referred to as the Super Kamiokande-II data.


Super Kamiokande-III

In July 2005, preparation began to restore the detector to its original form by reinstalling about 6,000 new PMTs. It was finished in June 2006. Data taken with the newly restored machine was called the SuperKamiokande-III dataset.


Super Kamiokande-IV

In September 2008, the detector finished its latest major upgrade with state-of-the-art electronics and improvements to water system dynamics, calibration and analysis techniques. This enabled SK to acquire its largest dataset yet (SuperKamiokande-IV), which continued until June 2018, when a new detector refurbishment involving a full water drain from the tank and replacement of electronics, PMTs, internal structures and other parts will take place.


Tokai To Kamioka (T2K)

The "Tokai To Kamioka" long baseline experiment started in 2009. It is making a precision measurement of the atmospheric neutrino oscillation parameters and is helping ascertain the value of . It uses a neutrino beam directed at the Super Kamiokande detector from the Japanese Hadron Facility's 50
GeV GEV may refer to: * ''G.E.V.'' (board game), a tabletop game by Steve Jackson Games * Ashe County Airport, in North Carolina, United States * Gällivare Lapland Airport, in Sweden * Generalized extreme value distribution * Gev Sella, Israeli-Sou ...
(currently 30 GeV)
proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...
synchrotron A synchrotron is a particular type of cyclic particle accelerator, descended from the cyclotron, in which the accelerating particle beam travels around a fixed closed-loop path. The magnetic field which bends the particle beam into its closed p ...
in
Tōkai Tōkai ( 東海, literally ''East Sea'') in Japanese may refer to: * Tōkai region, a subregion of Chūbu * Tōkai, Ibaraki, a village, also known as "Tokaimura" (Tokai-village) * Tōkai, Aichi, a city * Tōkai University, a private university in T ...
such that the neutrinos travel a total distance of . In 2013 T2K observed for the first time the neutrino oscillations in the appearance channel: transformation of muon neutrinos to electron neutrinos. In 2014 the collaboration provided the first constraints on the value of CP violating phase, together with the most precise measurement of the mixing angle .


KamLAND

The KamLAND experiment is a liquid scintillator detector designed to detect reactor
antineutrino A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is ...
s. KamLAND is a complementary experiment to the
Sudbury Neutrino Observatory The Sudbury Neutrino Observatory (SNO) was a neutrino observatory located 2100 m underground in Vale's Creighton Mine in Sudbury, Ontario, Canada. The detector was designed to detect solar neutrinos through their interactions with a large t ...
because while the SNO experiment has good sensitivity to the solar mixing angle but poor sensitivity to the squared mass difference, KamLAND has very good sensitivity to the squared mass difference with poor sensitivity to the mixing angle. The data from the two experiments may be combined as long as CPT is a valid
symmetry Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definit ...
of our
universe The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. Acc ...
. The KamLAND experiment is located in the original KamiokaNDE cavity.


Cryogenic Laser Interferometer Observatory (CLIO)

CLIO is a small gravity wave detector with arms which is not large enough to detect astronomical gravity waves, but is prototyping cryogenic mirror technologies for the larger KAGRA detector.


KAGRA

The KAmioka GRAvitational wave detector (formerly LCGT, the Large-scale Cryogenic Gravitational Wave Telescope) was approved in 2010, excavation was completed in March 2014, and the first phase is commissioning in 2016. It is a laser interferometer with two arms, each 3 km long, and when complete around 2018, will have a planned sensitivity to detect coalescing binary neutron stars at hundreds of Mpc distance.


XMASS

XMASS is an underground liquid scintillator experiment in Kamioka. It has been searching for
dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...
.


NEWAGE

NEWAGE is a direction-sensitive dark-matter-search experiment performed using a gaseous micro-time-projection chamber.


Future experiments


Hyper-Kamiokande

There is a program to build a detector ten times larger than Super Kamiokande, and this project is known by the name
Hyper-Kamiokande Hyper-Kamiokande is a neutrino observatory being constructed on the site of the Kamioka Observatory, near Kamioka, Japan. The project started in 2010 as a successor to Super-Kamiokande. It was ranked as among the 28 top priority projects of the J ...
. First tank will be operable in the mid-2020s. At the time of 'inauguration' in 2017 the tank(s) is announced to be 20 times greater than the last one (1000 million liters in
Hyper-Kamiokande Hyper-Kamiokande is a neutrino observatory being constructed on the site of the Kamioka Observatory, near Kamioka, Japan. The project started in 2010 as a successor to Super-Kamiokande. It was ranked as among the 28 top priority projects of the J ...
against 50 million in
Super-Kamiokande Super-Kamiokande (abbreviation of Super-Kamioka Neutrino Detection Experiment, also abbreviated to Super-K or SK; ja, スーパーカミオカンデ) is a neutrino observatory located under Mount Ikeno near the city of Hida, Gifu Prefecture ...
).


See also

*
MINOS In Greek mythology, Minos (; grc-gre, Μίνως, ) was a King of Crete, son of Zeus and Europa. Every nine years, he made King Aegeus pick seven young boys and seven young girls to be sent to Daedalus's creation, the labyrinth, to be eaten ...
* Supernova Early Warning System *
Super-Kamiokande Super-Kamiokande (abbreviation of Super-Kamioka Neutrino Detection Experiment, also abbreviated to Super-K or SK; ja, スーパーカミオカンデ) is a neutrino observatory located under Mount Ikeno near the city of Hida, Gifu Prefecture ...
*
Hyper-Kamiokande Hyper-Kamiokande is a neutrino observatory being constructed on the site of the Kamioka Observatory, near Kamioka, Japan. The project started in 2010 as a successor to Super-Kamiokande. It was ranked as among the 28 top priority projects of the J ...


References


External links


The official Super-Kamiokande home page

American Super-K home page

Official report on the Super-K accident (in PDF format)

T2K website
{{coord, 36, 25.6, N, 137, 18.7, E, type:mountain_region:JP-21, display=title, name=Mt. Ikeno (Ikenoyama), notes= (Mt. Ikeno) Underground laboratories Neutrino observatories Research institutes in Japan Particle experiments Buildings and structures in Gifu Prefecture Laboratories in Japan Hida, Gifu