Kamioka Observatory

Coordinates: 36°25.6′N 137°18.7′E / 36.4267°N 137.3117°E / 36.4267; 137.3117 (Mt. Ikeno (Ikenoyama)) (Mt. Ikeno)
Source: Wikipedia, the free encyclopedia.

The Kamioka Observatory,

decades. All of the experiments have been very large and have contributed substantially to the advancement of particle physics, in particular to the study of neutrino astronomy 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 Mining and Smelting Co. Mitsui Kinzoku Archived 2016-11-14 at the Wayback Machine).[1]: 1  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. The disease caused weakening of the bones and extreme pain.

Although mining operations have ceased, the smelting plant continues to process zinc, lead and silver from other mines and recycling.[1]: 2, 6–7 

While current experiments are all located in the northern Mozumi mine, the Tochibora mine 10 km south[2]: 9  is also available. It is not quite as deep, but has stronger rock[1]: 22, 24, 26  and is the planned site for the very large Hyper-KamiokaNDE caverns.[2][3]: 19 

Past experiments

KamiokaNDE

A model of KamiokaNDE

The first of the Kamioka experiments was named KamiokaNDE for

muons in such a large detector located on the surface of the Earth would be far too large. The muon rate in the KamiokaNDE experiment was about 0.4 events per second, roughly five orders of magnitude smaller than what it would have been if the detector had been located at the surface.[4]

The distinct pattern produced by Čerenkov radiation allows for

muons
, in contrast, produce very sharp rings as their heavier mass allows them to propagate directly.

Construction of the Kamioka Underground Observatory (the predecessor of the present Kamioka Observatory, Institute for Cosmic Ray Research,

tank which contained 3,000 tons of pure water and had about 1,000 50 cm diameter photomultiplier
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,

physicists
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

billiard balls), so the electrons "point back" to the Sun. Fourth, neutrino-electron scattering is an elastic process, so the energy distribution
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

resolution. 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 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 joined the collaboration and supplied new electronics 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, and the outer detector provided a veto for cosmic ray muons.[4][5]

With the upgrades completed, the experiment was renamed KamiokaNDE-II, and started taking data 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 the Sun over random directions.[4] The directional information was the smoking gun 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 and the radiochemical and water Čerenkov detectors became known as the solar neutrino problem.

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

systematic errors 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
. 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

light years away in the Large Magellanic Cloud. The neutrinos arrived at Earth
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 awarded the Nobel Prize in Physics in 2002. Raymond Davis Jr. and Riccardo Giacconi were co-winners of the prize.

K2K

The KEK To Kamioka experiment[6] 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 41.4 m (136 ft) tall and 39.3 m (129 ft) 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 shared the 2015 Nobel prize with Arthur McDonald.

Super Kamiokande-II

On November 12, 2001, several thousand photomultiplier tubes in the Super-Kamiokande detector imploded, apparently in a chain reaction as the shock wave 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 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 θ13. It uses a neutrino beam directed at the Super Kamiokande detector from the

GeV (currently 30 GeV) proton synchrotron in Tōkai
such that the neutrinos travel a total distance of 295 km (183 mi).

In 2013 T2K observed for the first time the neutrino oscillations in the appearance channel: transformation of muon neutrinos to electron neutrinos.[7] 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 θ23.[8]

KamLAND

The KamLAND experiment is a

antineutrinos. KamLAND is a complementary experiment to the Sudbury Neutrino Observatory 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 of our universe
. The KamLAND experiment is located in the original KamiokaNDE cavity.

Cryogenic Laser Interferometer Observatory (CLIO)

CLIO is a small gravity wave detector with 100 m (330 ft) 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,

Mpc
distance.

XMASS

XMASS is an underground liquid scintillator experiment in Kamioka. It has been searching for dark matter.

NEWAGE

NEWAGE is a direction-sensitive dark-matter-search experiment performed using a gaseous micro-time-projection chamber.[10][11]

Future experiments

Hyper-Kamiokande

There is a program [3] to build a detector ten times larger than Super Kamiokande, and this project is known by the name Hyper-Kamiokande. First tank will be operable in the mid-2020s.[12] 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 against 50 million in Super-Kamiokande).

See also

References

  1. ^ a b c Nakagawa, Tetsuo (9 April 2005). Study on the Excavation of the Hyper-KAMIOKANDE Cavern at Kamioka Mine in Japan (PDF). Next Generation of Nucleon Decay and Neutrino Detectors. Aussois, Savoie, France.
  2. ^
    Toyama
    . Retrieved 27 August 2011.
  3. ^ ].
  4. ^ a b c Nakahata, Masayuki. "Kamiokande and Super-Kamiokande" (PDF). Association of Asia Pacific Physical Societies. Retrieved 2014-04-08.[permanent dead link]
  5. ^ Nakamura, Kenzo. "Present Status and Future of Kamiokande" (PDF). Institute for Cosmic Ray Research, University of Tokyo. Retrieved 2018-09-15.
  6. ^ "Long Baseline neutrino oscillation experiment, from KEK to Kamioka (K2K)". Retrieved 2008-09-10.
  7. S2CID 2586182
    .
  8. .
  9. ^ "Excavation of KAGRA's 7 km Tunnel Now Complete" (Press release). University of Tokyo. 31 March 2014. Retrieved 2015-06-07.
  10. S2CID 103159914
    .
  11. .
  12. ^ "The Hyper-Kamiokande Project is in the MEXT Large Projects Roadmap". HyperKamiokande. 4 August 2017. Archived from the original on Aug 14, 2022.

External links

36°25.6′N 137°18.7′E / 36.4267°N 137.3117°E / 36.4267; 137.3117 (Mt. Ikeno (Ikenoyama)) (Mt. Ikeno)