Kamioka Observatory
The Kamioka Observatory,
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
The first of the Kamioka experiments was named KamiokaNDE for
The distinct pattern produced by Čerenkov radiation allows for
Construction of the Kamioka Underground Observatory (the predecessor of the present Kamioka Observatory, Institute for Cosmic Ray Research,
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,
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
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
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
Supernova 1987A
The Kamiokande-II experiment happened to be running at a particularly fortuitous time, as a
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
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
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,
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
- MINOS
- Supernova Early Warning System
- Super-Kamiokande
- Hyper-Kamiokande
References
- ^ 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.
- ^ Toyama. Retrieved 27 August 2011.
- ^ ].
- ^ a b c Nakahata, Masayuki. "Kamiokande and Super-Kamiokande" (PDF). Association of Asia Pacific Physical Societies. Retrieved 2014-04-08.[permanent dead link]
- ^ Nakamura, Kenzo. "Present Status and Future of Kamiokande" (PDF). Institute for Cosmic Ray Research, University of Tokyo. Retrieved 2018-09-15.
- ^ "Long Baseline neutrino oscillation experiment, from KEK to Kamioka (K2K)". Retrieved 2008-09-10.
- S2CID 2586182.
- S2CID 34184232.
- ^ "Excavation of KAGRA's 7 km Tunnel Now Complete" (Press release). University of Tokyo. 31 March 2014. Retrieved 2015-06-07.
- S2CID 103159914.
- .
- ^ "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
- The official Super-Kamiokande home page
- American Super-K home page
- Official report on the Super-K accident (in PDF format)
- T2K website
36°25.6′N 137°18.7′E / 36.4267°N 137.3117°E (Mt. Ikeno)