XMASS is a multipurpose
physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
experiment in
Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
. It is a large
cryogenic storage dewar
A cryogenic storage dewar (or simply dewar) is a specialised type of vacuum flask used for storing cryogens (such as liquid nitrogen or liquid helium), whose boiling points are much lower than room temperature. It is named after inventor James De ...
, a tank of liquid
xenon
Xenon is a chemical element; it has symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
equipped with photosensors monitoring flashes of light that might be caused by interactions with hypothetical
dark matter
In astronomy, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravity, gravitational effects that cannot be explained by general relat ...
particles. Unlike a
cryogenic particle detector, it operates at temperatures relatively far from
absolute zero
Absolute zero is the lowest possible temperature, a state at which a system's internal energy, and in ideal cases entropy, reach their minimum values. The absolute zero is defined as 0 K on the Kelvin scale, equivalent to −273.15 ° ...
(specifically, ). In addition to searching for dark matter, XMASS is also studying neutrinoless double beta decay and solar neutrinos. The project is conducted by a team at
Institute for Cosmic Ray Research,
University of Tokyo
The University of Tokyo (, abbreviated as in Japanese and UTokyo in English) is a public research university in Bunkyō, Tokyo, Japan. Founded in 1877 as the nation's first modern university by the merger of several pre-westernisation era ins ...
.
Its results have not confirmed the annual variation seen in some earlier experiments.
History
Construction started in April 2007. The detector was completed in September 2010. Commissioning run was conducted between October 2010 and June 2012. Scientific data taking begun in November 2013. The detector is sometimes called XMASS-I, as it is planned to be superseded by an upgrade called XMASS-1.5 (a 5-ton detector) and eventually XMASS-II (24 ton detector).
The XMASS-I experiment shut down and ceased data taking 20 February 2019.
Results were published in 2021.
Detector
The detector is located 1000m underground in the
Kamioka Observatory in Japan. It contains about 800 kg of xenon.
About XMASS : Detector
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See also
*
References
External links
Direct Dark Matter Search by Annual Modulation [Results from XMASS] Sept 2015
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