XMASS experiment aims to directly detect the cold dark matter using liquid Xenon (at about -100℃). Dark matter is unknown matter which is 5~6 times quantity of ordinary visible matter in the universe (for more detail). Dark matter plays an important role to form the present structure of the universe. If the direct detection of the dark matter is achieved, it can be a great help to solve the mysteries of the universe and also to discover new particles.

The experimental hall for XMASS was completed in August 2008. The construction of about 800 ton water tank (Φ10m x H10m) to reduce radioactive backgrounds from the outside was finished in autumn same year and The XMASS detector using about 1 ton of liquid xenon was installed in this tank in Oct 2010.

After the commissioning run of XMASS, we refurbished the detector to reduce the background. From autumn 2013, we have started to run our detector.

History of XMASS
October, 2008	Construction of the water shield tank was started.
March, 2009	Construction of the water shield tank was completed.
November, 2009	Construction of the XMASS detector was started.
September, 2010	Construction of the XMASS detector was completed.
October, 2010	Comissioning run started.
June, 2012	Run stopped due to the refurbishment works.
November, 2013	Run started after the refurbishment works and continuous running.
2015~	Continuous running.

• Technique

  

• Detector