Super-Kamiokande (SK) is a water Cherenkov detector located 1,000 m underground in Kamioka Observatory, ICRR, University of Tokyo in Japan. It consists from a cylindrical stainless steel tank, 50,000 ton of purified water, and 11,000 of 20-inch PMTs, as shown in Fig. 1. The fiducial volume of the SK detector is 22.5 kton. The experiment was started in April 1996, and currently phase IV (SK-IV) is running (Fig. 2). SK has been the world largest water Cherenkov detector with purified water in underground since 1996. SK has a variety of measurement or physics targets, namely, solar neutrinos, atmospheric neutrinos, supernova neutrinos, neutrinos produced by the accelerator in J-PARC (as T2K experiment), and search for nucleon decay.
In near future, we are going to move to the next phase, that is SK-Gd. In the SK-Gd phase, we are planning to add 0.1% of gadolinium to the current SK detector in order to enhance neutron tagging efficiency, and then try to achieve the first observation of supernova relic neutrinos (SRN) (or diffuse supernova neutrino background (DSNB)). The initial work in this upgrade project will be started in June 2018.
In this presentation, a brief summary of the SK experiment, recent solar neutrino results, and recent atmospheric neutrino results will be reported as the current status (Fig. 3). As a future plan, the purpose of SK-Gd and status of the upgrade work will be reported.