One of the primary sources of near-field gravitational waves [GW] are core collapse supernova [SN] explosion. SN neutrinos, famously observed from SN1987A, provide a unique and vital probe into the inner dynamics of these dramatic events. Released together with GW during the initial stellar collapse, neutrinos and GW are both certain to travel through any obscuring dust or gas and remain undiminished upon their arrival at Earth. Neutrinos also carry information regarding the end state of the star: for explosions within our galaxy, collapses into neutron stars or black holes, the eventual sources of far-field GW, can be differentiated via observations of neutrino emissions.
During FY2018, we began upgrading the existing Super-Kamiokande [SK] detector to be an advanced-technology, gadolinium-loaded SN neutrino detector. This was the first time SK was drained and serviced since 2006.
There were four main tasks: 1) fix a longstanding water leak in the SK tank; 2) clean up the interior of the detector; 3) replace failed photomultiplier tubes, and; 4) install additional piping for better circulation of Gd-loaded water.
On the theory side, SN simulations by 6D Boltzmann equation were performed on the K-computer to clarify the effects of SN core rotation in neutrino emission and transport. Moreover, the properties of SN dynamics and neutrino bursts for different progenitors and sets of the equation of state were explored as an evaluation of uncertainty in neutrino signals. We developed numerical codes for supernovae suitable for use on GPU systems.