Development of New Data Acquisition System for Nearby Supernova Bursts at Super-Kamiokande

Abstract

Abstract Super-Kamiokande (SK), a 50-kiloton water Cherenkov detector, is one of the most sensitive neutrino detectors. SK can be used also for supernova observations by detecting neutrinos generated at supernova. In order to improve the performance of the detector for supernovae, we are developing two new features, one for recording all information within one minute and the other for recording calorimetrical information for nearby supernovae. The currentSKdata acquisition(DAQ)systemreadsoutallthe photomultipliertube(PMT)hits, includingthedark noise,andappliessoftwaretriggerto selecteventsto record. Therefore,thePMThits causedbyverylow energyevents below the threshold are not stored. Since supernovaburstisavery rare phenomenon and detailsof theburst mechanism are not known yet, all possible data should be recorded without anybias in the trigger system. To accomplish this, we are addinganew featuretotheDAQsystemto recordallthePMThit information beforeand aftertheburst occursfor about one minute. The neutrinoburst froma supernovafarther than about 1300 light years canbe recorded without lossof databy the currentDAQsystem.However,ifa supernovaburst occurred withinafew hundredsoflight years,the neutrinoevent rate can be more than 30 MHz and the system can record only about 20% of the events. To overcome this inefficiency, wearedevelopinganewDAQsystemthatcanhandlesuchhigh-rate neutrinoevents. ThisnewDAQsystemrecords the number of hit PMTs so that we can count the neutrinos and obtain a time profile of the number of neutrinos emitted at the supernova. We will present the implementation of these improvements and show the results of the tests with the prototype.