The Development of the new Data Acquisition System without Hardware Trigger for the Super-Kamiokande Experiment

The online system of the underground neutrino detector, super-Kamiokande is scheduled to be upgraded in the spring of 2008 together with the front-end electronics. This detector consists of 50000 ton of pure water equipped with about 13000 photo-multipliers (PMTs) to detect Cherenkov light. The new online system will receive the dataflow of 500-800 MB/s from the front-end electronics and process them for the offline analysis. We will utilize Gigabit Ethernet network and parallel data processing to handle the large data flow. The system also needs high availability for the continuous measurement 365 days a year. In the new data acquisition scheme, we will not use the hardware event-trigger but read out every hit data from the front-end electronics and process them by the online farm. Therefore, there is no threshold of the number of PMT hits and the detector will become more sensitive to the important cosmic-ray events such as low energy solar neutrino and relic neutrino from supernova. In this paper, we will explain the detailed design of the upgraded online system and testing activities using prototype.