The KOTO data acquisition system (DAQ) collects detector PMT waveform signals and saves digitized events to permanent storage using frontend ADC modules, two levels of hardware triggers, and a computing farm. The KOTO DAQ system ran stably in 2013 with 24 kW beam power. To maintain high DAQ livetime with increasing beam power, we implemented lossless data compression inside the ADC modules and developed a new L3 computing farm. The upgraded KOTO DAQ system was able to maintain livetime above 80% with 42 kW beam power during the 2015 and 2016 runs. To sustain high DAQ livetime for data taking with beam power of 50 kW and above, an upgrade of our hardware trigger is proposed.

The KOTO experiment at J-PARC in Tokai, Ibaraki, Japan, aims to observe rare neutral kaon decay mode K L → π 0 νν. Followed by the first KOTO physics run in May 2013 with 24 kW beam power, we upgraded the KOTO data acquisition system in 2015 to accommodate efficient and reliable data collection with higher beam intensities. Lossless data compression inside the ADC modules was implemented to reduced the size of data packets. The lossless data compression enhanced the data collection rate by a factor of three. We designed a new software trigger, which consists of 47 computer nodes. It uses Infiniband hardware with MPI protocol to establish mesh network within the computer cluster and parallel data processing. The upgrades of the KOTO data acquisition system were commissioned in 2015 and used to successfully collect data with beam intensity up to 42 kW. In preparation for increasing beam intensities in 2016 runs, we are developing the hardware trigger upgrades using the RCE Platform Technology (RPT).