Development of the Data Acquisition System for CANGAROO-III

In this paper we report the development of the data acquisition system (DAQ) of the CANGAROO-III imaging Cherenkov telescope. Multi-pixel cameras at the prime focus of the first and second 10m telescopes consist of 552 and 427 PMTs, respectively. The charge from each PMT is measured with a ADC and the time each PMT is triggered is measured by a TDC with a time resolution of 1 ns. Since these modules are connected to a fast VME-bus and are read out by a CPU board running a Linux OS, the DAQ system of the second telescope can handle a trigger rate as high as 500 Hz. In stereoscopic observations, the DAQ of each telescope records shower events independently and these events are reconstructed in offline.