Data acquisition system of the CANGAROO-III telescope

Abstract

We report the development of the data acquisition system of the CANGAROO-III imaging Cherenkov telescope. Multi-pixel cameras consisting of 552 and 427 PMTs are placed at the prime focus of the first and second telescopes respectively. The charge and hit timings of each PMT are measured with ADCs and TDCs respectively via a fast VME-bus which is selected to reduce the data acquisition time. The VME-bus data are read by computers ruuning a linux OS. Furthermore a module to select hit pattern in hardware whether triggered PMTs are adjacent or not will be installed to the second telescope. In CANGAROO-III observations, a global trigger is generated by the coincidence of the local triggers of the four telescopes, and the event data is collected via fast-ethernet, and analyzed with the central event-builder. The data acquisition system of each telescope is designed to accept triggers up to 100Hz.