Hirosaki Air Shower Array II

In order to study the arrival time of successive air shower, a new air shower array(Hirosaki Air Shower Array II;AS-Array II) has been constructed on the roof of Building No.1 of the Faculty of Science and Technology, Hirosaki University. This array consists of five fast timing detectors (FT detectors) using GPS antenna. A 2-fold coincidence within 100 ns is used on the triggering condition. The event rate is about 18k events/day. This array is located in south 125 m of the air shower array I(AS-Array I). Two compact AS arrays are operating simultaneously and independently at distant arrays. Most importantly, for the network observations, each station has the GPS receiver as the common clock, so we can compare arrival times of extensive air shower observed at different stations with a high accuracy of 1μs. By comparing arrival times and arrival directions of two stations, analysis of arrival time of successive air shower within 1μs is enabled.