Calibration of the Yangbajing air-shower core detector

Aiming at the observation of cosmic-ray chemical composition at the `knee' energy region, a new type air-shower core detector (YAC, Yangbajing Air shower Core array) consisting of a lead plate of 3.5 cm thick and a scintillation counter with an area of 0.5 m2 has been developed and set up at Yangbajing, 4300 m a.s.l. in Tibet, China since 2014. The main purpose of YAC detector is to separate primary cosmic-ray mass by detecting high energy electromagnetic particles at the air-shower (AS) core generated by the secondary particles after passing through the lead plate. In order to precisely measure the number of shower particles, the calibration procedure of the YAC detector is described in this paper. We found that the linear relationship between YAC scintillation detector output and incident particles is good below 5×106 MIPs while the non-linearity is less than 3%. Such a wide dynamic range shows that YAC experiment may make it possible to obtain the primary mass composition and energy spectrum covering and above the `knee' energy region.