Development of cosmic ray detector using an imaging plate

We have been developing a new type of relativistic ultraheavy particle detector using an Imaging Plate, which is used as dE/dx detector. We have investigated the characteristics in the past experiments. However, the heavy particle detector is made of both dE/dx detector and the calorimeter. So we start to study the calorimeter which is made of a scintillator. In particular, the cost of GSO(Ce) has been getting lower and lower and it has high atomic number. Moreover, GSOZ (Ce) is developed by Hitachi Co. Ltd. It is made by doping Zirconium to GSO (Ce). The doping is useful to improve the clarity of the crystal and hence the collection efficiency of the scintillation light goes up. However, the characteristics for the activation due to cosmic ray injection has not been measured, yet. So we investigated activation characteristics of GSOZ. (author)