Characterization of polyethylene terephthalate (PET) detector to search for rare events in cosmic rays.

Search for exotic particles (e.g. strangelets) in cosmic rays is an active field of research. An ideal choice of detectors to look for rare events in cosmic rays at very high mountain altitudes are solid state nuclear track detectors (SSNTDs). In our work we are using a commercially available polymer, polyethylene terephthalate (PET), as a SSNTD. It was found to have a higher detection threshold compared to many other widely used SSNTDs and hence is particularly suited for rare event search in cosmic rays as it eliminates the huge low Z background. A SSNTD has to be properly characterized before it can be used as charged particle detector. So systematic studies were carried out on PET to determine the ideal etching condition for it. Also the charge response of PET was studied using various ion beams from accelerators. The results of such studies and also the calibration curve obtained for PET is presented.