Polyethylene terephthalate polymers at mountain altitude as cosmic ray heavy particle detector

We exposed a stack of polyethylene terephthalate (PET) detectors each of thickness 100μm with an area of 21cm×30cm along with a separate stack of the standard solid state nuclear track detector (SSNTD) CR-39 (Intercast Europe Co., Italy) of thickness 630μm and area 20cm×24cm at Darjeeling, India in the Eastern Himalayan Range, under an atmospheric pressure of 765 hPa. The SSNTDs were kept horizontally in the open air for ∼1.5×107s. After etching the PET detectors in 6.25 N NaOH solution at 55±0.1∘C, and partial scanning, it is found that the PET detectors recorded 188 particle tracks of near normal incidence within an area ∼0.37cm2. The observed flux being ∼10-5/(cm2ssr) we have tried to explain our observation on PET detector vis-à-vis the tracks recorded in CR39 exposed simultaneously under similar conditions.