Preliminary results from the extended-trek detector

Abstract

Extended-Trek is the continuation of the Trek ultraheavy cosmic-ray project. The Trek detector consisted of an array of stacks of 16 sheets of BP-1 track-etch glass. The detector was exposed on the Mir space station between 1991 and 1995. The first results of the Trek experiment were based on a maximum of 12 signal measurements for each cosmic-ray event. Extended-Trek will increase this to a maximum of 32 measurements for a selected sample of cosmic-ray tracks. The selected sample comes from detector stacks which were calibrated with 10.6 A GeV Au at two zenith angles. The anticipated improvement in charge resolution may allow a direct measurement of the abundance of Ir in the cosmic rays. Because of bound-state β − decay of 193 Ir, a measurement of Ir abundance is essentially a measurement of the isotopic abundance of 191 Ir.