Measurements of secondary charged particle fragmentation cross sections produced by high energy heavy ions using silicon strip detectors

Measurements of high multiplicity final states produced in relativistic heavy ion collisions with nuclei applicable to space radiation applications were made. The measurements are of particular interest for space radiation protection as validation for transport models and improvement of nucleus-nucleus interaction models. The silicon strip detector system developed for this work allows direct measurement of the high multiplicity events in contrast to previous experiments with transmission mounted monolithic silicon detectors . The silicon strip detector system was used to measure the nuclear fragments produced in collisions of 290 and 400A MeV 12C ions with elemental and composite targets at the National Institute of Radiological Sciences Heavy Ion Medical Accelerator in Chiba, Japan. Measurements of three and two He coincidences were made including the spatial distribution of the three He events. Measurements of charge changing, and inclusive and exclusive fragment production cross sections were made. The cross section results were compared directly with the nuclear fragmentation code NUCFRG2 where possible. The results from multiplicity measurements of three and two He fragments suggest that many ions contribute to the spectra observed in monolithic silicon detectors. Three He events were found to be composed of approximately 50% Li+He events and 25% true three He events. The Li events in the monolithic silicon detector were composed of 50% true Li events and 35% two He events averaged over all targets and energies. The spatial distributions of the three He events about the beam center are approximately 3.3° ± 1.0° averaged over all targets and energies. The exclusive cross sections measured compare well with the measured fragment production cross sections and are within 10% for all targets except H. The exclusive fragmentation cross sections are in good agreement with the NUCFRG2 predictions and are typically within 10 to 20 percent for fragments from B to He. The charge changing cross sections are compared with several theoretical models with results within the errors for all but the Pb and H target data. The H target data were inferred from the measurements with CH2 introducing larger errors in the H target data.