A Bevalac Calibration of a Scintillating Optical Fiber Hodoscope

As part of instrument definition activities for the Advanced Composition Explorer (ACE) we have evaluated a hodoscope comprised of scintillating fibers for possible use in the Cosmic Ray Isotope Spectrometer (CRIS). The hodoscope would determine the trajectories of individual cosmic ray nuclei with 3 ⩽ Z ⩽ 40 and energies up to several hundred MeV/n which stop in four silicon solid state telescopes. We report on the analysis of data from a December 1990 Bevalac calibration of a CRIS test model in which the hodoscope consisted of 200 μm, square cross section, scintillating fibers, and which used silicon detectors for dE/dx - E_(Tot) measurements. The positional resolution obtained with the fiber hodoscope was ∼ 60 μmfor iron nuclei at angles from 0–30° with respect to the normal to the fiber planes. The detection efficiency for iron and silicon nuclei was determined to be > 99% for beam angles of ⩾ 20°