Cosmic ray isotope resolution obtained using a new Cherenkov-total energy -d E/d x telescope

Abstract

In the summer of 1972 we flew a new large area cosmic ray telescope on a balloon at Ft. Churchill. This telescope was designed to study the isotopic composition of Z > 2 nuclei using a new technique employing a combination of Cherenkov and total energy counters (C × E), as well as simultaneous measurements using a more conventional d E/d x × E technique. The theoretical response of the various telescope elements, and the mass resolution using both the d E/d x × E and C × E techniques are discussed. Mass resolutions ranging from 0.2 amu for He nuclei, 0.35 amu for C nuclei, and increasing to ≃1.5 amu for Fe nuclei are obtained for the energy range 100–600 MeV/nucl. using the d E/d x × E technique. The C × E technique may only be used for nuclei with Z ≥ 10, over limited energy ranges between 300 and 700 MeV/nucl., however, the mass resolution using this technique is considerably superior. The C × E technique achieves mass resolutions ≲ 0.4 amu for Si nuclei increasing to ≈0.8 amu for Fe nuclei. The mass resolution using this latter approach shows considerable scope for improvement and mass resolutions < 0.4 amu for Fe and lighter nuclei are easily within reach of present technology. Several possible future developments to extend the energy range of applicability and improve still further the mass resolution obtainable using this technique are discussed. This includes systems employing several Cherenkov counters, and multi-dimensional mass analysis techniques employing combinations of C × E and d E/d x × E systems.