Production Cross Sections of Fragments from Beams of 400-650 MeV per Nucleon 9Be, 11B, 12C, 14N, 15N, 16O, 20Ne, 22Ne, 56Fe, and 58Ni Nuclei Interacting in a Liquid Hydrogen Target. I. Charge Changing and Total Cross Sections

We have measured the charge changing cross sections from 10 individual beams of isotopes from 8 different nuclei between Be and Ni which were accelerated to energies from 400-650 MeV nucleon^-1 at the SATURNE Accelerator in France in 1993 and 1994. These nuclei interacted in a 1.52 g cm^-2 thick liquid hydrogen target and the fragments were observed. This is the first use of a pure hydrogen target to measure cross sections that has a thickness approximating the amount of hydrogen traversed by cosmic rays in our Galaxy. Several of the beam charges such as ⁹Be, ¹¹B, ¹⁵N, and ²²Ne have not had their fragmentation cross sections measured previously. The cross sections from the ¹²C, ¹⁴N, ¹⁶O, ²⁰Ne, ⁵⁶Fe, and ⁵⁸Ni beams are compared with earlier measurements by our group using a CH₂ - C target subtraction technique to determine the hydrogen cross sections. The overall agreement between the new measurements and the earlier measurements using CH₂ - C subtraction is excellent with a systematic consistency between measurements of 3%-5%. Using these new cross sections the predictions of both the B/C and Z = (21-23)/Fe ratios at ~1 GeV nucleon^-1 now agree with HEAO measurements to ~1%-2%, thus obviating the need for truncation of the exponential path length distribution path length distribution that is expected from uniform propagation models. Also, these new charge changing cross sections along with the isotopic cross sections reported in paper two of this series, define the production of cosmic-ray beryllium and boron nuclei in the galaxy and also the secondary isotopes ¹⁰Be, ¹³C, ¹⁴N, ¹⁵N, ¹⁸O, and all of the Fe secondary isotopes to a level of precision of 3%-5% or better. These cross sections are important for determining the abundance of these rare isotopes and others in the cosmic-ray sources as well as tracing the detailed propagation history of cosmic rays in the Galaxy. These measurements also provide high precision cross sections for the study of the nuclear physics of the interaction process.