Alpha-spallation cross sections at 920 MeV (230 MeV/N) in Al27, O16, C12, and Be9, and application to cosmic-ray transport

Jonathan R. Radin, Alan R. Smith, and Nickey Little
Phys. Rev. C 9, 1718 – Published 1 May 1974
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Abstract

We investigated the effects on cosmic rays from spallation reactions between cosmic rays and interstellar helium. The spallation cross sections were measured by exposing thin-sandwich targets to the 920-MeV (230-MeV/N) external α-particle beam of the 184-in. cyclotron at Lawrence Berkeley Laboratory. Cross sections were measured for the production: from Al27 of F18 (12.5±0.5 mb); from O16 of O15 (46.4±2.7 mb), N13 (6.75±0.5 mb), C11 (18.5±0.9 mb), and Be7 (18.5±1.3 mb); from C12 of Be7 (20.0±1.2 mb); and from Be9 of Be7 (12.6±0.8 mb). We constructed spallation cross-section ratios for the ratio of α-particle-induced to proton-induced reactions (Σpα). We parametrized this ratio by the nucleon difference (ΔA) between the target initial and final states and we fitted this ratio [Σpα(ΔA)] to a linear function in ΔA. We used this function [Σpα(ΔA)] to obtain all of the α-particle-spallation cross sections from the corresponding proton-spallation cross sections for targets and products in the elemental range 3Z8, and we applied these cross sections to a cosmic-ray transport calculation wherein we investigated the sensitivity of the cosmic-ray LM ratio [=(Li + Be + B) / (C + N + O)] and of the abundances of the L and M elements to the helium fraction of the interstellar gas.

[NUCLEAR REACTIONS Al27(α,x)F18; O16(α,x)O15, N13, C11, Be7; C12(α,x)Be7; Be9(α,x)Be7, E=920 MeV; measured σ; NaI detector. Examined effect interstellar He on cosmic rays.]

  • Received 29 November 1973

DOI:https://doi.org/10.1103/PhysRevC.9.1718

©1974 American Physical Society

Authors & Affiliations

Jonathan R. Radin*

  • Tel-Aviv University, Department of Physics & Astronomy, Ramat Aviv, Israel

Alan R. Smith and Nickey Little

  • Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720

  • *Work performed in part while at New York University, Department of Physics, New York City, N. Y. 10003.

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Vol. 9, Iss. 5 — May 1974

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