Cross sections for the proton-induced production of krypton isotopes from Rb, Sr, Y, and Zr for energies up to 1600 MeV

The production by proton-induced reactions of stable and long-lived Kr-isotopes from Rb, Sr, Y, and Zr was investigated by using isotope dilution mass spectrometry of targets irradiated at PSI/CH, TSL/S and LNS/F. Cumulative cross sections were determined for energies between 81;Ind 1600 MeV, between 15.4 and 1600 MeV, and between 70 and 1600 MeV for the target element Rb, Sr, and Y, respectively. For Zr, three energies of 156, 569 and 1200 MeV were investigated. As a by-product, cross sections for the production of short-lived radionuclides from Rb are reported which were measured by gamma-spectrometry prior to mass spectrometry. Flux determination and absolute calibration of cross sections was done by the reaction Al-27(p,3p3n)Na-22. The new experimental data are consistent with a large database established during recent years for describing the interactions of cosmic ray protons with matter. They provide a first complete basis for model calculations of cosmogenic krypton in stony meteoroids and planetary surfaces. For the target element Rb we report the first measurements at all. For Sr, only one earlier measurement existed. For Y, our data confirm earlier measurements up to 200 MeV and extend the data set up to 1600 MeV, while for Zr three new energy points complement and check the consistency of the new investigations with earlier work from Bordeaux. The new experimental data are compared with theoretical excitation functions calculated on an a priori basis using the hybrid model of pre-equilibrium reactions, an intranuclear cascade/evaporation model in form of the HET/KFA2 code and the semi-empirical systematics by Silberberg, Tsao and coworkers. The differences between theories and experiments demonstrate severe shortcomings of the predictive power of existing models and emphasize the importance of experimental determinations if high-quality data are required for applications. (C) 1998 Elsevier Science B.V. All rights reserved.