PRODUCTION OF CA-41 AND K, SC AND V SHORT-LIVED ISOTOPES BY THE IRRADIATION OF TI WITH 35 TO 150 MEV PROTONS - APPLICATIONS TO SOLAR COSMIC-RAY STUDIES

In order to accurately model Ca-41 production from solar cosmic ray (SCR) proton interactions on titanium at the lunar surface, we have measured the (nat)Ti(p,3pxn) Ca-41 excitation function for E(p) = 35-150 MeV. The irradiated Ti foils were initially analyzed for their induced gamma-activity to identify short-lived products and subsequently measured for their Ca-41 content by accelerator mass spectrometry. Excitation curves, over the above energy range, were also obtained for K-42,K-43, (Sc44g,Sc44m,Sc46,Sc-47,SC-48 and V-48. The results for Ca-41 are compared to both semi-empirical and model-based nuclear spallation calculations. We also used it to determine the magnitude and energy spectrum of the SCR flux from the measured Ca-41 production profile in the Ti-rich lunar basalt, 74275. The results for K, Sc and V radionuclides were compared to previous measurements and agree favourably at low energies (E < 50 MeV) but are larger by approximately 10-30% for higher energies.