Large area isotopic silicon targets for astrophysical reaction rate studies in Si-26

For measurements of stellar reaction rates of proton rich nuclei involving resonance levels just above threshold, targets of Si-28 were used in studies of the Si-21(He-4, He-6)Si-26 reaction using the Research Center for Nuclear Physics (RCNP) Ring Cyclotron at Osaka University. Resonance structure observed in Si-26 above the 5.5 MeV proton threshold identified levels populated in the astrophysically important reaction Al-26(p,gamma) Si-26 and help to determine the yield of Al-26 gamma-rays seen in Novae. A few isolated states were also observed above the 9.2 MeV alpha threshold in the (He-4, He-6) reaction which can be used to improve the present stellar rate calculations. We describe here the involved preparation of large area Si-28 metal targets used for these experiments produced by the method of electron beam evaporation. The parting agent used was betaine. To obtain the 0.7 Mg/cm(2) Si-28 target thickness needed for the experiment, several mounted layers were assembled together by stacking. This formidable approach therefore required many foils. Two targets stacks of 0.7 Mg/cm(2) and 0.5 mg/cm(2) Si-28 were delivered to Osaka for the run. Published by Elsevier B.V.