Intense Beams of Radioactive Halogens Produced by Means of Surface Ionization

Abstract A negative surface-ionization source has been developed for on-line separator use in order to make intense ion beams of nuclear-reaction produced halogens. It consists of a planar LaB 6 surface onto which the mixed volatile nuclear reaction products are allowed to impinge. A transverse permanent magnetic field and an intermediate electron catcher electrode, inserted before the separator extraction gap, is used to separate the ion and electron fractions. The efficiency of the source is shown to be up to 50% for the halogens, Br and I. i.e. very similar to that obtained by the same process for positive ionization of alkalis on a tungsten surface. During periods of several weeks the source has been used for a number of on-line experiments and has allowed the identification of a series of new nuclei. Yields and halflives of 42,43 Cl and 70,71,72m,76m,93,94 Br are reported.