An ion source with bunched beam release

As a continuation of a preceding study, the possibility of bunched beam release from a FEBIAD-82 ion source was investigated for the alkali metals, the alkaline-earths, Al, the transition elements Sc-Ni and for Yb. With an appropriate choice of the cooling/heating system and of the trap material, efficient bunching is reached for the alkalies, Ca, Mn and Yb, which have enthalpies of adsorption within 2,6 ≤ ΔHa < 5 eV, the window useful for bunching. Utilizing deduced values of the mean sticking time at a surface of defined temperature, ΔHa-values up to approximately 6 eV can be determined. Thus the conditions can be specified, which should allow bunching and chemical separation for various other elements which are too refractory for the present device. Experimental and semi-empirical ΔHa-values are in good agreement for the transition elements and Al but exhibit strong deviations for the alkali metals, the alkaline-earths, Yb and probably some other lanthanides. On-line mass separation of neutron-deficient isotopes of Cd, In and Sn with a high degree of selectivity demonstrates the chemical separation power of bunched beam release. (orig.)