THE FAST CYCLIC NEUTRON-ACTIVATION TECHNIQUE AT THE KARLSRUHE 3.75 MVVAN-DE-GRAAFF ACCELERATOR AND THE MEASUREMENT OF THE AG-107,AG-109(N,GAMMA)AG-108,AG-110 CROSS-SECTIONS AT KT=25 KEV

The neuton activation technique is studied for product nuclides with h alf-lives more than a year down to a few seconds. A new system for the measurement of Maxwellian averaged capture cross sections with this t echnique was developed especially for isotopes with induced activities with half-lives of only a few seconds. In order to collect sufficient capture events the two phases of an activation, irradiation and activ ity counting, are repeated periodically. This fast cyclic activation m ethod is described and activation measurements on (107,109)AG are repo rted. The Maxwellian averaged capture cross sections of Ag-107, and Ag -109 at kT=25 kev were found to be 786+/-60mb and 887+/-75mb, respecti vely. The abilities of the activation method to measure cross sections of only a few mu barns are discussed.