Modification of the Center Region for Better Beam Quality at JULIC

The effect of precessional mixing on the external beam quality is studied using deflecting plates on the third turn for the variation of the radial coherent betatron amplitude. A detailed comparison between experiment and calculation for the features of the present center region proves the validity of the IONAN calculation. The proposed modification of the center region should improve the present radial coherent betatron amplitude from now 3 mm to 1 mm and should have additional advantages as for instance a smaller contribution of the center region optics to the radial incoherent betatron amplitude and a much slower variation of the radial coherent amplitude with the RF voltage.