Beam Quality Improvement at JULIC

To improve the external beam quality at JULIC, three different measures have been undertaken: the development of a systematic procedure for beam phase optimization, the precise adjustment of the center region to nominal values as well as the installation of harmonic coils near the cyclotron center and the introduction of two axial phase slits according to calculations for proper axial imaging. Starting with a cyclotron as it was tuned in the former day by day operation, the successive application of the above means resulted in an improvement of the radial emittance by a factor of 2 to 10 mm.mrad and of the energy resolution by a factor of 3 to below 1.5.10-3. The three different means for better machine tuning and their effect on the external beam quality are described.