DEVELOPMENT OF HIGH-QUALITY INTENSE PROTON BEAM AT THE RCNP CYCLOTRON FACILITY

An upgrade program for increase of beam intensity and improvement of beam quality is in progress at the cyclotron facility of Research Center for Nuclear Physics(RCNP). A 2.45 GHz ECR proton source was modified to increase 392 MeV proton beam intensity. Rated output power of a microwave power supply was increased from 200 W to 2 kW. A water-cooled waveguide system for high power microwave transfer is being installed for the proton source. A 15 keV proton beam with intensity of 0.6 mA was stably produced for output microwave power of 200 W. Emittance of 50 to 100  mm-mrad was obtained for 0.05 to 0.1 mA proton beams in the LEBT system. Beam transmission, defined by the ratio of the beam intensity between a Faraday cup placed in the axial injection beam line and an inflector electrode of the AVF cyclotron, was improved from 25 % for a 0.07 mA proton beam to more than 90 % for 0.03 mA, which indicated that the beam transmission was limited by the acceptance of the axial injection beam line. A new active gradient corrector is being designed for horizontal beam focusing in the extraction region of the AVF cyclotron and for reducing a beam loss at the vacuum chamber in the extraction region. An asymmetric dee voltage distribution at an acceleration gap is being analyzed for improvement of a flat-top acceleration system of the AVF cyclotron.