Improvement and development of the cyclotron

At the large cyclotron (NIRS-930), the following improvements were applied. A phase probe and single gap buncher were installed, which enabled the adjustment of isochronous magnetic field by measuring beam phase, resulting in a significant reduction in the time for the acceleration adjustment of cyclotron inside. The single gap buncher was improved so as to solve the problems, and it could be used for the actual beam provision. An orbital calculation program to simulate beams under the full 3-dimensional electromagnetic field distribution was established. It was confirmed that the beam pattern and beam passing efficiency that were calculated for 30 MeV protons well reproduced the conditions of actual operation. The prefabrication of beam attenuator capable of adjusting beam intensity without giving a change in the emittance of beams has been completed, which is scheduled for future installation. Since cooling capacity was insufficient causing a trouble due to a decrease in cooling water flow rate at magnetic channel, the magnetic channel has been updated so that the beam intensity can be secured. At the small cyclotron (HM-18), the phase probe that can measure and adjust beam phase has been introduced and is presently under adjustment. (A.O.)