Influence of injection beam emittance on beam transmission efficiency in a cyclotron

Kurashima, Satoshi; Kashiwagi, Hirotsugu; Miyawaki, Nobumasa; Yoshida, Kenichi; Okumura, Susumu

The JAEA AVF cyclotron accelerates various kinds of high energy ion beams for research in biotechnology and materials science. Beam intensity of an ion species of the order of 10 to 10 ampere is often required for various experiments sequentially performed within a day. To provide the ion beam sufficiently and stably, an operator has to retune an ion source in a short time. The beam intensity downstream of the cyclotron, however in most cases, doesn't increase proportionally to the intensity at the ion source. To understand the cause of this beam behavior, transmission efficiencies of a C beam from the ion source through the cyclotron were measured for various conditions of the ECR ion source. Moreover, a feasible region for acceleration in the emittance of the injection beam was clarified using a transverse-acceptance measuring system. We confirmed that the beam emittance and profile changed depending on the condition of the ion source and the matching between the emittance and the acceptance of the cyclotron got worse. After fine-tuning to improve the matching, the beam intensity downstream of the cyclotron increased.