Transverse-acceptance Measurement System for Jaea Avf Cyclotron

We are developing an acceptance measurement system to evaluate the matching of the emittance of an injection beam to the acceptance of the AVF cyclotron. The system is composed of a phase-space collimator in the low energy section and beam intensity monitors which are installed just after the phase space collimator and in the high energy section. The phase-space collimator, which consists of two pairs of movable slits, is used to inject beams with very small-emittance into the cyclotron by defining position and divergence angle of the beam from an ion source. The acceptance is measured as the phase space distribution of the ratio of the beam intensity at the high energy section to that at the phase space collimator. In the preliminary test, only a part of distribution for the acceptance was measured because the injection-beam emittance from an ion source did not cover the whole acceptance. A steering magnet has been added to expand measurable area by scanning the injection beam in synchronization with the acceptance measurement. The result of a test experiment showed the emittance of the injection beam was able to be enlarged more than ten times. It was confirmed that this technique was valid as the method of increasing the injection emittance for measuring the whole of the acceptance.