A Transverse emittance and acceptance measurement system in a low-energy beam transport line

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

A transverse beam emittance and acceptance measurement system has been developed to visualize the relation between the injected beam emittance and the acceptance of a cyclotron. The system is composed of two pairs of slits for horizontal and vertical phase-space selection, a beam intensity detector downstream of the slits for emittance measurement and a beam intensity detector in the cyclotron for acceptance measurement. The emittance is obtained through measuring beam intensity distribution by scanning the slits. The acceptance is obtained through measuring the distribution of relative transmission by injecting small emittance beams with scanning the slits. In the acceptance measurement, the beam from an ion source is deflected using a steering magnet upstream of the slits so that the effective emittance covers the entire acceptance to be measured. Measurements tests were carried out for a O beam injected at 50.2 keV and accelerated to 160 MeV. The emittance of the injection beam and the acceptance for the accelerated beam at the entrance of the extraction deflector were measured. The typical values of emittance and acceptance were 59 mm mrad and 112 mm mrad respectively. The relation between emittance and the acceptance was successfully visualized by displaying them overlapped in the same phase-plane.