Intensification of the KOTRON-13 cyclotron by optimizing the ion source

The KOTRON-13 cyclotron, which is employed as an internal ion source to generate negative hydrogen ions, was developed in South Korea and was introduced to regional cyclotron centers to produce short-lifetime medical radioisotopes. However, this cyclotron has limited capacity to extract a relatively low beam current; thus, compared with other commercial cyclotrons, the yield of fluorine-18 production was relatively low in the original model. We herein study how to improve the extracted beam current by changing the anode diameters and arc hole sizes in a Penning ion gauge (PIG) system. The optimal anode diameter for a maximum beam current is observed to be 8.0 mm; diameters larger than 8.0 mm do not affect the beam current. The beam current increases linearly as the size of the arc hole becomes large up to a diameter of 7.5 mm; beyond a size of 7.5 mm, the beam current decreases. Additionally, the lifetime of the cathodes is increased when the position of the hydrogen inlet is about 1.7 times the initially installed bottom position for the bidirectional position and 8.3 times the initially installed bottom position for the upper position. Consequently, the beam current of the KOTRON-13 was increased from 50 μA to 120 μA on a dummy target by optimizing the internal ion source structure, which is interpreted by computer simulation.