Improvement of the RF cavity for the SKKUCY-10 cyclotron

Abstract

The SKKUCY-10 cyclotron based on 83.2 MHz, 40 kV half-wave RF cavity was developed at Sungkyunkwan University for the production of medical radioisotopes. The resonant frequency $f_{{{\text{RF}}}}$ of the cyclotron and the RF coupling coefficient $\beta _{{\text{c}}}$ of the RF cavity system were measured at various vacuum, and temperature conditions. The normalized multi-pacting intensities at four positions in the power coupler were analyzed to predict the multi-pacting power. Differences, $\Delta f_{{{\text{RF}}}}$ and $\Delta \beta _{{\text{c}}}$, caused by the vacuum, and temperature conditions were modified based on the coupler and tuner gap distances. During the RF conditioning, a constant 15 kW pulse mode and a variable 1 to 15 kW continuous wave mode were employed. The values of the reflection coefficient $\Gamma$ and $\beta _{{\text{c}}}$ were 1.2% and 0.8, respectively, when the cavity dissipation power was 12.4 kW at 83.2 MHz. Good agreement between the simulation and experimental data was obtained.