Design and relative calibration of a beam profile measurement system for the SC200 superconducting cyclotron

The SC200 superconducting cyclotron promoted by the ASIPP (Hefei, China) and the Joint Institute for Nuclear Research (Dubna, Russia) has made significant progress. A new beam profile measurement system (BPMS) has been developed to operate inside the cyclotron to acquire information of the transverse beam profile. We present the structural layout of the BPMS in frame of the SC200 superconducting cyclotron operating scenario with many details, e.g. high magnetic field, compact structure, high radio frequency interference and strong irradiation, etc. The influences of the magnetic field, heat-dissipating method, and other factors on the BPMS were described in detail and solved. The energy loss, spectral matching, and the temperature dependency of the scintillation screen, as well as the directional characteristic of the imaging system were all taken into account for a relative calibration of the BPMS. The BPMS was adopted for beam diagnosis during the initial commissioning phase of the SC200, and the experimental results of light output and horizontal beam sizes were calibrated to provide quantitative information. Furthermore, the beam loss and vertical distribution of the beam were calculated, which provide important basis for beam tuning and optimization of the cyclotron. The successful application of the BPMS inside the compact cyclotron is of great significance for further shimming and optimization of the isochronous field.