DEVELOPMENT OF THE IBA-JINR CYCLOTRON C235-V3 FOR DIMITROVGRAD HOSPITAL CENTER OF THE PROTON THERAPY

The Dimitrovgrad project, the first Russian hospital center of the proton therapy, was approved in 2010. The JINR-IBA collaboration developed and constructed the C235-V3 proton cyclotron for this center. The assembly and the beam tests of the machine were done in 20112012 in special experimental hall in JINR. This cyclotron is a substantially modified version C235-V3 of the IBA C235 serial cyclotron. C235-V3 has the improved extraction system which was constructed and tested. This system allows raise the extraction efficiency up to 77% from 50% in comparison with serial C235. Special mapping system (for Br-component) of the magnetic field was developed and constructed by JINR for the shimming of the Br-field in the middle plane of the cyclotron. Tests with accelerated and extracted beam were performed in August 2012 in JINR. Beam vertical motion in the cyclotron is in the acceptable limits ( Zbeam 3 mm). Transmission from r=300mm to 1030 is 72% without beam cutting diaphragms. This allows reduce irradiation dose of the machine elements in comparison with serial C235. Extraction efficiency is 62%. Total efficiency of the machine is 45%. Further improvement of the parameters expected after final tuning of the cyclotron in Dimitrovgrad. Recommendations are formulated to modify the magnetic system and reduce sensitivity of the machine to the magnetic field imperfections. Most of changes concerned with the increasing of the vertical focusing at the final radii where the aperture equals two vertical size of the beam.