The design and commissioning of the rf system for cyciae-14 cyclotron

The CYCIAE-14 project was launched by BRIF division of CIAE in year 2010, to build a 14MeV compact proton cyclotron for medical applications. The beam energy, intensity as well as other parameters of the machine is selected in such a way, so that the cyclotronbased production of technetium-99m (Tc-99m) can be evaluated. The commission of this cyclotron was successfully finished in the middle of year 2012, with extracted beam energy equals to 14.6MeV and intensity high than 100uA. The RF system of the CYCIAE-14 cyclotron includes a set of lambda by four cavities (connected with each other under central region), a 20kW triode amplifier and related 1 inch rigid line power transmission system. It also includes a set of Low Level RF control circuits, which takes advantages of modern digital technologies such as DSP and DDS to achieve close-loop regulation of the accelerating voltage and frequency. The design of this RF system starts from the middle of year 2010. Most of the equipments are manufactured and shipped to site before the end of year 2011. The installation and commission of this RF system was started in the beginning of year 2012 and finished about 3 months later, the measured voltage stability is better than 0.1%. The design and difficulties in the commission was reviewed in this paper, on particular, the instability introduced by transmission line taped with high Q load as well as the problems caused by RF leakage during the commission was also analyzed. INTRODUCTION The modern PET/CT system might be divided into two major parts, the clinical scanner and the cyclotron, the latter provides an FDG production service to support the former. As in these years, the local medical demands for the PET/CT system raised rapidly in china, a medical cyclotron project has been launched by BRIF division of CIAE in year 2010 . The construction cycle for this project is limited to be two years, and it has been successfully finished in time. For small medical cyclotron, most of the design adopts internal ion source for both simplicity and efficiency considerations. It should be admitted that in most cases it suits the case, and can provide 50uA to 100uA beam without major limitations. While for the CYCIAE-14 cyclotron, aiming at higher beam intensity, e.g. 400uA of proton beam, the system takes advantage of external ion source and axial injection and spiral inflector design. One of the design goals is to evaluate the cyclotron-based production of technetium-99m (Tc-99m) by using reaction of Mo(p, 2n)Tc . DESIGN OF THE RF SYSTEM The RF system of CYCIAE-14 cyclotron includes a set of λ/4 cavities, a 20kW triode amplifier and a set of low level controls, as shown in Fig.1. The two cavities are connected internally with each other under central region.