[en] The project of a 14 MeV PET cyclotron aiming at medical diagnosis and treatment was proposed and started at CIAE in 2010. The low-level RF system is designed to stabilize acceleration voltage and control the resonance of the cavity. Based on the experience of the existing CRM Cyclotron in CIAE, a new start-up sequence is developed and tested. The frequency sweeping is used to activate the RF system. Before the tuner is put into use, a new state called “DDS tuning” is applied to trace the resonance frequency to the designed value. This new option state helps to cover the tuning range, if a large frequency variation occurs because of a thermal cavity deformation. The logic control unit detects the spark, reflection, Pulse/CW state and the frequency of the RF source to perform all kinds of protection and state operations. The test bench and on-line test are carried out to verify the initial design. -- Highlights: • The low-level RF system is designed and verified for PET cyclotron CYCIAE-14. • The frequency sweeping is used to activate the RF system. • A new state called “DDS tuning” is applied to trace the resonance frequency. • This new option state helps to cover the tuning range. • Protection module allows a quick restart after an alarm and improves cyclotron's efficiency

[en] To meet the control requirement of the amplitude, phase, startup logic, interlock and online parameter modification of cyclotron, a general DSP firmware based on finite state machine was proposed. The firmware is divided into 5 states, and they are blockading RF signal, searching cavity resonance, enhancing power, phase match-ing, and phase closed-loop control. The firmware communicates with the local and remote control machines through the serial port and modifies the parameter of the RF system online. It adopts asynchronous event drive method to achieve fast response to spark and reflection. The firmware is successfully applied in the CYCIAE-100 cyclotron low level RF system. In the CYCIAE-100 cyclotron beam commission process, the firmware solves the problem of starting up and ensures the safety of the equipment. The firmware is stable and reliable and meets the requirement of accelerator RF system. (authors)

[en] A new method for measuring cyclotron RF voltage through bremsstrahlung γ ray spectra is described

[en] The CYCIAE230 is a low-current, compact superconducting cyclotron designed for proton therapy. The Radio Frequency system consists of four RF cavities and applies second harmonic to accelerate beams. The driving power for the cavity system is estimated to be approximately 150 kW. The LLRF controller is a self-made device developed and tested at low power using a small-scale cavity model. In this paper, the resonator systems of an S.C. cyclotron in history are reviewed. Contrary to those RF systems, the cavities of the CYCIAE230 cyclotron connect two opposite dees. Two high-power RF windows are included in the system. Each window carries approximately 75 kW RF power from the driver to the cavities. Thus, the RF system for the CY-CIAE230 cyclotron is operated in driven push–pull mode. The two-way amplifier-coupler-cavity systems are operated with approximately the same amount of RF power but 180° out of phase compared with each other. The design, as well as the technical advantage and limitations of this operating mode, of the CYCIAE230 cyclotron RF system is analyzed.

[en] To realize the remote monitoring and control of CYCIAE-100 cyclotron RF system and establish the interlock mechanism with the main control system, an embedded IOC based on ARM9 processor was developed. Linux was chosen as the operating system. EPICS was used to build the IOC as the control software. The slave number of ARM9 processor's SPI bus was extended through software and hardware co-design. The EPICS device drivers and Linux drivers of the ADC and DAC devices were developed. EPICS serial device support program was developed with Python language. After a long-term operation, the embedded IOC is stable and reliable, and meets the need of remote monitoring and control. (authors)

[en] The Beijing Radioactive Ion-beam Facility project is being constructed by BRIF division of China Institute of Atomic Energy. In this project, a 100 MeV high intensity compact proton cyclotron is built for multiple applications. The first successful beam extraction of CYCIAE-100 cyclotron was done in the middle of 2014. The extracted proton beam energy is 100 MeV and the beam current is more than 20 μA. The RF system of the CYCIAE-100 cyclotron includes two half-wavelength cavities, two 100 kW tetrode amplifiers and power transmission line systems (all above are independent from each other) and two sets of Low Level RF control crates. Each set of LLRF control includes an amplitude control unit, a tuning control unit, a phase control unit, a local Digital Signal Process control unit and an Advanced RISC Machines based EPICS IOC unit. These two identical LLRF control crates share one common reference clock and take advantages of modern digital technologies (e.g. DSP and Direct Digital Synthesizer) to achieve closed loop voltage and phase regulations of the dee-voltage. In the beam commission, the measured dee-voltage stability of RF system is better than 0.1% and phase stability is better than 0.03°. The hardware design of the LLRF system will be reviewed in this paper.

[en] The RF system of CYCIAE-100 cyclotron has two cavities, which are driven separately by two identical 100-kW RF amplifiers.Due to the power on sequence issue of the three DDSs in the LLRF systems, each time when the system is individually switched on, the phase relationship may not satisfy the requirements of beam acceleration. Instead of adding an extra reset logic to the system, a search and validation algorithm based on the decision tree has been carried out to make sure the phase of the two cavities is correct right after applying power to the cavities, taking advantage of existing hardware resources. In the first year of operation, there are more than 20 times of scheduled shutdown of the cyclotron system. For each time when the cyclotron RF system is completely shutdown and powered on again, the operator confirmed that the phase matching of the two cavities can be done automatically within 30 s. The related work, including the optimization of the phase detector and the development and validation of the algorithm, is reported in this paper. (authors)

[en] This paper describes the recent status of a RF System for the 100 MeV Cyclotron including the structure and numerical calculation results of cavities, RF power generator, frequency, phase and Dee voltage stabilization control loops, etc. The 100 MeV Cyclotron as a compact machine requires all RF cavities locate in the magnet valleys. The fixed RF frequency feature needs a fine-tuning system to keep cavity resonance circuit to operate at satisfied conditions. The main specifications of RF system and possible problems to be encountered are also given. (author)

[en] In the paper, some methods of numerical simulation of RF performance for accelerator cavity are introduced. In the design of a 70 MHz cyclotron cavity, to meet with the structure of magnet, RF frequency and Q value are researched, and a code based on finite element method is applied to simulate the process of RF experiment. The preliminary design of the cyclotron cavity will serve for the further physical and engineering design. (author)

[en] In a cyclotron, the RF cavity is the key device to accelerate ions. The RF cavity design for the 100 MeV H"- cyclotron is very complex since the space is narrow and the Dee voltage is 60 kV at the center and 120 kV at the extraction region. CST MICROWAVE STUDIO is used in the design, and real model has been made. The test result on the model is in good agreement with the simulation result. (authors)