Abstract:
Background The China Institute of Atomic Energy has designed of a 9.5 MeV ultra-compact cyclotron to support the independence of Positron Emission Tomography (PET) cyclotrons. A high-performance control system is critical for the equipment, as the stability of the acceleration field directly impacts beam quality.
Purpose In order to ensure the stable acceleration of the accelerator beam, this study aims to develop a Low-Level Radio Frequency (LLRF) control algorithm based on a fully digital hardware platform.
Methods To enhance control precision and increase the feedback rate, a high-speed Digital Down-Conversion (DDC) demodulation system was designed. Addressing the issue where the IQ sequence after digital down-conversion may be distributed in arbitrary quadrants, an innovative quadrant preprocessing module was developed to extend applicability across the Cartesian plane. A position-type Proportion-Integral-Derivative (PID) tuning loop was implemented for automatic frequency compensation, integrating adaptive protection, timed detection, and one-click startup. Furthermore, a robust cross-clock-domain data path was constructed to ensure accurate and stable amplitude regulation.
Results Closed-loop tests verified the reliability of the demodulation system. During the joint commissioning with the accelerator, a stable internal target beam current of 100 μA was successfully extracted. The system achieved a cavity voltage amplitude stability of 0.047% (RMSE) and maintained a detuning angle of 0.46°(RMSE).
Conclusion The experimental results demonstrate that the proposed LLRF system fully meets the control requirements of the accelerator. The design ensures high stability and precision, providing reliable technical support for the operation of the 9.5 MeV ultra-compact cyclotron.
下载: