数字化I/Q技术用于磁控管频率控制  

Digital I/Q technology used for magnetron frequency control

作　　者：钟少鹏[1] 赵明华[1] 张俊强[1] 

机构地区：[1]中国科学院上海应用物理研究所嘉定园区,上海201800

出　　处：《核技术》2014年第4期11-14,共4页Nuclear Techniques

摘　　要：采用磁控管做功率源的低能电子直线加速器在医疗、辐照、X射线检测等领域得到较为广泛的应用。磁控管产生的微波信号输入到加速管,对电子束进行加速,磁控管的工作频率稳定性对加速器电子束能量、能散及发射度产生直接的影响。但磁控管是一种振荡器,其频率受到温度、振动、负载牵引的影响会产生漂移,所以需要一套自动频率控制系统(Automatic Frequency Control,AFC)机构对磁控管进行频率控制。目前普遍采用的AFC机构主要是行波控相或双腔鉴频,对两路检波信号差分放大进而控制伺服电机进行调谐的方法实现磁控管的频率稳定。随着数字化I/Q和FPGA(Field-Programmable Gate Array)技术的不断发展,运用该技术进行磁控管的频率控制完全具备可行性。本文从理论和工程设计上阐述了数字化I/Q技术在磁控管频率控制上的应用。Background： Low-energy electrons linear accelerator with magnetron as power source has been more widely used in medical, radiation, X-ray detection and other fields. Purpose： The aim is to control magnet＇s operating frequency in an industry accelerator. Methods： A set of automatic frequency control （AFC） system is developed by using digital I/Q technology combined with Field-Programmable Gate Array （FPGA）. Microwave signal generated by the magnetron tube accelerates the electron beam in accelerator, the magnetron frequency stability is important for beam energy, energy spread and emittance. But magnetron is an oscillator with its frequency affected by temperature, vibration, load-pull effect, which will produce frequency drift, the AFC system, which includes travelling wave phase control and dual-cavity frequency discriminator, can stabilize frequency accurately. Results： Experimental results show that the frequency drift could be detected through phase discrimination and then be used for feedback control to achieve effective magnetron frequency control. In machine commissioning frequency drift is controlled within 1 kHz, to meet the requirement of less than 500 kHz. Conclusion： The theory and engineering design of digital UQ technology proposed in the paper provide a feasible and achievable solution in the magnetron frequency control.

关 键 词：数字化I Q 鉴相 磁控管 自动频率控制系统(Automatic Frequency Control AFC) 谐振腔 

分 类 号：TL542.2[核科学技术—核技术及应用]