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1.中国科学院上海应用物理研究所 嘉定园区 上海 201800
2.中国科学院大学 北京 100049
[ "孙思思, 女, 1990年出生, 2013年毕业于烟台大学, 现为硕士研究生, 研究领域为低电平控制系统", "SUN Sisi, female, born in 1990, graduated from YanTai University in 2013, master student, focusing on LLRF control system" ]
赵明华, E-mail:zhaominghua@sinap.ac.cn ZHAO Minghua, E-mail:zhaominghua@sinap.ac.cn
收稿日期:2017-01-23,
修回日期:2017-03-21,
纸质出版日期:2017-06-10
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孙思思, 张俊强, 李林, 等. SXFEL装置上速调管输入输出特性曲线的线性化[J]. 核技术, 2017,40(6):060102
Sisi SUN, Junqiang ZHANG, Lin LI, et al. Linearization of the input and output characteristic curve of a klystron for SXFEL[J]. Nuclear techniques, 2017, 40(6): 060102
孙思思, 张俊强, 李林, 等. SXFEL装置上速调管输入输出特性曲线的线性化[J]. 核技术, 2017,40(6):060102 DOI: 10.11889/j.0253-3219.2017.hjs.40.060102.
Sisi SUN, Junqiang ZHANG, Lin LI, et al. Linearization of the input and output characteristic curve of a klystron for SXFEL[J]. Nuclear techniques, 2017, 40(6): 060102 DOI: 10.11889/j.0253-3219.2017.hjs.40.060102.
在上海软X射线自由电子激光(Soft X-ray Free-electron Laser,SXFEL)中的微波低电平控制系统中,通过对各速调管的输出信号进行测量和控制,保证加速器的稳定运行并且达到技术指标。另一方面,SXFEL中的脉冲速调管的输入输出特性存在非线性的关系,这种电子管放大器不理想的非线性特性会导致微波低电平(Low Level Radio Frequency,LLRF)控制系统调节的效率降低。基于SXFEL装置,采用基于现场可编程门阵列(Field Programmable Gate Array,FPGA)的数字预失真方法,在LLRF控制系统中设计了一套实现高功率速调管放大器线性化的在线系统。S波段加速装置和其相应的东芝E3730A速调管及高压调制器和低电平系统实地测试结果表明,在LLRF控制系统中建立的在线系统能够有效补偿速调管带来的非线性问题,提高微波低电平控制系统的精度及准确性。
Background
2
The output signal of klystrons for the soft X-ray free-electron laser (SXFEL) is processed by the low level radio frequency (LLRF) measurement and control system to ensure the stable operation of the amplitude and phase of the electric field of an radio frequency (RF) structure in the linear accelerator (LINAC). However
the nonlinearity of the input-to-output characteristic curve of the klystron makes the radio frequency regulation of the LLRF control system inefficient.
Purpose
2
The study aims to design an online system to compensate the nonlinearity characteristic from klystrons in SXFEL.
Methods
2
The online system uses the FPGA-based digital predistortion method
including three algorithms:third order polynomial
direct lookup table
and lookup table with linear interpolation.
Results
2
In the on line experiment
the input-to-output characteristic curve of the klystron is linearized
and the system effectively compensates the nonlinearity characteristic introduced by the klystron.
Conclusion
2
The online system improves the precision and accuracy of the LLRF control system
which meets the requirements of the SXFEL.
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李林. 软X射线自由电子激光LLRF控制系统建模及算法研究[D]. 上海: 中国科学院上海应用物理究所, 2015.
LI Lin. RF system modeling and research on algorithm of digital low level RF system of soft X-ray free electron lasers[D]. Shanghai:Shanghai Institute of Applied Physics, Chinese Academy of Sciences, 2015.
张 俊强 , 殷 重先 , 高 永强 , . FPGA实现次谐波聚束器的幅相控制 . 核技术 , 2012 . 35 ( 7 ): 499 - 502 . http://www.cnki.com.cn/Article/CJFDTOTAL-HJSU201207005.htm .
Junqiang ZHANG , Chongxian YIN , Yongqiang GAO , . Energy feedback control for Linac of SSRF . Nuclear Techniques , 2012 . 35 ( 7 ): 499 - 502 . http://www.cnki.com.cn/Article/CJFDTOTAL-HJSU201207005.htm .
Zeng R, McGinnis D, Molloy S. Control performance improvement by using feedforward in LLRF[C]. Proceedings of IPAC 2012, New Orleans, Louisiana, USA, 2012.
Rapp C. Effects of HPA-nonlinearity on a 4-DPSK/OFDM-signal for a digital sound broadcasting signal[C]. European Conference on Satellite Communications, Liege, Belgium, 1991:179-184.
A Cann . Nonlinearity model with variable knee sharpness . IEEE Transactions on Aerospace and Electronic Systems , 1980 . ( 6 ): 874 - 877 . DOI: 10.1109/TAES.1980.309016 http://doi.org/10.1109/TAES.1980.309016 .
Omet M, Michizono S, Matsumoto T, et al . Development of FPGA-based predistortion type linearization algorithms for klystrons within digital LLRF control systems for ILC-like electron accelerators[C] . Proceedings of LINAC 2014, Geneva, Switzerland, 2014.
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