Nuclear Techniques ›› 2016, Vol. 39 ›› Issue (7): 70402-070402.doi: 10.11889/j.0253-3219.2016.hjs.39.070402

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Implementation of FPGA-based feedforward function in LLRF system for electron LINAC

LI Song1,2, ZHANG Junqiang1, ZHANG Meng1, ZHAO Minghua1   

  1. 1 Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Jiading Campus, Shanghai 201800, China;
    2 University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2016-01-28 Revised:2016-03-02 Online:2016-07-10 Published:2016-07-08
  • Supported by:

    Supported by Strategic Pilot Science and Technology Project of Chinese Academy of Sciences (No.XDA02010100)

Abstract:

Background: Due to the existence of transient beam loading effect in cavity, the energy of the bunch head is higher than the other part in 15-MeV linear accelerator (LINAC) designed for thorium molten salt reactor (TMSR) photo-neutron source. This uneven distribution of energy leads to high energy spread, thus depresses transmission efficiency of beam. Purpose: This study aims to develop a digital feedforward compensation to reduce the influence of beam loading effect and decrease energy spread of the beam. Methods: The Field Programmable Gate Array (FPGA) programming language VHDL (Very-High-Speed Integrated Circuit Hardware Description Language) was used to design the feedforward module. This module was added to the original FPGA modules of low level radio frequency (LLRF) control system to cut down the intensity of head of radio frequency (RF) field. Results: The experimental test shows that the feedforward function of LLRF control system suppressed the energy spread to an ideal level and the transmission efficiency of the beam current had also been significantly improved. Conclusion: The digital feedforward method overcomes the deflection of traditional beam compensation method which malfunctions in the situation of big bunch and high beam current.

Key words: FPGA, First in first out(FIFO), Serial conversion, Feed-forward control, Low-level radio frequency, LINAC

CLC Number: 

  • TL53