太赫兹自由电子激光的受激饱和实验

黎明; 杨兴繁; 许州; 束小建; 鲁向阳; 黄文会; 王汉斌; 窦玉焕; 沈旭明; 单李军; 邓德荣; 徐勇; 柏伟; 冯第超; 吴岱; 肖德鑫; 王建新; 罗星; 周奎; 劳成龙; 闫陇刚; 林司芬; 张鹏; 张浩; 和天慧; 潘清; 李相坤; 李鹏; 刘宇; 杨林德; 刘婕; 张德敏; 李凯; 陈亚男

doi:10.7498/aps.67.20172413

摘要

中国工程物理研究院基于半导体光阴极高压直流电子枪和超导直线加速器的高平均功率太赫兹自由电子激光达到了受激饱和，并实现了太赫兹光输出频率可调.在1.99，2.41和2.92 THz三个频率点上进行测试，测得太赫兹宏脉冲内平均功率大于10 W，最高达17.9 W.本文介绍了太赫兹自由电子激光装置的主要组成部分及受激饱和实验的结果.

关键词:

China Academy of Engineering Physics terahertz free electron laser (CAEP THz FEL,CTFEL) is the first THz FEL oscillator in China,which is jointly built by CAEP,Peking University and Tsinghua University.It is designed as a high-repetition-rate and high-duty-cycle linac-based FEL facility. This THz FEL mainly consists of a gallium arsenide (GaAs) photocathode high-voltage direct current (DC) gun,a superconducting radio frequency (RF) linac,a planar undulator,and a quasi-concentric optical resonator. The DC gun provides a high-brightness electron beam with the bunch charge of about 100 pC and the repetition rate of 54.167~MHz.The normalized emittance of the electron beam is less than 10m,and the energy spread is less than 0.75%.A 24-cell superconducting RF accelerator provides an effective field gradient of about 10 MV/m and energizes the electron beam to 6-8~MeV.The beam then goes through the undulator and generates the spontaneous radiation,which is reflected back and forth in the optical resonator and then stimulated by the electron beam. The first stimulated saturation of CTFEL in the macro-pulse mode was obtained in August,2017.In this paper,the THz spectrum is measured by a Fourier spectrometer (Bruker VERTEX 80 V).The macro-pulse energy is measured by an absolute energy meter from Thomas Keating Instruments.The longitudinal beam length is preliminarily calculated by the auto-correlation curve from the time-domain signal of the spectrometer.The macro-pulse duration is captured by a GeGa cryogenic detector from QMC Instrument.The measurement results indicate that the terahertz laser frequency is continuously adjustable from 2 THz to 3 THz.The macro-pulse average power is more than 10 W and the micro-pulse power is more than 0.3 MW.The single-pass gain is larger than 2.5%. This facility is now working in macro-pulse mode in the first step,also called step one.The minimum macro-pulse duration is about 50s and the maximum is about 2 ms.The macro-pulse repetition is 1 Hz or 5 Hz.The typical pulse duration and repetition rate are 1 ms and 1 Hz,respectively.In the middle of 2018,the duty cycle will upgrade to more than 10% as step two.And the continuous wave (CW) operation will be obtained in step three by the end of 2018.The spectrum adjustment range will also be expanded to cover from 1 THz to 4 THz by then. Some application experiments have been carried out on the platform of CTFEL.This facility will greatly promote the development of THz science and its applications in material science,chemistry science,biomedicine science and many other cutting-edge areas in general.

Keywords:

free electron laser /
terahertz /
photocathode high-voltage direct-current electron gun /
radio-frequency superconducting accelerator

作者及机构信息

1.
中国工程物理研究院应用电子学研究所, 绵阳 621900;

2.
四川省国防科技工业办公室, 成都 610051;

3.
北京应用物理与计算数学研究所, 北京 100094;

4.
北京大学重离子物理研究所, 北京 100871;

5.
清华大学工程物理系, 北京 100084

通信作者: 吴岱, wudai04@163.com

基金项目: 国家重大科学仪器设备开发专项（批准号：2011YQ130018）和国家自然科学基金（批准号：11475159，11505173，11505174，11575264，11605190，11105019）资助的课题.

Authors and contacts

1.
Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900, China;

2.
Sichuan Defense Science and Technology Industry Office, Chengdu 610051, China;

3.
Institute of Applied Physics and Computational Mathematics, Beijing 100094, China;

4.
Institute of Heavy Ion Physics, Peking University, Beijing 100871, China;

5.
Department of Engineering Physics, Tsinghua University, Beijing 100084, China

Corresponding author: Wu Dai, wudai04@163.com

Funds: Project supported by the National Key Scientific Instrument and Equipment Development Project of China (Grant No. 2011YQ130018) and the National Natural Science Foundation of China (Grant Nos. 11475159, 11505173, 11505174, 11575264, 11605190, 11105019).

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施引文献

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[2]	Cohn K, Blau J, Colson W, Blau J, Ng J 2015 Proceedings of FEL 2015 Daejeon, Korea, August 23-28, 2015 p625
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[10]	McSweeney S, Fromme P 2014 Nature 505 620
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[12]	Yin Y Z 1983 Acta Phys. Sin. 32 1407 (in Chinese)[尹元昭 1983 物理学报 32 1407]
[13]	Hui Z X, Yang Z H 1983 Free Electron Laser (Beijing:National Defense Industry Press) (in Chinese)[惠中锡, 杨震华 1983 自由电子激光 (北京:国防工业出版社)]
[14]	Li J, Pei Y J, Hu T N, Chen Q S, Feng G Y, Shang L, Li C L 2014 Chin. Phys. C 38 103
[15]	Jia Q K 2017 Chin. Phys. C 41 18101
[16]	Xie J L, Fu E S 1994 High Energy Physics and Nuclear Physics 18 572 (in Chinese)[谢家麟, 傅恩生 1994 高能物理与核物理 18 572]
[17]	Zhou C M 1993 High Power Laser and Particle Beams 2 1 (in Chinese)[周传明 1993 强激光与粒子束 2 1]
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[37]	Murokh A, Rosenzweig J B, Hogan M, Suk H, Travish G, Happek U 1998 Nucl. Instrum. Methods Phys. Res., Sect. A 410 452

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