中国物理B ›› 2018, Vol. 27 ›› Issue (12): 125201-125201.doi: 10.1088/1674-1056/27/12/125201

• PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES • 上一篇    下一篇

Preliminary computation of the gap eigenmode of shear Alfvén waves on the LAPD

Lei Chang(苌磊)   

  1. School of Aeronautics and Astronautics, Sichuan University, Chengdu 610065, China
  • 收稿日期:2018-09-04 修回日期:2018-10-13 出版日期:2018-12-05 发布日期:2018-12-05
  • 通讯作者: Lei Chang E-mail:leichang@scu.edu.cn
  • 基金资助:

    Project supported by the National Natural Science Foundation of China (Grant No. 11405271), the China Postdoctoral Science Foundation (Grant No. 2017M612901), the Fund from Chongqing Science and Technology Commission (Grant No. cstc2017jcyjAX0047), Chongqing Postdoctoral Special Foundation (Grant No. Xm2017109), the Fundamental Research Funds for Central Universities, China (Grant No. YJ201796), the Pre-research Key Laboratory Fund for Equipment (Grant No. 61422070306), and the Fund from the Laboratory of Advanced Space Propulsion (Grant No. LabASP-2017-10).

Preliminary computation of the gap eigenmode of shear Alfvén waves on the LAPD

Lei Chang(苌磊)   

  1. School of Aeronautics and Astronautics, Sichuan University, Chengdu 610065, China
  • Received:2018-09-04 Revised:2018-10-13 Online:2018-12-05 Published:2018-12-05
  • Contact: Lei Chang E-mail:leichang@scu.edu.cn
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Grant No. 11405271), the China Postdoctoral Science Foundation (Grant No. 2017M612901), the Fund from Chongqing Science and Technology Commission (Grant No. cstc2017jcyjAX0047), Chongqing Postdoctoral Special Foundation (Grant No. Xm2017109), the Fundamental Research Funds for Central Universities, China (Grant No. YJ201796), the Pre-research Key Laboratory Fund for Equipment (Grant No. 61422070306), and the Fund from the Laboratory of Advanced Space Propulsion (Grant No. LabASP-2017-10).

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摘要：

Characterizing the gap eigenmode of shear Alfvén waves (SAWs) and its interaction with energetic ions is important to the success of magnetically confined fusion. Previous studies have reported an experimental observation of the spectral gap of SAW on the on Large Plasma Device (LAPD) (Zhang et al. 2008 Phys. Plasmas 15 012103), a linear large plasma device (Gekelman et al. 1991 Rev. Sci. Instrum. 62 2875) possessing easier diagnostic access and lower cost compared with traditional fusion devices, and analytical theory and numerical gap eigenmode using ideal conditions (Chang 2014 Ph.D Thesis at Australian National University). To guide experimental implementation, the present work models the gap eigenmode of SAWs using exact LAPD parameters. A full picture of the wave field for previous experiment reveals that the previously observed spectral gap is not global but an axially local result. To form a global spectral gap, the number of magnetic mirrors has to be increased and stronger static magnetic field makes it clearer. Such a spectral gap is obtained for the magnetic field of B0(z)=1.2+0.6cos[2π (z-33.68)/3.63] with 7.74-m magnetic beach. By introducing two types of local defects (corresponding to Eθ(z0)=0 and Eθ'(z0)=0 respectively), odd-parity and even-parity discrete eigenmodes are formed clearly inside the gap. The strength of these gap eigenmodes decreases significantly with collision frequency, which is consistent with previous studies. Parameter scans show that these gap eigenmodes can be even formed successfully for the field strength of B0(z)=0.2+0.1cos[2π (z-33.68)/3.63] and with only four magnetic mirrors, which are achievable by the LAPD at its present status. This work can serve as a strong motivation and direct reference for the experimental implementation of the gap eigenmode of SAWs on the LAPD and other linear plasma devices.

关键词: gap eigenmode, shear Alfvén wave, LAPD, number and depth of magnetic mirror, linear plasma

Abstract:

Characterizing the gap eigenmode of shear Alfvén waves (SAWs) and its interaction with energetic ions is important to the success of magnetically confined fusion. Previous studies have reported an experimental observation of the spectral gap of SAW on the on Large Plasma Device (LAPD) (Zhang et al. 2008 Phys. Plasmas 15 012103), a linear large plasma device (Gekelman et al. 1991 Rev. Sci. Instrum. 62 2875) possessing easier diagnostic access and lower cost compared with traditional fusion devices, and analytical theory and numerical gap eigenmode using ideal conditions (Chang 2014 Ph.D Thesis at Australian National University). To guide experimental implementation, the present work models the gap eigenmode of SAWs using exact LAPD parameters. A full picture of the wave field for previous experiment reveals that the previously observed spectral gap is not global but an axially local result. To form a global spectral gap, the number of magnetic mirrors has to be increased and stronger static magnetic field makes it clearer. Such a spectral gap is obtained for the magnetic field of B0(z)=1.2+0.6cos[2π (z-33.68)/3.63] with 7.74-m magnetic beach. By introducing two types of local defects (corresponding to Eθ(z0)=0 and Eθ'(z0)=0 respectively), odd-parity and even-parity discrete eigenmodes are formed clearly inside the gap. The strength of these gap eigenmodes decreases significantly with collision frequency, which is consistent with previous studies. Parameter scans show that these gap eigenmodes can be even formed successfully for the field strength of B0(z)=0.2+0.1cos[2π (z-33.68)/3.63] and with only four magnetic mirrors, which are achievable by the LAPD at its present status. This work can serve as a strong motivation and direct reference for the experimental implementation of the gap eigenmode of SAWs on the LAPD and other linear plasma devices.

Key words: gap eigenmode, shear Alfvén wave, LAPD, number and depth of magnetic mirror, linear plasma

中图分类号:  (Magnetohydrodynamic waves (e.g., Alfven waves))

  • 52.35.Bj
52.55.Jd (Magnetic mirrors, gas dynamic traps) 52.25.Xz (Magnetized plasmas)