A new method of out-of-focus millimeter wave imaging in fusion plasma diagnostics using Bessel beams

Journal Article · 24 September 2018 · Review of Scientific Instruments

DOI: https://doi.org/10.1063/1.5012778 · OSTI ID:1540147

Li, J. X.  ^[1]; Zhu, Y. L. ^[2]; Chen, M. ^[2]; Cao, J. H. ^[2]; Dannenberg, J. ^[2]; Domier, C.  ^[2]; Luhmann, N. C. ^[2]

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1. Zhejiang Univ., Hangzhou (China). College of Optical Science and Engineering, State Key Lab. of Modern Optical Instrumentation; DOE/OSTI
2. Univ. of California, Davis, CA (United States)

Electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry diagnostics have been employed on a number of magnetic fusion plasma confinement devices. The common approach is based on a Gaussian beam assumption, which generates good spatial resolution (centimeter level). However, the radial focal depth is limited by the poloidal resolution, which is comparable with the Rayleigh length (~150 mm). By contrast, a new Bessel beam approach has been developed and demonstrated to generate much longer focal depth with the property of propagation stability. To test the new approach, the DIII-D tokamak LCP ECEI optics have been re-designed to support a Bessel beam approach based on an axicon lens. The achievable radial coverage can exceed that of the current Gaussian approach by 3×. Finally, the imaging result is discussed in this paper based on the simulation analysis and laboratory testing result.

• Research Organization: Univ. of California, Davis, CA (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC)
• Grant/Contract Number: SC0012551
• OSTI ID: 1540147
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 9 Vol. 89; ISSN 0034-6748
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English