Liquid crystal polymer receiver modules for electron cyclotron emission imaging on the DIII-D tokamak

• Published in: Review of scientific instruments 2018-10, Vol.89 (10), p.10H120-10H120
• Main Authors: Zhu, Y., Ye, Y., Yu, J-H., Tobias, B., Pham, A-V., Wang, Y., Luo, C., Domier, C. W., Kramer, G., Ren, Y., Diallo, A., Nazikian, R., Chen, M., Yu, G., Luhmann, N. C.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Arrays; Channels; Cyclotrons; Diagnostic software; Diagnostic systems; DIII-D; edge localized mode; Electron Cyclotron Emission Imaging; Electron Cyclotron Emission Imaging, DIII-D, monolithic microwave integrated circuit, edge localized mode; Electron energy; Emission; Gallium arsenide; Integrated circuits; Intermediate frequency amplifiers; Liquid crystal polymers; Liquid crystals; Low noise; Millimeter waves; MMIC (circuits); Modules; monolithic microwave integrated circuit; Noise; Noise levels; Noise reduction; Noise temperature; Polymers; Scientific apparatus & instruments; Shielding; Substrates; Tokamak devices
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.5035373

A new generation of millimeter-wave heterodyne imaging receiver arrays has been developed and demonstrated on the DIII-D electron cyclotron emission imaging (ECEI) system. Improved circuit integration, improved noise performance, and enhanced shielding from out-of-band emission are made possible by using advanced liquid crystal polymer (LCP) substrates and monolithic microwave integrated circuit (MMIC) receiver chips. This array exhibits ∼15 dB additional gain and >30× reduction in noise temperature compared to previous generation ECEI arrays. Each LCP horn-waveguide module houses a 3 × 3 mm GaAs MMIC receiver chip, which consists of a low noise millimeter-wave preamplifier, balanced mixer, and IF amplifier together with a local oscillator multiplier chain driven at ∼12 GHz. A proof-of-principle partial LCP instrument with 5 poloidal channels was installed on DIII-D in 2017, with a full proof-of-principle system (20 poloidal × 8 radial channels) installed and commissioned in early 2018. The enhanced shielding of the LCP modules is seen to greatly reduce the sensitivity of ECEI signals to out-of-band microwave noise which has plagued previous ECEI studies on DIII-D. The LCP ECEI system is expected to be a valuable diagnostic tool for pedestal region measurements, focusing particularly on electron temperature evolution during edge localized mode bursting.