Toward Integrated Microwave Diagnostics for Future Fusion Devices: Design of a Compact Waveguide Diplexer
Abstract
Microwave diagnostics are essential for plasma control and physics studies in magnetic confinement fusion, providing measurements of electron density, electron temperature, and energetic-particle behavior. However, diagnostic access in future burning-plasma reactors will be severely constrained by breeding blankets, neutron shielding, and compact reactor geometries, requiring reduced blanket opening areas while maintaining diagnostic capability. This work presents a compact waveguide diplexer for front-end integration of multiple microwave diagnostics. The proposed diplexer combines a waveguide T-junction with two iris-coupled sixth-order Chebyshev bandpass filters, enabling microwave reflectometry and electron cyclotron emission (ECE) diagnostics to share a common transmission line while operating in separate frequency bands. As an initial study, the diplexer is designed for the 65-70 GHz reflectometry and 85-90 GHz ECE systems on the J-TEXT tokamak. Full-wave electromagnetic simulations demonstrate insertion losses below 1 dB and channel isolation exceeding 40 dB across both operating bands. The proposed methodology provides a compact and scalable approach to microwave diagnostic integration and establishes a practical basis for multi-diagnostic front-end systems in future fusion devices.
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BibTeX
@misc{li2026toward,
title = {{Toward Integrated Microwave Diagnostics for Future Fusion Devices: Design of a Compact Waveguide Diplexer}},
author = {Xiaoliang Li and Valerian Hall-Chen and Umesh Kumar and Eddie Chua and Tengfei Tang and Andy Yeoh and Khadija Rahman and Xinhang Xu and Yilun Zhu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.34881},
eprint = {2610.34881},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.34881},
}
RIS
TY - UNPB
TI - Toward Integrated Microwave Diagnostics for Future Fusion Devices: Design of a Compact Waveguide Diplexer
AU - Xiaoliang Li
AU - Valerian Hall-Chen
AU - Umesh Kumar
AU - Eddie Chua
AU - Tengfei Tang
AU - Andy Yeoh
AU - Khadija Rahman
AU - Xinhang Xu
AU - Yilun Zhu
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.34881
UR - https://arxiv.org/abs/2610.34881
AB - Microwave diagnostics are essential for plasma control and physics studies in magnetic confinement fusion, providing measurements of electron density, electron temperature, and energetic-particle behavior. However, diagnostic access in future burning-plasma reactors will be severely constrained by breeding blankets, neutron shielding, and compact reactor geometries, requiring reduced blanket opening areas while maintaining diagnostic capability. This work presents a compact waveguide diplexer for front-end integration of multiple microwave diagnostics. The proposed diplexer combines a waveguide T-junction with two iris-coupled sixth-order Chebyshev bandpass filters, enabling microwave reflectometry and electron cyclotron emission (ECE) diagnostics to share a common transmission line while operating in separate frequency bands. As an initial study, the diplexer is designed for the 65-70 GHz reflectometry and 85-90 GHz ECE systems on the J-TEXT tokamak. Full-wave electromagnetic simulations demonstrate insertion losses below 1 dB and channel isolation exceeding 40 dB across both operating bands. The proposed methodology provides a compact and scalable approach to microwave diagnostic integration and establishes a practical basis for multi-diagnostic front-end systems in future fusion devices.
ER -