Receiver circuit improvement of dual frequency-comb ka-band Doppler backscattering system in the large helical device (LHD).

Doppler-backscattering (DBS) has been used in several fusion plasma devices because it can measure the perpendicular velocity of electron density perturbation v, the radial electric field E, and the perpendicular wavenumber spectrum S(k) with high wavenumber and spatial resolution. In particular, recently constructed frequency comb DBS systems enable observation of turbulent phenomena at multiple observation points in the radial direction. A dual-comb microwave DBS system has been developed for the large helical device plasma measurement.

3D metal powder additive manufacturing phased array antenna for multichannel Doppler reflectometer.

Measuring the time variation of the wavenumber spectrum of turbulence is important for understanding the characteristics of high-temperature plasmas, and the application of a Doppler reflectometer with simultaneous multi-frequency sources is expected. To implement this diagnostic in future fusion devices, the use of a phased array antenna (PAA) that can scan microwave beams without moving antennas is recommended. Since the frequency-scanning waveguide leaky-wave antenna-type PAA has a complex structure, we have investigated its characteristics by modeling it with 3D metal powder additive manufacturing (AM).

W-band millimeter-wave back-scattering system for high wavenumber turbulence measurements in LHD.

A 90 GHz W-band millimeter-wave back-scattering system is designed and installed for measuring electron scale turbulence (kρ ∼ 40). A metal lens relay antenna is used for in-vessel beam focusing, and a beam diameter of less than 40 mm is achieved in the plasma core region. This antenna can be steered at an angle of 159° ± 6°, which almost covers the plasma radius.

Simulation, design, and first test of a multi-energy soft x-ray (SXR) pinhole camera in the Madison Symmetric Torus (MST).

A multi-energy soft x-ray pinhole camera has been designed and built for the Madison Symmetric Torus reversed field pinch to aid the study of particle and thermal-transport, as well as MHD stability physics. This novel imaging diagnostic technique combines the best features from both pulse-height-analysis and multi-foil methods employing a PILATUS3 x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. Further improvements implemented on the new cooled systems allow a maximum count rate of 10 MHz per pixel and sensitivity to the strong Al and Ar emission between 1.

A computational tool for simulation and design of tangential multi-energy soft x-ray pin-hole cameras for tokamak plasmas.

A new tool has been developed to calculate the spectral, spatial, and temporal responses of multi-energy soft x-ray (ME-SXR) pinhole cameras for arbitrary plasma densities ( ), temperature ( ), and impurity densities ( ). ME-SXR imaging provides a unique opportunity for obtaining important plasma properties (e.g.