High spatial resolution upgrade of the electron cyclotron emission radiometer for the DIII-D tokamak

Journal Article · Sat Nov 15 00:00:00 EST 2014 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4889737· OSTI ID:22308607

Austin, M. E. ^[1]

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1. Institute for Fusion Studies, University of Texas, Austin, Texas, 78712 (United States)

The 40-channel DIII-D electron cyclotron emission (ECE) radiometer provides measurements of T{sub e}(r,t) at the tokamak midplane from optically thick, second harmonic X-mode emission over a frequency range of 83–130 GHz. The frequency spacing of the radiometer's channels results in a spatial resolution of ∼1–3 cm, depending on local magnetic field and electron temperature. A new high resolution subsystem has been added to the DIII-D ECE radiometer to make sub-centimeter (0.6–0.8 cm) resolution T{sub e} measurements. The high resolution subsystem branches off from the regular channels’ IF bands and consists of a microwave switch to toggle between IF bands, a switched filter bank for frequency selectivity, an adjustable local oscillator and mixer for further frequency down-conversion, and a set of eight microwave filters in the 2–4 GHz range. Higher spatial resolution is achieved through the use of a narrower (200 MHz) filter bandwidth and closer spacing between the filters’ center frequencies (250 MHz). This configuration allows for full coverage of the 83–130 GHz frequency range in 2 GHz bands. Depending on the local magnetic field, this translates into a “zoomed-in” analysis of a ∼2–4 cm radial region. Expected uses of these channels include mapping the spatial dependence of Alfven eigenmodes, geodesic acoustic modes, and externally applied magnetic perturbations. Initial T{sub e} measurements, which demonstrate that the desired resolution is achieved, are presented.

• OSTI ID: 22308607
• Journal Information: Review of Scientific Instruments, Vol. 85, Issue 11; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ALFVEN WAVES
DISTURBANCES
DOUBLET-3 DEVICE
EIGENFREQUENCY
ELECTRON CYCLOTRON-RESONANCE
ELECTRON EMISSION
ELECTRON TEMPERATURE
FREQUENCY MIXING
GEODESICS
GHZ RANGE
MAGNETIC FIELDS
MHZ RANGE
MICROWAVE RADIATION
OSCILLATION MODES
OSCILLATORS
RADIOMETERS
SPACE DEPENDENCE
SPATIAL RESOLUTION