Davis Millimeter-Wave Research Center

Microwave/Millimeter Wave Technology

Plasma Diagnostics

 

 

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Plasma diagnostics

 

µ-wave vacuum electronics

 

µ-wave solid state technology

 

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Director:
Prof. N.C. Luhmann, Jr.

 

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MIR on EAST

 

 

 

The UC Davis Plasma Diagnostic Group plans to build and install a Microwave Imaging Reflectometry (MIR) system on the EAST tokamak. The planned EAST MIR system intimately resembles the DIII-D system, having 16 × 4 = 64 channels (expanding to as many as 16 × 16 = 256 channels), consisting of a 16 element imaging array, a 4-frequency (later expanding to a 16-frequency) illumination source and 16 MIR electronics modules, together with all required power supplies and controllers. The probing frequencies are independently controlled and tunable on a time scale <500µs. The illumination and imaging optics will be made from low-loss high-density polyethylene (HDPE) lenses and/or metallic mirrors.

 

 

 

Above: EAST tokamak

 

 

EAST aims to produce high performance plasmas for long pulse operations. In the 2012 campaign, lower-hybrid current drive (LHCD) and ion-cyclotron-resonance frequency (ICRF) heating are used to realize 1MA plasma operation. 400s-long L-mode and 30s-long H-mode discharges are achieved.

Microwave reflectometry is a radar technique employed to infer the electron density characteristics by probing the density-dependent cutoff layer. The fundamental issue confronting reflectometry of density fluctuations concerns the interpretation of the measured amplitude and phase of the reflected waves. Unless the density fluctuation level is extremely low and/or the fluctuation wavelength at the cut-off layer is very long, conventional reflectometry methods face a challenge in interpreting the measured amplitude and phase except for measurements made in close proximity to the plasma edge. MIR is a technique in which large aperture optics at the plasma edge are used to collect as much of the scattered wave-front as possible and optically focus an image of the cutoff surface onto an array of detectors (see figure below), thus restoring the integrity of the phase measurement.

 

 

 

Description: Description: MIR Concept

Schematic illustration of the principles governing MIR

 

 

 

 

 

 

More details regarding the MIR system on EAST will be added as development progresses.

 

    
 
 
 
 
 
 
 
 
 
 
 
 
              
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