[Objectives]
The 3ch O-mode reflectometer is designed for density
fluctuation measurement. The targets of the reflectometer system are the change
of fluctuation level, correlation and position of the cutoff layer, during
formation of the transport barrier, H-L and L-H transition, ELM and MARFE
activities.
[Diagnostic Method]
The O-mode reflectometer is configured as a heterodyne
system having two separate sources. The probe beams from oscillators are
launched to the plasma through the corrugated waveguide, which is shared between
X-mode and O-mode reflectometer. Two IF (Intermediate Frequency) signals with
the frequency of 140 MHz are produced, one comes from plasma and the other is
used as a reference. The quadrature-type phase detection system provides sin-
and cosine-components of reflected signal in each channel. Therefore, we can
analyze both of the phase and amplitude of reflected signals.
[Specifications]
The measured position (cutoff position) in O-mode
propagation depends only on the electron density. To cover target plasma region,
3 frequencies in Q-band are chosen.
| - Cutoff density | : 1.4x1019m-3 (34GHz), 1.4-2.0x1019m-3 (34-40GHz), 2.8-3.1x1019m-3 (48-50GHz) |
| - Time resolution | : 1 micro sec (Typical) |
| - Toroidal position | : P-5 section, midplane port (Z=0.1m) |
[Referense]
N Oyama and K Shinohara, Rev. Sci. Instrum. 73, 1169 (2002)