TJ-II:Electron Cyclotron Emission: Difference between revisions

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-Electron cyclotron emission measurements are routinely performed in TJ-II stellarator by means of a multichannel heterodyne radiometer. The radiometer is absolutely calibrated and measures the temperature profile with high temporal resolution.
+Electron temperature profiles are measured at [[TJ-II]]
-The diagnostic provides 12 measurement channels, corresponding to 12 values of the major radius ''R''.
+by means of a 16 channel heterodyne radiometer,
+covering the frequency range 50–60 GHz, corresponding to the second harmonic of electron cyclotron emission (ECE) in X-mode polarization at a magnetic field of 0.95 T on the plasma axis.
+The measurements are performed from the low field side (LFS) in the horizontal midplane.
+Each frequency corresponds to a different value of the major radius ''R''.
+The system is operated close to the strong [[TJ-II:Electron Cyclotron Resonant Heating|ECR heating source]] (f<sub>ECRH</sub> = 53.2 GHz).
+To protect the radiometer against stray radiation from the gyrotron, the radiometer band is split into two parts.
+The second harmonic emission above and below 53.2 GHz are measured separately by means of microwave couplers in the signal path.
+The system is calibrated absolutely by comparing room temperature with liquid nitrogen temperature.
 <ref>[http://link.aip.org/link/?RSINAK/72/379/1 E. de la Luna, J. Sánchez, V. Tribaldos, and T. Estrada, ''Multichannel electron cyclotron emission radiometry in TJ-II stellarator'', Rev. Sci. Instrum. '''72''', 379 (2001)]</ref>
 <ref>[http://dx.doi.org/10.1016/S0920-3796(00)00492-0 E. de la Luna et al, ''Electron cyclotron emission measurements on TJ-II stellarator plasmas'', Fusion Engineering and Design '''53''', Issues 1-4 (2001) 147-151]</ref>
 The emission can be simulated by the [[TRECE]] ray tracing code.
 <ref>[http://dx.doi.org/10.1088/0029-5515/36/3/I02 V. Tribaldos and B. P. van Milligen, ''Electron cyclotron emission calculations for TJ-II stellarator'', Nucl. Fusion '''36''', 283 (1996)]</ref>
-The sampling rate is 100 kHz.
+The typical sampling rate is 100 kHz.
-The signals are called 'ECE1' ... 'ECE12' in the [[TJ-II:Shot_database|TJ-II database]].
+The signals are called 'ECE1' ... 'ECE16' in the [[TJ-II:Shot_database|TJ-II database]].
 The measured ECE amplitude is proportional to the electron temperature, provided certain conditions are met.
 == References ==
 <references />