Design and first plasma measurements of the ITER-ECE prototype radiometer

Area of Science:

• Plasma Physics
• Fusion Energy Research
• Diagnostic Instrumentation

Background:

• ITER requires accurate electron temperature (T_e) measurements for plasma control.
• Second harmonic optically thick electron cyclotron emission (ECE) is the designated diagnostic for T_e on ITER.
• A prototype radiometer operating at 220-340 GHz has been developed to meet ITER's specifications.

Purpose of the Study:

• To investigate the requirements and capabilities of the ITER ECE radiometer system.
• To validate the performance of the prototype radiometer through plasma measurements.
• To assess the accuracy of the prototype radiometer for electron temperature diagnostics.

Main Methods:

• Development of a prototype radiometer by Virginia Diodes, Inc. for the 220-340 GHz frequency range.
• In-situ plasma measurements using the prototype instrument on the DIII-D tokamak.
• Simultaneous data acquisition with a Michelson interferometer for cross-calibration.
• Lab bench tests and measurements of third through fifth harmonic ECE from high T_e plasmas.

Main Results:

• The prototype radiometer successfully acquired its first plasma measurements on the DIII-D tokamak.
• ECE measurements from third through fifth harmonics were performed on high electron temperature plasmas.
• Comparison with an absolutely calibrated Michelson interferometer demonstrated accurate millimeter radiation measurements by the prototype receiver across its band.

Conclusions:

• The prototype ITER radiometer demonstrates accurate measurement capabilities for electron temperature diagnostics.
• The instrument's performance is validated by simultaneous measurements on the DIII-D tokamak.
• The developed radiometer meets the accuracy requirements for electron temperature measurements on ITER.