Development of reflectometry for plasma density measurements at JET

A. E. Costley

doi:10.1117/12.2298555

30 August 1993 Development of reflectometry for plasma density measurements at JET

A. E. Costley

Proceedings Volume 2104, 18th International Conference on Infrared and Millimeter Waves; 21043F (1993) https://doi.org/10.1117/12.2298555
Event: 18th International Conference on Infrared and Millimeter Waves, 1993, Colchester, United Kingdom

Abstract

Although the basic physics of millimetre wave reflectometry has been known for many years, it is only recentlythat reliable measurements have been obtained with the technique in applications on tokamak plasmas. This is primarilybecause for these plasmas the electron density is a rapidly fluctuating parameter and these fluctuations generate broad-band'noise' in the measurement systems. Also, several important experimental requirements were not originally realised.Recently, special techniques and hardware for processing the signals have been developed, and appropriate care taken indesigning and implementing the measurement systems. As a result, reliable measurements are now being obtainedroutinely and are being used extensively in plasma physics studies.Reflectometry has the potential to provide measurements of the spatial dependence of the electron density, ie. theelectron density profile, during quasi-stationary periods of the plasma. It can also provide measurements of themovement of specific density layers during fast phenomena, ie. density transients. In principle, information on the broadband density fluctuations can also be obtained.Extensive use is made of reflectometry at JET where substantial systems have been developed. In this paper, wediscuss the principles of the technique and describe the instrumentation on JET. Results demonstrating the performanceof the reflectometers are presented.

Citation Download Citation

A. E. Costley "Development of reflectometry for plasma density measurements at JET", Proc. SPIE 2104, 18th International Conference on Infrared and Millimeter Waves, 21043F (30 August 1993); https://doi.org/10.1117/12.2298555

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KEYWORDS

Reflectometry

Plasma

Waveguides

Optical filters

Signal detection

Heterodyning

Antennas

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