New reflectometer design for density profile measurements on JET

Abstract

New transmission lines and antennas recently installed at Join European Torus (JET) under the European Fusion Development Agreement enhancement project millimeter wave access meet the performance requirements of broadband reflectometry for density profile measurements. A fast swept frequency modulation continuous wave [H. Bottollier, Curtet-, Rev. Sci. Instrum. 58, 539 (1987); F. Simonet, ibid. 56, 664 (1985); A. Silva, ibid. 70, 664 (1999); S. Hacquin, ibid. 75, 3834 (2004)] using coherent detection of the reflected signal was developed to probe the midplane plasma in the X -mode polarization in the 50-75 GHz frequency range, aiming at measuring the edge density profile in the JET advanced scenarios with an axial magnetic field of 2.4 T. The operating principles of the new system are described and some preliminary results obtained with it are presented. Special attention is given to the capability of operating on bistatic antenna arrangements over long waveguides using a local generated reference, as these will be the conditions proposed for the ITER reflectometers. © 2006 American Institute of Physics.