Electron cyclotron emission radiometer upgrade on the Joint European Torus (JET) tokamak

The capabilities of the Joint European Torus (JET) electron cyclotron emission (ECE) diagnostics have recently been extended with an upgrading of the heterodyne radiometer. The number of channels has been doubled to 96 channels, with a frequency separation corresponding to <1 cm for JET magnetic field gradient, and with a frequency response of 1 MHz. This enhancement has increased the radial coverage of the ECE electron temperature measurements in JET to approximately the full plasma column (limited at R>2.6 m for the X-mode due to harmonic overlap) at almost all magnetic field values used at JET (1.7 T<BT<4 T), while maintaining the high sensitivity and spectral resolution of the previous system. In this paper an overview of the upgraded radiometer is presented along with some results showing its performance.