Status and prospects for mm-wave reflectometry in ITER
Vayakis, G., C.I. Walker, F. Clairet, R. Sabot, V. Tribaldos, T. Estrada, E. Blanco, J. Sánchez, G.G. Denisov, V.I. Belousov, F. da Silva, P. Varela, M.E. Manso, L. Cupido, J. Dias, N. Valverde, V.A. Vershkov, D.A. Shelukhin, S.V. Soldatov, A.O. Urazbaev, E. Yu Frolov and S. Heuraux
Reflectometry with wavelengths in the centimetre to millimetre-wave range will be used in ITER to measure the
density profile in the main plasma and divertor regions and to measure the plasma position and shape in order to
provide a reference for the magnetic diagnostics in long pulses. In addition, it is expected to provide key information
for the measurement of density fluctuations. A set of reflectometers to meet the relevant ITER measurement
requirements has been included in its present outline as part of the ITER design since 2001 and is being adapted to
the present ITER baseline and to accommodate progress with reflectometry techniques and measurement capabilities.
It comprises low and high field side (HFS and LFS, respectively) ordinary (O-) mode systems for the measurement
of the density profile in the gradient regions, a LFS extraordinary (X-) mode system for the detailed study of the edge
profile, an HFS X-mode system operating in the left hand cutoff to measure the core profile, a dedicated O-mode
system for plasma-wall gap measurement and a multi-band, multiple line of sight O-mode system to measure divertor
density profiles. This paper describes the evolution of the design, in particular some recent improvements in the
engineering implementation and improvements aimed at enhancing the measurement capability. It concludes with
a brief assessment of the likely measurement performance against the ITER measurement requirements for the
parameters of interest and the overall confidence that the technique will be implanted on ITER.