Pulsed radar reflectometry and prospects for fluctuation measurements

A four-channel pulsed radar reflectometer has been developed for the Rijnhuizen tokamak project. The system combines a high temporal resolution (2 μs) and a good spatial resolution (1 cm) with limited access demands. It has been used to diagnose steady state density profiles, as well as to follow strong density variations, as a result of magnetohydrodynamic instabilities, disruptions and pellet injection. The pulsed radar reflectometer is presently installed at the TEXTOR tokamak and is being upgraded to a 10-channel pulsed radar system. Additionally, two frequency-tunable channels will be added for performing correlation measurements. (orig.)