1 µs broadband frequency sweeping reflectometry for plasma density and fluctuation profile measurements

International audienceFrequency swept reflectometry has reached the symbolic value of 1 µs sweeping time, thisperformance has been made possible due to an improved control of the ramp voltage drivingthe frequency source. In parallel, the memory depth of the 1 Gs/s acquisition system has beenupgraded and can provide up to 200 000 density profiles during a plasma discharge.Additionally, improvements regarding the trigger delay determination for the acquisition, whichneeds to be precisely set and the frequency sweep linearity required by this ultra-fast techniquealong with the stability of the ramp voltage driving the VCOs, have been made. While thisdiagnostic is traditionally dedicated to the density profile measurement, such a fast sweepingrate can provide the study of fast plasma events and turbulence with unprecedented time andradial resolution from the edge to the core and thus compete with the fixed frequency systems.Experimental results obtained on ASDEX Upgrade plasmas will be presented to demonstratethe performances of the diagnostic