Doppler reflectometry with optimised temporal resolution for the measurement of turbulence and its propagation velocity
Doppler reflectometry selects electron density perturbations with a finite wave vector K by a line of sight, which is non-perpendicular with respect to the reflecting layer. This provides, simultaneously, a local measurement of their propagation velocity v (K) and of changes in their fluctuation amplitude n(K). In the multichannel Doppler reflectometer at the Stellarator W7-AS the antenna system and signal detection are optimised for maximum temporal resolution in order to study transport bifurcations such as the transitions between L- and H-mode. For the conditions in W7-AS the quantities v and n can be measured with a temporal resolution of less than 10mu s as shown for the example of an H to L back-transition. The dual antenna system installed allows us to supplement Doppler reflectometry with a simultaneous time-of-flight measurement, which is the complementary method to determine v.
Bibliographic Reference: An article published in: Plasma Physics and controlled Fusion 46 (2004) pp. 593-609
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: http://www.iop.org/EJ/journal/0741-3335
Record Number: 200417559 / Last updated on: 2004-06-17
Original language: en
Available languages: en