title: Performance and data analysis aspects of the new DIII-D monostatic profile reflectometer system.
abstract: A new frequency-modulated profile reflectometer system, featuring a monostatic antenna geometry (using one microwave antenna for both launch and receive), has been installed on the DIII-D tokamak, providing a first experimental test of this measurement approach for profile reflectometry. Significant features of the new system are briefly described in this paper, including the new monostatic arrangement, use of overmoded, broadband transmission waveguide, and dual-polarization combination/demultiplexing. Updated data processing and analysis, and in-service performance aspects of the new monostatic profile reflectometer system are also presented. By using a raytracing code (GENRAY) to determine the approximate trajectory of the probe beam, the electron density (ne) profile can be successfully reconstructed with L-mode plasmas vertically shifted by more than 10 cm off the vessel midplane. Specifically, it is demonstrated that the new system has a capability to measure ne profiles with plasma vertical offsets of up to ±17 cm. Examples are also presented of accurate, high time and spatial resolution density profile measurements made over a wide range of DIII-D conditions, e.g., the measured temporal evolution of the density profile across a L-H transition.
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90095, USA.
authors.forename: L
authors.initials: L
authors.lastname: Zeng
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90095, USA.
authors.forename: W A
authors.initials: WA
authors.lastname: Peebles
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90095, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Doyle
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90095, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Rhodes
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90095, USA.
authors.forename: N
authors.initials: N
authors.lastname: Crocker
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90095, USA.
authors.forename: X
authors.initials: X
authors.lastname: Nguyen
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90095, USA.
authors.forename: C W
authors.initials: CW
authors.lastname: Wannberg
authors.affiliation: Physics and Astronomy Department, University of California, Los Angeles, California 90095, USA.
authors.forename: G
authors.initials: G
authors.lastname: Wang