title: Characterization of cross-section correction to charge exchange recombination spectroscopy rotation measurements using co- and counter-neutral-beam views.
abstract: Measurements of rotation using charge exchange recombination spectroscopy can be affected by the energy dependence of the charge exchange cross section. On DIII-D, the associated correction to the rotation can exceed 100 kms at high temperatures. In reactor-relevant low rotation conditions, the correction can be several times larger than the actual plasma rotation and therefore must be carefully validated. New chords have been added to the DIII-D CER diagnostic to view the counter-neutral-beam line. The addition of these views allows determination of the toroidal rotation without depending on detailed atomic physics calculations, while also allowing experimental characterization of the atomic physics. A database of rotation comparisons from the two views shows that the calculated cross-section correction can adequately describe the measurements, although there is a tendency for "overcorrection." In cases where accuracy better than about 15% is desired, relying on calculation of the cross-section correction may be insufficient.
authors.affiliation: Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA. wsolomon@pppl.gov
authors.forename: W M
authors.initials: WM
authors.lastname: Solomon
authors.forename: K H
authors.initials: KH
authors.lastname: Burrell
authors.forename: R
authors.initials: R
authors.lastname: Feder
authors.forename: A
authors.initials: A
authors.lastname: Nagy
authors.forename: P
authors.initials: P
authors.lastname: Gohil
authors.forename: R J
authors.initials: RJ
authors.lastname: Groebner