title: Observation of compressional Alfvén modes during neutral-beam heating on the national spherical torus experiment.
abstract: Neutral-beam-driven compressional Alfvén eigenmodes at frequencies below the ion cyclotron frequency have been observed and identified for the first time in the National Spherical Torus Experiment. The modes are observed as a broad spectrum of nearly equally spaced peaks in the frequency range from approximately 0.2omega(ci) to approximately 1.2omega(ci). The frequency has a scaling with toroidal field and plasma density consistent with Alfvén waves. The modes have been observed with high bandwidth magnetic pickup coils and with a reflectometer.
authors.affiliation: Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA.
authors.forename: E D
authors.initials: ED
authors.lastname: Fredrickson
authors.forename: N
authors.initials: N
authors.lastname: Gorelenkov
authors.forename: C Z
authors.initials: CZ
authors.lastname: Cheng
authors.forename: R
authors.initials: R
authors.lastname: Bell
authors.forename: D
authors.initials: D
authors.lastname: Darrow
authors.forename: D
authors.initials: D
authors.lastname: Johnson
authors.forename: S
authors.initials: S
authors.lastname: Kaye
authors.forename: B
authors.initials: B
authors.lastname: LeBlanc
authors.forename: J
authors.initials: J
authors.lastname: Menard
authors.forename: S
authors.initials: S
authors.lastname: Kubota
authors.forename: W
authors.initials: W
authors.lastname: Peebles