title: Status and characterization of the lithium beam diagnostic on DIII-D.
abstract: The 30 keV lithium beam diagnostic on DIII-D is suitable to measure both the radial electron density and poloidal magnetic field profiles in the pedestal. The refurbished system features a new setup to measure the Doppler shift allowing accurate alignment of the spectral filters. The injector has been optimized to generate a stable lithium neutral beam with a current of I = 15-20 mA and a diameter of 1.9 ± 0.1 cm measured by beam imaging. The typical temporal resolution is Δt = 1-10 ms and the radial resolution of ΔR = 5 mm is given by the optical setup. A new analysis technique based on fast Fourier transform avoids systematic error contributions from the digital lock-in analysis and accounts intrinsically for background light correction. Latest upgrades and a detailed characterization of the system are presented. Proof-of-principle measurements of the poloidal magnetic field with a statistical error of typically 2% show a fair agreement with the predictions modeled with the Grad-Shafranov equilibrium solver EFIT within 4%.
authors.affiliation: Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831-0117, USA.
authors.forename: H
authors.initials: H
authors.lastname: Stoschus
authors.forename: D M
authors.initials: DM
authors.lastname: Thomas
authors.forename: B
authors.initials: B
authors.lastname: Hudson
authors.forename: M
authors.initials: M
authors.lastname: Watkins
authors.forename: D F
authors.initials: DF
authors.lastname: Finkenthal
authors.forename: R A
authors.initials: RA
authors.lastname: Moyer
authors.forename: T H
authors.initials: TH
authors.lastname: Osborne