Imaging Neutral Particle Analyzer Measurements of Alfven Eigenmode (AE) Induced Fast Ion Transport in DIII-D
ASDEX Upgrade Seminar
- Date: Jan 9, 2019
- Time: 12:15 PM - 01:15 PM (Local Time Germany)
- Speaker: M.A. Van Zeeland
- Location: Garching
- Room: Seminarraum L6, 2.Stock Süd
- Host: IPP
A new imaging neutral particle analyzer (INPA), which provides
unprecedented energy-resolved radial profiles of confined fast ions, has
been fielded on the DIII-D tokamak. The INPA measures charge-exchanged
energetic neutrals by viewing an “active” neutral beam through a 1D
pinhole camera with a rear collimating slit that defines the neutral
particle collection sightlines. The incident neutrals are ionized by
stripping foils and the local tokamak magnetic field acts as a magnetic
spectrometer to disperse ions on the scintillator. A fast camera
provides 2D images of the escaping neutrals mapped to energy and radial
position in the plasma. The INPA clearly shows fast ion transport in
localized regions of phase space due to AEs. Measurements in reversed
magnetic shear current ramp experiments have revealed for the first time
a large preferential transport of stagnation orbits over passing orbits
at nearby radii. The data also show a large net outflow across the
plasma midplane during strong AE activity while at lower amplitude,
redistribution occurs from the core to larger radii.