Speaker
Gregor Birkenmeier
(Max Planck Institute for Plasma Physics)
Description
We present a conceptual study and the potential physics investigations of an imaging heavy
ion beam probe (i-HIBP), which is planned to be developed for the ASDEX Upgrade tokamak. The main feature of this new type of a heavy ion beam probe (HIBP) is the imaging of the
secondary beams by means of an in-vessel scintillator screen in combination with a high speed
camera. The spatio-temporal pattern on the scintillator contains two-dimensional information
about the plasma density, the plasma potential and the poloidal magnetic field at the points of
ionization of the primary beam, where the secondaries are created. Due to the use of a neutral
beam as primary beam and the in-vessel imaging of the secondaries, the i-HIBP system is much
more compact than a classical HIBP.
A numerical study for a neutral 80 keV cesium beam as primary beam has shown, that
information about the density, the plasma potential and the poloidal magnetic field from 10 cm
inside the last closed flux surface up to the far scrape-off layer can be obtained for a typical
low-density ASDEX Upgrade plasma. On large time scales (several milliseconds) the i-HIBP
data could be used to estimate the electron density profile by means of a forward modelling
approach as already standard for beam emission spectroscopy applications. On the same time
scale, a more accurate estimation of the equilibrium poloidal magnetic field can be used to study
the edge current density evolution during an ELM cycle. On smaller time scales, the expected
resolution allows for radially resolved signatures of geodesic acoustic modes and zonal flows.
In general, the expected radial resolution and the possibility to get 2D information indicates that
the i-HIBP could become an excellent diagnostics for edge physics investigations.
Primary author
Gregor Birkenmeier
(Max Planck Institute for Plasma Physics)
