Speaker
Örs Asztalos
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1014.pdf
Feasibility of pedestal density fluctuation measurement by beam emission
spectroscopy on the ITER diagnostic beam
O. Asztalos1, S. Zoletnik2, G. Boguszlavszkij1, M.v. Hellerman3,
M. De Bock4, G.T.A. Huijsmans5,6, G.I. Pokol1
1
Institute of Nuclear Techniques, Budapest University of Technology and Economics, Budapest,
Hungary
2
Wigner Research Center for Physics, Budapest, Hungary
3
Institue for Plasma Physics, IEK4 Forschungszentrum Jülich, 52428 Jülich, Germany
4
ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance
Cedex, France
5
CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
6
Eindhoven University of Technology, Eindhoven, The Netherlands
ITER constitutes a critical milestone on the road to fusion energy production, which requires
understanding of the scaling of turbulent density fluctuations and pedestal dynamics to ITER sized
machines. This need facilitates the development of various fluctuation diagnostics.
Fluctuation beam emission spectroscopy (BES) is an active plasma diagnostic used for
density measurements that has sufficient spatial and temporal resolution for the study of turbulent
density fluctuations and associated flows. A high energy neutral beam is shot into the plasma
consisting of hydrogen isotopes or light alkali metal atoms, and through various collisional
processes with plasma particles the beam atoms get to excited states, and their spontaneous
emission is collected by an observation system. In the present contribution, the feasibility of
pedestal density fluctuation measurement by BES is discussed that would be proposed to make
piggy-back use of the pedestal CXRS periscope viewing the diagnostic neutral beam.
Forward modelling was used to estimate the signal to background (SBR) and signal to
noise (SNR) ratios, as well as the spatial resolution. These were evaluated in view of possible
applications of the diagnostic. A 10 x 15 channel observation system was put forward that would
not interfere with the baseline CXRS diagnostic system using the same periscope. Narrow-band
optical filters were optimized for each detector column to eliminate as much as possible of the
high continuous background expected on ITER. Resulting SBR of each column was determined
using Simulation of Spectra [1], which models the Doppler shifted BES spectrum for each detector
channel. The RENATE 3D BES modelling code [2], which handles realistic magnetic geometries
and accounts for the spatial effects of the diagnostic, was used to determine the expected photon
flux on each detector channel in order to derive the expected SNR. Fluctuation response analysis
was performed on the system to determine the extent of the fluctuation sensitive volumes for each
detector revealing the amount of expected cross-talk between detector channels and the
performance of the diagnostic system.
Applications of turbulence models and non-linear MHD codes, such as JOREK [4], in
conjunction with RENATE as a synthetic diagnostic are discussed, as well, to prove the
performance of the proposed fluctuation diagnostic.
The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.
[1] M.v Hellermann, et.al. 2006 IAEA IT/P1-26
[2] D. Guszejnov, et.al. 2012 RSI 83, 113501
[3] G.T.A. Huijsmans, et.al. 2007 NF 47, 659
