Speaker
Benedetta Baiocchi
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1015.pdf
Collective Thomson Scattering in FTU: first comparison between numerical
predictions and experimental observations
B. Baiocchi , W. Bin , A. Bruschi , L. Figini , U. Tartari , E. Alessi ,
1 1 1 1 1 1
P. Buratti , V. Cocilovo , O. D’Arcangelo , E. Giovannozzi , M. Lontano , G. Pucella
2 2 2 2 1 2
1
Institute of Plasma Physics “P.Caldirola”, National Research Council of Italy
via R. Cozzi 53, 20125 Milan, Italy
2
ENEA Fusion and Nuclear Safety Department, C. R. Frascati
via E. Fermi 45, 00044 Frascati (Roma), Italy
The Collective Thomson Scattering (CTS) diagnostic allows the investigation of ion
populations in fusion plasma devices, studying the characteristic emissions, stimulated by the
injection of a powerful microwave probing beam. From the shape of the emitted spectrum,
plasma parameters such as ion temperature, drift velocity and ion composition can be inferred
[1, 2]. The availability in FTU of a CTS diagnostic system at 140 GHz and the possibility of
“non-resonant” plasma scenarios, i.e. scenarios in which the Electron Cyclotron (EC) layer
(and harmonics) resonant with the probe frequency are out of the plasma region, allow to
carry out studies on ions characteristics. In fact, in presence of EC resonances, the Electron
Cyclotron Emission (ECE) background (at probing frequency) can significantly overwhelm
the signals due to thermal CTS. In recent experiments, focused on the investigation of the
effects of Parametric Decay Instabilities (PDI) in plasma with magnetic islands stimulated by
neon injection [3], a few shots were performed in non-resonant plasmas at 3.6 T, plasma
19 20 -3
current of 350 kA and densities ranging from 5*10 to 1.2*10 m . The scattered signal of
the 140 GHz, 350 kW probe beam has been detected by the upgraded CTS system [4] and
further analysed with the Thermal Collective Scattering code (TCS) [5]. The TCS has been
developed for the analysis of thermal ions spectral functions and recently upgraded with tool
providing absolute calibrated spectra (in eV). The CTS emission predicted by the code was
compared with the new calibrated spectra collected during the non-resonant discharges. The
fitting of these spectra allows an estimate of ion temperature and of the fraction of neon
impurities (injected to stimulate magnetic island) whose characteristic emissions have been
also simulated by the code.
References
[1] Stejner M et al 2015 Plasma Phys. Control. Fusion 57 062001
[2] Stejner M et al 2011 Plasma Phys. Control. Fusion 53 065020
[3] Bruschi A et al 2017 Nucl. Fusion 57 076004
[4] Bin W et al 2015 J. Instrum. 10 P10007
[5] Bin W et al 2015 Fusion Eng. Des. 96-97 733-737
