Prime pagine RA2010FUS:Copia di Layout 1 - ENEA - Fusione

010
progress report
2010
chapter 1
magneticconfinement
The alternation of extremely scientifically productive years with technically critical ones seems to continue on FTU.
Following the very productive year 2009, in 2010 the FTU time effectively used for the experimental activity has been
extremely limited. The spring campaign was devastated by a series of vacuum leaks and eventually ended by a failure on
the flywheel generator feeding the toroidal magnet. The autumn campaign was affected by several failures, mostly linked
to poloidal circuits, producing at the end only a few shots useful for experimental programmes.
As a consequence, during the 2010 year, more emphasis was given to completion of analyses of existing data and of new
realisation on diagnostic and heating systems.
However reduced in number, plasma operations were always benefitting of liquid lithium limiter, either used to limit the
plasma or to condition the walls through depositing lithium on plasma facing surfaces. In such discharges pellet were
successfully injected for the first time, obtaining extremely peaked density profiles at very high density values as high as
6×10 20 m –3 . Detailed linear microstability analysis was performed on lithized discharges, proposing a possible mechanism
for generating the density peaking. A detailed analysis has also been completed for the discharges were, thanks to edge
optimisation, it was demonstrated that lower hybrid (LH) waves can penetrate plasmas with ITER like density profile.
These results, relevant for future applications of LH waves have been published in Nature Communication and have
triggered a multi-machine joint experiment coordinated by International Tokamak Physical Activity (ITPA)– Integrated
Operation Scenario (IOS) group. More experiments, at higher power, are planned on FTU to quantify the LH current
drive (CD) in these conditions as well as to complete the systematic comparisons between experiments and theory of
electron fishbones in the frame of the general fishbone–like dispersion relation. Looking forward to a positive decision for
future application of LH to ITER, a complete revision of the system design for ITER has been also completed in
collaboration with CEA Association.
Experimental activities on electron cyclotron (EC) physics have been conducted at high priority on FTU. Runaway
electrons have been suppressed; applying EC waves in heating scheme during the flattop phase of the discharge, at an
electric field value a factor ∼2 larger than the predicted collisional threshold field, E R ∼0.09×n e (10 20 m –3 ). EC on FTU
has contributed to ITPA joint experiments on assisted breakdown and on MHD control in particular controlling sawteeth
period through the localization of EC waves (injected in heating and CD scheme) with respect to q=1 surface. These
experiments will greatly benefit from the installation of the new real time steerable antenna, that will inject 0.5 MW of
EC waves through two front mirrors real time steerable poloidally and toroidally. The launcher has been fully tested in
laboratory, achieving all design performances, and was ready to be installed on FTU in the 2010–2011 shutdown.
By end of 2010, also two new diagnostics were completed and fully tested in laboratory. A new electro–optic probe able
to simultaneously detect the electric spike and the ionization radiation generated by the impact of dust particles and a
fast camera, which, able of up to 500000 frames/s, will allow diagnosing fast plasma evolution from breakdown to
disruptions.
Plasma theory progressed along the traditional lines of Frascati theory team. Beta induced Alfven eigenmodes (BAE),
observed on FTU during the first part of islands growth, were found to agree with theoretical predictions for sufficiently
low magnetic island amplitudes, consistently with perturbative theory. Significant efforts have been devoted to analysing
nonlinear behaviours in burning plasmas of fusion interest, their complex dynamics and the issues that arise when
modelling these phenomena with increasingly more realistic physics and equilibrium descriptions. Many of these
theoretical activities significantly contributed to advancing the FAST conceptual design; the activities specifically carried
out within the framework of this project are summarized in the specific FAST section.
Being JET operations suspended for the installation of the new ITER like wall (ILW), ENEA scientists have focused their
activity in the analysis of the data gathered during last campaigns and finalized journal papers and contribution to
international conferences, such as EPS, SOFT, IAEA and others. They also actively participated in the elaboration of the
JET programme for 2011