1. magnetic confinement - ENEA - Fusione

1. MAGNETIC CONFINEMENT
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1.2 FTU Facilities
profiles from the neutron-camera data. Good agreement was found between the
experimental profiles and the results of transport analysis simulations.
[1.53] F.M. Poli, et al.,
Disruption generated
runaways in the FTU high
field tokamak, presented
at 43 rd APS Conference,
(Long Beach 2001)
Disruptions in FTU plasmas were analysed using data from the neutron detectors
(BF 3 chambers). A database was prepared to investigate the dependence of the
photoneutron production on the toroidal field (B T ) and then extended to the results
obtained on other devices (TS, JT-60U) to magnetic fields B T > 4 T. Results show that
the generation of runaways is due the Dreicer mechanism and that the increase in
runaway production observed at higher toroidal fields could be due to the effect of
the plasma current profile [1.53].
The studies on runaway electrons in FTU continued in collaboration with the
Universidad Carlos III (Madrid). The time evolution of the energy distribution
function of runaway electrons in several FTU discharges was evaluated and
compared with spectral measurements of γ-rays produced by runaway electrons
hitting the limiter/vessel structures.
Tests on organic scintillator neutron detectors (NE213, stilbene and anthracene) were
carried out in collaboration with the TRINITI Institute, Moscow to verify the detector
light outputs. The light-output spectra were acquired using a 137Cs gamma source
and a VME-based acquisition system. The results indicate that stilbene scintillators
have higher light output than NE213 (respectively 82% and 51%, compared to
anthracene).
1.3.1 Introduction
1.3 Plasma Theory
The plasma theory activities are directed along two major lines of research: direct
support to the FTU research program, in terms of modelling and interpretation of
experimental data; and investigation of more fundamental physics problems
regarding turbulent transport and fast-particle-induced collective effects. In what
follows, the highlights and results of the more basic physics research efforts are
reported.
The theoretical model of ion Bernstein wave (IBW)-induced poloidal rotation was
further developed in the framework of both fluid and kinetic models and reached a
remarkable reliability level in predicting the formation and control of internal
transport barriers (ITBs) for the FTU experiments. The peculiar features of IBWs
makes it possible to achieve significant results at moderate levels of injected power,
as low as a few hundred kWs (sec. 1.3.2).
To understand turbulent transport, it is crucial to assess the role of self-generated and
time-varying sheared flows (zonal flows) in (self)-regulating the turbulence level.
Section 1.3.3 addresses this issue with particular attention paid to the role of drift-
Alfvén instabilities. The effect of partial cancellation of the Reynolds vs. Maxwell
stress tensor is discussed.
For the plasma stability studies relevant to ITB formation, new, interesting
investigation tools are available within a novel and unified mathematical
formulation for analysing both “small but finite” and “vanishing” magnetic shear
near a minimum-q surface (sec. 1.3.4).
The confinement properties of fusion products and, in general, of fast ions may
deteriorate because of the onset of collective modes of the Alfvén branch. The
stability properties of the modes in reversed shear and “advanced” tokamak
equilibria are analysed in section 1.3.5. It is shown that energetic particle driven