2000 PROGRESS REPORT - ENEA - Fusione

1. Magnetic Confinement
After completion of the vacuum
tests, setup of the power supplies
and of all the electrical
connections, re-building of a new
cooling system and preliminary
formation of the plasma in the
duoPIGatron source, the system is
ready for operation.
The characterization of the beam
quality will be initially based on
optical observations of its intrinsic
emission and on infrared
observations of a target hit by the
beam itself.
Fig. 1.14 - Overall view of the vacuum chamber containing the neutral
source
Development of diagnostics. a)
MSE. The beam attenuation and
the brightness of the main Stark
component expected in a discharge
with a 1020 m-3 average
electron density are shown in
fig. 1.16. The figure also reports
the radial dependence of the
polarization angle to be measured.
Laboratory test of the Photoelastic
Modulators (PEM) [1.10]
polarimeter on a laser source have
yielded the desired accuracy of the
polarimeter angle (0.1°). The PEM
frequencies (40/46 kHz) and fast
data acquisition (5 Ms/s) will
allow for time resolution of a few
ms on the MSE measurements.
Fig. 1.15 - Internal view of the vacuum chamber showing the grids, the
neutraliser tube and the electron trap (conical cup)
A second polarimeter, based on the
polarization modulation given by a
half-wave plate rotating around its
axis, has been developed and
compared with the PEM
polarimeter. This polarimeter has
the advantage of depending on
phase only, rather than on intensity
measurements. Although comparable
in accuracy, the system
needs further development to obtain
modulation speeds as high as the
PEM ones [1.11].
Special care has been taken in the
design of the optical transport
system for the diagnostic in FTU in order to avoid refractive optics, which could be subject to
Faraday rotation perturbations by the high magnetic field of the tokamak. The optical layout is
reported in fig. 1.17.
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