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

074
progress report
2010
T(keV)
30
20
Δt=1 s
a)
Original
Reconstructed
%
20
10
Δt=1 s
Precision
Accuracy
b)
Figure 3.39 – Ion temperature
profile reconstruction using
unfolding of RNC line–
integrated pulse height spectra:
a) comparison between original
and reconstructed Ti profiles; b)
accuracy and precision in the
reconstruction
10
0
0
0.4
ψ
0.8
1
0
0
0.4
ψ
0.8
1
T(keV)
20
10
Original
Reconstructed
a)
%
20
10
Precision
Accuracy
b)
Figure 3.40 – Ion temperature
profile reconstruction using
RNC integrated flux measurements
and other plasma
parameters’ measurements: a)
comparison between original
and reconstructed Ti; b)
accuracy and precision in the
reconstruction
0
0
0.4
ψ
0.8
1
0
0
0.4 ψ 0.8 1
0.2
0.1
a)
strong variability of the neutron reactivity with temperature, and
because of the accuracy foreseen for density, effective charge and
impurity density profiles measurements. An example of the Ti
reconstruction is given in figure 3.40.
0.0
0.0 0.4 0.8
r/a
0.4
0.2
0.0
0.0 0.4 0.8
r/a
Figure 3.41 – a) Average reconstructed
fuel ratio profile (including error bars); b)
precision (dashed) and accuracy (solid) of
the reconstruction
b)
Measurement of fuel ratio profiles with the ITER radial neutron
camera
The study of the capabilities of the ITER RNC equipped with
liquid scintillator detectors as a diagnostic for the fuel ratio (n T
/n D
,
ratio of the tritium to deuterium density) is being investigated in the
frame of an EFDA task (WP10–DIA–01–03). To diagnose the
n T
/n D
profile, the RNC should be able to provide simultaneously
DD (2.5 MeV) & DT (14 MeV) neutron emissivity profiles
measurements and a measurement of the ion temperature profile;
the success of the measurement strongly relies on the background
due to scattered 14 MeV neutrons that, depending on its
magnitude, may preclude the measurement of the DD spectral
component. The following measurement procedure is proposed
and applied to ITER scenario 2: 1) unfolding of RNC
line–integrated spectra to recover separated DD and DT brightness
components. 2) Spatial inversion of DD and DT brightness signals
to determine separate DD and DT emissivites. 3) Determination of the ion temperature profile. Montecarlo
calculations (using MCNP) have been performed for a representative subset of the 45 RNC lines of sight, in
order to characterize the background due to 14 MeV scattered neutrons at the RNC detectors' position. The
calculations have been carried out by including the RNC in the latest MCNP 40° ITER model (Alite–4). The
results indicate that the RNC might measure flat n T
/n D
profiles with values between 0.01 and 0.1 (with 20%
accuracy and precision and 100 ms time resolution) up to r/a < ∼0.8. An example is shown in figure 3.41 for