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

magnetic confinement (cont’d.)
progress report
2010
041
the agreement between MSE and MHD mode locations remains good, whereas the agreement is spoiled if
measured poloidal rotation is used. More investigation is needed to understand this discrepancy. For reversed
profiles, uncertainties in q values near the axis are higher than those for monotonic profiles, although in some
cases they are seen to be corresponding to experimental data from x–ray tomography and the observation of
Alfvén Cascades [1.94].
Upgrade of neutron profile monitor (KN3N)
The performances of the new digitizing system for the neutron profile monitor (NPM) has been assessed by
means of the analysis of data collected during JET plasma discharges [1.95]. The signals from the NPM
NE213 scintillators are acquired by a set of five digital pulse shape discrimination (DPSD) boards, each one
with 4 acquisition channels (20 channels in total: 19+1 spare) with 14 bit resolution and 200 MHz sampling
rate. Each DPSD acquisition board is fully configurable: thanks to the ethernet port and the embedded Linux
operating system integrated in the field programmable gate array (FPGA), it is possible to set the parameters
of the acquisition, to poll the state of the system as well as to start/stop the acquisitions.
The system has been demonstrated to be capable to provide simultaneous 2.5 (DD) and 14 MeV (DT) neutron
count rates. An example is given figure 1.51 for line of sight #4 (discharge #79698); the plot also shows
neutrons due to fast ion tails (FAST), corresponding to the proton energy range 3.5–10 MeV. For the same
discharge, figure 1.52 shows the line–integrated neutron emission
profiles for the DD and DT cases. Note the different rise times of
LOS#4 #79698
the DD and DT profiles at 9.5 s and 10 s due to the triton slowing
800
down time.
6×104
Work on the implementation of the KN3N data acquisition and
processing within the JET CODAS system has been started in 2010.
Elaboration of JET programme for 2011
The ENEA–Frascati team has also actively participated in the
elaboration of the JET programme for 2011 by sending its
representatives to the main Planning Meetings held in Culham, and
by joining many working group meetings from remote. A number
of experiments have been proposed in view of the new wall
conditions, which are now in the process of being selected and
rationalized in an executable time-line. Main areas are of interest
include: current profile and recycling control to access hybrid and
steady state regimes, pellet studies, detection and control of intrinsic
impurities, bulk tungsten tile response to heat loads, impact of edge
parameters on LHCD efficiency, threshold for the L to H–mode
transition with Be/W versus carbon wall, dust detection following
disruptions, integration of MHD, MSE and polarimetry data for
q–profile reconstruction.
Coordination of other Italian partners
ENEA has also coordinated the contribution of other Italian
partners to JET activity and taken an active part in their execution.
During the shut–down, scientific papers have been produced, based
on former Campaigns and also some enhancements have been
carried on mainly in the field of plasma diagnostics (University of
Rome Tor Vergata) and plasma control (CREATE Consortium).
In the field of diagnostics, in collaboration with Tor Vergata Rome
University, a detailed statistical analysis of the polarimetric
measurements, acquired during the campaigns 2003–2009, has
been performed [1.96] thus highlighting some calibration problems
Counts DD (s–1)
2×10 4
0
48
DD
DT
DT
52 56
Time (s)
400
0
Counts DT,FAST (s –1 )
Figure 1.51 – Neutron count rates for DD,
DT and FAST energy windows (pulse
#79698)
Counts/s
Counts/s
1×105
6×10 4
2×104
0
0
400
200
49.5 s DD (1.8-3.5 MeV)
50.0 s
a)
50.5 s
53.0 s
55.0 s
#79698
10 20
Channel
49.5 s
DT (10-16 MeV)
50.0 s
b)
50.5 s
53.0 s
55.0 s
#79698
0
0 10
Channel
Figure 1.52 – Neutron profiles for pulse
#79698: DD a), DT b)
20