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

020
progress report
2010
Power
(Linear amplitude)
Power
(Linear amplitude)
1.0
0.8
0.4
0
1.0
0.8
0.4
0
W tor =18.0 mm d in =800 mm
W tor =20.8 mm d in =700 mm
W tor =24.5 mm d in =600 mm
a)
-20 0 20 60
Probe position (mm)
ν pol =19.2 mm d in =800 mm
ν pol =22.1 mm d in =700 mm
ν pol =27.6 mm d in =600 mm
b)
0 20 40 60 80
Probe position (mm)
Figure 1.18 – Output beam profiles in the toroidal a) and poloidal b) direction,
obtained with the upper antenna (W is the beam radius in the toroidal and poloidal
direction, respectively; d in is the input distance between the input beam waist and
the focusing mirror). Dots correspond to the acquired data, curves to the Gaussian
fit of the beam profile
Vertical probe position (mm)
80
60
40
20
0
Power (dB) - angles: α=0°, β=0°
Speed ref.
motor 2
Speed ref.
motor 1
MIRROR POSITION CONTROLLER
(with real–time plasma ray tracing)
Plasma
feedback
-20 0 20 20 60
Horizontal probe position (mm)
Figure 1.19 – Beam amplitude pattern (dB) obtained from
the upper antenna set in the reference configuration:
contour levels are shown, where the –8.7 dB level
corresponds to the definition of beam radius w
PROTECTION SYSTEMS
Alarm
MOTOR 1 + DRIVE
(speed and torque controller)
MOTOR 2 + DRIVE
(speed and torque controller)
Position
motor 1
Position
motor 2
Figure 1.20 – Scheme of mirror control and
protection systems
coupling rods, to the external motors, put at the rear of
the port. After these tests, a revision of the joints design
was necessary. The new solution ensured better results in
terms of the overall performances and reliability in the
mechanical transmission of the movement, from the
motor to the steering mirror unit.
Low power tests were carried out after an optical
alignment of the antenna, performed by using a laser
mounted outside the port flange with beam aligned with
the microwave beam axis and markers used to check the laser spot position on each mirror of the beam line.
The tests have been made by using a 140 GHz horn–mirror antenna to launch a Gaussian beam matching a
field close to the one measured at the aperture of the FTU transmission line. A vector network analyzer (VNA)
was used to perform the tests, with a receiving antenna made with a properly shielded truncated waveguide.
The upper and lower antennas output beams were measured. The beam zooming effect was verified by
measuring the launched beam dimension (fig. 1.18) for different positions of the sliding mounting, and
comparing them with the expected values. Also 2–D beam pattern measurements and 1–D scans were
acquired, to evaluate the diffraction effects (fig. 1.19).
The functionality of the brushless motors chosen for the last steering mirror movement, was tested in presence
of an external magnetic field (B MAX
=0.1 T) estimated at the location foreseen for the motors in the FTU hall,
in real conditions of typical plasma operations. A 3–D model provides maps of the local value of the stray
field surrounding FTU during the shot (fig. 1.20). Such a model gave a maximum of ≈0.058 T for the stray
magnetic field expected at the motors location during typical plasma discharges. A permanent magnetic field
source, able to produce 0.1 T as a maximum field in correspondence of the poles and 0.05 T in the air gap,
was used for dynamical tests: they confirmed that such an external stray magnetic field does not affect the
correct operations of either the brushless motors or the resolver system.
The control and protection systems (shown in fig. 1.20 for one mirror) were tested in order to identify the
parameters of the drive and the mechanical system. Several tests have been repeated with this open-loop
configuration, with and without any mechanical load. In particular, the tests aimed to acquire the system step
response, so the speed reference input was a step with finite length; different step amplitudes have been used
to test the linearity of the system (fig. 1.21). The responses obtained showed that the non–linearity is not