IPP Annual Report 2007 - Max-Planck-Institut für Plasmaphysik ...

20 channels each which are collimated by two separate slitapertures
in order to achieving the required wide viewing
angle view. A first design of the water cooled aperture plate
and detector holder has been completed. FE calculations
(ANSYS) of these designs are presently being performed
to evaluate the temperature of the camera components for
W7-X steady state operation conditions (~50 kW/m 2 ). A
study of the neutral pressure sensitivity of the metal foil
detectors has shown that blind-channels need to be integrated
into the design of the bolometer cameras to monitor this
effect. The detailed design of the video diagnostics – which
is being developed by KFKI-RMKI Budapest – was finished
in 2007. For the video observation the 10 equivalent
tangential AEQ-ports of the W7-X vacuum vessel will be
used giving nearly full coverage of the entire plasma vessel.
In the elaborated design the Sensor Module (SM) of the
Event Detection Intelligent Camera (EDICAM) is located at
the plasma end of the ports. The mechanics that transports
and docks the camera capsule – containing the SM to the
front window was manufactured and its mechanical and
thermal tests will be completed in 2008. Also the design of
the diagnostic front end, consisting of an air – vacuum
window, a small shutter and a water cooled plasma facing
front plate with a pinhole for plasma observation has been
completed by IPP Greifswald. The manufacturing of the
prototype is still ongoing. Radiation resistance test had been
performed on the first version of the Sensor Module. The
current version of the SM consists of only the essential electronics
in order to allow testing the performance of the
CMOS sensor itself, without the possible influence from a
more complex electronics. The SM was irradiated at different
gamma (between 0.1 Gy/h and 5 Gy/h) and fast neutron
(between 0.7 Gy/h and 1.4 Gy/h) dose rates in fission
research reactors. The evaluation of the images obtained
during the gamma irradiation test shows no enduring damage
on the CMOS sensor. Gammas cause only short time
flashing of the effected pixels. During the neutron irradiation
test the SM absorbed about 60 Gy total dose (about the
quadruple of the expected upper limit of the annual dose at
W7-X) revealing a clear increase of the dark current of the
individual pixels with increasing accumulated dose, but it
still remained functional. The development of the EDICAM
Image Processing and Controlling Unit (IPCU) and 10 Gbit
fibre link connecting the SM to the IPCU advances according
to the plans. The hardware kit for the IPCU (FPGA development
board with PCI express PC connector, ALTERA)
was purchased. The 10 Gbit fibre link is expected to be ready
in 2008.
7.2.5 Thomson Scattering
The design of a polychromator prototype for analysing the
scattered light was continued and successfully tested at
ASDEX-Upgrade. A water cooled shutter was designed, to
Wendelstein 7-X
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protect the vacuum window in front of the observation port.
A design study for the observation optics has been performed
with the optical design program ZEMAX.
7.2.6 Soft X-Ray and Magnetic Diagnostics
The design for the integration of the in-vessel X-ray tomography
camera system (XMCTS) beneath the heat protection
roof (designed by KiP) has been finalised. The camera
design including the cooling is completed and finite element
calculations were performed proving the effectiveness of the
cooling with respect to the expected heat fluxes. Several
components for the XMCTS are being manufactured for
prototype testing. Notably, the vacuum feed-through connectors
between the photo diode array and the electronic
box have been designed and manufactured by the company
Schott. The shutter prototype (protecting the photo diodes
during glow discharges and allowing for offset drift correction
during long discharges) was tested. Its mechanical
design is based on a pressurised manometer tube spring
attached to a lid. It was demonstrated that the shutter is
capable of more than 100,000 cycles under vacuum conditions
with additional heating cycles. The robustness of the
design is therefore sufficient, but small improvements are to
be considered for optimal operation in the W7-X vessel. The
continuation of the work on the preamplifiers was very difficult
throughout the year due to the lack of manpower in the
Greifswald electronics department. The cross-talk problem
between channels has been overcome to a large extent. One
of the main tasks in 2008 will be the test of a preamplifier
board fitted into the vacuum-tight electronic box. Further
major tasks in 2008 are the in-vessel cable routing and the
assembly of a prototype camera. The legacy code for the
tomographic inversion of W7-AS SX-ray data is being ported
from a specific AIX/W7-AS environment to a general Linux
version, which will be advantageous with respect to the
processing speed and portability. The code was simplified,
generalized and optimised and converted to a more consistent
and object-oriented design. The long discharge
lengths of W7-X pose a severe challenge to the data analysis
task. The amount of data from the XMCTS system in continuous
acquisition for a 30 min discharge sums up to about
500 GBytes. A method for an online method giving information
on the plasma shape and possibly mode onsets on a
human time scale is desirable. One approach to this challenge
involves the application of neural networks, which are
real time capable after a time-consuming training phase.
This work was done in collaboration with IST and IPP
Garching. First results were presented on the Plasma 2007
conference. The collaboration contract with the IPPLM in
Warsaw on X-ray pulse height analysis and on an electron
temperature monitor system based on the filter foil method
has to be extended. The main focus in 2007 was on the layout
of the filter system and on suitable data analysis algorithms.