verhoeven@rijnh.nl, FOM-Institute for Plasma Physics Rijnhuizen, Association
EURATOM-FOM,
Trilateral Euregio
Cluster, Nieuwegein, The Netherlands, www.rijnh.nl/ITERECRH,
*Forschungszentrum
Karlsruhe, Association FZK-EURATOM **CNR, Milan, ***Univ Stuttgart
****Max-Planck, Garching, *****Ciemat, Madrid, ******EFDA, Garching
The design of the mm-wave
system for the ITER Upper Ports is being carried out with the aim to inject
Electron Cyclotron Waves (ECW) in the ITER plasma to stabilize neoclassical
tearing modes (NTM). Each of the four upper-port launchers consists of six
mm-wave lines capable of transmitting high power up to 2 MW at 170 GHz.
In order to exploit the
capability of ECW for localized heating and current drive over a large range of
plasma radii in ITER, the ECH&CD upper port launcher needs a beam steering
capability. To avoid movable mirrors at the plasma-facing end of the launcher, remote
steering (RS) is used for the mm-wave beams, having the steerable optics
placed outside of the first confinement boundary of the vacuum vessel.
Steering of the beam over a range of +/- 12° is achieved by a mirror system consisting of a combination of curved and rotating mirrors. Via the mirror system the beam will be directed into a square corrugated waveguide. A single diamond-disk window and an isolation valve provide the tritium boundary between the primary and secondary vacuum. At the end of the square corrugated waveguide, mm-wave beams will be guided through penetrations in the front-shield blanket module by a set of 2 mirrors towards the ITER plasma. This “dog-leg” set-up will have focusing properties in both directions. The resulting, effective steering range is around +/- 8°.
The design analysis has demonstrated the feasibility
of the remote-steering approach in the ITER environment. The detailed design of
the mm-wave system aims at a consistent integration into the ITER environment.
Furthermore, a full-scale mock-up line at 170 GHz has been designed, procured
and installed. Low-power tests, both of all components individually as well as
of the complete system, are in progress at Rijnhuizen. Testing at high power
around 1 MW will start in July 2005 using the coaxial, short
pulse gyrotron at FZK, Karlsruhe.
This work is being carried out under the EFDA technology research programme activities,
EFDA technology
task TW3-TPHE-ECHULA/B, with financial support from NWO