22D02
Development of ITER EC Launcher components
ITER ECランチャー要素機器の開発	 
Koji Takahashi, Ken Kajiwara, Yasuhisa Oda, Noriyuki Kobayashi, Norio Naruiand Keishi Sakamoto
高橋幸司、梶原	  健、小田靖久、小林則幸、成井紀男、坂本慶司	 
Japan Atomic Energy Agency, 801-1, Mukoyama, Naka, Ibaraki 311-0193 Japan801-1, Mukoyama, Naka, Ibaraki 311-0193 Japan
日本原子力研究開発機構 〒311-0193	  茨城県那珂市向山801-1
The ITER equatorial EC launcher is designed assuming the HE11 mode propagation and that thetransmission efficiency of wave propagating in the launcher is 99.5 %. The launcher mock-up wasfabricated based on the design and the high power experiments were carried out. The RF transmission
was successfully demonstrated as designed and some stray RF radiation in the beam duct was however
obtained. The torus window mock-up was fabricated based on the current design and the loss tangent of
the diamond disk was evaluated to be 5.54 x 10-6, based on the results of the high power experiment

1. Introduction
An electron cyclotron heating and current drive(EC H&CD) system is an indispensable tool toimprove fusion plasma performance. The ITER
EC H&CD system (Figure 1) consists oftwenty-four(six) 170GHz, ≥1MW gyrotrons, atransmission line composed of twenty-fourwaveguide lines and five antennas injecting
millimeter (mm) wave beam power into plasma.
The gyrotrons are placed in the RF building and thelaunchers are installed in both equatorial (one) andupper port (four) of the vacuum vessel in thetokamak building. One side of the transmission
line is connected to the gyrotrons and the other side
is to the launchers. The torus diamond windows
used to be installed at the interface between thelauncher and the transmission line and it has been
modified that the windows are installed in the portcell area, far back from the end of the launcher.
2. ITER equatorial EC launcher
The schematic picture of the ITER equatorial EC
launcher (EL) is shown in figure 2. It shall becapable of injecting a 170GHz, 20MW millimeter(mm) wave beam into plasma. A toloidal steeringof the beams (20º≤ΘT≤40º) is also required. Thelauncher design has been modified to a partial
quasi-optical (QO) layout consisting of the movablemirrors, the focusing mirrors and the dog-legged
waveguide lines without changing the opening sizeof the blanket shield modules (BSMs) located infront, resulting some advantages such as a simpler
configuration and a possible reduction offabrication cost. The transmission efficiency ofthe mm wave beam on the QO layout is kept to be
99.5% [1]. This modification also derives thereduction of heat load on the steering mirror to be
one-third of the reference design, which relaxes thethermal design of the mirrors [1-2].
Gyrotrons

LauncherTransmission lineFig. 1. ITER EC H&CD system : Gyrotrons andtransimission line and launchers.

Fig. 2. Present design of ITER equatorial EC launcher :The 20MW power is provided by three beam bundles
and one of them is injected for the evolution of countercurrent drive.

Based on this QO design, the full scale EL
mock-up was fabricated. The mirrors are locatedin front of the waveguide structure composed by thewaveguide lines. One of the line is authentic andmm wave can propagate in the line. Figure 3
shows the power distribution of the mm-wave beamat the mirrors and the outlet of the EL mock-up
measured by using an IR camera. The measured
pattern at the steering mirror agrees with thecalculation. However, the measured pattern of thefocusing mirror (M1) is inconsistent with thecalculation. The high order modes other than
HE11 could also be radiated from the waveguideoutlet and the measured field patterns at M1 werepossibly the mixture of those modes and HE11.
This could be a reason of the inconsistency.

estimated to be 5.54 x 10-6, which was the lowest
value that had ever obtained. It should be notedthat the deposited power includes the power (orheat) penetrated into the copper cylinder that arebrazed to the window disk and the window housing.
Therefore, it is expected that the loss tangent of thediamond disk itself is lower than the above.
H2O out

Waveguide

H2O inHousing

Diamond disk
Fiber head

Waveguide
Fig. 4. Photograph of a torus diamond window prototype
for ITER EC H&CD system.
Fig. 3. Measured field pattern of radiated beam at thesurface of M1 and M2 and the outlet of the EL mock-up.

3. Window development
Figure 4 shows the photograph of the torus
window prototype fabricated on the current designbasis. A pair of copper cylinder are brazed to bothsides of the disk edge and they are welded to astainless steel window housing that has a coolingwater channel. The corrugated waveguides areinserted to both side of the window disk and weldedto the window housing. The inner diameter of the
waveguide is 63.5mm that is the same size of theITER transmission line. The gap between thewaveguide and the disk is 0.5mm. A thin copperlayer (≤5µm) is coated onto the inner surface of thecorrugation to minimize ohmic wall loss due to thehigh order modes propagation in the waveguides.
Transmission of both 430 kW and 740 kW wasdemonstrated and the successful pulse length was
100 sec on both cases. Temperature increase ofcooling water was saturated to be 0.18 ºC in 25 sec
at the transmitted power of 430kW. When thetransmission power/pulse length of the propagatedwave is 430kW/30sec, the deposited power into thewindow cooling water was measured to be 30W.
Then, the loss tangent of the diamond disk was

4. Conclusion
The EL design to perform the high efficienttransmission of mm waves power and to reduce theheat load on the mirrors is obtained assuming theHE11 mode propagation in the transmission line.
The efficiency is 99.5 %. The EL mock-up wasfabricated based on the design and the RFtransmission experiments were carried out. Somestray RF radiation in the beam duct wasqualitatively obtained.
The torus window
mock-up was fabricated based on the current design
and the high power RF transmission experiment
was carried out. The loss tangent of the diamonddisk was evaluated to be 5.54 x 10-6, which was thelowest value that had ever obtained.
References[1] Takahashi, K. et al. Improved design of an ITER
equatorial EC launcher // Nucl. Fusion 2008. V. 48,No. 5. P. 054014.
[2] Kajiwara, K. et al. Design of a high power
millimeter wave launcher for EC H&CD system on
ITER // Fusion Eng. Design 2009. V. 84. P. 72.
[3] Takahashi, K. et al. Progress of ITER Equatorial
Electron Cyclotron Launcher Design for Physics
Optimization and toward Final Design // Fusion Eng.
Design 2011. V. 86. P. 982.