  CEA/IRFM is conducting R\&D efforts in order to validate the critical RF
components of the 5 GHz ITER LHCD system, which is expected to transmit 20 MW
of RF power to the plasma. Two 5 GHz 500 kW BeO pill-box type window prototypes
have been manufactured in 2012 by the PMB Company, in close collaboration with
CEA/IRFM. Both windows have been validated at low power, showing good agreement
between measured and modeling, with a return loss better than 32 dB and an
insertion loss below 0.05 dB. This paper reports on the window RF design and
the low power measurements. The high power tests up to 500kW have been carried
out in March 2013 in collaboration with NFRI. Results of these tests are also
reported. In the current ITER LHCD design, 20 MW Continuous Wave (CW) of
Radio-Frequency power at 5 GHz are expected to be generated and transmitted to
the plasma. In order to separate the vacuum vessel pressure from the cryostat
waveguide pressure, forty eight 5 GHz 500kW CW windows are to be assembled on
the waveguides at the equatorial port flange. For nuclear safety reasons, forty
eight additional windows could be located in the cryostat section, to separate
and monitor the cryostat waveguide pressure from the exterior transmission line
pressure. These windows are identified as being one of the main critical
components for the ITER LHCD system since first ITER LHCD studies [1] [2] [3]
or more recently [4] [5] , and clearly require an important R\&D effort. In
this context and even if the LHCD system is not part of the construction
baseline, the CEA/IRFM is conducting a R\&D effort in order to validate a
design and the performances of these RF windows. In order to begin the
assessment of this need, two 5 GHz 500 kW/5 s pill-box type windows prototypes
have been manufactured in 2012 by the PMB Company in close collaboration with
the CEA/IRFM [6]. The section 2 of this paper reports the RF and mechanical
design of a 5 GHz window. Some features of the mechanical design and the
experimental RF measurements at low power are reported in section 3. High power
results, made in collaboration with NFRI, are detailed in section 4. The
development of CW windows is discussed in the conclusion. 2-RF AND MECHANICAL
DESIGN The proposed 5 GHz RF window is based on a pill-box design [2] , i.e. a
ceramic brazed in portion of a circular waveguide, connected on either side to
a rectangular waveguide section. Typical design rules of thumb of such device
are circular section diameter about the same size of the diagonal of the
rectangular waveguide (cf. FIGURE 1). Without taking into account the ceramic,
the circular section length is approximately half a guided wavelength of the
circular TE 11 mode, in order for the device to act as a half-wave transformer.
Once optimized, taking into account the ceramic, matching is correct only for a
narrow band of frequency and is very sensitive to the device dimensions and the
ceramic relative permittivity. The heat losses in the ceramic, which have to be
extracted by an active water cooling, depends on the inside electric field
topology and of ceramic dielectric loss (loss tangent). Undesirable modes due
to parasitic resonances can be excited in the ceramic volume, raising the
electric field and
