Distance between exposed object and exposure source
A detailed description of the radial transmission line used for exposure has been reported in several publications [Moros et al., 1998 and 1999]. The RTL was formed by two horizontal parallel conductive plates, 43 mm apart. The 6 mm thick bottom AL plate was highly thermally conductive thus minimising temperature gradients among flasks. A central conical AL antennaemitted TEM waves propagating radially outward and terminated by an annulus of RF-absorbing foam material braced by a thin lamina of perforated aluminium at 533 mm from the centre.
A total of 16 T-75 culture flasks could be distributed angularly around the antenna with their centres located at a radius of 292 mm. The cell layer was between 247 and 338 mm from the centre. Each flask was dielectrically loaded with a 3 mm thick shim of alumina (Al2O3) in order to boost and homogenise the SAR distribution.
"The above power settings were selected to produce a nominal time-averaged cell-layer SAR of 5.0 ± 2.1 W/kg for both signals." (?!)
Measurement and calculation details
This SAR value is based on a series of comprehensive measurements and includes variations due to the position of the flask but does not include potential measurement uncertainty usually estimated at ±10%. The degree of inhomogeneity (SD) is typical for this type of arrangement and has been validated by independent FDTD simulation studies [Pickard et al., 2000, publication 5405]. The larger than usual amount of medium was found to reduce the SAR non-uniformities.
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