Figure 2
Calculated x-ray intensity distribution inside a planar
wedge, with
and with the incident standing wave matched to various input modes, for different values of the phase mismatch parameter
. The gray scale is linear in amplitude (not intensity); the magnification insets use a different color scheme for clarity. Note that the
axes have identical scales, but the
axes have not. (a) Evolution of input mode
at low mismatch (
); the inset shows the contour of half the local (
-dependent) intensity maximum, demonstrating that
FWHM is the minimum beam size. (b)–(d) Configuration mimicking the experiment, with
,
, a
input mode, and
adjusted to give (b)
; (c)
, close to the actual experimental geometry, with the inset demonstrating the appearance of an intensity maximum: peaking at
the incident intensity and much narrower (
) than the exit width; (d)
. (e) Low-pass filter: the
mode (with low mismatch,
) ceases to be transmitted and radiates out of the waveguide as
falls below
. The rapid intensity oscillations are due to the additional mismatch at the upper plate between the incident sinusoidal wave and the wedge modes which have an exponential tail inside the
.
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