TRENDS AND FUTURE PROSPECTS - Total-Reflection X-Ray Fluorescence Analysis and Related Methods - page 439

Figure7.2. (a) Waveguide collimator after Ref. [43]. Two rectangular microscope slides, ∼ 1mm
thick and made of simple glass, are pressed together. The lower slide is 70 mm × 25 mm, the upper
slide is only 50 mm × 25 mm. A molybdenum tube with a line focus of 10 mm × 0.1 mm is used for
excitation. The sample is placed on the right side of the lower slide. Figure from Ref. [43],
reproduced with permission. Copyright1996, John Wiley and Sons. (b) Waveguide collimator
after Ref. [44]. Two flat and even quartz-glass plates are mated together with a clearance of 30 nm.
The upper plate is 100 mm long with a“diagnostic”hole on the right with 1 cm diameter. The sample
carrier is placed right of the lower plate just beyond the“diagnostic”hole. Figure from Ref. [44],
reproduced with permission. Copyright2000, ICDD.
quartz glass. The sample carrier is placed next to the lower and shorter plate
and pressed against the upper plate beyond a“diagnostic”hole. A simple Mo
tube with 25 keV was chosen for excitation and a Si(Li) detector was used for
spectra registration within 1000 s. Detection limits for contaminations on a
silicon wafer showed a geometric mean of 2 × 10 10 atoms/cm 2 for the Fe-group
elements.
In a review article, the peculiarities of waveguides for X-ray propaga-
tion were clarified [46]. Two optically polished quartz-glass plates of 100 × 33
× 2.5 mm 3 with a roughness of 5 nm were kept apart by small strips of titanium
and uniformly pressed together. The thickness of the strips was controlled by
Rutherford backscattering. A set of 14 different waveguides with a slit width
between 43 nm and 120 μ m was studied. Furthermore, a“slitless”collimator
was built without Ti strips and its width was determined by attenuated internal
total reflection (AITR) with a laser beam ( λ = 680 nm). Measurements at slit-
widths between 43 and 300 nm led to a value of ∼ 30 nm for the“slitless”
collimator by extrapolation.
The intensity of the K α peak of a Cu X-ray tube was measured after passing
the different waveguides with a divergence of ± 0.2 ° . It was shown that an X-ray
beam can propagate through a narrow slit between two plates of 100 mm length
and 33 mm height in two extreme cases [45]: (1) If the slit width is greater than
3 μ m, a direct propagation of the incoming beam with multiple total reflections