Overview
2
MiniFlex 600: Benchtop X-ray Diffractometer
Optical System using SC
Fig. 1.1 outlines the optical system of MiniFlex 600 using the scintillation counter.
This optical system adopts focusing geometry used in powder XRD generally and
irradiates the sample with divergent X-rays limited by a divergent slit. The features
of this geometry are the high diffracted X-ray intensity, which is provided by
diffracted rays from the sample concentrating on the RS (Receiving slit), and
high-resolution analysis patterns.
An X-ray beam from the X-ray tube (focal point F) is emitted in the direction 6 °
below the horizontal direction. With respect to this incident beam, the sample is
rotated by θ and the detector by 2θ. The diffraction pattern is obtained by rotating
2θ /θ repeatedly and measuring the diffracted rays from the sample.
A counter monochromator is available as an optional accessory. This accessory is
placed behind the RS (further side from the sample) shown in Fig. 1.1. The counter
monochromator cuts not only the K
β
rays but also fluorescent X-rays and
continuous X-rays, which have an adverse effect for detecting micro peaks, thus
lowers the background and offers data with a higher P/B ratio. (Refer to “
the Counter Monochromator (Optional)
”).
Although omitted in Fig. 1.1, an auxiliary variable DS (Divergence slit) is placed
between the DS and Soller slit. This auxiliary slit helps to achieve the DS width of
0.1 mm at the time of optical axis adjustment. It also limits the radiation width to
"sample width + α" to prevent the irradiated area to spread outside the sample
without limit, thus improves the P/B ratio at low angles. The slit functions in the
background, and there is no need to concern about it on a daily basis.
DS (Divergence slit) is a slit to determine the width of the irradiation. Width of
1.25° and 0.625° are available. The 0.625
°
DS slit is used for measuring a sample
whose main peaks concentrate at low angles (2θ < 20
°
), such as organic sample.
For the RS (Receiving slit), the 0.3 mm RS is available. SS (Scattering slit) is a slit
to cut the scattered radiation from outside of the sample. Usually, the SS with the
same receiving angle as DS is used.
The Soller slits on the incidence and receiving sides limit the diffracted rays to
spread out in vertical direction (the top and bottom direction of this manual is the
vertical direction in the figure), thereby preventing the peak resolution from
decreasing.
Fig. 1.1 Outline of the optical geometry
