Incident Beam Part consists of X-ray Tube and Incident Beam Optics.

To see detailed overview, please click on items listed on the left.

 

 

 

 

 

 

 

 

 

 

 

X-ray Tube

Glass diffraction x-ray tube

 

Main Properties

Anode Material	Wavelength Ka1 (Å)	Wavelength Ka2 (Å)	Wavelength Ka (Å)
Cu	1.54056	1.54439	1.54184
Focus	Focus Type	Focus Dimensions
Point	NF (Normal Focus)	10 mm X 1.0 mm
Be window diameter	Be window thickness	Working Power
14 mm	300 mm	45 kV / 30 mA

Crossed Slit Collimator

Crossed Slit Collimator (CSC) is usually used in a texture point focus experiments. The collimator acts like a divergence slit and a beam mask at the same time.

The crossed slits assembly consists of two manually adjustable orthogonal slits with a maximum size of 10 mm to define both axial and equatorial divergence of the x-ray beam emitted by the point focus of the x-ray tube.

The aperture on the crossed slits collimator is adjustable by means of two knobs: one vertical and one horizontal. The slits can be manually adjusted from 0 to 10 mm (the scales are marked 0.02 mm divisions). The adjustment accuracy is ± 0.02 mm.

Determination of the Irradiated Area

The size (length and width) of the area on the sample irradiated by the incident beam depends on the size of the x-ray beam and the position of the sample with respect to the beam. The irradiated length and width can be calculated as follows:

L = irradiated length on the sample,
R = radius of the goniometer,
h = height of the incident beam, as set by CSC,
ph = height of the point focus (~ 1.2 mm),
f = distance from the x-ray tube focus to the crossed slits,
y = tilt angle - angle between the sample surface normal and the equatorial plane,
w = angle between the incident beam and the sample surface.

W = irradiated width on the sample,
R = radius of the goniometer,
pw = width of the point focus (~ 1.0 mm),
w = width of the incident beam, as set by CSC,
f = distance from the x-ray tube focus to the crossed slits,
y = tilt angle - angle between the sample surface normal and the equatorial plane.

 

Bartels Monochromator

High resolution Bartels monochromator is based on the U-shaped blocks of single-crystal nearly perfect Ge. The crystals have (110) surfaces and are preset for the Ge(220) or (Ge440) Cu Ka1 reflections. The monochromator can be changed between 220 and 440 reflections by rotating U-shaped blocks. X-ray beam will emerge from the hole C. It is also possible to rotate the second block so that it does not intercept the beam from the first block. This is two crystal mode of the monochromator. In this mode the output beam exits though the aperture D in the monochromator housing.

The wavelength spread is less than the natural line width of the CuKa1 line. The divergence of the beam exiting the housing is approximately equal to the width of the Darwin-Prins curve, which defines the angular range of the Bragg reflections that will occur in a perfect crystal. Each reflection at the crystal surfaces sharpens the flanks of the diffraction profile, thus giving a very low background intensity at angles only few sec away from the main peak.

Characteristics of Bartels monochromator

Mode	Focus type	FWHM	Relative intensity
4 x Ge(220)	Point	12"	1
4 x Ge(440)		5"	0.08
2 x Ge(220)		600	3
2 x Ge(440)		250	0.3

 

Changing the incident beam optics

It is possible to change between using the crossed slit collimator and the Bartels monochromator in a few seconds. Rotate the handle of the interchange mechanism with your right hand whilst holding the shutter plate in position with your left hand. Make sure you have selected appropriate filter (i.e. "none" if you are using the monochromator). Gently guide the collimator/monochromator into the shutter aperture and press the collimator or monochromator and tube together.

X-ray Tube

Beta Filter

Crossed Slit Collimator

Bartels Monochromator

Changing the Incident Beam Optics