X-ray Lab X'Pert

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

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

High Resolution
Incident Beam Optics

Medium Resolution
Incident Beam Optics

X-ray Tube

Ceramic 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
Line	LFF (Long Fine Focus)	12 mm X 0.4 mm
Be window diameter	Be window thickness	Working Power	Standby Power
14 mm	300 mm	45 kV / 40 mA	30 kV / 20 mA

Beam Attenuators & Filters

Beam attenuator is an absorber which is placed in the x-ray beam to reduce its intensity by a specific factor.

Specific beam attenuators are designed for use with x-ray mirrors and hybrid monochromators.

Attenuation Factors for Cu Ka radiation

Copper foil (0.1 mm)	Combined Copper (0.2 mm) / Nickel (0.02 mm)
~ 100	~ 10,000

Automatic Beam Attenuator contains a Ni foil that can be set to be switched in and out of the x-ray beam either at a fixed angle or at a fixed intensity. Operation is controlled by the Data Collector software.

Automatic Beam Attenuator Operating Modes

Mode	Application
Do not switch (Activated/Deactivated)	Beam attenuator stays either inserted into the x-ray beam path or removed over a whole angular range and for the full measuring time.
At pre-set intensity	Beam attenuator is inserted into the beam when the specified count rate ("activate" level) is reached, and/or is removed from the beam when the count rate drops below another specified value ("deactivate" level).
At pre-set angle	Beam attenuator is inserted into the beam when diffractometer position on th scan axis is inside the specified interval. The interval is given by the activate and deactivate angles.

Beta-filter

Tube Anode	Beta-filter	Thickness (mm)	Kb intensity reduction (%)	Ka intensity reduction (%)
Cu	Ni	20	99	58

Fixed Divergence Slits

Divergence slits are fitted in the incident beam path to control the equatorial divergence of the incident beam.

Four fixed divergence slits marked 1/2o, 1/4o, 1/16o, and 1/32o are used in X'Pert diffractometer. Fixed divergence slits must be inserted into the slot for fixed divergence slits on the PreFIX module.

The length of the area on the sample that is irradiated by the incident beam is dependent on the divergence of the x-ray beam and the position of the sample with respect to the beam. It can be calculated as follows:

L - irradiated length of the sample,
R - radius of the goniometer (R = 320mm),
d - divergence angle as is engraved on the fixed divergence slit,
w - angle between incident beam and the sample surface.

Incident Beam Masks

Beam masks are fitted in the incident beam path to control the axial width of the incident beam, defining the amount (width) of the sample that is irradiated by the incident x-ray beam.

The size of the beam mask opening must be such that the incident x-ray beam is completely accepted by the sample during the complete measurement.

The total width of the area on the sample irradiated by the incident beam is dependent on the size of the x-ray beam and the position of the sample with respect to the beam.

X-ray Mirror

The graded multilayer parabolic x-ray mirror is a special kind of beam conditioner, which is able to convert the divergent x-ray beam from a line focus tube to an intense monochromatic quasi-parallel beam. X-ray mirror provided with X'Pert diffractometer is designed to diffract characteristic Ka radiation. Kb radiations suppressed to a level below 0.5% of its original level.

The x-ray mirror accepts ~0.8o of the x-ray beam from the line focus of the x-ray tube. The quasi-parallel beam diffracted by the mirror has a small horizontal (equatorial) divergence (< 0.05o). The beam from the x-ray mirror is ~1.2mm high and ~20mm wide. The beam emitted from the x-ray mirror is offset relative to the direst beam from the x-ray tube. This offset angle is referred to as the "mirror offset". The data collector software will always apply an offset whenever the x-ray mirror is present in the incident beam path.

Slit size and the irradiated length

Slit Marking	Beam height (mm)	Irradiated length (mm)
1/2o	1.2	0.12 + 1.2 / sin(w)
1/4o	0.6	0.12 + 0.6 / sin(w)
1/8o	0.3	0.12 +0.3 / sin(w)
1/16o	0.15	0.12 + 0.15 / sin(w)

w - angle between the incident beam and the sample surface.

Hybrid Monochromator

The hybrid monochromator is a special kind of beam conditioner, which is able to convert the divergent x-ray beam from a line tube focus to a quasi-parallel beam with a pure Ka1 radiation component. It consists of a parabolic-shaped multilayer mirror and a special channel-cut Ge crystal.

Hybrid monochromator will offset the x-ray beam. The hybrid monochromator passes slightly broader spectral range than traditional four-crystal monochromator and therefore delivers a much more intense parallel beam of Ka1 radiation. Ka2 component is suppressed to a level below 0.1%. It may become visible during reciprocal space mapping with large dynamic range.

X-ray Lab owns hybrid monochromator 4X, consisting of a combination of an x-ray mirror and a 2-crystal Ge(220) 4-bounce monochromator. The acceptance angle from line focus of the x-ray tube is 0.8o. The height of the x-ray beam emerging from the hybrid monochromator is 1.2 mm.