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The X’Celerator, how does it work?

An introduction to the workshop

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Introduction

• Since 2001, we shipped almost 1000 X’Celerators

• X’Celerators can be found in almost all countries in the world

• Used in a wide variety of applications …• … and more will surely come

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The X’Celerator• 128 parallel strips on a substrate• Real Time Multiple Strip (RTMS) technology• Speed & resolution

• Housing is designed for high 2Theta range

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The X’CeleratorModes of operation

• Modes of operation:– Scanning Mode– Receiving Slit Mode– (Static Mode)

• Parameters to be controlled:– Step size & counting time– Active length– (PHD levels)

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Scanning mode

active length

Each strip acts as an individual detector

Polycrystalline sample

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What is RTMS technology? (2)X’Celerator

Polycrystalline sample

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What is RTMS technology? (3)X’Celerator

Polycrystalline sample

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What is RTMS technology? (4)X’Celerator

Polycrystalline sample

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Step sizes in scanning mode

• Step size is determined by:– strip size– goniometer radius

• Minimum step size is ≈ 0.002º 2θ @ 240 mm radius

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Active length in scanning mode

• Software allows reduction of active length• Could reduce defocusing error• Effect is hard to see in practice

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Receiving slit mode

Results from strips are added up and give one 2Theta value

“receiving slit”

+

Polycrystalline sample

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Receiving slit mode

• Allows recording of pole figures (Phi and Psi scans)

• Useful for alignment of samples etcetera• Latest software versions allow display of count

rate on console display:– choose Stationary Measurement Program– choose appropriate measurement time

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Adjustment of the PHD level

• Pulse Height Discrimination is used in the X’Celerator

• Useful for suppression of – higher harmonics – sample fluorescence

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Other devices related to the X’Celerator

• Slots in housing for – Soller slits (0.08, 0.04, 0.02, 0.01 rad)– Beta filter

• Fixed anti-scatter slits• Programmable anti-scatter slits• Beam knives• X’Celerator monochromator

– for Cu or Co radiation

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The spectrum from a Cu tube

Inte

nsity

Wavelength

Cu Kα

W Lα

Cu Kβ

• Is a an X-ray tube monochromatic?

Cu Kα1 100%Cu Kα2 50%Cu Kβ 25%W Lα <1%

+ white radiation

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The beta filter

Inte

nsity

Wavelength

Cu Kα

W Lα

Cu Kβ

Ni filter

• Material with absorption matched to anode material

Ni for Cu tubeFe for Co tube….

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Example: NIST SRM 1976 Al2O3

20 30 40 50 60 70 80 90 100 110 120 130

NIST SRM 1976, Al2O340000

Counts

30000

20000

10000

0

Position [°2Theta]

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Example: NIST SRM 1976 Al2O3

25 30 35 40

NIST SRM 1976, Al2O3

Al2O3 Kα1 + Kα2

Mullite (Al6Si2O13)

Al2O3 Kβ

Ni absorption edge

40000

Counts

10000

0

Position [°2Theta]

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Instruments in which the X’Celerator is used• Diffractometer:

X’Pert PRO or CubiX FAST

X’Pert PRO CubiX FAST

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Summary

• Introduction to the themes of the workshop • Overview of X’Celerator modes of operation

and options

• Questions?