Rigaku R-XAS User manual

Cat.No. 2170L101/L102
R-XAS Looper
Instruction Manual
Manual No. ME12044A02

Thank you for your purchase of Rigaku’s product.
This manual describes the correct use of the product as well the usage precautions to be observed. To
obtain full-expected performance from the product, thoroughly read this manual.
Also, store this manual at an easily accessible place so that you can promptly refer to it whenever
it is necessary.
NOTICE
1. This manual described in it may not be disclosed to a third party or copied, in whole or in part,
without the written consent of Rigaku.
2. As a rule, one set of the instruction manual has to be purchased for each product.
3. If there are any missing or incorrectly collated pages in the delivered instruction manual,
contact the nearest Rigaku branch office or sales office for instruction manual replacement.
4. In no event will Rigaku be responsible for the results of the use of this manual.
5. The contents of this manual are subject to change without prior notice.

ME12044A−i
Contents
1. OVERVIEW.................................................................................................................................. 1
2. PRINCIPLE OF MEASUREMENT............................................................................................ 2
3. CONFIGURATION...................................................................................................................... 3
4. SPECIFICATIONS....................................................................................................................... 5
4.1 Goniometer Section...................................................................................................................5
4.2 Counter and Electronic Circuit Section .......................................................................................5
5. INSTALLATION.......................................................................................................................... 6
5.1 Preparations for Adjustment......................................................................................................6
5.2 Adjustment of Optical Axes.......................................................................................................8
5.2.1 Setup of the divergence slit (DS).....................................................................................8
5.2.2 Model with a direct-beam monitor ...................................................................................8
5.2.3 Model without a direct-beam monitor...............................................................................9
6. MEASUREMENT...................................................................................................................... 10
6.1 Preparations for Measurement.................................................................................................10
6.2 Adjustment of the Monochromator...........................................................................................10
6.3 Adjustment of the Detector .....................................................................................................10
6.4 Measurement .........................................................................................................................10
6.5 Example of Measurement........................................................................................................11
6.5.1 Installing the analyzing crystal.......................................................................................11
6.5.2 Moving the goniometer .................................................................................................11
6.5.3 Setting the detector provisionally....................................................................................12
6.5.4 Setting the slits.............................................................................................................12
6.5.5 Adjusting the monochromator........................................................................................13
6.5.6 Adjusting the detector...................................................................................................16
6.5.7 Measurement...............................................................................................................18
6.6 Switching the Measurement Mode ...........................................................................................19
7. WARRANTY.............................................................................................................................. 22
8. WARNINGS................................................................................................................................ 23
9. MAINTENANCE AND SAFETY............................................................................................... 24
10. TROUBLESHOOTING............................................................................................................. 25
11. WHEN A SIX-SAMPLE CHANGER IS IN USE (OPTIONAL ITEM).................................... 26
11.1 General..................................................................................................................................26
11.2 Configuration..........................................................................................................................26
11.3 Operating Method...................................................................................................................27
11.3.1 Mounting the sample holders.........................................................................................27
11.3.2 Mounting the turret.......................................................................................................27
11.3.3 Installing the sample changer in the equipment and connecting it......................................27
11.4 Software Operation.................................................................................................................28
11.4.1 Setup...........................................................................................................................28
11.4.2 Operation.....................................................................................................................28
11.4.3 Measurement conditions ...............................................................................................29
11.4.4 Set-reset Mode Measurement.......................................................................................30

ME12044A−ii
First Edition: May 27, 2003
Second Edition: May 27, 2003

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ME12044A
1. OVERVIEW
Each of the elements contained in a material has X-ray absorption edges of specific energies. When the
absorption coefficient is precisely measured near and beyond the absorption edges, a oscillatoryvibration
of the X-ray absorption as a function of photon energy is observed. This is the X-ray Absorption Fine
Structure (XAFS), which can be further divided into an X-ray Absorption Near-Edge Structure (XANES)
observed near the absorption edge,and an Extended X-ray Absorption Fine Structure (EXAFS) observed
along approximately 1 keV on the higher-energy side above the edge. While information on the valence
state of an atom is obtained from the XANES spectrum, analysis of the EXAFS spectrum provides
information on the local structure. The R-XAS Looper is the equipment developed for the measurement of
XAFS spectrum in a laboratory.
Figure 1.1General View of the System (D010524A01)

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ME12044A
2. PRINCIPLE OF MEASUREMENT
In XAFS measurement, an absorption coefficient is measured accurately by varying the energy of X-rays
irradiated onto the sample. Because a highly monochromatic X-ray (∆E < 10 eV) is required, it is
necessary to perform crystal spectrometry. However, the ordinary spectrometry using a plane crystal can
utilize only a small divergent angle, and therefore the intensity of the X-rays that can be used remains low,
which would increase the time required for measurement. For this reason, the R-XAS Looper adopts an
optical system that performs spectrometry and collection simultaneously using a Johann-type or
Johannson-type curved crystal. In Figure 2.1, S is an X-ray source, A the center of the monochromator
crystal, and F a receiving slit. These three points are arranged on the Rowland circle with radius R, in such
a manner that the relation SA = AF will be satisfied. The energy of the X-rays is varied by controlling that
distance.
The monochromatic X-rays selected in this way are irradiated onto the sample, thereby measuring the
intensity of the X-rays transmitted through the sample. By determining the ratio between that X-ray
intensity and that of the incident X-rays, the absorption coefficient can be measured.
R
O
θ
θ
L
L
F
S
Ax
y
B
Figure 2.1Principle of the Focusing Optical System

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ME12044A
3. CONFIGURATION
The R-XAS Looper is composed of two sections: the spectrometer section,which selects monochromatic
X-rays by applying spectrometry to the continuous X-rays emitted from an X-ray generator, and the
sample section, in which the intensity of X-rays transmitting through the sample (or emitted from the
sample) is measured and the intensity of incident X-rays is monitored at the same time. The left-hand part
of the illustration in Figure 3.1 represents the spectrometer section, while the smaller chamber on the right
side is the sample section.
Figure 3.1View with the Cover Opened (D010524A02)
The spectrometer section is consisted an X-ray generator, spectrometer (goniometer), divergence slit,
receiving slit, and monochromator (Figure 3.2). The X-ray generator is a fixed-target tube of 3 kW. The
spectrometer adopts the so-called “Linear spectrometer”method, which employs stepping motors to exert
control such that the distance from the X-ray source to the monochromator crystal and the distance from
the monochromator crystal to the receiving slit remain equal, thereby allowing X-rays of any desired
energy level can be selected. The divergence slit (DS) and the receiving slit (RS) are variable slits driven
by stepping motors, with their width controlled from a computer. The monochromator is provided with the
three axes, namely of ω, tilt, and Z. A Johann-or Johannson-type monochromator crystal with a Rowland
circle radius of 320 mm is mounted on the monochromator, which is then controlled from a computer.

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ME12044A
(D010524A03) (D010524A04)
Figure 3.2Spectrometer Section and Detection Section
The intensity monitor (I0-detector) for incident X-rays consists of a semi-transmission-type proportional
counter with Be window on both side, and provides linearity of up to 1 million cps through combined use
with a high-speed electronic circuit. On the other hand, the intensity monitor (I-detector) for X-rays
transmitted through the sample employs a high-speed scintillation counter, and is capable of counting
X-rays with a high degree of detection efficiency over a broad range of energy levels.
XG
Shutter
Monochromator
Receiving slit
Proportional counter
Sample
Scintillation counter

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ME12044A
4. SPECIFICATIONS
4.1 Goniometer Section
(1) Spectrometer section
(a) Optical system :Curved-crystal spectrometer system
(b) Rowland circle radius :320 mm
(c) Scanning method :Biaxial link pulse-motor driven
(d) Scanning range :2θ= 30°to 90°
(2) Monochromator section
Movable range (Min. step) :ω-axis ±3°(1/1000°)
tilt-axis ±3°(1/1000°)
Z-axis ±3 mm (1/100 mm)
(3) Slit section
Movable range (Min. step) :Divergence slit: 0 to 8 mm (1/100 mm)
Receiving slit: 0 to 8 mm (1/100 mm)
4.2 Counter and Electronic Circuit Section
(1) Proportional counter (S-PC)
I0(Incident X-ray intensity) detection
(a) Amplifier :Fixed gain
(b) High-voltage power supply and pulse-height analyzer (HV/PHA)
(i) Lower level :0 to 5 V
(ii) Upper level :0 to 5 V
(iii) Output voltage :0 to 1500 V
(c) Filled gases
Ne :For the low-energy region (5 to 7 keV)
Ar :For the medium-energy region (6 to 15 keV)
Xe :For the high-energy region (Over 15 keV)
(2) Scintillation counter (SC)
For measurement of transmission X-rays and florescence (common use)
:Diameter: 1.5 inches
(a) Amplifier :Fixed gain
(b) Pulse-height analyzer (PHA)
(i) Lower level :0 to 5 V
(ii) Upper level :0 to 5 V
(c) High-voltage power supply for detectors
Output voltage :0 to 1500 V

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5. INSTALLATION
To ensure accurate XAFS measurement, optical system must be adjusted precisely. While the positional
adjustment of the monochromator crystal is performed by controlling the axes of the monochromator using
a computer, the position of the X-ray generator is adjusted manually. The relevant procedure will be
described below. (The adjustment procedure for optical axes varies somewhat between models supplied
with a direct-beam monitor and those without one. The following explanation covers both cases.)
5.1 Preparations for Adjustment
With the spectrometer placed in the datum position (2θ= 90 degrees), remove the two screws
(indicated by the arrows in Figure 5.1) fastening the monochromator to the spectrometer,and detach
the monochromator. In that operation, the Insulock ties that clamp the cable to the monochromator
may have to be cut off in some cases. Exercise caution when cutting off the tie using nippers or the
like, to prevent damaging the cables. After the monochromator has been removed, install the
optical-axis adjustment slit in the same location. Then, place the direct-beam monitor immediately
behind the slit. On a model not provided with a direct-beam monitor, install the scintillation counter
immediately behind the optical-axis adjustment slit. This scintillator counter is the same one that is
employed for measurement. Connect its cable to the counter through the hole between the
spectrometer section and the sample section.
Figure 5.1Monochromator (D010524A05)
Figure 5.2After Removing the Monochromator (D010524A06)
Screws