Beamline practice at BL01B1 (XAFS)
ver. 2009/10/23

K. Kato, H. Tanida, T. Uruga (JASRI)

1. Introduction
The bending magnet beamline, BL01B1, is used for various applications of XAFS over a wide
energy range from 3.8 to 113 keV. In the practical training course, we plan to show how to measure
XAFS spectra, which covers alignment of X-ray optics and sample position. We will also
demonstrate in-situ time-resolved quick scanning XAFS measurement of catalyst samples underreaction condition.

2. Plan of practice
9:00-Introduction of beamline, alignment of optics, measurement system and major scientificactivities at BL01B1.

10:00-

Alignment of the x-ray optics.

11:00-

Setup of the measurement system for Quick XAFS in transmission mode.

11:30-

X-ray energy calibration using standard sample.

12:00-

Introduction of preliminary process of XAFS spectra using software ATHENA.

12:30-------- Lunch -----------

13:30-

Introduction of in-situ XAFS experiment and sample preparation.

14:00-

Setup of in-situ XAFS experiment system.

15:00-

Measurement of in-situ XAFS spectra of catalysts during reduction and oxidation process.
During the measurement, data treatment and preliminary analysis of XAFS spectra.

17:00

Close.

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3. Alignment of x-ray optics and experimental stage
Figure 1 shows schematic layout of BL01B1.
Main operation in alignment of x-ray optics is follows.
Switch of diffraction plane of monochromator crystals between Si(111), Si(311) andSi(511) to cover energy range for XAFS measurements.
Change of glancing angle of mirror to remove higher-harmonic x-rays.
Above operation slightly changes beam height downstream of monochromator.
Fine adjustment of slits and mirrors in the optics hutch is done by measuring x-ray intensity
using 1st ionization chamber in the experimental hutch (Fig. 2).
The height of experimental stage in the experimental hutch is adjusted to x-ray beam byscanning in vertical direction.
Fixed beam condition is achieved by adjusting the rotation angle of 1st crystal of
monochromator around beam axis to 2nd crystal.
The control program for operation of x-ray optics realizes following x-ray beam.
Quite low contamination (<10-5) of higher harmonics.
Fixed beam position during XAFS scans passing through the center of slits in theexperimental hutch.
Focused beam in vertical direction (0.1-0.2 mm).
In the BL practice, the participants will align the optics following the manual upped on theWEB site, http://bl01b1.spring8.or.jp/BL01B1opticsmanEng040213.html.

Optics hutch

Experimetal hutch
Measurement
systemX-aryFig. 1 Schematic layout of BL01B12

4. Quick XAFS measurement in transmission mode
Quick XAFS measurement is realized by data storage of x-ray detector output signals andBragg angles of monochromator in each memory board during continuous scanning.
The arrangement and control system for transmission mode Quick XAFS measurements areshown in Figs. 2 and 3.
Setup the ionization chambers.
Select and flow adequate gases for ionization chamber.
Gases are selected to have the following absorption ratio of incident x-rays; 10-30 % for I0chamber and 70-90 % for I chamber, respectively.
Gases are listed in the WEB site, http://bl01b1.spring8.or.jp/RatioI0.html andhttp://bl01b1.spring8.or.jp/RatioI1.html.
Setup of measurement system
Set the beam size incident on the sample by slit opening.
Set the gain of current amplifiers (Amp) for each ionization chamber.
Operation of program of Quick XAFS measurement
Set the following parameters in the operation program
Energy range and step for a XAFS spectrum
Total measurement time for a XAFS spectrum.

5. Preliminary process of XAFS spectra using software ATHENA
The row data of Quick XAFS spectra are processed to the ATHENA-readable data format.
ATHENA processes the measured XAFS spectra, such as background removal and Fouriertransforms.
ATHENA is one of most popular free software for processing XAFS data.
http://cars9.uchicago.edu/~ravel/software/Model fitting of XAFS data is done by another software ARTEMIS including interfaces toATOMS and FEFF.

3Sample

I0 ionizationchamber

X-ray

I1 ionizationchamberFig. 2 Setup of transmission mode XAFS

Monochromator

2nd Mirror

1st Mirror

X-rayθ axisEncoder
MemorySample
I0I

AmpAmp

VFC

VFC
ScalarStepper motor
controller

MemoryBeamline
Work StationPCfor control andmeasurement

Piezo
DriverDAC

Fig. 3 Control system of QXAFS measurement system in transmission mode4

6． Measurement of in-situ XAFS spectra in transmission mode
6.1 Sample preparation
The sample for XAFS measurement is form into thin disks of 7 mm diameter by pressmachine with very weak pressing force.
Put adequate number of disk samples (around 20) into sample holder to achieve edge jumpabsorbance around 1.

Fig. 4 Mount of disk sample into inner holder of sample cell5

6.2 Setup of in-situ XAFS equipments
Experimental condition in this in-situ measurement
Sample: Pd/USY catalyst
Measurement energy: around Pd K-edge (24.3 keV)
Sample temperature: room temperature
Reaction gases: H2, O2, He and their mixture
Set the sample cell including disk samples.
Connect Q-mass to outlet of sample cell to monitor the concentration of each outlet gas.

Sample cellQ-massFig. 5 Setup of in-situ XAFS equipments

66.3 In-stu XAFS measurement of catalyst during reduction and oxidation process
XAFS measurement of catalyst in initial state.
Flow 100%-He 90 ccm into sample cell.
Measure Quick XAFS spectra in transmission mode.
The measurement time of each XAFS spectra during this experiment is about 30 s.
XAFS measurement of sample during reduction process.
Flow 8%-H2/He 90 ccm (H2: 7ccm, He: 83 ccm) into sample cell for 15-20 min.
Measure Quick XAFS spectra every 30 s during gas flow.
Check change of Fourier transform-XAFS spectra during reduction process usingATHENA.
Stop 8%-H2/He flow.
Flow 100%-He for 10-15 min until no residual H2 in sample cell (checking by Q-mass).
Measure Quick XAFS spectra.
XAFS measurement of sample during oxidation process.
Flow 8%-O2/He 90 ccm (O2: 7ccm, He: 83 ccm) into sample cell for 5-10 min.
Measure Quick XAFS spectra every 30 s during gas flow.
Stop 8%-O2/He flow.
Flow 100%-He for 10-15 min until no residual O2 in sample cell (checking by Q-mass).
Measure Quick XAFS spectra.
XAFS measurement of sample during reduction process in second cycle.
Flow 8%-H2/He 90 ccm (H2: 7ccm, He: 83 ccm) into sample cell for 15-20 min.
Measure Quick XAFS spectra every 30 s during gas flow.
Stop 8%-H2/He flow.
Check the sample color.

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