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2013 J. Phys.: Conf. Ser. 463 012006(http://iopscience.iop.org/1742-6596/463/1/012006)
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11th International Conference on X-ray Microscopy (XRM2012)
Journal of Physics: Conference Series 463 (2013) 012006

IOP Publishingdoi:10.1088/1742-6596/463/1/012006

Construction of the Scanning Transmission X-ray Microscope
Beamline at UVSOR
T Ohigashi1, H Arai1, T Araki2, N Kondo1, E Shigemasa1, A Ito1,3, N Kosugi1 andM Katoh11

Institute for Molecular Science, 38 Nishigo-naka, Myodaiji, Okazaki, Aichi 4448585, Japan
2

TOYOTA Central R&D Labs., Inc., 41-1, Yokomichi, Nagakute, Aichi 480-1192,
Japan
3

Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan

E-mail: ohigashi@ims.ac.jp

Abstract. Construction of a scanning transmission x-ray microscope (STXM)
beamline is in progress at UVSOR (Okazaki, Japan). To obtain high brilliancewith high resolving power for the incident x-rays, the combination of an invacuum undulator and a Monk-Gillieson mounting monochromator with avaried line spacing plane grating was adopted. Resolving power, spectrum andsize of the incident x-rays of the beamline were discussed through simulations
Then the photon flux at a sample of ~108 photons/s at the resolving power of
5,000 in the photon energy range from 100 to 700 eV is expected. As the firstresults, spectrum of calcium in chalk is shown.
1. Introduction
The scanning transmission x-ray microscopy (STXM) is a powerful tool to perform 2-dimensional
mapping of the x-ray spectroscopy with spatial resolution of several tens of nm. This method isappropriate for using the soft x-ray region covering the K absorption edges of light elements and the Labsorption edges of transition metals. These absorption edges make the STXM useful for study offunctional materials, such as polymers and carbon nanotubes. In addition, using the energy range
between the K absorption edges of carbon and oxygen (282~539 eV), called the “water window”
region, enables us to observe samples in water, such as cells, with high spatial resolution. For thesefeatures, the STXM used in the soft x-ray region becomes a unique technique in broad research fields.
To achieve a satisfactory performance of the STXM, a tunable x-ray source with high brilliance, suchas a synchrotron radiation, is necessary. In these years, several STXM systems have been installed atsynchrotron radiation facilities, Advanced Light Source [1, 2], Swiss Light Source [3], BESSY [4],Canadian Light Source [5], National Synchrotron Light Source [6], Shanghai Light Source Facility[7], Elettra [8] and more to come. The UVSOR facility (Okazaki, Japan), is a synchrotron light source(750 MeV, 300 mA) designed for using the photon energy from IR to soft x-rays. In 2012, the storage
ring of the UVSOR-II was upgraded to UVSOR-III to increase the brilliance by reducing theContent from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Published under licence by IOP Publishing Ltd111th International Conference on X-ray Microscopy (XRM2012)
Journal of Physics: Conference Series 463 (2013) 012006

IOP Publishingdoi:10.1088/1742-6596/463/1/012006

emittance from 27 to 15 nmrad. In the upgrade project, an in-vacuum undulator was also installed at
the short straight section for the new STXM beamline, BL4U. These improvements and energy
specification of the facility are suitable to operate the STXM with a satisfactory performance so thatthe construction project of the new STXM beamline, BL4U, has been launched.
In this report, the concept of the STXM beamline project, its current status and the perspectives areshown.

1016

Brightness[photons/s/0.1%b.w/mrad2]

2. Construction of the beamline
To achieve a satisfactory performance of theSTXM, it is important to use the incident xrays with high brilliance and stability. In ourbeamline, the in-vacuum undulator is used as
an x-ray source. The undulator has 26
magnetic periods with the period length of 38
mm pitch and the gap width can be changed
from 13 to 40 mm. Brightness of the x-ray
source with the undulator, calculated by using
SPECTRA [9], was plotted in Fig. 1 against
the energy with changing the gap width. Theseplots show that the photon energy range from100 to 700 eV can be used effectively.

101510141013

Energy [eV]Fig. 1: Calculated brightness of the x-ray
source with the in-vacuum undulator withchanging the gap

2.1. Monochromator
Our beamline employed a variable-includedangle
Monk-Gillieson
mounting
monochromator with a varied line spacing Top View
1500
3500
plane grating (VLSPG) [10]. The4500
2000 1290
To
monochromator consists of 3 mirrors,S2
M
2GMM
STXMUS1
0
1grating and two slits. A schematic image ofthe optical system is shown in Fig. 2. TheSide View
incident x-rays from the undulator enters atoroidal mirror M0 (R=3725.09 m and Fig. 2: Schematic images of the optical system of BL4U,
=0.2193 m), which is set 6.5 m
where U: the in-vacuum undulator, S1: the slit, M0: thedownstream from the light source with thetoroidal mirror, M1: the plane mirror, G: the varied line
spacing plane grating, M2: the cylindrical mirror and S2:incident angle of 88 through a slit, S1. The
M0 mirror focuses the incident x-rays onto a
the fixed exit slit. The unit of the length is mm.
fixed exit slit, S2, downstream 6.29 m
vertically and collimates the x-ray horizontally. The collimated beam is reflected vertically by a planemirror, M1, and enters the VLSPG. The line spacing of the VLSPG, N, is given by
N=N0(1+a1x+a2x2+a3x3), where x is a position on the VLSPG and its parameters as follows; N0=500
lines/mm, a1=-3.953410-4 mm-1, a2=1.166810-7 mm-2 and a3=-3.104410-11 mm-3. Sum of theincident angles of the M1 and the VLSPG varies from 167 to 176. The beam is focused onto the S2
horizontally by a cylindrical mirror, M2 (R=85.963 m) with the incident angle of 88. Ray-trace
simulations of shapes of the beams at the S2 with changing the resolving power, E/E, of 3,000, 5,000,10,000 and 20,000 with their vertical FWHMs are shown in Fig. 3. The main photon energy was fixedat 285 eV. These ray-tracing simulations were performed by X.O.P [11]. From Fig. 3, the FHWMs of
the vertical beam size (i.e. required width of the S2) become smaller with increasing the E/E andconverge at around that of 22 µm. Therefore, the E/E of 10,000~ is considered as the maximum
resolving power of our beamline from Fig. 3(c) and 3(d). Practically, it is effective for performance of2

11th International Conference on X-ray Microscopy (XRM2012)
Journal of Physics: Conference Series 463 (2013) 012006

IOP Publishingdoi:10.1088/1742-6596/463/1/012006

the STXM to use more photon flux rather than the higher E/E than 5,000 (i.e. width of the S2 is set as
30 µm).
(a)(b)
49.4 µm(c)(d)

31.7 µm23.4 µm21.4 µm

Fig. 3: Ray-trace simulations of the shapes of the monochromatized beams at the fixed exit slit at
the E/E of (a) 3,000, (b) 5,000, (c) 10,000 and (d) 20,000 with their vertical FWHMs. The main
photon energies are 285 eV. The unit of length is µm.

Diffraction efficiency [a.u.]

2.2. Scanning transmission x-ray microscope
A Fresnel Zone Plate (FZP) is used as a focusing optical
0.10
device. By using the S2 as a virtual source, the FZP placed
Nickel0.08
at 1,334 mm downstream from the S2 focuses the x-rays
onto the sample through an order sorting aperture. With0.06
raster scanning of the sample by piezo stages, thetransmitted x-rays are detected by a photon multiplier0.04
tube with scintillator.
Gold0.02
We have been preparing two FZPs, whose parameters
are the outermost width of 25 nm, the diameter of 240
0.00100167278464774µm, the number of the zones of 2,400 and the pattern
Energy [eV]material of gold or nickel of 100 nm thick. Calculated
efficiencies of the FZPs made of gold and nickel,
Fig. 4: Calculated efficiencies of theincluding transmittance of Si3N4 support membrane ofFZPs made of gold and nickel
100 nm thick, are plotted in Fig. 4. In these plots, theincluding transmittance of Si3N4
efficiency of the nickel FZP is better than the energy
substrate membraneregion from 170 to 504 eV so that using the nickel one ismore effective to analyze the elements in this region, such as carbon andnitrogen. Totally, by taking into account of efficiency of the FZP, the photon
1.5
flux of ~108 photons/sec at the sample at E/E=10,000 is expected for ourbeamline.
To obtain the diffraction-limited spatial resolution for the STXM, theexpected focusing spot size of ~30 nm, the FZP should be illuminated by the1.9
incident x-rays with longer coherent length than its diameter and with theE/E bigger than number of the zones of the FZP, 2,400. The radius of thecoherent area R with coherency of 0.88 is given by R=0.32z/D, where z isthe distance between the source and the FZP,  is the wavelength of theFig. 5: Simulated shapeincident x-ray and D is size of aperture of the fixed exit slit, S2. For theof the incident beam atcoherent illumination at C K-edge (285 eV), D should be set as 15.5 µm
the FZP for thewhile the E/E becomes more than 10,000. Then, a simulated shape of thediffraction-limited
incident beam at the FZP is shown in Fig. 5. This beam size of 1.5 (H)spatial resolution. The
1.9 (V) mm2 is large enough to illuminate whole FZP, 240 µm. Therefore,
unit of length is mm.
the diffraction-limited spatial resolution is available in this condition.

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11th International Conference on X-ray Microscopy (XRM2012)
Journal of Physics: Conference Series 463 (2013) 012006

IOP Publishingdoi:10.1088/1742-6596/463/1/012006

However, the photon flux is estimated to be about one order less than the condition of S2 for E/E=10,000.

Optical Density

Optical Density

3. Commissioning of the beamline
1.2
In late September 2012, the construction of the beamline1
was finished and its alignment is started in October. The
monochromator is calibrated by measuring K absorption
0.8
edge spectrum of nitrogen gas (shown in Fig. 6) with setting
0.6
the S2 as 30 µm width. From ratio of heights of * peak and0.4
valley, the E/E was estimated as around 6,000 and this0.2
result was reasonable compared with Fig. 3 (b). From0399 399.5 400 400.5 401 401.5 402
December, the STXM is commissioned and grinded
Energy [eV]particles of a chalk on microgrid were observed as the firstFig. 6: Spectrum of nitrogen gas
sample by noticing L absorption edge of calcium. 91
Transmitted x-ray images were acquired every 0.1 eV from 346 to 356 eV and the image at 346 eV isshown in Fig. 7 (a) as an example. From area in Fig 7 (a) indicated by a dotted circle, spectrum of
optical density of calcium of the chalk is obtained and is shown in Fig. 7 (b). Four peaks, which areassumed to be calcium oxide, are clearly seen on the plot.
We have been improving our beamline for using wider energy region, stability and calibrations.
Our beamiline is due to open for general users in June 2013.
1.8(a)
(b)
1.6
1.4
1.2
1
0.8
0.6

1 µm

346

348

350

352

354

Energy [eV]Fig. 7: STXM observation of chalk particles on microgrid (a) transmission image at 346 eV and(b) spectrum of the chalk indicated by a dotted circle in (a)References[1] Kilcoyne A L D et al 2003 J. Synchrotron Rad. 10 125-136[2] Bluhm H et al 2006 J. Electron Spectrosc. Relat. Phenom. 150 86-104[3] Raabe J et al 2008 Rev. Sci. Instrum. 79 113704[4] Wiesemann U et al 2003 J. Phys. IV France 104 95-98[5] Kaznatcheev K V et al 2007 Nucl. Instr. Meth. Phys. Res. A 582 96-99[6] Kirz J et al 1992 Rev. Sci. Instrum. 63 557-563[7] Xue C et al 2010 Rev. Sci. Instrum. 81 113502[8] Kaulich B et al 2006 IPAP Conf. Series 7 pp 22–25[9] http://radiant.harima.riken.go.jp/spectra/index.html[10] Koike M and Namioka T 1995 Rev. Sci. Instrum. 66 049501[11] http://www.esrf.eu/computing/scientific/xop2.1/

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