SPring-8 Information, Volume 15, No. 1 (2010) pp.14-19
SPring-8 利用者情報／2010年２月 14-19
http://user.spring8.or.jp/sp8info/?p=3138

ビームライン

Status of the

RIKEN Quantum NanoDynamics Beamline (BL43LXU):
The Next Generation for Inelastic X-Ray Scattering.
Alfred Q. R. Baron
Materials Dynamics Laboratory, RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148
Research and Utilization Division, SPring-8/JASRI, 1-1-1 Kouto, Sayo, Hyogo 679-5198

Abstract
BL43LXU, the RIKEN Quantum NanoDynamics Beamline will be a world-leading facility using non-resonant
inelastic x-ray scattering (IXS) to investigate atomic and electronic dynamics by directly probing the A2 contribution
to the dynamic structure factor, S(Q,ω). Resolutions from <1 to ~100 meV will be available via two spectrometers: ahigh-resolution instrument with a 10 m arm; and a medium-resolution instrument with a 2 m arm. Here we describe
the status and over-all design of the beamline, including the source, which is expected to provide unprecedented fluxand brilliance between 14.4 and 26 keV. First light is expected before the end of 2011.

The RIKEN Quantum NanoDynamics Beamline,

IXS experiments. The beamline has been funded by

BL43LXU, will be a next generation facility for inelastic

MEXT through RIKEN with a 3-year maru-sai budget,

x-ray scattering (IXS). The purpose of the beamline is

beginning in FY2009. Several workshops have been held

investigation of atomic and electronic dynamics withto discuss the scientific case for the beamline [1] (Figure

resolution from <1 meV to ~100 meV, spanning1), and, even before those discussions, a team of scientists

momentum transfers from ~0.1 nm-1 to ~150 nm-1, andfrom SPring-8 had begun conceptual design work toenergy transfers from ~0.5 meV to >10 eV, via non-address some of the associated technical hurdles [2].

resonant inelastic x-ray scattering. Of particular note is
the use of a long insertion device to increase flux on the

The present article describes the design and expected

sample by about a factor of 10 over present instruments, aperformance of BL43LXU. As this is a short report in a

crucial improvement given the flux-limited nature of many

facility-based publication, the focus will be an overview

Figure 1

Photograph during the NanoDynamics Beamline workshop in 2008.
SPring-8 利用者情報／2010年２月 14

BEAMLINESof the expected capabilities of the beamline for thosein Figure 2. Importantly, the short undulator period andwith some background in synchrotron radiation

8 GeV electron energy of the storage ring allows this range

instrumentation. For a broader context as to how theof x-ray energy to be covered in the fundamental of the

instrument and the applications discussed here fit into theundulator, leading to a favorable ratio of useful flux toover-all picture of solid-state physics and x-ray scattering,heat load. However, to achieve the small gap for thiswe refer the reader to, e.g., the recent overview issue of

requires intermediate focusing of the electron beam, with

Kotai Butsuri [3].

One crucial issue, though, is that whilemagnets (quadrupoles and sextupoles) between the

IXS experiments provide superior quality data, with nearly

undulator segments, to keep the electron beam size small

no background (see discussion in [4]), they remain severely

enough for the 6 mm gap, and to retain sufficientcount-rate limited. This is true for measurements ofinjection aperture [6]. While this reduces the length of theatomic dynamics in complex materials, or with complex

insertion device to 15 m (as compared, say, to the 24 m ID

sample environments, where scan times can be days. It is

at BL19LXU) there is still a large gain in both brillianceeven more of an issue for measurements of electronic

and flux over the desired energy range (see Figure 2).

dynamics, where the cross sections are reduced. Thus,

For those who may wonder about the performance of thisthe improved source strength is a very important aspect ofbeamline as compared to the SPring-8 x-ray free electron

the beamline. Also of note is that BL43LXU will do non-laser (XFEL), we note that the XFEL is a pulsed source

resonant high-resolution investigation of electronic

and, while the peak pulse intensity is very large, theexcitations at larger momentum transfer, which might betime-averaged flux per unit bandwidth (which is theconsidered the momentum-resolved extension of opticalrelevant figure of merit for IXS) of the XFEL will be

or IR or Raman spectroscopy. This new field will allow

much (~103 times) less than at BL43LXU.

access to both correlations in low-energy transitions (suchas orbitons) and access to the higher order multipole
character of localized transitions.
At the time of the writing of this article, January of
2010, most of the specifications for equipment for
BL43LXU have been fixed, and the main components
are now out for bid, with contracts to be set before Aprilof 2010. Thus, the over-all design of the beamline iswell established. First light is expected late in 2011, andfirst experiments in 2012. One should note that thepresent paper discusses the expected performance when
the beamline is fully operational - achieving these goals
will encompass the first few years of beamline operation.
BL43LXU will take advantage of the strengths of theSPring-8 storage ring, including the high, 8 GeV, electron
beam energy, the availability of a long (30 m) straightsection, and in-vacuum undulator technology to produce auniquely powerful source in the hard x-ray region.
Specifically, the use of a three 5 m insertion devices (IDs)in series, each with a 19 mm period and a 6 mm minimum
magnetic gap, will allow unprecedented flux andbrilliance between 14.4 and 26 keV (kmax=1.56 at 14.4 keV,
k~1 at 22 keV). Calculated flux and brilliance is shown
15 SPring-8 Information／Vol.15 No.1 FEBRUARY 2010

Figure 2

Flux and Brilliance
Calculated flux and brilliance for a standard
SPring-8 insertion device (ID), 4.5 m long, 32 mm
period, as at BL35XU, the 24 m ID at BL19LXU(also 32 mm period), and the 15 m, 19 mm
period, ID planned for BL43LXU. Calculations
using SPECTRA［5］. Flux calculations haveassumed a fixed front-end slit size for each ID.
For BL19LXU, only the Brilliance is shown, andthe gap in the tuning curve is due to the large(12 mm) minimum aperture at BL19LXU, which
has no intermediate electron-beam focusing.
For BL43LXU, the calculations have been done
assuming a single undulator of 15 m length.

ビームラインThe power load on the pink-beam components is areduce this even to the 0.1 microradian level by gently

serious concern. While operation of the insertion device inbending the mirror. A diamond monochromator was also

the fundamental improves the flux to power load ratio, theconsidered, but difficulties in removing the expectedlong insertion device still has a large total power, ~47 kW

power deposition (~100 W, even for a thin diamond) andat minimum gap, and an extremely high peak powerissues of crystal quality and performance (especially at(about 3 MW/mrad 2 ) based on calculations using

higher energy) led to a preference for the nitrogen cooled

SPECTRA [5]. With some re-design, and thanks to thesilicon mirror. A matched mirror (M2 in Figure 4) will

good thermal properties of glidcop, the front-end is

be installed after the mono to return the beam to

expected to survive these power loads [7].

However thehorizontal. It is worth noting that mirror technology has

power onto the monochromator remains a serious

progressed to a point where substantially sub-problem, with the central cone expected to be ~1.8 kW at

microradian slope errors are possible on long flat mirrors

minimum gap. Liquid nitrogen cooling of a silicon(the mirrors are specified to have <0.3 micro-radianmonochromator crystal has been shown to be effective up

tangential slope error over the central 800x60 mm2).

to ~700 W [8], but the expected power at BL43LXU is
more than double that, with a substantially higher power

The beamline will have two main instruments, as shown

density. BL43LXU will therefore use a liquid nitrogenin the layout presented in Figure 4: a large high-resolution

cooled mirror upstream of the monochromator (M1 inspectrometer and a smaller medium-resolution spectrometer.

Figure 4) to reduce the power onto the monochromator

The high-resolution spectrometer will be for measurementsby removing the x-rays form the higher undulator

with good momentum resolution, a small fraction of aharmonics (see Figure 3). Cooling the silicon using

Brillouin zone (typical analyzer acceptance between ~1x5

liquid nitrogen to a temperature near to the zero in theand 10x10 mrad2, or momentum resolution in one dimension

thermal expansion, and the large beam footprint, should

between about ~0.1 and 1 nm-1), and energy resolution

reduce the thermal distortion of the mirror from ~ 1 kW

between <1 and 40 meV (see also Table 1). The better

absorbed power to ~0.4 microradians [9].

energy resolution will be used for measuring atomic

It is hoped to

dynamics, with the relaxed resolution (6 and 40 meV) topermit higher rates for lower cross-section experiments,
especially those investigating electronic excitations. The
medium resolution instrument will be primarily forelectronic excitations, and will have larger acceptance(~50x50 mrad2) analyzers on a short, ~2 m, arm. It will
operate primarily at 15.816 keV (corresponding to theSi(888) back reflection for the analyzer crystals) andis expected to have energy resolution between 10 and
100 meV, depending on the choice of incident beam
monochromatization. Both spectrometers will operatewith a horizontal scattering plane. The high-resolution
spectrometer will have a maximum scattering angle of
Figure 3 Calculated spectra and integrated power forseveral settings of the BL43LXU undulator.
The front-end slit size has been chosen to keep
the power absorbed by the first mirror < 1 kW andthe power absorbed by the mono <550 W. The
power is the flux integrated from low energy to
the value given on the x-axis. The mirror will
act to cut-off that part of the power at energies
above the fundamental, so at the first plateauof the power curve.

~55 degrees, while the medium resolution spectrometer
will scan to ~130 degrees in two-theta. For scattering
angles near to 90 degrees on the medium resolution
spectrometer, a diamond half-wave plate will be
employed to rotate the plane of the polarization tovertical and to reduce losses from pi-polarized Thomson
scattering. We note that early designs considered asingle spectrometer with an arm length of about 6 m.
SPring-8 利用者情報／2010年２月 16

BEAMLINES

Figure 4

Planned hutch layout for BL43LXU.
Beam from the undulator is incident from the left, and for the high resolution spectrometer, isbackscattered by the BX mono (far right), and impinges on the sample from the right. M1 is the nitrogencooled mirror, M2 the matched mirror to return the beam to horizontal and M3 the focusing cylindrical mirror
for the high resolution scattering. The length of the displayed hutches is 47 m.

optimal for many experiments: the 6 m arm length, as

resonance in 57 Fe. This resonance has an intrinsic
linewidth of <10 µeV, so, in principle, using time-gatingcompared to the 10 m now planned, would make sub-and a nuclear analyzer, as discussed in [10], very highmeV work difficult, while for medium resolution aresolution experiments will be possible (estimates

shorter, ~2 m, arm was desirable to increase analyzer

suggest 0.3 meV resolution should be possible). Table 1

solid angle and therefore count rates.

summarizes the expected operating conditions.

However, this was finally discarded, as being less than

It is worth taking a moment to comment on the planned

The medium resolution spectrometer will use analyzers

operating energy range, and modes of operation. The

operating at the silicon (888) back-reflection with aenergy range is largely dictated by using silicon optics intemperature gradient [11] to allow large space at thea near-backscattering geometry: silicon remains the

sample with a resolution of ~10 meV. This resolution

material of choice when large-area highly-perfect crystals

can then be relaxed to gain flux by increasing theare needed, while the backscattering geometry (Bragg

incident bandwidth. It is worth emphasizing that one ofangles near to 90 degrees) is desirable to get maximum

the reasons to use the (888) analyzer reflection instead ofangular acceptance for a given energy resolution, as can,be seen by differentiating Bragg s law. However, siliconthe (555) as is sometimes done, is the relatively goodbackscattering optics quickly become inefficient at higher

increase as the square of their width − if ∆E D is theenergy, with reflectivity dropping fast as x-ray energies

intrinsic (energy) Darwin width of the reflection (nearly

approach 30 keV. Meanwhile, from the point of view ofthe full width at half maximum) centered at E 0 thesample investigation, higher energy, for a fixed incident

reflectivity at an energy E with E − E0 >> ∆E D is justflux (in units of photons/s/meV), is almost always better,R ≈ (∆E D ) /(4(E − E 0 )) . Relaxing the resolution, increasing

as this allows one to get higher rates from larger samples∆ED, of the analyzer in an effort to get more counts,

due to reduced photoelectric absorption, and also to more

results in tails increasing as the square of the width,

easily penetrate into complex sample environments.

which is a very serious concern for measurements atThus, the 15-26 keV energy range, which covers intrinsic

smaller energy transfers. Figure 5 shows the resolution

resolutions in backscattering from about 4 to 0.3 meV

function from a setup where a single-reflection Si(888)(single reflection bandwidth in silicon) is a very

monochromator is used with a Si(888) analyzer, which

reasonable one. Finally, the extension of the operating

has been used to measure a d-d excitation in NiO [12].

energy range down to 14.4 keV is to match the nuclear

The integral intensity of the d-d excitation was some

17 SPring-8 Information／Vol.15 No.1 FEBRUARY 2010

response of the tails. The tails of Bragg reflections

2

2

ビームライン

Table 1 Expected operating conditions for BL43LXU.
All operating conditions, except the last two lines, refer to the large high-resolution
spectrometer with a 10 m two-theta arm. Qmax and Emax are the maximum momentum andenergy transfers accessible. ΔQmax is the maximum acceptance for a single analyzer - thelower limit will be <0.1 nm-1 (limited by count-rate) for the high-resolution spectrometer. The
last two lines are for the medium resolution spectrometer for electronic excitations, and thenuclear resonant scattering (NRS) setup, respectively. The resolution, in energy andmomentum, for the NRS setup, will be primarily count-rate limited, with the values listed
based on an estimate for a sample with relatively high rate (light elements).
Source Flux

Resolution

X-Ray Energy

ΔQmax

Emax

Qmax

（meV）

（keV）

（nm-1）

（eV）

（Å-1）

<0.9

25.7

1.2

4.9

12

Si（13 13 13）

140

1.4

21.7

1.0

4.1

10

Si（11 11 11）

230

2.8

17.8

0.8

3.4

8.3

Si（9 9 9）

390

6.0

15.8

0.7

3.0

7.4

Si（8 8 8）

440

40

15.8

0.7

10

7.4

Si（8 8 8）440

10−100

15.8

3.4

>10

16

Si（8 8 8）

440

>0.3

14.4

>0.3

>10

15

Analyzer（GHz/meV）

57

Fe Nuclear

430

3 orders of magnitude less than phonon intensity, and theWe briefly mention some of the expected improvements,

peak some 4 orders of magnitude reduced. Thus the tails

in addition to higher flux, beyond the instrument

are very important. Comparing the Si(888) with its

BL35XU. The first is that the analyzer array on the 10 m

4 meV Darwin width, against the Si(555) which has aarm will be increased in size, with a planned goal of 42

14 meV width at 10 keV, one can expect measureelements (as opposed to the 12 at BL35XU). As the data

excitations about a factor of 2 to 3 closer to phonon lines

rate, for some experiments, scales linearly with theusing the Si (888) analyzer.

number of analyzers, this is a large improvement. In
addition, these analyzers will take advantage of a new
design concept so that when a temperature gradient isapplied to them [11], combined with an efficient position
sensitive detector (such a detector is being developed
now [13]), improved resolution may be possible. The
long-term goal is ~0.7 meV at 25.7 keV and 1.3 meVresolution at 21.7 keV (FWHM). The default beam size
at BL43LXU is expected to be smaller, compared to that
at BL35XU due to improvements in mirror technology
and placement. In particular, the bent cylindrical mirror(M3) is expected to focus the beam to about 20x35 µm2
in the full width at half maximum, including the effectsof mirror slope error. This is good for focusing an entire

Figure 5 Resolution function using the silicon (888)reflection. (4 meV Darwin width for the analyzer
and the monochromator). Note points removed
near 100 and 350 meV correspond to known
excitation bands in the plexi-glass sample used
to simulate inelastic an elastic response. The
solid line is a smooth curve fit to the data.

beam at ~20 keV without losses, and will allow mostexperiments to be performed. Focusing to smaller size,~5 microns or less, is expected, and is underconsideration, though it will reduce the flux onto thesample.

SPring-8 利用者情報／2010年２月 18

BEAMLINES

The paper has introduced the RIKEN Quantum
NanoDynamics beamline, BL43LXU, discussing theworkshop on “Spectroscopy and Instrumentation for
IXS” (SIIXS) in 2009.

main capabilities and over-all design. Science at the［2］The team included A. Q. R. Baron, T. Mochizuki,

beamline will (1) directly build on the studies of atomic

H. Tanaka, K. Soutome, T. Takahashi, T. Tanaka,

dynamics at BL35XU, and (2) enter the new field of

H. Ohashi and S. Goto, among others.

high-resolution measurement of electronic excitations.

［3］固体物理, 44, For IXS in particular, see A.Q.R.

Directions of work in the first category include phonons

Baron, 固体物理, 44 (2009) 727-742. (Solid Statein larger-unit-cell correlated materials where both goodPhysics (Kotai Butsuri), 44 (2009) 727-742).

momentum and good energy resolution are required,［4］A. Q. R. Baron : 分光研究第58巻第5号 (2009)

extreme and geologically relevant environments

pp.205-214 (Journal of The Spectroscopical Society(including high-pressure and high temperature conditionsof Japan, Vol. 58, #5 (2009) 205-214 (Japanese) orin diamond anvil cells), atomic dynamics associated with

arXiv 0910.5764 (English)).

liquid phase transitions, and the detailed behavior of the［5］T. Tanaka and H. Kitamura : Journal of Synchrotron

atomic dynamics of glasses. All of these fields are now

Radiation 8 (2001) 1221and http://radiant.harima.

limited by count-rate at present instruments, and theirriken.go.jp/spectra/index.html.

extension, and the path to new and important data at［6］K. Soutome, Y. Shimosaki, J. Schimizu, M. Takao, M.

BL43LXU, is relatively straightforward. In addition, theOishi, M. Shoji, Y. Okayasu, K. Fukami, C. Mitsuda

high-resolution measurements of electronic dynamics

and H. Yonehara : unpublished.

(with demonstration experiments recently done) will

［7］S. Takahashi, Private Communication and S.

provide a window into new science, with one target

Takahashi, M. Sano, T. Mochizuki, A. Watanabe

being dispersion of low-energy electronic excitationsand H. Kitamura : Journal of Synchrotron Radiationsuch as orbitons, and another being the details of

15 (2008) 144.

structure of electronic transitions, including extending［8］A.I. Chumakov : Private Communication.

investigations of features known from more conventional［9］Based on finite element (ANSYS) calculations by T.

spectroscopic methods (IR, oprical, Raman) to higher

Mochizuki.
［10］A. I. Chumakov, A. Q. R. Baron, R. Ruffer, H.

momentum transfers.

Grunsteudel, H. F. Grunsteudel and A. Meyer :Acknowledgements:
This project has had help from many of the scientists andadministrative staff at SPring-8. The contributions of M.

Phys. Rev. Lett. 76 (1996) 4258.
［11］D. Ishikawa and A. Q. R. Baron : Journal of
Synchrotron Radiation, 17 (2010) 12-24.

Abe, H. Aoyagi, H. Arita, K. Fukami, H. Fukui, Y.

［12］A. Q. R. Baron et al.: Unpublished.

Furukawa, S. Goto, Y. Harada, D. Ishikawa, Y. Ishizawa,［13］H. Toyokawa, Y. Furukawa, T. Hirono, H. Ikeda, K.

H. Kimura, H. Kitamura, H. Konishi, T. Matsushita, T.

Kajiwara, M. Kawase, T. Ohata, G. Sato, M. Sato, T.

Mochizuki, H. Ohashi, T. Ohata, H. Ohkuma, M. Oishi,

Takahashi, H. Tanida, T. Uruga and S. Watanabe :S. Sasaki, J. Schimizu, Y. Senba, M. Shoji, K.

To Be Published in the Proceedings of the Hiroshima

Sorimachi, K. Soutome, S. Takahashi, M. Takata, K.

Symposium On The Development And Application

Takeshita, T. Takeuchi, H. Tanaka, T. Tanaka, S.

Of Semiconductor Tracking Detectors.

Tsutsui, H. Uchiyama, J. Yahiro, H. Yamazaki, and thestrong support of the RIKEN SPring-8 Center Director,
T. Ishikawa, are gratefully acknowledged.
References［1］Workshops included the “Workshop on HighResolution IXS” in 2006, the “Workshop for a
NanoDynamics Beamline:” in 2008, and a
19 SPring-8 Information／Vol.15 No.1 FEBRUARY 2010

Alfred Q.R. Baron
Materials Dynamics Laboratory,
RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148&
Research and Utilization Division
SPring-8/JASRI, 1-1-1, Kouto, Sayo, Hyogo 679-5198
TEL：0791-58-0803 x 3883 FAX：0791-58-1816