X-ray Beam Stabilization by
MOSTABMOSTAB = Monochromater Stabilization

Yoshinori Nishino
SPring-8 / RIKEN

Collaborators• Throughout the WorkT. Kudo, T. Ishikawa• Experiment at BL29XU
M. Suzuki, T. Hirono, K. Tamasaku• Experiment at BL38B1
Y. Furukawa, H. Tanida• Manufacturing the MOSTAB Module
E. Ohtake (Teikoku Denki)
I. Morimoto (Mitsubishi Electric Engineering)•Private Communication
D. Novikov (HASYLAB, DESY)

Layout of Beamline
SRExperim ental hallU ndulator

Fro nt-endOH050

Opt ics H utch55

EH4

EH 1-3DC M

601 00Experim ental
Hut ch 165

BL19LX U

130160 (m )

EH 3

EH 4

EH 2707580130

13 5 (m )BL19LXU: M. Yabashi et al., NIM A 467-468, 678 (2001).

• Photon Source• Frontend• Optics Hutch
DCM = Double Crystal Monochromator• Experimental Hutches

Fixed Exit Double Crystal Monochromater (DCM)θ stageta lsyr
2nd Ctalsyr
1st C oPiez

geats
Y

geats
Z cam

• Bragg reflection fromtwo crystals• Tuning the energy bychanging the incident angle

λ = 2d sin θ B• Energy Resolution∆E≈ 10 −4E• Diffraction planes of the twocrystals should be parallel.
• Piezo actuator to control
the parallelity

Question:
What happens when the two crystalsof DCM are not parallel?
Answer:• decrease in intensity• shift in position• shift in energy

Dependence of X-ray Beam Intensityand Position on Detuning Angle
X-ray Beam Intensity and Vertical Position(EH1, BL29XU)

Detuning Angle = ∆θ
Exit Beam Angle = 2∆θθ+2∆θ2∆θθ+∆θlinear fit: 85.7 mm/arc sec = 17.7 m/raddistance from monochromator to BPM: ~ 9 m

Dependence of X-ray Beam Energy on
Detuning Angle
Pt LIII absorption edge scanwith different detuning angle

binding energy of 2p3/2 state = 11.564 keV

Energy Shift of X-ray Photons(EH1, BL29XU)

linear fit: -0.46 eV/arc sec
theoretical value:3
E cot θ B = −0.48 eV / arc sec
2Question:
What happens when the two crystalsof DCM are not parallel?
Answer:• decrease in intensity• shift in position• shift in energy

Intensity, position and energy of x-rays can be simultaneously
stabilized by stabilizing the parallelity of DCM.

Necessary Condition: Electron beam is stable.

Improvements of Hardware• Pin-post water cooling
T. Ishikawa, H. Yamazaki, K. Tamasaku, M. Yabashi, M. Kuroda & S. Goto,
Proc. SPIE 3448, 2 (1998).

• Cryogenic cooling
K. Tamasaku, M. Yabashi, D. Miwa, T. Mochizuki, T. Ishikawa,
Proc. SPIE (2002).

Nitrogen gas

Helium gas
Helium refrigerators

High Head Load on
Monochromator
1st Crystal

To mono.

LN2 tank

From mono.

LN2 pump
Vacuum chamber

g=9.6 mm
FE slits 1x1 mm2
E=16.4 keV (Si 111)
P=478 W @100 mA
pm=27 W/mm2

MOSTABMOSTAB (Monochromator Stabilization) module
applies a feedback voltage to the piezo actuator of DCM.

Reference:
Krolzig, Materlik, Swars & Zegenhagen, NIM 219, 430 (1984).

Digital MOSTAB with PID-Control
Operation Modes• Intensity (I0 ) Stabilization- ∆θ drifts in time
• I0/Iring Stabilization- ∆θ is stabilized at a fixed energy• Position Stabilization- Stabilization at any ∆θ (including ∆θ=0)
and at any energy
R. F. Fischetti et al., RSI 73, 1518 (2002).

Ethernet connection for remote control,
and to obtain Iring from the database system.

Sources of Instability
Oscillation of intensity and vertical position
are caused by the same source.

The common source of instability
around 40Hz is storage ring.

(EH1, BL29XU, March 2002)(EH1, BL29XU, March 2002)

Intensity & Vertical Position

BPM @ FE & BPM @ EH
BPM @ FE & Intensity

Frequency Response
Response of X-ray Intensity to Piezo Voltage(BL38B1, Sep. 2002)

Feedback is effective below 10 Hz.

SPring-8 Standard Monochromator

Monochromator
at BL29XU

Simultaneous Stabilization ofIntensity and Position of X-ray Beam
Stability of X-ray Intensity(EH1, BL29XU, March 2002)

Stability of X-ray Beam Position(EH1, BL29XU, March 2002)

RMS: 6.4x10-3, 1.7x10-4, 9.4x10-4

RMS: 1.98µm, 0.37µm, 0.13µm

N.B. Data was taken at rocking curve shoulder,
where the intensity oscillation is large.

Stabilization in Energy Scan
Stability in Energy Scan
ID Gap was optimized at each energy.

(EH1, BL29XU, March 2002)

RMS: 7.0x10-3, 2.1x10-4, 2.3x10-4

Test of MOSTAB at 1 km Beamline

1 km Beamline
RIKEN BL29XU

Correlation among Oscillations
Oscillation of intensity and vertical position
are NOT caused by the same source.

Oscillation of x-ray beam positionis due to storage ring.

(EH1, BL29XU, Dec 2002)(EH1, BL29XU, Dec 2002)

Intensity & Vertical Position

BPM @ FE & BPM @ EH
BPM @ FE & Intensity

Test of Simultaneous Stabilization
Without Feedback(BL29XU, Dec 2002)

With Intensity @ EH1 FB(BL29XU, Dec 2002)

Simultaneous stabilization of x-ray beam intensity and position
was not possible due to electron beam instability.

Stability of X-ray Intensity
at 1 km from Source
Stability of X-ray Intensity(EH2, BL29XU, Dec 2002)

Applications of MOSTAB• Users of synchrotron radiation need …
– high flux (small signal)– coherence– tunable energy• These requirements are closely related to thestability of x-ray beam.
My personal experience with MOSTAB• Atomic Resolution Holography• X-ray Absorption SpectroscopyInstallation of MOSTAB to Beamlines• already installed (prototype analogue MOSTAB )– BL35XU (High Resolution Inelastic Scattering) A. Baron– BL12XU (Taiwan BL) Y. Cai• planning to install– BL01B1 (XAFS) T. Uruga– BL13XU (Surface and Interface Structures) O. Sakata– BL29XU (RIKEN Coherent X-ray Optics) K. Tamasaku, M. Yabashi– BL38B1 (R&D) H. Tanida, K. Miura– BL39XU (Magnetic Material) M. Suzuki

Summary• Simultaneous stabilization of intensity, position,energy of x-ray beam is possible with MOSTAB.
• Feedback is effective < 10 Hz.
• Intensity Stabilization: 6.4x10-3
1.7x10-4• Position Stabilization: 1.98µn0.13µm• Stability of accelerator is crucial for a successful
MOSTAB operation.