The Variable Polarization XUV beamline P04 at PETRA III ... - IWXM

The Variable Polarization XUV beamline P04 at PETRA III: 

Optics, Mechanics and their Performance. 

Jens Viefhaus, DESY Hamburg, FS-PE 

4th International Workshop on Metrology for 

X-ray Optics, Mirror Design, and Fabrication 

Barcelona, Spain, July 4-6, 2012 

DESY

Acknowledgements 

> Optics and Metrology: Frank Siewert, Jana Buchheim (HZBerlin) 

> P04 review team: Nick Brookes (ESRF), Rolf Follath (HZBerlin), 

Hermann Franz (DESY), Michael Martins (Uni HH), Ruben Reininger (SAS), 

Fred Senf (HZBerlin), Edgar Weckert (DESY), Wilfried Wurth (Uni HH) 

> P04 group@PETRA III: Sascha Deinert, Leif Glaser, Markus Ilchen, 

Frank Scholz, Jörn Seltmann, Ivan Shevchuk, Beata Terka 

(former members :) Olof Gutowski, Peter Walter, Michael Wellhöfer 

> Whole PETRA III team (FS-PE) 

> Further collaborators: 

Markus Braune (FLASH, DESY), 

Jens Buck (WP-74 Diagnostics, European XFEL), 

Group of Uwe Becker (Fritz-Haber-Institut der MPG, Berlin) 

> DESY workshops: ZM, ZE, HASYLAB groups: FS-BT, FS-EC, FS-TI, FS-US 

> Raytracing Software: Shadow/XOP, RAY, REFLEC 

Jens Viefhaus | 4th International Workshop on Metrology for X-ray Optics, Mirror Design, and Fabrication | July 4, 2012 | page 1 

DESY

PETRA III Parameters - Actual Performance in 2011/12 

> Beam energy 6 GeV 

> Beam current (top up) 100 mA 

> Circumference 2304 m 

> Revolution period 7.685 µs 

> Bunches 240/60/40(320) 

> Bunch period 32/96/192 ns 

> Bunch length (FWHM) 100 ps 

> Emittance (horizontal) 1 nmrad 

> Coupling 1 % 

DESY NEWS 

The finest beam of the world 

PETRA III reaches design emittance 

Shortly after start-up, the PETRA III accelerator already set a world 

record in “lowest emittance”. The measure of the size of the light 

spot is a key parameter of the facility, making PETRA III the best 

storage ring light source worldwide. 

2009/10/21 

In this summer, a total of 20 so-called wiggler magnets were built in 

and gradually started operation in the north and west sector of the 

2.3-kilometre-long PETRA III accelerator. The wigglers “damp” the 

positron beam to guarantee the reduction of the beam’s transverse 

size in longitudinal direction. Only with a small beam it is possible 

to provide the experimenters with small and highly intense light 

spots. 


DESY

PETRA III Beamlines 

> 9 straight sections - 14 undulator beamlines: 

PETRA III 

20 m device nuclear resonant scattering (ps-resolut.) 

2 x 2 m devices 

powder diffr./extreme conditions 

micro/nano SAXS/WAXS 

5 m undulator 

5 m device XUV 


e+ 

5 m device 


imaging/tomography 

Fluoresence/XAFS 

High energy material sci. 

2 x 2 m undulators 

5 mrad 

e+ 

5 m device 


resonant scattering 

high resolution diffr. 

coherence appl. 

e+ 

SR beam 


BioImag 

BioSAX 

BioPX 

BioµPX 

BioPX 

• Usage of canted undulators to enlarge the number of beamlines 

Cartoon made 

by O. Seeck 


DESY

PETRA III - a Unique Soft X-ray Source 

> An VUV/XUV Beamline at PETRA III (6 GeV!) 

• Exceptionally wide range of photon energies: 

~250-3000 eV with variable polarization 

(especially interesting for circularly polarized SR, 

using the 1 st harmonic only) 

Brilliance 

(s -1 mm -2 mrad -2 (0.1%BW) -1 (100mA) -1 ) 

• High stability, low emittance (damping wigglers) 

⇒ diffraction limited source (except horizontal source size) 

10 20 

10 19 

10 18 

500 1000 1500 2000 2500 3000 

Photon energy (eV) 

Divergence FWHM (µrad) 

60 

40 

20 

e + -beam div. (h x v): 

7 µrad x 2 µrad (rms) 

horizontal 

vertical 

500 1000 1500 2000 2500 3000 


Source size FWHM (µm) 

300 

200 

100 

horizontal 

e + -beam size (h x v) 142 µm x 5 µm (rms) 

vertical 

500 1000 1500 2000 2500 3000 


• Large facility ⇒ space for dedicated experiments 


DESY

PETRA III P04 - Scientific Fields and Experimental Techniques 

> Interest of P04 user community: 

• Gas Phase Studies 

m 

m 

• Soft X-ray Scattering 

n 

n 

• Magnetic Spectroscopy 

• High-Resolution Photoelectron Spectroscopy 

• Surface Chemistry 

• Spectro-Microscopy 

Atomic number 

C 

N 

N-shell 

M-shell 

La Ce Pr NdPmSm EuGdTb DyHoErTmYb 

Cs Ba 

L-shell 

Br 

As Se 

Cu Zn Ga Ge 

MnFe Co Ni 

V Cr 

O 

F 

Ne 

Na 

Mg 

Al 

Au Pt 

Kr Rb Sr 

Si P 

K-shell 

Y 

Lu Hf Ta W 

S 

Zr 

Nb 

Cl 

Mo 

Electron binding energy (eV) 


DESY

Variable Polarization XUV Beamline P04 at PETRA III - Layout 

> Plane grating monochromator with Varied Line Space grating 

Top 

z 

x 

y 

SMU PM/PG-U EXSU RMU 

178.4° 

178° 

Sample 

Side 

z 

x y 

undulator 

tunnel wall 

M 1 

M 2 

G VLS1/2/3/4/5 

M 3 M 4 

Switching-Mirrors 

Unit 

plane 

mirror 

apertures 

Collimator 

Plane-Mirror/ 

Plane-Grating Unit 

plane 

mirror 

plane 

VLS grating(s) 

1.2° 

Exit-Slit- 

Unit 

Refocusing- 

Mirrors-Unit 

Plane-elliptic 

Mirror(s) 

178.8° 

Plane-elliptic 

Mirror(s) 

Diagnostic 

Unit 

Sample 

Distance between optical elements [m] 

35 9/11 20/25 7.5 0.6 1.9 

0 35 44/46 64/71 71.5/78.5 72.1/79.1 74/81 

Distance to source [m] 

• As few as possible, only plane(-elliptical) optical elements ⇒ high transmission 


DESY

P04 - Beamline Performance 

30000 

20000 

10000 

Resolving power 

exit slit size: 

"0 µm" 

10 µm 

20 µm 

40 µm 

100 µm 

> Photon energy range: ( Resolving power: >10 4 (up to >3 x 10 4 @1 keV) 

> Photon flux: >10 12 photons/s (up to 5 x 10 12 ) 

> Spot size at sample: 10 x 10 µm 2 / 50 x 50 µm 2 

> Polarization (switching rate): circular, linear hor./vert. (

P04 - Plane Mirror/Plane Grating Unit (PM/PG-U) 

2 high precision rotations 

(pre-mirror/grating in UHV) 

> angular resolution: 

50 nrad (±7° range) 

> new motor concept for 

both "high" accuracy and 

"high" speed (10 eV/s) 


DESY

P04 PM/PG-U Characterization with Autocollimator Elcomat HR 

> DESY is a big building site! 

Performance at the cellar of 

building 25b (courtesy of B. Steffen) 

Elcomat HR: 0.006-0.016" rms 

Noise at P04: 0.01-0.06" rms 

Grating angle (arcsec) 

> 0.02"-steps (100 nrad) quite OK 

(i. e. in specs) 

0.01"-steps (50 nrad) borderline case 

RON 

Elcomat HR 

(avg. of 5) 

~10 meV 

@1 keV 

(1200 l/mm) 

Time (s) 


DESY

P04 - EXit Slit Unit (EXSU) 

> Exit slit unit monochromatizes the radiation diffracted by the grating 

slit height repeatability: 

±100 nm (0-2 mm range) 

free from backlash 

(flexure hinge) 

1429 1429 

movable ±500 mm along optical axis 

(~1µm height accuracy) 

1471,1 

1203,87 

1909 

1238,43 

64 


DESY

P04 - Refocusing Mirrors Unit (RMU) 

> 2 In-air hexapods 

act on 2 pairs of 

KB-mirrors in UHV 

> rigid KB-mirrors for 

2 different 

focal spots 

angular accuracy: 

2 µrad (±0,3° range) 

fine pitch: ~40 nrad 

(350 µrad range) 

translational 

accuracy: 1 µm 

(±45 mm range) 

current test 

shows: 

0.5 µm p-p 

during daytime 

0.2 µm p-p 

during night 

or weekends 

climatization 

is important! 


DESY

Multiple Electron Time-of-Flight Spectrometer Setup 

Photoionization cell 

(online insert-/removable) 

> Online beamline monitor at P04 for: 

• Photon flux (≤1% absolute, ≤0.1% relative) 

Angular resolving electron 

Time-of-Flight-spectrometers 

Differential 

pumping sections 

(on both sides) 

• Beam position (≤1 µm) 

• Photon energy (≤∆E, ≤1/10,000) 

• Degree of polarization (accuracy ≤1%) 

Connection to 

user experiment 

Helium 1s 

reference line 

has: 

β = 2 

Linear horizontally polarized light: 

S 1 = 1.0/0.9/0.8/0.7/0.6/0.5/0.4/0.3/0.2/0.1/0.0 

• Precise reference lines necessary for all hν 


DESY

P04 Optics - How to cope with heat load 

> proposed by R. Reininger et al.: 

"cured" via optimisation of optics 

at exit slit: 

FWHM: 

10 µm 20 µm 500 µm 25 µm 

20 µm 

2 mm 

(c ff -factor). 

at target: 

FWHM: 

ideal 

with 

figure error 

with 

f. e. + 

with 

f. e. + 

"heat bump" "heat bump" + 

c-factor correction 

8x3 µm 2 12x15 µm 2 45x90 µm 2 45x20 µm 2 12x20 µm 2 

> Plane mirror and VLS grating 

form a "zoom" optics (c ff 

-factor). 

Plane mirror 

c ff 

20 µm 

20 µm 

Plane VLS-grating 

Exit slit 


ideal 

with 

figure error 

with 

f. e. + 

with 

f. e. + 

with + + + 

mirror movement 

"heat bump" "heat bump" + 

c-factor correction 

DESY

P04 - Optics Summary 

> Most of the optics have been delivered and they have been surveyed 

at the HZBerlin (BESSY) by Frank Siewert and Jana Buchheim 

item Size Figure Roughness (nm σ) Slope error (arcsec σ) 

(L x W x H, mm) Specs Measured Specs Measured 

M1 400 x 60 x 60 plane 0.5 0.1 0.06 

M2 560 x 60 x 60 plane 0.5 0.05 

FLASH-type, to be 

replaced by intrins. 

lN 2 cooled 

VLS 400 l/mm 

laminar 

G1 145 x 32 x 23 plane 0.5 0.3-0.4 0.05 0.037 

VLS 1200 l/mm 

G2 130 x 32 x 23 plane 0.5 0.5-0.7 0.05 0.024 

laminar 

M3b1 500 x 30 x 60 plane-ellipse 0.5

Problem: Slope Errors of the Grating 

VLS-PGM c ref = 2 (@ 1 keV), 1200 lines/mm 

> High quality of the source 

⇒ slope error is main factor 

for resolving power 

> even "world record" 

slope errors degrade the 

theoretical performance 

> so far 10 grating blanks 

delivered with slope 

errors of 0.024 - 0.06 arcsec 

and a rms-roughness of 

0.1 - 0.2 nm (before coating) 

Resolving power Resolving power Resolving power 

40000 

20000 

40000 

20000 

30000 

20000 

10000 

exit arm 20 m 

(a) no figure errors 

(b) M2/PG 0.03 arcsec (rms) 

(c) M2/PG 0.05 arcsec (rms) 

"0 µm" 

exit slit size: 

10 µm 

20 µm 

40 µm 

100 µm 

25 m 

30 meV 

@ 1 keV 

500 1000 1500 2000 2500 3000 500 1000 1500 2000 2500 3000 




DESY

Improved Raytracing - (More) Realistic Numbers? 

Resolving Power 

50000 

30000 

10000 

"0 µm" 

1200 l/mm 

> Using the NOM results 

10 µm ideal optics 

"realistic" optics for the residual height 

20 µm 

as an input for the 

40 µm 

Shadow raytracing, we 

expect more realistic 

results 

100 µm 

Focus FWHM (µm) 

10 

0 

vertical 0.1 arcsec 

horizontal 0.1 arcsec 

horizontal ideal optics 

vertical ideal optics 

500 1000 1500 2000 2500 3000 


horizontal "realistic" optics 

horizontal ideal optics 

vertical "realistic" optics 

vertical ideal optics 

500 1000 1500 2000 2500 3000 


• For example: 

The raytracing results of the 

"realistic" optics is showing 

focal properties close to the 

0.1 arcsec case while having 

0.2 arcsec slope error. 

This can be explained by the 

fact that the "inner region" of 

the mirror has a much better 

sloper error (0.07 arcsec) 


DESY

P04 Time Table 2012 

> "Test beam" for "friendly users" since March 19, 2012 

> Alignment of the beam into PIPE successful, further beamline tests in parallel. 

> First high quality pre-mirror will arrive July 2012, installation August 2012. 

> Starting end of August, "high" photon energy resolution possible. 

> For July/August two sets of KB-mirrors are scheduled. 

> August/September small focus mode could be available. 


DESY

Summary 

> P04 is a powerful XUV beamline with unique properties (open to users 2012): 

• Very wide photon energy rage: 250-3000 eV 

• High flux with simultaneously high spatial and energy resolution 

• Variable Polarization for different types of dichroism studies 

> Instruments for diagnostics at P04 have been developed. 

• Fixed unit built into the P04 ⇒ ideal for commissioning 

• Transportable unit ⇒ available for collaborations 

Brilliance 

(s -1 mm -2 mrad -2 (0.1%BW) -1 (100mA) -1 ) 

10 20 

10 19 

10 18 

500 1000 1500 2000 2500 3000 


> Many challenges in terms of optics have still to be solved: 

• Mirrors: internally cooled mirrors, lN 2 

cooling, improved KB-mirror schemes, ... 

• Gratings: HZBerlin developments, small blaze angles (

The Variable Polarization XUV beamline P04 at PETRA III ... - IWXM

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