coherence measurements at p04 petr skopintsev p04 users meeting, 13.06.2014 collaboration between:...

Coherence measurements at P04

Petr SkopintsevP04 Users Meeting, 13.06.2014

Collaboration between:Jens Viefhaus (P04 – Beam line)Axel Rosenhahn (Analytical Chemistry Group, Ruhr-University Bochum)Ivan Vartanyants (Coherent Imaging Group)

DESY, Hamburg, Germany

NRC “Kurchatov Institute”, Moscow, Russia

Petr Skopintsev | Coherence measurements at P04 | 13.06.2014 |

Outline

>Theory of spatial coherence measurements

>First P04 experiment Comparison of NRAs and Double Pinholes

>Second P04 experiment Additional investigation with NRAs

>Summary


Spatial coherence

Intensity Сoherence Factor

Degree of spatial coherence

𝟎≤𝜁 ≤𝟏Incoherentfield

Coherentfield

𝐼 (𝒓 )=Г (𝒓 ,𝒓 ) 𝛾 (𝒓 𝟏 ,𝒓𝟐 )=Г (𝒓𝟏 ,𝒓 𝟐)

√𝐼 (𝒓𝟏 ) 𝐼 (𝒓 𝟐 )


Young’s Experiment

Fourier transform of I(q)

𝐼 (𝑞 )=𝐼 𝐴 (𝑞) (𝟏+¿𝛾12∨𝐜𝐨𝐬 (𝒒 ∙𝒅+𝛼12))

~𝐼 (𝑥)=𝑻 (𝒙 )+¿𝛾12∨

¿2

[𝑒𝑖𝛼12𝑻 (𝒙−𝒅 )+¿+𝑒− 𝑖𝛼12𝑻 (𝒙−𝒅 ) ] ¿

Double pinholes diffractionintensity distribution I(q)

IncoherentCoherentPart. coherent

, , ,



Modulus of complex degree of spatial coherence is a function of distance between slits:

|

J.W. Goodman, Statistical optics

Δx-Δx Δx

𝐶0=𝐼 1+ 𝐼2

𝛾12



Modulus of complex degree of spatial coherence is a function of distance between slits:

|

J.W. Goodman, Statistical optics

Δx-Δx Δx

𝐶0=𝐼 1+ 𝐼2

𝛾12

𝒍𝒄


10 points10 peaks

𝐶𝑖𝑗=¿𝛾 𝑖𝑗∨√ 𝐼𝑖 𝐼 𝑗

, 1 experiment with 5 slits =

10 experiments with 2 slits

Non-Redundant Array of Slits


P04 beamline (PETRA III) experiment

Undulator tuned to400 eVA

B Exit slit openings: 40 µm and 230 µm

* Vacuum chamber constructed by Hans Peter Oepen group (Hamburg University)


Data: Typical Intensity Scans

NRA

Double pinholes

Detector plane Fourier Transform

NRA



NRA

Double pinholes


NRA

400 eV

800 eV

800 eV

400 eV

Second harmonics(monochromator)

R

2R

2R

R



NRA

Double pinholes


NRA

400 eV

800 eV

800 eV

400 eV

Second harmonics(monochromator)


Data: Typical Intensity ScansN

RA

Do

ub

le

pin

ho

les



Data: Beam Profile Scans

FWHM=42± 2 µm

µmµm

FWHM=11± 1 µm

Exit slit 230 µmExit slit 40 µm

• Performed on double pinholes separated by 15 µm• FWHM found with double Gauss functions fits


Results: NRA & D.P. are identical

Exit Slit width 40 µm Exit Slit width 230 µm

Double pinholes data pointsNRA data pointsE = 400 eV


P04 beamline experiment

C Exit slit cut out 396.5, 400 and 403 eV fraction of the beam

Beam defining slit opening variedD

* Vacuum chamber constructed by Hans Peter Oepen group (Hamburg University)


Beam defining slit variation

Exit Slit width 230 µmE = 396.5 eV, 400 eV, 403 eV

𝜻=𝟎 .𝟎𝟓÷𝟎 .𝟖 𝜻=𝟎 .𝟏𝟐÷𝟎 .𝟏𝟒 𝜻=𝟎 .𝟐𝟒÷𝟎 .𝟐𝟓

Features of coherence dependence on beam defining slit opening observed


Second experiment at P04

Aim – measure spatial coherence prior to ptychography experiment


Second experiment at P04

1. 50 μm2. 100 μm3. 200 μm

500 eVa. Horizontalb. Vertical

NRA orientationExit slit openingUndulator energy

* HORST chamber constructed by Axel Rosenhahn group (Ruhr-University Bochum)


P04 diffraction patterns

Typical diffraction image Fourier transform

Area for further analysis


P04 Vertical coherence

Exit slit:

Bea

m

prof

ileC

oher

ence

FWHM = 29.5 μmFWHM = 12.6 μmFWHM = 7 μm

lc = 4.2 μm

lc = 2.4 μm

lc = 7.5 μm ζ = 0.37

50 μm 100 μm 200 μm

ζ = 0.10ζ = 0.73


P04 Horizontal coherence

FWHM estimated as 100 μm

lc = 12.4 μm

lc = 12.4 μm lc = 12.5 μm ζ = 0.14 ζ = 0.14ζ = 0.15C

oher

ence

Exit slit: 50 μm 100 μm 200 μm


PETRA III vs BESSY II


Conclusions

1. NRA allows to measure full spatial coherence function in one exposure

2. Results with NRAs and double pinholes are identical

3. NRA method works especially well with large beams

4. This approach can be effectively used prior to any

coherent imaging experiment

5. May be useful for measuring single pulse coherence

properties of FELs


Thanks to

Thank you for your attention!

DESY:A. SingerO.Y. GorobtsovD. DzhigaevA. ShabalinO.M. YefanovM. RoseR.P. KurtaI.A. Vartanyants

Bochum:T. Senkbeil A. Buck T. Gorniak A. Rosenhahn

Uni. Hamburg:J. BachB. BeyersdorffR. FrömterH.P. Oepen

DESY:L. Glaser

L. MüllerS. SchleitzerG. Grübel

SLAC:A. SakdinawatJ. Viefhaus


S1. Temporal coherence

𝐸∆𝐸

≈ 1000

𝑙𝑡 ≈ λ𝐸

∆𝐸=3.1𝜇𝑚

15𝜇𝑚

𝟖𝟎𝒄𝒎

𝟔𝟐𝒎𝒎


S2. Two-dimensional NRA

Image taken from Gonzalez, A. I. & Meja, Y. (2011). J. Opt. Soc. Am. A, 28(6), 1107-1113


S3. Non-uniformity of coherence

0 7.5 15-15 -7.5

0

7.5

15

-15

-7.5

15-15 0 7.5-7.5𝑟1

𝑟2

𝑟1

Г (𝒓 𝟏 ,𝒓𝟐 )


S3. Non-uniformity of coherence

0 7.5 15-15 -7.5

0

7.5

15

-15

-7.5

50 μm

100 μm

200 μm𝑟1

𝑟2Г (𝒓 𝟏 ,𝒓𝟐 )


S4. More data on coherence

400 eV396.5 eV 403 eV

𝑫𝒆𝒔=4.7 mm

𝜻=𝟎 .𝟎𝟓÷𝟎 .𝟖 𝜻=𝟎 .𝟏𝟐÷𝟎 .𝟏𝟒 𝜻=𝟎 .𝟐𝟒÷𝟎 .𝟐𝟓

𝑫𝒆𝒔=1 .7 mm 𝑫𝒆𝒔=0 . 8 mmEnergy:

coherence measurements at p04 petr skopintsev p04 users meeting, 13.06.2014 collaboration between:...

Documents

slit variationexit slit

mexit slit width

identicalexit slit width

slit opening variedd

experiment undulator

points10 peaks1 experiment

ev fraction

beam profile scans