High purity x-ray polarimetry

Ingo Uschmann

B. Marx, K. Schulze, S. Hoefer, R. Loetzsch, T. Kämpfer, O. Wehrhan, H. Marschner, E. Förster, M. Kaluza, H. Gies, G. Paulus, T. Stöhlker

Helmholtz-Institut Jena, Helmholtzweg 5, Institut für Optik und Quantenelektronik, Friedrich-Schiller-

Universität, 07743 Jena C. Detlefs, T. Roth, J. Härtwig, ESRFR. Röhlsberger, H.C. Wille, K. Schlage, DESY -PETRA IIIW. Wagner, FZD Dresden

Petawatt-Lasers at Hard X-ray Light Sources, Dresden, 08.09.2011

Content

1.History and Motivation2.Method and Realization3.Experimental Results4.Summary and Outlook

First polarization experiment with x-rays

1906J. BarklaX-ray scattering1917 Nobel prize

First observation of optical activity in the x-ray range

1981

0.8 kW X-ray tubeCu KPresicion of 5 arcmin (1.4 mrad)after 24 hours accumulation

M. Hart, A.R.D. Rodrigues, 1981

Faraday effect in the x-ray range

1991Source synchrotron:Divergence: 200 µradError of rotation: 2.10-4 radSensitivity: 70 µradPolarization ratio: 2 x 10-6

M. Hart P. Siddons et al., RSI, 1991

X-ray polarimetry at Synchrotrons is today a standard method for study of magnetic Materials and resonant nuclear scattering

1997 R. Roehlsberger, T. Toellner, polarization purity of ~4x10-8

Motivation of further development of x-ray

polarizers Observation of vacuum birefringence

At photon energies small compared to the electron mass electrons and positrons will not generally produced as real particles.But: Euler and Heisenberg: „ … even in situations where the photon energy is not sufficient for matter production, its virtual possibility will result in a ´polarization of vacuum´ and hence in an alteration of Maxwell´s equations“ 1936

T. Heinzl et al. 2006

Strong electric field induced phase shift of a electromagnetic wave in birefrigent vacuum:

= 4/15 z0/ Io/Ic k , for I0=1022 W/cm2 and = 1 A … ellipticity ~ ()2~10-11

- Sommerfelds fine structure constantz0 interaction length - wavelengthIo –electric laser fieldIc = 1.3 x 1018 V/m critical field for pair production in constant electric field

Proposed QED-experiment with high Power Laser

This challenging experiment consist of three subprojects1- development of X-ray polarimetry2- development of the X-ray source3- development of the Petawatt laser

Basics for x-ray polarizerdynamical theory of x-ray diffraction with perfect crystals

Ewalds sphere for the two beam case

K0

KhG

Polarisation state depends on the scattering angle 2Integrated reflectivityRi

~ 1 for - polarizationRi

~ cos (2) for – polarization

Ko incident beamKh diffracted beamG reciprocal lattice vector Bragg angle

Reflection curves for sigma- and pi- component at 10° Bragg angle

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0 Bragg angle 10°, Si 111, =1.08 A sigma - polarization pi - polarization

I / I 0

B / arcsec

B

Reflection curves for sigma- and pi- component at 47° Bragg angle

-2 0 2 4 6 8 10 12

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0 Bragg angle 47°, Si 333, =1.54 A sigma - polarization pi - polarization

I / I 0

B / arcsec

B

Generation of linear polarization state of x-rays

1. X-ray diffraction of x-rays at an Bragg angle close to 45°2. Borrmann effect in the transmission case

germanium 220, thickness t=1 mm, Cu K

Normal absorption µt = 34.17, exp(-µt)=1.5x10-15

sigma µe=1.3, exp(-µe

t)=0.272

pi µe=11.9, exp(-µe

t)=6.5x10-6

3. Channel cut by using multiple reflection4. Using transmitted x-rays of a collimated X-ray beam, Bragg reflected by

a crystal

Energy dependent rocking curves for Bragg angles at 45°,only sigma component

-20 -10 0 10 20 30 40 50 60 70 80 90 100 110

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

kinematical Bragg angle rocking curves for linear polarizersat photon energies: = 45°

Si 111: 2.8 keV Si 333: 8.0 keV Si 555: 14 keV

I / I

-B / arcsec

B

Linear polarization by Bragg reflection close to B=45°

Integrated reflectivityRi

~ 1n for - polarization

Ri~ cos n (2) for – polarization

0 2 4 6 8 10 12

1E-4

1E-3

0.01

0.1

1

polarization purityintegral_pi/integral_sigma

0.03 0.0049 0.00012

Si 333, Cu K, Bragg angle 47,3 °

pi polarization 1 reflection 2 reflection 4 reflection

sigma polarization 1 reflection 2 reflection 4 reflection

I / I 0

B / arcsec

n=1

n=2

n=4

n-number of bounces

-200 -150 -100 -50 0 50 100 150 2000.00001

0.0001

0.001

0.01

0.1

1

400 reflection, Fe K bounces

4 theor. R=1,39E-5 4 No. 1 R=1,35E-5

6 theor. R=1,08E-5 6 No. 1 R=1,00E-5

8 theor. R=8,62E-6 8 No. 1 R=7,66E-6

I/I0

["]

Efficiencies of 4-, 6-,and 8- bounces channel-cut crystals

High purity x-ray polarimetry

44,88 44,96 45,04 45,121E-19

1E-16

1E-13

1E-10

1E-7

1E-4

0,11 crystal reflection

1 mrad

0.1 mrad

1 mrad

10 mrad

X-ray beam divergence:

4 crystal reflections

po

lari

zatio

n p

uri

ty

Bragg angle / deg

Best value before: 4x10-8 , at 14.4 keV and a Bragg angle of 45.1°, R.Roehlsberger et al., NIM 1997

1. Simulation of multiple diffraction, which disturbs the polarisation degree.

K0

Kh

G

Crystal Crystal

K0G1

Kh

KhG2

2. Simulation of multiple diffraction, which disturbs the polarisation degree.

Additional reflection Umweganregung

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

Nebenreflexe bei FeK ( = 0.19nm , Haupreflex = 400)

001

010

1. Simulation of multiple diffraction, which disturbs the polarisation degree.

It can be suppressed by well selected and precise crystal orientation.

All reflection calculated: Silicon crystal, =0.19 nm, 6.9 keV 400 reflection used

1. Simulation of multiple diffraction, which disturbs the polarisation degree.

All reflection calculated: silicon crystal, =0.055 nm, 22 keV, 888 reflection used

The first Jena X-ray polarimeter

X-ray sourceUndulator

x-ray polarizer4 reflection channel cut

ionization chamber

tunable x-ray analyzer

x-ray detector

4 reflection channel cut

The first Jena X-ray polarimeter

Jena, summer 2009

Si 333 reflection,Cu K, B= 47.43°,4 symmetric reflection at each channel cut,Time for the 90° curve took 3 days.

Rocking curves for different analyzer positions

Determined purity: 3.9x10-4, Limitation by X-ray tube (Brilliance and Bragg angle)

First polarization purity measurement – X-ray tube

Brilliance of present x-ray sources

Undulator parameters:1013….1014 photons/s/eVSource size: 30 µm x 300 µmDivergence: 42 µrad, 16.9 µrad

Authier, Dynamical theory of x-ray diffraction

X-ray hutchStorage ring

Experimental campaign at ID 06 at ESRF: 1.-7. December 2009

Undulator radiation: Alternative two undulators are available for 3…10 keV and 10 keV … (30 keV):

Highest photon flux is available at 10 keV (second undulator): ~1015 photons/s

Energy band width: ~ 10 eVPolarisation degree: > 99%, horizontal rms e--divergence: 10.3 µrad

Photons after the Silicon 111 monochromator (band width ~1 eV): ~1014 photons/sPhotons after the first polarizer: ~1012 photons/sPhotons after the second polarizer (parallel position): ~1010 photons/s

Experimental campaign at ID 06 at ESRF - Polarizer

Experimental campaign at ID 06 at ESRF - Analyzer

Rocking curves at parallel - and cross position

ESRF winter 2009

B. Marx et al., Opt. Commun., 284 (2011), pp. 915

Polarization purity measured at 6457 eV, Si 400

4 reflection channel cut

B. Marx et al., Opt. Commun., 284 (2011), pp. 915

Polarization purity measured at different photon energies

Si 444 Eph=11183 eV Si 800 Eph=12914 eV

B. Marx et al., Opt. Commun., 284 (2011), pp. 915

Polarization purity measured at different crystal azimuth

Si 800 Eph=12914 eV

Application: phase variation of x-rays by diffraction

0 1 2 3 4 50.01

0.1

1

10

100

1000

10000

100000

1000000

001 orientation, 200 µm thickness 94.5% absorption for 6457 eV photons

transmission at cross position without quartz

transmission at cross position considering absorption of quartz

quartz crystal between polarizer and analyzer azimut 1° angle azimut 0° angle

tra

nsm

issi

on

thro

ug

h p

ola

rim

ete

r

rotation angle of quartz crystal / deg

High Purity X-ray Polarimetry

-90.01 -90.00 -89.99

10000,9 arcsec shift

without sucrose solution with sucrose solution

accumulation of 11 measurements

cps

angle of analyzer [°]

Sensitive phase determination by the X-ray polarimeter

ESRF Sept. 2010

0 20 40 60 80 100

0.001

0.01

0.1

1

rel.

inte

nsi

ty d

iffra

cte

d b

y th

e a

na

lyze

r

analyzer angle / deg

Experimental campaign at ID 01 at PETRA III: August 2011

Polarization purity of the undulator at ID01: 4.4x10-4

Beam diameter 3 mm x 3 mm

Summary

-We measured a polarization purity of

-The detection of ellipticity of the order of 10-11 becomes possible-for Laser pump-X-ray probe the synchrotron of third generation has to long pulses and high repetition rate-alternative source – x-ray laser

-The polarisation purity can still be improved by more sophisticated methods1. tilted channel cuts2. asymmetric reflection3. suppression of multiple reflections and thermal diffuse scattering

crystals with lower Z, diamondcrystal cooling

-The new extremly sensitive method, presently not existing will be able to detect newly weak polarisation effects in the x-ray regime Cotton-Mouton effect Fararday effect

2.4 x 10-10 at 6457 eV6.2 x 10-10 at 12913 eV

Outlook

1. Experiments at LCLS: next step to the QED experiment:

Synchrotron: 350 MHz repetition, 30000 photons per pulse, pulse duration: 100 ps

LCLS: 10 Hz repetition, 1012 photons per pulse, pulse duration: 70 fs

weak effects becomes visible in single x-ray pulses!!!

??? Nonlinear effects might destroy the purity???

2. High purity polarimeter as optical shutter similar to optical polarimeter by using fast

processes, i.e. optical phonons or piezzo effect

3. Optical pump laser: 1. high intensity, pulse duration ~ like XFEL 2. small focus size 1…3 µm,

3. high temporal average of energy, rep. rate like XFEL