high purity x-ray polarimetry ingo uschmann b. marx, k. schulze, s. hoefer, r. loetzsch, t....
TRANSCRIPT
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