Prsentation PowerPoint

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Investigation of OFI seeded soft x-ray lasers
Stéphane SEBBAN J. Ph. Goddet, Ph. Zeitoun, J.
Gauthier and C. Valentin Coherent x-ray group
(SCX) LABORATOIRE DOPTIQUE APPLIQUEE (LOA)
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Collaborators
O. Guilbaud, S. Kazamias, K. Cassou, A. Klisnick,
D. Ros, J. Benredjem, and G. Jamelot LIXAM,
France G Maynard, B. Cros, and A. Boudaa LPGP,
France T. Mocek, M. Kozlova, and K.
Jakubczak Department of X-ray Lasers, Czech
Republic D. Joyeux and S. de Rossi Laboratoire
Charles Fabry de lInstitut dOptique, France
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Coherent XUV sources (3-60 nm)
XRL
VUV-FEL
Harmonics
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There is a large variety of ASE soft x-ray lasers
Laser drivers
Soft x-ray laser output
500 J 600 ps
Up to 10 mJ 100 ps
Less than 100 J 100 ps
Few 100 µJ 20-40 ps
Few J few ps
20-30 µJ 2-5 ps
few 100 mJ 30-50 fs
Up to 1 µJ 5 ps
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ps ASE XRL ehibits an inhomogeneous beam profile
Source micro-sources spatially incoherent and
temporally coherent
O. Guilbaud et al. Europhysics Lett. 74 (2006) 823
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Objective build a soft XRL chain by coupling
harmonics to a soft XRL amplifying plasma?
Oscillator
Imaging optic
Soft x-ray amplifier

• High order harmonics
• Beam quality
• Tunable
• Coherent
• Short duration
• Not costly

XRL laser beam
T. Ditmire et al., Phys. Rev. A 51, 0R4337 (1995)
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The collisional excitation population inversion
scheme is the most robust
Pd-like xenon
Ni-like krypton
Rh-like ground state (4d9)
Co-like ground state (1s22s23p63s23p63d9)
3d95f
4d95f
1P1
1P1
3d94f
4d94f
3d94d
1P1
3D1
1P1
3D1
4d95d
3P1
3D1
65.9 Å
66.3 Å
1S0
1S0
96.3 Å
98.1 Å
99.1 Å
3d94p
3P1
3D1
4d95p
326 Å
3D1
1P1
418 Å
143.6 Å
120.1 Å
76.8 Å
76.3 Å
75.4 Å
1P1
3D1
3P1
1P1
3P1
167.6 Å
117.7 Å
165.3 Å
161.9 Å
115.7 Å
114.9 Å
Ni-like ground state (1s22s23p63s23p63d10)
Pd-like ground state (4d10)
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OFI collisional soft x-ray amplifier principle
? Ionization
? Pumping hot electrons
Xe8 I1.6 1016 W.cm-2 Kr8 I2.3 1016
W.cm-2
Lemoff, B.E., Barty, C.P.J. and Harris, S.E.,
Opt. Lett., 19, 8, 569 (1994)
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Modelling our collisionnal OFI XRL amplifier
B. Cros et al. PRA 73, 033801 2006
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OFI collisional soft x-ray amplifier 2D gain
distribution
Advantages Low density gradient (no
refraction) Longidudinal pumping no TW Circular
aperture Sharp edge filtering of seed possible
Disadvantages Low sat. fluence Lambda 32 nm
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 Salle jaune  laser (LOA)
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Coupling one harmonic to an XRL amplifier set up
20 mJ, 30 fs
Toroidal mirror
HHG cell
Delay line
l/4
1 J, 30 fs
XRL amplifier
Al filter
XRL laser beam
To diagnostics
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Evidence of amplification of the 32.8 nm Kr IX
laser
Wavelength
Ph. Zeitoun at al. Nature, Vol 431, 09/2004, pp.
466
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Amplification factor vs time Plasma density
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Absolute measurement of the gain duration
T. Mocek et al., Phys. Rev. Lett.95, 173902 (2005)
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Far field pattern of the 32.8 nm seeded x-ray
laser
Harmonic seed
Amplified harmonic
Amplification factor from 15 to 600 Divergence
1-2 mrad
Ph. Zeitoun at al. Nature, Vol 431, 09/2004, pp.
466
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The amplification preserves the polarization
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The amplifier can be used as a spatial filter
amplifier

• Possible improvement of
• the spatial coherence
• beam profile (energy distribution)
• wavefront distorsion

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Far field pattern of the 32.8 nm seeded x-ray
laser
HHG
45 mirror (B4CMoSi )
CCD
Al filter
XRL source
SXRL
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Far field pattern of the 32.8 nm seeded x-ray
laser
E0.7 µJ per shot Divergence 0.7 mrad
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Transverse coherence Youngs double slit
experiment
CCD
45 mirror
Double slits (100, 200, 300 µm)
XRL plasma
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High spatial coherence of the seeded soft
XRL (Young slit experiment)
100 µm
200 µm
300 µm
Oscillator
Amplifier
Soft x-ray laser
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Contrast of the fringes pattern (Young slit
experiment)
J. Ph. Goddet et al., Opt. Lett., 32, 1498 (2007)
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Principle of Hartmann wavefront sensor
Hole array
EUV CCD camera
F Dy/L
y
x
z
L
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Hartmann wavefront sensor Calibration setup at 32
nm
Perfect diffracted wavefront
Hartmann pattern
pinhole
diffraction pattern
LOA-Imagine Optic
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Wavefront measurement of the 32.8 nm laser
radiation
First diffraction limited soft x-ray laser
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Reconstruction of the intensity distribution of
the 32.8 nm laser beam at the exit of the
amplifying plasma column
amplifier
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Longitudinal coherence measurement
Wavefront division interferometer
A. Klisnick et al., J.Q.S.R.T 99, 970 (2006)
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Longitudinal coherence measurement
Longitudinal coherence measurement
Coherence time (tc) 5.5 ps Spectral bandwidth
(??) 1.11011 Hz
?? 3.61 mÅ
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Coherence time versus pulse duration
Duration of 5-6 ps
Coherence time fo 5.5 ps
This 32.8 nm seeded laser has reached the Fourier
limit
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Actual performances of the seeded OFI XRL
Wavelength 41.8 and 32.8 nm Photons/shot
11011 at 10 Hz (1 µJ) Dl/l
110-5 Divergence lt1 mrad Spatial profil
gaussian Wavefront l/17 at 32.8 nm Duration
about 5 ps Transverse coherence
Good Longitudinal coherence full Polarization
Yes

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Possible improvements of the system
IR Harm laser
Better coupling
IR OFI laser
Capillary amplifier longer focal length
25 mm
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Guiding techniques for OFI XRL
Hollow capillary tubes
Capillary discharge system
T. Mocek, Phys. Rev. A 71 (2005) 13805 B. Cros,
Phys Rev. A 73 (2006) 033801
Phys. Rev Lett 91 (2003) 205001 Phys. Rev A 70
(2004) 23821
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Calculated distribution of Xe charge states for
a 4 mm cell and a 25 mm capillary tube (Ø 300
µm)
Cell Xe, 20 mbar, I5 1017 cm-3
LASER
Capillary 10 mbar of Xe
LASER
300 µm
25 mm
LOA-LPGP
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Strong lasing action up to 55 mm promising
amplifier
X-ray signal (a.u)
Length (mm)
B. Cros, Phys Rev. A 73 (2006) 033801
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Conclusion
The 32.2 nm seeded SXRL has reach the diffraction
and the Fourier limit. (1 µJ, 1 mrad, coherent,
polarized, 10 Hz) Potential for amplifying
harmonics up to multi 10-µJ by using guiding
techniques or higher density plasma Excellent
scientific tool for applications such as soft
x-ray holography