high harmonic generation in a large-volume capillary for seeding of free-electron lasers
DESCRIPTION
High harmonic generation in a large-volume capillary for seeding of free-electron lasers. Siew Jean Goh. Outline. Motivation High Harmonic Generation Setup Result Overview and summary. Why Seed a Free-Electron Laser ?. Shorter FEL Wavelengths ?. - PowerPoint PPT PresentationTRANSCRIPT
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High harmonic generation in a large-volume capillary for seeding of free-electron lasers
Siew Jean Goh
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Motivation
High Harmonic Generation Setup
Result
Overview and summary
Outline
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3E. Allaria et al, Nature Photonics Vol 6, pg 699–704 (2012)
Why Seed a Free-Electron Laser ?
Shorter FEL Wavelengths?
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• Single order pulse energy ~100 nJ
• Seed wavelength range (30-40 nm)
• High pulse energy stability (< 10 %)
• High pointing stability (< 20 % of beam size)
High Harmonic Source for Seeding
0.3 mmSeed Beam
e-Beam15 m
Seeded Operation down to 5-6 nm
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High Harmonic Setup
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Large Capillary (Motivation)
• Assist phase matching with waveguiding
• Selective enhancement via pulse shaping
• Self-phase-modulation & self-compression
• Stabilize beam pointing by waveguiding
• Output scales with volume
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Typical High Harmonic Spectrum
• Drive laser energy = 6.5 mJ, pressure: 4 mbar• Spectrum determined by filter edge,cut-off and phase-matching
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Typical High Harmonic Beam Profile
Excellent spatial quality at 4 - 6mbar
20 shots integrated beam profile
5 mbar
1 mm
•Near gaussian and elliptical
•Energy content
•Center of gravity
•Standard deviation
Beam pointing and divergence
𝐸= ඵ 𝐼ሺ𝑥,𝑦ሻ∞−∞ 𝑑𝑥 𝑑𝑦
Divergence (x-axis)= 2σx / L= 3 mm / 9 m = 0.3 mrad
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High Harmonic Energy
From 20 consecutive measurements of 20 shots integrated beam profile
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Energy Jitter
From 20 consecutive measurements of 20 shots integrated beam profile
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DivergenceL = 9 m
From 20 consecutive measurements of 20 shots integrated beam profile
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Pointing Stability
From 20 consecutive measurements of 20 shots integrated beam profile
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Harmonic Selective Enhancement
• Selective enhancement of 2.5 (at 37 nm)
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Overview of ResultsStandard Capillary 150 m; 1.0 mJ,
53 mbar (Ar)(100 x single shot)
Large Capillary 508 m; 6.5 mJ
6 mbar (Ar)(20 x 20 Shots)
Seed Requirement
FERMI@Elettra
Wavelength 35 nm 32 nm 30 - 40nm
Divergence 1.5 mrad (x)1.6 mrad (y)
0.5 mrad (x)0.4 mrad (y)
< 10%
Pointing Stability
6% (x)17% (y)
11% (x) 9% (y)
< 20%
Energy Jitter 18 % 34 % < 10%
Energy 0.2 nJ 0.6 nJ ~100 nJ
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Output Energy
Possible problems Reabsorption in differential pumping section Absorption in oxide layer on Al filters Absorption in carbon layer deposit on XUV camera
Next steps Reduce gas flow, cleaning, absolute calibration Add amplitude shaping
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Summary
Large-volume capillary (d= 500 m)
Phase matching at 5 - 6 mbar
Selective enhancement (2.5-fold at 37 nm)
Beam pointing stability (~10%)
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Acknowledgements
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Acknowledgement
Thank you for your attention!