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High harmonic generation in a large-volume capillary for seeding of free-electron lasers

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 ?.

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High harmonic generation in a large-volume capillary for seeding of free-electron lasers

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  1. High harmonic generation in a large-volume capillary for seeding of free-electron lasers Siew Jean Goh

  2. Outline • Motivation • High Harmonic Generation Setup • Result • Overview and summary

  3. Why Seed a Free-Electron Laser ? Shorter FEL Wavelengths? E. Allaria et al, Nature Photonics Vol 6, pg 699–704 (2012)

  4. 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 Seed Beam 0.3 mm e-Beam 15 m Seeded Operation down to 5-6 nm

  5. High Harmonic Setup

  6. 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

  7. Typical High Harmonic Spectrum • Drive laser energy = 6.5 mJ, pressure: 4 mbar • Spectrum determined by filter edge,cut-off and phase-matching

  8. Typical High Harmonic Beam Profile • Neargaussianandelliptical • Energy content • Center of gravity • Standard deviation •  Beam pointinganddivergence 20 shots integrated beam profile 5 mbar 1 mm Divergence (x-axis) = 2σx / L = 3 mm / 9 m = 0.3 mrad • Excellent spatialquality at 4 - 6mbar

  9. High Harmonic Energy From 20 consecutive measurements of 20 shots integrated beam profile

  10. Energy Jitter From 20 consecutive measurements of 20 shots integrated beam profile

  11. Divergence L = 9 m From 20 consecutive measurements of 20 shots integrated beam profile

  12. Pointing Stability From 20 consecutive measurements of 20 shots integrated beam profile

  13. Harmonic Selective Enhancement • Selective enhancement of 2.5 (at 37 nm)

  14. Overview of Results

  15. 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

  16. Summary • Large-volume capillary (d= 500 mm) • Phase matching at 5 - 6 mbar • Selective enhancement (2.5-fold at 37 nm) • Beam pointing stability (~10%)

  17. Acknowledgements Acknowledgement Thank you for your attention! 17

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