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Photo desorption studies at the WINDY set-up at LNF

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  1. Photo desorption studies at the WINDY set-up at LNF Marco Angelucci1 R. Kersevan2, P. Chiggiato2, V. Baglin2 and R. Cimino1 1 - LNF-INFN, Frascati, Italy 2 - CERN, Genève, Switzerland FCC-Week 24-28/06/2019 Brussels

  2. Introduction Extreme Low working Pressure (<10-11 mbar) Inside beampipe • Beamscreen (BS) Interacts With: • Photons • Electrons • Ions • Residual Gas Marco Angelucci

  3. Introduction • Effects: • Gas Desorption • Production of Photo Electrons • Seeding SEY end e-Cloud • Single Bunch Instabilities • Surface Modification (Chemistry) • Heat Load • Reflected Photons • BS Interacts With: • Photons • Electrons • Ions Marco Angelucci

  4. Synchrotron Radiation …Induces Heat load Photo electrons and related instabilities Photo induced desorption Studies Reflectivity (where photons interact with BS) Photo Yield (Number of photo-el produced) Photo induced desorption Surface Chemistry Marco Angelucci

  5. DAFNE • High electron Current (1.5 A) • High Photon Flux Injections Marco Angelucci

  6. DAFNE-Light (XUV Lab) SR from Bending Magnet Bending Magnet Collimating Optics XUV Beamlines Collimating Optics near DAFNE ring Distance = 2m High flux collimated Beam in LAB Distance = 20m Marco Angelucci

  7. DAFNE-Light (XUV Lab) ~ 50 mm ~ 10 mm High flux collimated Beam in LAB Distance = 20m Marco Angelucci

  8. DAFNE-Light (XUV Lab) • Variable Photon energy: From 30 to 1000 eV • White and Monochromatic spectra • Small (1 cm2) and Long samples (3 m) • Temperature Range: from 10 K to RT Marco Angelucci

  9. DAFNE-Light (XUV Lab) • Variable Photon energy: From 30 to 1000 eV • Critical energy:LHC 40 eVHE-LHC 400 eVFCC-hh 4000 eV Marco Angelucci

  10. DAFNE-Light (XUV Lab) • Variable Photon energy: From 30 to 1000 eV • White and Monochromatic spectra • Critical energy:LHC 40 eVHE-LHC 400 eVFCC-hh 4000 eV • Low Energy Photons induce: Photo-Desorption and Chemistry Variation • White Light:Irradiation • Monochromatic:Irradiation and Spectroscopic Studies Marco Angelucci

  11. DAFNE-Light (XUV Lab) • Small (1 cm2) and Long samples (3 m) • Temperature Range: from 10 K to RT • Small Sample:Study of surface modification with spectroscopic techniques (XPS, SEY, Thermal Desorption) • Long Sample:Realistic Beam-Pipe • Temperature Range:Studies for Low Temperature parts in Accelerators Marco Angelucci

  12. DAFNE XUV Beamlines XUV 1 (Low Energy) • Small Sample • From 10 K • WL and Monochromatic Light • Range Energy: from 30 to 150 eV XUV 2 (High Energy) • Small Sample • From 10 K • WL and Monochromatic Light • Range Energy: from 60 to 1000 eV WINDY • Long Tube • From Liquid Nitrogen • Wight Light • Range Energy: up to ~200 eV Three different beamlines Marco Angelucci

  13. DAFNE XUV Beamlines XUV 1 (Low Energy) • Small Sample • From 10 K • WL and Monochromatic Light • Range Energy: from 30 to 150 eV XUV 2 (High Energy) • Small Sample • From 10 K • WL and Monochromatic Light • Range Energy: from 60 to 1000 eV WINDY • Long Tube • From Liquid Nitrogen • Wight Light • Range Energy: up to ~200 eV Three different beamlines Marco Angelucci

  14. DAFNE XUV Beamlines (XUV 1) Low Energy (30-150 eV) White light ~ 1 mA on sample (to be optimized) Marco Angelucci

  15. DAFNE XUV Beamlines XUV 1 (Low Energy) • Small Sample • From 10 K • WL and Monochromatic Light • Range Energy: from 30 to 150 eV XUV 2 (High Energy) • Small Sample • From 10 K • WL and Monochromatic Light • Range Energy: from 60 to 1000 eV WINDY • Long Tube • From Liquid Nitrogen • Wight Light • Range Energy: up to ~200 eV Three different beamlines Marco Angelucci

  16. DAFNE XUV Beamlines (XUV 2) High Energy (60-1000 eV) White light >50 mA on sample Marco Angelucci

  17. DAFNE XUV Beamlines (XUV 2) High Energy (60-1000 eV) • Photo Stimulated Desorption (PSD) • Photon Electron Yield (PY) • Surface Modification (Chemistry) (Photo-scrubbing) New LT (10K) manipulator White light >50 mA on sample Marco Angelucci

  18. Photon Interaction (at RT) Preliminary results on PSD from small samples @ LNF/DAFNE Photo Stimulated Desorption Surface Chemistry Changes (Conditioning) Pressure Evolution Photon / Electron Scrubbing comparison Marco Angelucci

  19. Photon Interaction (at RT) Preliminary results from small samples Photon Scrubbing Surface Modifications Photo Yield SEY Strong variation of surface conditions at “low dose” Finale State SEY=1.3 Slow variations at “high doses” Marco Angelucci

  20. Photon Interaction (at RT) Preliminary results from small samples XPS Surface Modifications Modification of Carbon C-1s From sp3 to sp2 XPS Map Scrubbing Area Spot Dimension Same chemical process of Electron Scrubbing Marco Angelucci SEYMax Decreases to?

  21. DAFNE XUV Beamlines XUV 1 (Low Energy) • Small Sample • From 10 K • WL and Monochromatic Light • Range Energy: from 30 to 150 eV XUV 2 (High Energy) • Small Sample • From 10 K • WL and Monochromatic Light • Range Energy: from 60 to 1000 eV WINDY • Long Tube • From Liquid Nitrogen • Wight Light • Range Energy: up to ~200 eV Three different beamlines Marco Angelucci

  22. White Light Line for Desorption Yields • Photon Stimulated Desorption • Easily accessible Long Beam-Pipe sample • Grazing Angles CERN collaboration: K E 3 7 2 4 / T E / H L - L H C - Addendum N o. 4 to Agreement TKN3083 Marco Angelucci

  23. WINDY Low Energy Beamline High Energy Beamline Mirror Chamber WINDYBeamline Collimated Light Marco Angelucci

  24. WINDY Diagnostic Chamber (Gauge, Mass Spec.) End Chamber (Screen, Absorber) Sample (tube up to 3 m) Collimator Chamber (Slits, BPM, Screen) Marco Angelucci

  25. WINDY Low Energy Beamline High Energy Beamline WINDYBeamline Marco Angelucci

  26. WINDY Marco Angelucci

  27. WINDY Collimator Chamber after bakeout Marco Angelucci

  28. Conclusions • We can characterize samples studying different properties: • Photon and Electron Stimulated Desorption • Photon Yield • Secondary Electron Yield • Surface Chemistry (XPS, UPS) • Cross correlated phenomena Marco Angelucci

  29. Conclusions • Study samples as close as possible to the real conditions in Accelerators (Low Temperature and Long Tube) • The data acquired on small samples can be linked to get an overall laboratory description of all phenomena occurring in the accelerator • Study the difference between electron and photon scrubbing process Marco Angelucci

  30. Future Work • Data acquisition with synchrotron radiation will follow the DAFNE proposed calendar • Realization of new Chamber to measure Reflectivity, Photo Desorption and Photon Yield on ~30cm long sample in order to connect the obtained results on Long and Small samples Marco Angelucci

  31. Thank You for Your Attention

  32. WINDY Marco Angelucci

  33. Electron Interaction (surface properties) Electron Scrubbing (with e-gun) (Conditioning) sp3 C-H Surface Modification C-O O-C=O sp2 sp3 SEY Chemistry (XPS) Formation of Carbon sp2 (Graphite like) from sp3 (impurities) • Variation • From d=2.2 • To d=1.05 sp2 sp3 R. Cimino et al. PRL 109 064801 (2012) Marco Angelucci sp2

  34. DAFNE XUV Beamlines (upgrade) Photon interaction studies Room Temperature Cryogenic temperature XUV 2 New Manipulator Marco Angelucci