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Overview of Recent Achievements in Crystal Measurements at UA9 Collaboration Meeting

This document summarizes the discussions and findings presented at the UA9 Collaboration meeting held at CERN on November 10, 2009. Key topics include advancements in crystal fabrication and characterization, torsion removal methods, and the performance of H8 and H4 crystals. The use of anisotropic etching to create sub-surface damage-free crystals is highlighted, along with detailed results of on-beam characterizations such as planar channeling efficiency and MVR (Multi-Particle Resonance) in single crystals. The conclusions emphasize the reproducibility in removing torsion and the successful experiments with new materials.

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Overview of Recent Achievements in Crystal Measurements at UA9 Collaboration Meeting

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  1. Review of recently achieved measurements on crystals UA9 Collaboration meeting AndreaMazzolari University of Ferrara and INFN - Italy CERN, 10 Nov 2009

  2. Outlook • Crystal fabrication • Crystal characterization • Torsion removal • H8 Crystals for SPS • H8 New materials and technologies • H8 Crystals for H4 • H4 axial channeling • H4 MVR in a single crystal • Conclusions

  3. Anisotropic etching I Anistropic etching is a feasible way to realize sub-surface damage free crystals entirely by wet chemical methods Etch rate on different silicon planes for KOH 20% at 40 °C

  4. Photolithography a) Starting material: (110) silicon wafer, off-axis: 120 μrad b) LPCVD deposition of silicon nitride thin layer c) Silicon nitride patterning d) Etching of Si in KOH solution, silicon nitride acts as masking layer e) Silicon strips release f) Removal of silicon nitride

  5. Fabrication of multistrips Fabrication of either a multistrip or a batch of strips is possible through wet chemical methods JPD 41, 24 (2008)

  6. Characterization High-quality surfaces achieved via ACE Lateral surface (AFM) Entry surface (HRTEM) <111> Sub-nm roughness was achieved Sub-nm roughness was achieved

  7. On-beam characterization R = 4.5 m R = 2.4 m • ST9 crystal was characterized with 400 GeV protons in the external line H8 and installed in SPS ring • Planar channeling efficiency is very high R = 8.6 m R = 38 m

  8. On-beam characterization • Single-pass efficiency of planar channeling exceeds 75% and 85% with quasi-parallel particles

  9. On-beam characterization • Dependence of VR defection angle and its spread vs. crystal curvature • Comparison with theoretical model PRL 101, 234801 (2008) V. Maisheev Phys. Rev. ST Accel. Beams 10 (2007) 084701

  10. Torsion removal

  11. Torsion removal II

  12. Torsion removal III

  13. H8 – ST 16 for SPS • Thickness: 2 mm • Ch planes: (110), mis-cut: -1500±20 urad • Bending angle: 150 urad, • Ch efficency: about 80% • Torsion: about 1urad/mm

  14. H8 – ST18 for SPS • Thickness: 2 mm • Ch planes: (110), mis-cut: -200±20 urad • Bending angle: 176 urad, • Ch efficency: about 80% • Torsion: about 0.6urad/mm

  15. H8 – QM1 for SPS • Thickness: 0.93 mm • Ch planes: (111), miscut: <300 urad • Bending angle: 130 urad • Ch efficency: to be analyzed • Torsion: to be analyzed

  16. H8 – QM24 for SPS • Thickness: 4.0 mm • Ch planes: (111), miscut: 90 urad • Bending angle: 120 urad • Ch efficency: to be analyzed • Torsion: 5.3 urad/mm

  17. H8 – Si-Ge crystal

  18. H8 – Si-Ge crystal

  19. H8 – QM-Ge crystal

  20. H8 – Lithium Niobate

  21. H8 – Multistrips

  22. H8 – Grooved crystal

  23. H8 – Preparation of stripfor MVR on H4 I • Thickness: 4 mm • Ch planes: (110) • Bending angle: 738 urad • Ch efficency: about 27% • Torsion: about 2.6urad/mm

  24. H8 – Preparation of strip for MVR on H4 II • Thickness: 2 mm • Ch planes: (110) • Bending angle: 670 urad, • Ch efficency: about 31% • Torsion: about 4.3urad/mm

  25. H8 – Preparation of strip for axial ch on H4 I • Thickness: 8 mm • Ch planes: (110) • Bending angle: 178 urad • Ch efficency: about 55% • Torsion: about 4.6urad/mm

  26. H8 – Preparation of strip for axial ch on H4 II • Thickness: 2 mm along the beam • Ch planes: (110) • Bending angle: 105 urad, • Ch efficency: about 65% • Torsion: about 1.8urad/mm

  27. H4 – Axial channeling I • Thickness: 2mm • Ch planes: (110), ch axis: <111> • Bending angle: 105 urad

  28. H4 – Skew planes Main plane Skew plane

  29. H4 – MVR in a single crystal I Under proper axial alignement VR from main and skew planes collapse in MVR in a single crystal

  30. H4 – MVR in a single crystal II • Thickness: 2mm • Ch planes: (110), ch axis: <111> • Bending angle: 738 urad • MVR deflection angle: about 60 urad First observation of MVR in a single crystal with negative particles

  31. Conclusions • Established a reproducible method to remove torsion in strip crystals • Two strip crystals fully characterized and ready for installation in SPS • Started researches on channeling and VR with new materials and technologies • First observation of MVR in a single crystal with negative particles • Succeffully observed planar and axial deflection of negative particles at large bending angles

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