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Quasimosaic crystals

Quasimosaic crystals. Yu.M.Ivanov. Elastic quasimosaic (Sumbaev) effect. Studied by Sumbaev in 1957 Resulted in broadening of gamma-ray diffraction peaks from bent quartz plates

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Quasimosaic crystals

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  1. Quasimosaic crystals Yu.M.Ivanov

  2. Elastic quasimosaic (Sumbaev) effect • Studied by Sumbaev in 1957 • Resulted in broadening of gamma-ray diffraction peaks from bent quartz plates • Caused by bending of the reflecting atomic planes (initially flat and normal to large faces of plate) due to crystal anisotropy • Depends on choice of crystallographic plane and orientation angle of plate cutting relative to a normal to the chosen crystallographic plane Figure from article: O.I.Sumbaev, Reflection of gamma-rays from bent quartz plates, Sov. JETP 32(1957)1276

  3. Quasimosaic effect in silicon • Calculations of deformed crystal plate done by V.M.Samsonov (Preprint No. 278, LIYaF AN SSSR, 1976). • Resulted in predictions of elastic quasimosaic effect for some other quartz and silicon plate orientations • Large elastic quasimosaicity for (011) plane of silicon predicted • Zero result in the first experiments in 1999 • New calculations using Samsonov approach and new measurements: - (111) plane, not (011) - published in JETP Letters 81, 99, 2005 Figure from article: V.M.Samsonov and E.G.Lapin, On some possibilities and pequliarities of a curved crystal use in crystal diffraction instruments, Preprint No. 587, LIYaF AN SSSR, 1980

  4. Elastic quasimosaic in dependence on cut angle for Si (111) plane Plate bending radius R = 1 m Dq= 2k9 T , where T – thickness of plate k9 – deformation coefficient ( formula taken from V.M.Samsonov, E.G.Lapin, Preprint No. 587, LIYaF AN SSSR, 1980 )

  5. Silicon cuts Oriented ingot Cut without quasimosaic φ Cut with quasimosaic

  6. Quasimosaic effectin Si with X-rays Rocking curves for Si plate with quasimosaic before and after bending. Rocking curves for Si plate without quasimosaicbefore and after bending.

  7. Shape of bent Si plate with elastic quasimosaic

  8. Bending device

  9. First quasimosaic silicon crystal prepared in 2002 for channeling experiment with 70 GeV protons

  10. 70 GeV p-beam Crystal 1 Magnets Collimator 5 m Crystal 2 S1 R=3 m 30 m Emulsion 1 Emulsion 2 S2 S3 Channeled_2 Channeled_1 35 m 4.6 m 1.3 m Background Layout of experiment at IHEP in April, 2002

  11. Profile of 70 GeV proton beampassed through the crystal measured with emulsion: superposition of channeling and volume reflection effects

  12. Explanation of the observed picture on emulsions Proton trajectories crossing the crystal and emulsions in horizontal plane (top view)

  13. Samples 0.3 mm and 2.7 mm with ~0.4 mrad bending angle

  14. Sample 10 mm with ~100 μrad bending angle

  15. Crystals for experiment on extraction of high entensive proton beam at IHEP Plane (111) Length along beam 2.65 mm Bending angle 400 μrad

  16. Crystal station at IHEP ring

  17. Crystal mounted on station

  18. Result Beam in the U-70 ring 5.5∙1012p Intensity of extracted beam 4.0∙1012 p Efficiency 70%

  19. Experiment on observation of volume reflection effect with 1 GeV protonsat PNPI, Gatchina Beam divergence ~ 160 μrad Beam size ~ 0.8 mm Critical angle for channeling ~ 170 μrad Crystal length along beam ~ 30 μm Bend angle of (111) planes ~ 380 μrad

  20. One of unsuccessful attempts to bend a 30 μm crystal on 20 mm radius

  21. Bent crystals in bending devices

  22. Check of crystal shape with laser ~1m

  23. Measurement of bending angle with X-rays

  24. Collimator Crystal mounted on goniometer

  25. Horizontal profiles of the p-beam vs. crystal angle measured with PPC p-beam channeling Crystal angle, step 62.5 μrad reflection p-beam Channel number, step 200mm

  26. Channeling experiment with 400 GeV protons CRYSTAL area FAR_DETECTOR area H8 beam line

  27. QM2

  28. QM2

  29. QM2 Channeling angle (68.2  0.4) μrad Volume reflection deflection (12.7  0.6) μrad Volume capture ε (1.8  0.7) %

  30. QM1

  31. QM1

  32. QM1 Channeling angle (77.0  0.4) μrad Volume reflection deflection (11.6  0.8) μrad Volume capture ε (2.6  0.8) %

  33. QM2+QM1

  34. QM2+QM1

  35. QM2+QM1 Channeling angle Volume reflection deflection (23.4  0.7) μrad Volume capture ε (5  1) %

  36. QM3

  37. QM3

  38. QM3 Channeling angle (72.7  0.8) μrad Volume reflection deflection (11.9  0.7) μrad Volume capture ε (5  1) %

  39. QM4

  40. QM4

  41. QM4 Channeling angle (120.0  0.4) μrad Volume reflection deflection (12.7  0.5) μrad Volume capture ε (4.4  0.7) %

  42. Design: sequence of quasimosaic crystals cut from a single initial plate p 1 Si plate 0.3 x 30 x 60 mm3 12 Si plates 0.3 x 8 x 14 mm3

  43. Check of plate wedging with optical goniometer

  44. Prototype assembly from 5 plates

  45. Check with narrow X-ray beam Δθ N1 N2 ΔX N, counts ΔN=N2-N1 ΔN Δθ≈0.017x ΔN μrad ΔX Δθ < 40 μrad X, mm

  46. Need to provide or to compensate plate wedging

  47. Realization with evaporation technique Al-layer of 0.14 μm thickness Δθ = 0.14 μm / 12 mm = 12 μrad

  48. Further steps • to improve prototype assemly for experimental run in May’07 at CERN • to prepare larger plates and assemble them for experiments at CERN and IHEP in the Fall’07

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