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Quartz preparation (quality check and prototype status)

Quartz preparation (quality check and prototype status). BPAC, 12th Nov. 2011. Y. Horii (Nagoya University). Introduction. The quartz bars must transmit Cherenkov photons over long optical length with a number of internal reflections . In this talk, we show

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Quartz preparation (quality check and prototype status)

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  1. Quartz preparation(quality check and prototype status) BPAC, 12th Nov. 2011 Y. Horii (Nagoya University)

  2. Introduction • The quartz bars must transmit Cherenkov photons over long optical length with a number of internal reflections. • In this talk, we show • optical qualities of the bars and • status of preparing prototype for the beam test. Examples of photon paths inprototype for beam test in 2010.

  3. Quality check

  4. Optical properties • Number of photons • Resolution of Cherenkov angle naively depends on square root of number of photons. • Require to retain 80% after bulk transmittance andreflections. • Photon-path shifts • Resolution of Cherenkov angledepends on photon-path shifts. • Require the shift to be < 0.5 mradafter reflectionsand by striae.

  5. Quartz bars Suprasil-P710 polished by Okamoto Co. Corning 7980 0Dpolished by Zygo Co. 131 x 45 x 2 cm2 120 x 45 x 2 cm2 Highest striaegradein MIL-G-174 standard Highest striaegradein ISO 10110-4 standard Better flatness Better squareness in general

  6. Equipments for checking quality of bars Laser: Wavelength = 405 nm(typical for TOP). Prism splitter and reference PDto calibrate fluctuations. Position adjustable on motorizedstages with a precision of O(mm). CCD: 4.4 x 4.4 mm2/pixel. 1600 x 1200 pixels. Position adjustable onmotorized stages witha precision of O(mm). Photodiode: efficiency stable forat least 6x 6 mm2.

  7. Bulk transmittance Requirement: > 98%/m. Bulk transmittance tobtained using intensities I0 and I1 measured by PD and reflectances R0 and R1 calculated. y z x 7 x 5 incident points. Suprasil-P710: Ave. = 99.44%/m Max. = 99.57%/m Min. = 99.27%/m Corning 7980 0D: Ave. = 99.35%/m Max. = 99.50%/m Min. = 99.25%/m (Error of individual measurement: ±0.17%/m.) For both bars, enough bulk transmittance for all incident points.

  8. Internal surface reflectance Requirement: > 99.90%. • Measure the reflectance for several angles of reflections in 56-70°. • For both bars, enough reflectance for interested angles. y z Surface reflectance aobtained using intensities I0 and I1 measured by PD,reflectances R0 and R1 calculated,and the exponential of bulk transmittance. N: number of bouncesL/b: length/thickness of bar L: coefficient of bulk transmittance Suprasil-P710: Max. = 99.98% Min. = 99.92% Corning 7980 0D: Max. = 99.97% Min. = 99.92% (Error: ±0.02%.)

  9. Possible effect of striae • Data taken by CCD. • Bitmap (histogram) fitted with 2-D Gauss + 2-D linear. • Scan the positions of laser/CCD simultaneously in y direction. y z Scan. y x Means and widths of 2-D Gauss in interest.

  10. Possible effect of striae Requirement: path shift < 0.5 mrad. Mean in y direction most significantly fluctuates for both bars. Suprasil-P710 polished by Okamoto Corning 7980 0D polished by Zygo y > 20 mm:laser through air. Displacement btwy < 20 and > 20 mm:due to deviation ofincident angle from 0. Path shift within ±0.15 mrad Path shift within ±0.33 mrad These path shifts can be explained by surface non-flatness. Effects of striae smaller.

  11. Possible effect of striae • Other checks: • No larger path shifts for other x positions. • No larger path shifts for another incident angle of 30°. • No larger path shifts for scan of laser/CCD in x direction. • Finer scan for estimating finer periodic structure of striae: Larger variation for y width.But still can be explainedby surface non-flatness.No significant effect for PID.

  12. Glue the bars/mirror

  13. Strategy of the gluing • Put the Okamoto bar downstream of photon path since squareness of Okamoto bar is worse. • Use glue of NOA63 for bar-bar joint (higher viscosity). • Use glue of NBA107 for mirror (temporary since mirror is smaller).

  14. Jig for gluing

  15. Control of angles and positions • Relative angle of bars • Adjust using micrometerheads. • Measure using autocollimator. • Relative position of bars • Adjust using polyacetal headsand plungers. • Measure using laser sensor. Precision = ±0.01 mrad, requirement = ±0.2 mrad. Precision = ±5 mm, requirement = ±100 mm.

  16. Gluing Glue goes down. Takes ~1 hour. Put glue using dispenser (head is soft). Cured by UV light. Takes <5 hours.

  17. Check after the gluing • Quartz-quartz joint • No significant bubbles are seen. • Angles and displacements satisfy the requirements. • Angles of S4/C and S1/E = 0.03 and 0.10 mrad, respectively. • Displacements at S4/C, S3/D, and S1/E = 90, 60, and 40 mm, respectively. • Quartz-mirror joint • Small amount of bubbles (photon loss < 0.1%). • Angles and displacements satisfy the requirements. • Angle = 0.03 mrad. • Displacement = 50 mm. Requirement for angle: 0.2 mrad. Requirement for displacement: 100 mm.

  18. Summary • Optical qualities checked. • Bulk transmittance, surface reflectance, and effect of striaefortwo bars of Suprasil-P710/Okamoto and Corning 7980 0D/Zygo. • All results satisfy the requirements. • Glue of bars and mirror. • Prototype ready for beam test in Dec. 2011. • Method of glue ready for productions for Belle II.

  19. Backup slides

  20. Quartz bars Suprasil-P710 polished by Okamoto Co. Corning 7980 0D polished by Zygo Co.

  21. Laser Photodiode CCD

  22. Bulk transmittance Suprasil-P710 Corning 7980 0D

  23. Internal surface reflectance Requirement: > 99.90%.

  24. Roughness • Roughness and reflectance are related by a scalar scattering theory: d: RMS of roughness q: angle of reflectance l: wavelength of laser Okamoto bar:d = (12 ± 4) Å Zygo bar:d = (17 ± 4) Å

  25. Possible effect of striae Requirement: path shift < 0.5 mrad. Suprasil-P710 polished by Okamoto Corning 7980 0Dpolished by Zygo Results corresponds to path shift < 0.3 mrad. Can be explained by surface non-flatness.

  26. Surface non-flatness and path shifts y measured by Zygo blue z green S6 S5 Quartz Laser CCD 0.1-0.3mrad shift can be generated.

  27. Quality check of the mirror • In addition to the bars, we do several checks for the mirror. Bulk transmittance Reflectance at quartz-Al Result = (99.20 ± 0.38)% Result = (88.5 ± 0.2)% Safely large. Will require better value for TOP.

  28. Jig for gluing Micrometers Quartz bar (Placed on polyacetal balls.) Vinyl chloride plate (Placed for avoiding quartz-Al contact.) Upper Al plate (Position adjustable using micrometers.)(Surface flatness < 100 mm.) Lower Al plate Rails. (Position adjustable on the rails.)

  29. Lower Al plate Overall configuration (one bar) Upper Al plateand micrometer-head

  30. Polyacetal head to adjustthe position of the bar. Bar, polyacetal balls, and plastic plate. Plunger to keepthe position of the bar.

  31. Flatness of the bars • Flatness of the bars after adjusting the angles and positions is measured by using autocollimator. • The flatness is safely nice for the gluing. Suprasil-P710 Corning 7980

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