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

Introduction 2  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 in prototype for beam test in 2010.

3 Quality check

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

Quartz bars 5 Suprasil-P710 polished by Okamoto Co.Corning D polished by Zygo Co. 131 x 45 x 2 cm x 45 x 2 cm 2 Highest striae grade in MIL-G-174 standard Highest striae grade in ISO standard SpecificationActualRequir e Roughness (nm rms) Squareness (arc min.) Flatness S6, S5 (  m) 2.0, Flatness S4, S3 (  m) 0.8, Flatness S1, S2 (  m) 4.9, SpecificationActualRequir e Roughness (nm rms) Squareness (arc min.) Flatness A, B (  m) 0.8, Flatness C, D (  m) 0.9, Flatness E, F (  m) 2.6, Better flatnessBetter squareness in general

Equipments for checking quality of bars 6 Laser: Wavelength = 405 nm (typical for TOP). Prism splitter and reference PD to calibrate fluctuations. Position adjustable on motorized stages with a precision of O(  m). Photodiode: efficiency stable for at least 6 x 6 mm 2. CCD: 4.4 x 4.4  m 2 /pixel x 1200 pixels. Position adjustable on motorized stages with a precision of O(  m).

Bulk transmittance 7 Bulk transmittance  obtained using intensities I 0 and I 1 measured by PD and reflectances R 0 and R 1 calculated. 7 x 5 incident points. Suprasil-P710: Ave. = 99.44%/m Max. = 99.57%/m Min. = 99.27%/m Corning D: Ave. = 99.35%/m Max. = 99.50%/m Min. = 99.25%/m Requirement: > 98%/m. For both bars, enough bulk transmittance for all incident points. (Error of individual measurement: ±0.17%/m.) x y z

Internal surface reflectance 8  Measure the reflectance for several angles of reflections in 56-70°.  For both bars, enough reflectance for interested angles. Requirement: > 99.90%. Surface reflectance  obtained using intensities I 0 and I 1 measured by PD, reflectances R 0 and R 1 calculated, and the exponential of bulk transmittance. N: number of bounces L/b: length/thickness of bar  : coefficient of bulk transmittance Suprasil-P710: Max. = 99.98% Min. = 99.92% Corning D: Max. = 99.97% Min. = 99.92% z y (Error: ±0.02%.)

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

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

Possible effect of striae 11  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 explained by surface non-flatness. No significant effect for PID.

12 Glue the bars/mirror

Strategy of the gluing 13  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

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

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

Check after the gluing 17  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  m, respectively.  Quartz-mirror joint  Small amount of bubbles (photon loss < 0.1%).  Angles and displacements satisfy the requirements.  Angle = 0.03 mrad.  Displacement = 50  m. Requirement for angle: 0.2 mrad. Requirement for displacement: 100  m.

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

Backup slides 19

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

21 Laser PhotodiodeCCD

Bulk transmittance 22 Suprasil-P710Corning D

23

Internal surface reflectance 24 Requirement: > 99.90%. Angle of incidence (°) Angle of reflection (°) Number of bounces Reflectance  for Suprasil-P710 (%) Reflectance  for Corning D (%) ± ± − ± − ± − ± − ± − − 0.01

Roughness 25  Roughness and reflectance are related by a scalar scattering theory:  : RMS of roughness  : angle of reflectance : wavelength of laser Okamoto bar:  = (12 ± 4) Å Zygo bar:  = (17 ± 4) Å

Possible effect of striae 26 Requirement: path shift < 0.5 mrad. Suprasil-P710 polished by OkamotoCorning Dpolished by Zygo Results corresponds to path shift < 0.3 mrad. Can be explained by surface non-flatness.

Laser CCD S6 S5 blue green measured by Zygo Surface non-flatness and path shifts 27 z y mrad shift can be generated.

Quality check of the mirror 28  In addition to the bars, we do several checks for the mirror. Bulk transmittanceReflectance at quartz-Al Result = (99.20 ± 0.38)%Result = (88.5 ± 0.2)% Safely large.Will require better value for TOP.

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

30 Lower Al plate Upper Al plate and micrometer-head Overall configuration (one bar)

31 Plunger to keep the position of the bar. Polyacetal head to adjust the position of the bar. Bar, polyacetal balls, and plastic plate.

Flatness of the bars 32  Flatness of the bars after adjusting the angles and positions is measured by using autocollimator.  The flatness is safely nice for the gluing. Suprasil-P710Corning 7980