Quartz preparation (quality check and prototype status) Y.
Horii (Nagoya University) 1 BPAC, 12th Nov. 2011
Slide 2
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.
Slide 3
3 Quality check
Slide 4
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.
Slide 5
Quartz bars 5 Suprasil-P710 polished by Okamoto Co.Corning 7980
0D polished by Zygo Co. 131 x 45 x 2 cm 2 120 x 45 x 2 cm 2 Highest
striae grade in MIL-G-174 standard Highest striae grade in ISO
10110-4 standard SpecificationActualRequir e Roughness (nm
rms)0.440.5 Squareness (arc min.) 0.171 Flatness S6, S5 ( m) 2.0,
2.025 Flatness S4, S3 ( m) 0.8, 0.96.3 Flatness S1, S2 ( m) 4.9,
5.16.3 SpecificationActualRequir e Roughness (nm rms)0.40.5
Squareness (arc min.) 0.1-3.85 Flatness A, B ( m) 0.8, 0.91.3
Flatness C, D ( m) 0.9, 1.11.3 Flatness E, F ( m) 2.6, 3.06.3
Better flatnessBetter squareness in general
Slide 6
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. 1600 x 1200 pixels.
Position adjustable on motorized stages with a precision of O(
m).
Slide 7
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 7980 0D: 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
Slide 8
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 7980 0D: Max. = 99.97% Min. = 99.92% z
y (Error: 0.02%.)
Slide 9
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
Slide 10
Possible effect of striae 10 Requirement: path shift < 0.5
mrad. Corning 7980 0D 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.
Slide 11
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.
Slide 12
12 Glue the bars/mirror
Slide 13
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).
Slide 14
14 Jig for gluing
Slide 15
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.
Slide 16
Gluing 16 Put glue using dispenser (head is soft). Glue goes
down. Takes ~1 hour. Cured by UV light. Takes
Internal surface reflectance 24 Requirement: > 99.90%. Angle
of incidence () Angle of reflection () Number of bounces
Reflectance for Suprasil-P710 (%) Reflectance for Corning 7980 0D
(%) 56 4599.95 0.0199.92 0.01 50593999.96 +0.02 0.01 99.93 0.01
45613599.97 +0.02 0.01 99.93 0.01 39653199.92 +0.02 0.01 99.93 0.01
35672799.96 +0.02 0.01 99.93 0.01 30702399.98 +0.02 0.01 99.97
+0.02 0.01
Slide 25
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) Zygo bar: = (17 4)
Slide 26
Possible effect of striae 26 Requirement: path shift < 0.5
mrad. Suprasil-P710 polished by OkamotoCorning 7980 0Dpolished by
Zygo Results corresponds to path shift < 0.3 mrad. Can be
explained by surface non-flatness.
Slide 27
Laser CCD S6 S5 blue green measured by Zygo Surface
non-flatness and path shifts 27 z y 0.1-0.3 mrad shift can be
generated.
Slide 28
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.
Slide 29
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.)
Slide 30
30 Lower Al plate Upper Al plate and micrometer-head Overall
configuration (one bar)
Slide 31
31 Plunger to keep the position of the bar. Polyacetal head to
adjust the position of the bar. Bar, polyacetal balls, and plastic
plate.
Slide 32
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
