KAGRA Vacuum System 130801　VAC (YS)

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1. Layout (interferometer and survey map)**tilting the optical plane of interferometer

for draining water.**horizontal floors in each room prepared for

installing chambers.**position of chamber/mirror is to be

described in “map coordinates (survey map) of tunnel”

Y-ar

m

X-armBS

SRM

PRMMC

EYCEYV

IYCIYV

EXCEXV

IXCIXV IXA EXA

IYA

EYA

horizontal plane at Y end

x

y

Yopthorizontal plane at center room

horizontal plane at X end

Y arm

optical plane of interferometer X arm

Xopt

O (BS)

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130801　VAC (YS)KAGRA Vacuum System1. Layout (KAGRA location)

Japan rectangular plane coordinate: survey map(Xmap, Ymap, Ho)

Geodetic coordinates: Latitude, Longitude, Height (B, L, H+He)

3D terrestrial coordinate: KAGRA optical plane(X, Y, Z)

Takayama origin, zone VII, JapanHo: height from geoid surface

H; radius of GRS80 of ellipsoid earthHg; height of geoid surface from GRS80 surface

He (ellipsoid height) = Ho (orthometric height) + Hg (geoid height)

Z

X

Y

Xmap

Ymap

B

L

H

GRS80

HR point of mirror

geodetic coordinate（ ITRF94, GRS80）B [ddmmss](latitude, N)

L [dddmmss](longitude, E)

He [m](ellipsoid height)

Beam Splitter (BS) 362442.6973 1371821.4418 414.181

X-front （ IXC） 362443.1216 1371822.3671 414.265

Y-front （ IYC） 362443.3522 1371820.9811 414.098

X-end （ EXC） 362531.1848 1372007.0707 424.407

Y-end （ EYC） 362607.9639 1371721.4846 403.934

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Number of baffles in the 3-km long armEvery 24-m, or longer, along the arm, 40-mm in height, 54-degree tilted

Requirement: baffle surface (coating)Specular reflection <10% @1064 nm， 0-60 deg incidenceTotal scattering <2% @1064, 12deg incidenceSurface roughness Ra <several microns or lessMechanical and thermal durability (film)

Flexural strength of plated film: JIS H8504Thermal shock strength: JIS H8504Friction proof: JIS H8503

Vacuum performanceOutgassing rate <3x10-7 Pa m3 s-1m-2

2. Optical baffles in beam tubes

130801　VAC (YS)KAGRA Vacuum System

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Structure

2. Optical baffles in beam tubes

130801　VAC (YS)KAGRA Vacuum System

θ = 36°

D=798

h = (D-d)/2 = 40 mm

d=720

w

RPCD = φ810

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Manufacturing process2. Optical baffles in beam tubes

130801　VAC (YS)KAGRA Vacuum System

1) Stainless steel sheet (SUS304 BA) of 0.8 mm thick2) Laser cutting for sector shape and serrated edge3) Rolling and welding for conical shape（ frustum)4) Removing oxidized layer of weld beads5) “Solblack” plating

alkaline degreasingelectrolytic cleaningacid cleaningNi plating (5 mm)Solblack plating (15 mm)chemical treatment for blackingthermal treatment (190°C 2.5hrs, in air)

6) Vacuum firing (220-250°C 4hrs, in vacuum)

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Manufacturing process2. Optical baffles in beam tubes

130801　VAC (YS)KAGRA Vacuum System

1) Stainless steel sheet (SUS304 BA) of 1 mm thick2) Laser cutting for sector shape and serrated edge3) Rolling and welding for conical shape（ frustum)4) Removing oxidized layer of weld beads5) “Solblack” plating

alkaline degreasingelectrolytic cleaningacid cleaningNi plating (5 mm)Solblack plating (15 mm)chemical treatment for blackingthermal treatment (190°C 2.5hrs, in air)

6) Vacuum firing (220-250°C 4hrs, in vacuum)

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Properties of “solblack coating”Specular reflection <10% @1064 nm， 0-60 deg incidenceTotal scattering <2% @1064, 12deg incidenceSurface roughness Ra <several microns or lessMechanical and thermal durability (film)

Flexural strength of plated film: JIS H8504Thermal shock strength: JIS H8504Friction proof: JIS H8503

Vacuum performanceOutgassing rate <3x10-7 Pa m3 s-1m-2

2. Optical baffles in beam tubes

130801　VAC (YS)KAGRA Vacuum System

8

Properties of “solblack coating”Specular reflection <10% @1064 nm， 0-60 deg incidenceTotal scattering <2% @1064, 12deg incidenceSurface roughness Ra <several microns or lessMechanical and thermal durability (film)

Flexural strength of plated film: JIS H8504Thermal shock strength: JIS H8504Friction proof: JIS H8503

Vacuum performanceOutgassing rate <3x10-7 Pa m3 s-1m-2

2. Optical baffles in beam tubes

130801　VAC (YS)KAGRA Vacuum System

Total scattering including specular reflection@ 8 deg incidence

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Properties of “solblack coating”Specular reflection <10% @1064 nm， 0-60 deg incidenceTotal scattering <2% @1064, 12deg incidenceSurface roughness Ra <several microns or lessMechanical and thermal durability (film)

Flexural strength of plated film: JIS H8504Thermal shock strength: JIS H8504Friction proof: JIS H8503

Vacuum performanceOutgassing rate <3x10-7 Pa m3 s-1m-2

2. Optical baffles in beam tubes

130801　VAC (YS)KAGRA Vacuum System

10

Properties of “solblack coating”Specular reflection <10% @1064 nm， 0-60 deg incidenceTotal scattering <2% @1064, 12deg incidenceSurface roughness Ra <several microns or lessMechanical and thermal durability (film)

Flexural strength of plated film: JIS H8504Thermal shock strength: JIS H8504Friction proof: JIS H8503

Vacuum performanceOutgassing rate <3x10-7 Pa m3 s-1m-2

2. Optical baffles in beam tubes

130801　VAC (YS)KAGRA Vacuum System

solblack: after vacuum baking