KAGRA Vacuum System VAC (YS) 1 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-arm X-arm BS SRM PRM MC EYC EYV IYC IYV EXC EXV IXC IXV IXA EXA IYA EYA horizontal plane at Y end x y Yopt horizontal plane at center room horizontal plane at X end Y arm optical plane of interferometer X arm Xopt O (BS)

VAC (YS) KAGRA Vacuum System 1. Layout (KAGRA location) Japan rectangular plane coordinate: survey map (X map, Y map, H o ) Geodetic coordinates : Latitude, Longitude, Height (B, L, H+H e ) 3D terrestrial coordinate: KAGRA optical plane (X, Y, Z) Takayama origin, zone VII, Japan H o : height from geoid surface H; radius of GRS80 of ellipsoid earth H g ; height of geoid surface from GRS80 surface H e (ellipsoid height) = H o (orthometric height) + H g (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) H e [m] (ellipsoid height) Beam Splitter (BS) X-front （ IXC ） Y-front （ IYC ） X-end （ EXC ） Y-end （ EYC ）

3 Number of baffles in the 3-km long arm Every 24-m, or longer, along the arm, 40-mm in height, 54-degree tilted Requirement: baffle surface (coating) Specular reflection nm ， 0-60 deg incidence Total scattering 12deg incidence Surface roughness Ra <several microns or less Mechanical and thermal durability (film) Flexural strength of plated film: JIS H8504 Thermal shock strength: JIS H8504 Friction proof: JIS H8503 Vacuum performance Outgassing rate <3x10 -7 Pa m 3 s -1 m Optical baffles in beam tubes VAC (YS) KAGRA Vacuum System

4 Structure 2. Optical baffles in beam tubes VAC (YS) KAGRA Vacuum System θ = 36° D=798 h = (D-d)/2 = 40 mm d=720 w R PCD =  810

5 Manufacturing process 2. Optical baffles in beam tubes VAC (YS) KAGRA Vacuum System 1) Stainless steel sheet (SUS304 BA) of 0.8 mm thick 2) Laser cutting for sector shape and serrated edge 3) Rolling and welding for conical shape （ frustum) 4) Removing oxidized layer of weld beads 5) “Solblack” plating alkaline degreasing electrolytic cleaning acid cleaning Ni plating (5  m) Solblack plating (15  m) chemical treatment for blacking thermal treatment (190°C 2.5hrs, in air) 6) Vacuum firing ( °C 4hrs, in vacuum)

6 Manufacturing process 2. Optical baffles in beam tubes VAC (YS) KAGRA Vacuum System 1) Stainless steel sheet (SUS304 BA) of 1 mm thick 2) Laser cutting for sector shape and serrated edge 3) Rolling and welding for conical shape （ frustum) 4) Removing oxidized layer of weld beads 5) “Solblack” plating alkaline degreasing electrolytic cleaning acid cleaning Ni plating (5  m) Solblack plating (15  m) chemical treatment for blacking thermal treatment (190°C 2.5hrs, in air) 6) Vacuum firing ( °C 4hrs, in vacuum)

7 Properties of “solblack coating” Specular reflection nm ， 0-60 deg incidence Total scattering 12deg incidence Surface roughness Ra <several microns or less Mechanical and thermal durability (film) Flexural strength of plated film: JIS H8504 Thermal shock strength: JIS H8504 Friction proof: JIS H8503 Vacuum performance Outgassing rate <3x10 -7 Pa m 3 s -1 m Optical baffles in beam tubes VAC (YS) KAGRA Vacuum System

8 Properties of “solblack coating” Specular reflection nm ， 0-60 deg incidence Total scattering 12deg incidence Surface roughness Ra <several microns or less Mechanical and thermal durability (film) Flexural strength of plated film: JIS H8504 Thermal shock strength: JIS H8504 Friction proof: JIS H8503 Vacuum performance Outgassing rate <3x10 -7 Pa m 3 s -1 m Optical baffles in beam tubes VAC (YS) KAGRA Vacuum System Total scattering including specular 8 deg incidence

9 Properties of “solblack coating” Specular reflection nm ， 0-60 deg incidence Total scattering 12deg incidence Surface roughness Ra <several microns or less Mechanical and thermal durability (film) Flexural strength of plated film: JIS H8504 Thermal shock strength: JIS H8504 Friction proof: JIS H8503 Vacuum performance Outgassing rate <3x10 -7 Pa m 3 s -1 m Optical baffles in beam tubes VAC (YS) KAGRA Vacuum System

10 Properties of “solblack coating” Specular reflection nm ， 0-60 deg incidence Total scattering 12deg incidence Surface roughness Ra <several microns or less Mechanical and thermal durability (film) Flexural strength of plated film: JIS H8504 Thermal shock strength: JIS H8504 Friction proof: JIS H8503 Vacuum performance Outgassing rate <3x10 -7 Pa m 3 s -1 m Optical baffles in beam tubes VAC (YS) KAGRA Vacuum System solblack: after vacuum baking