CPR2 Optical Cables

CPR2 Optical CablesJoey Huston

Michigan State University

…taking optical signals from edgeof CPR/crack detectors to PMT boxes mounted on backof wedges

Optical cables

Optical cables ~3-5m long take optical signals to PMT boxes mounted on back of wedges diameter of clear fiber

steps up to 1.1 mm in order to reduce alignment issues

Routing

Clear fibers are routed into 4 connectors of 16 channels each

– connector D has 6 fibers from CPR and 10 from crack detector

Light-tighting

Black plastic covering for optical cable

Sliding plastic shroud for connector region

Clear fiber attentuation length

Clear fiber tests conducted at Rockefeller

Attenuation length best fitted to 2-components

PolyHiTech and Kuraray give similar results

PolyHiTech used for cables

1000 m of Kuraray purchased for spares

Optical cable installation issues

Main Installation Issue for Preshower/Crack. Length of cables is at best an educated guess.

Need full scaffold and PMT boxes installed to measure best lengths. extra 50 cm of cable causes 10% loss of light yield,

and is a good place to cause fiber damage. PMT box placement changes depending on

wedge, and complete plan changed 4 times in last long access.

Plan is to make 50% of the optical cables before shutdown with educated guess, then after first week of shutdown make the rest (takes about 1.5 weeks per arch).

Determine step-by-step the additional lengths to add to these straight-line paths for optical cables.

Determining cable lengths

Approximate distances to add to the clear

fiber lengths (for normal wedges)

110 mm -- middle of wedge to farthest CPR connector

205 mm=8” -- distance across side window on wedge

915 mm=36” -- horizontal distance across wedge to PMT box

305 mm=12” -- vertical distance to PMT box

305 mm=12” -- lateral distance to PMT box

150 mm -- safety margin (?)

Step 2: The window height is known to be 8”, and the cables must enter the back of the wedge from the farther point on the window. Assume a straight line from the middle point on bottom of window to middle point on top of window. 8” = 205 mm

Electronics crate

Signal and HV cables

Optical cables

Black LED fibers for EM Cal

PMT access

3’ to middle

Step 3: 3’ from entry point at window to middle of plate holding PMT boxes. 3’ = 915 mm

Step 4: Plate that box sits on could be as high as 6”. Top cable for the box is about 6” high. So add about 12”=305mm for a vertical rise from the base of wedge to the PMT box.

Step 5: Optical cable entry point in the window will likely not line up with PMT box hole. Assume a 12”=305mm travel across wedge for this.

Tight spots

Tight fit in last long access!

Scraped sides of connector

on 1 arch, fine on the other

arch. MSU has since trimmed

connector by 1.5 mm.

4 PMT boxes mounted on sides of monkey bars

2 PMT boxes mounted on inside of cradle

6 PMT boxes mounted on “normal” wedges