ATLAS SCT BARREL HARNESS FIBRE LAYOUT

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ATLAS SCT BARREL HARNESS - FIBRE LAYOUT
1) With 6 doglegs positioned in jig, connect up
doglegs. before fibres are spliced 2)
arrange fibres so that they are not touching
the base of the doglegs. 3) Prepare an 800mm
long strip of thin plastic (approx 1mm thick x
25mm wide) by marking the positions of the
fibres in Z as they are at the optopackage -
along the top edge of the plastic strip (a).
Make marks along the bottom edge of the
strip approx. 18mm to the left of the fibre
positions for LH harness (b) or approx. 42
mm to the right of the fibre positions for the RH
harness. 4) Take Polyimide electrical adhesive
tape 19mm wide (single sided adhesive
Kapton tape - standard from RS) and lay this
adhesive side uppermost on the plastic
strip, fastening it down at either end. 5) Lay
the plastic strip across the base of the harness
on top of the connectors. (protect these if
necessary). Line up marks (a) vertically with
fibres at optopks. Fasten the ends to the
bench or jig to prevent it from moving.
plastic
kapton
a
b
2
6) Take the 3 fibres of dogleg 1 and lower them
over the strip in line with the mark (a1) ie
vertically from optopackage. 7) bend them to the
left to touch the lower edge of the adhesive
kapton at (b1) 8) keeping 2 fibres close
together (flat) bend them up towards the top
edge. Stop approx 2mm from top. Bring the
single fibre over them and route this along
the top of the tape to the left end. Bend the 2
fibres to run alongside below the single
fibre but leave ends loose beyond a2 until next
set is added. 9) take the 3 fibres of dogleg 2
and repeat as for 1 and do the same with the
other doglegs, finishing with dogleg 6. The
fibres from each dogleg are stuck down at
the bottom edge of the tape (b). The 6 single
fibres are together at the top. The
overlapping lengths must only occur between
clamp positions. 10) make sure all fibres are
adhering to the Kapton surface from points (b)
to the end, then undo and remove the
plastic strip from under the Kapton and
allow the Kapton to rest on the bases of the
doglegs and connectors. 11) fix temporary clamps
in position to the right of each dogleg (for LH
harness).
a1
opto
Surplus kapton tape can be removed
Barrel end LH harness
3 fibres above surface
a
end
b
One fibre stuck down
2 fibres stuck down to surface
3 fibres stuck down to surface
1 fibre goes across 2 fibres
b1
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Fibre layout where fibre forms a ribbon from
top edge of kapton tape downwards
LH Harness
6 single fibres
Dogleg 1
Barrel end
(single fibre is on OUTSIDE of bend at base of
dogleg)
12 fibres (6 pairs)
RH Harness
6 single fibres
Dogleg 1
Barrel end
(single fibre is on INSIDE of bend at base of
dogleg)
12 fibres (6pairs)
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A) View of harness with new fibre layout and some
permanent clips. 6 single fibres are arranged at
the top edge with the 12 fibre set below them.
Dogleg 1 fibres are at the top of each set. The
single fibres which overlap the other fibres must
not overlap where fibres go over connectors or
where temp. or permanent clips are placed.
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B) Fibre layout on Kapton tape with permanent
clips. The base of the fibre bend is positioned
so that the 3 fibres are in the correct place
when the permanent clip is applied. They fit in a
guide on the surface of the clip which is in the
same position for each dogleg - therefore the
fibre length through the bend and the bend radius
is the same for each dogleg. Allow enough slack
for sliding fibres into guide.
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C) Fibre layout with temporary clips. Each one is
removed just before the permanent clip is
installed, starting from dogleg 1. At no time is
there more than one clip missing from the
harness. Here the full width of the Kapton tape
is shown but surplus Kapton should be removed
before the backing strip of plastic is removed.