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Scintillating fibre tracker The scintillating fibre tracker reconstructs muon tracks before and
after the MICE cooling section in 4 T magnetic field to measure the relative change in emmitance of the muon beam
The tracker consists of five planar scintillating-fibre stations
Each station is composed of three planes of scintillating fibres laid out with 120 degrees radial spacing
Each fibre plane is comprised of a ‘doublet-layer’ in which the fibres in the first layer of the doublet are interleaved with those in the second
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Stations built so far Prototype stations 1 – 4; had problems:
Did not know which channel is the centre of the station Lots of problems on channel mapping Light loss due to hole mis-alignment at optical connectors
Station 5 – the first production version for trackers Built with new procedure that incorporates quality control to
rectify any errors occurred during manufacturing. Improvements:
Centre fibre clearly marked during ribbon production Optical connector hole alignment checked Number of bundles in a connector checked Number of fibres in a bundle checked Sequence of fibres checked
Should have rectified problems encountered for stations 1 – 4, yet to be confirmed
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Bundling - i Make bundle of seven fibres starting from the centre fibre
Seven fibres held together with rubber tube; single read-out channel
“comb” is used for bundling and QC procedure; bundles are stacked in grooves of the comb
bundles of four columns (5-6-5-6 or 5-6-5-4) for one connector
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Bundling - ii
comb
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Connectorisation - i A 22 way optical connector mates seven
scintillating fibres with one clear fibre waveguide;
alignment of connector holes at scintillating fibres and clear fibres sides are checked with ‘go/no-go gauge’
The scintillating fibre bundles are threaded through one of 22 holes of optical connector
Connectorisation mapping for view X
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Connectorisation - ii
“Bridge” a tool for QA
Fibre radius guide isused for connectorisation
Bridge with connectorsin place
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QA– counting - i Bundling/Connectorisation most labour intensive, source of errors Number of bundles for a connector as well as number of fibres in a
bundle are checked after bundling and connectorisation CCD images of one connector worth of bundles are taken then
analysed by software
Fibre bundles in comb Fibre bundles in connector
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QA – counting - ii Then software identifies bundles and fibres in the CCD image taken
Notifies operator if there are any failures
Twenty two bundles identified for comb/bridge Seven fibres in a bundle identified with different colours
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QA – scanning - i If counting QA was OK, move on to fibre
sequence check by LED scanning Scan fibre plane with UV LED at 1250
micron/seconds Capture image at 24.98 frames/seconds
=> 50 micron/frame
Trace sum of CCD intensity for 9 pixels around fibre centre
Bottom fibre signal distortedby the top fibres and glue
Top fibres
Bottom fibres
UV LED
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QA – scanning - ii Find frame # of intensity peak of each fibre;
Frame # of leading edge = maximum intensity * 0.5 Frame # of trailing edge = maximum intensity * 0.5 Frame # of peak = (leading edge + trailing edge)*0.5
Plot frame # of intensity peak of each fibre;
As frame # increases bundle # (channel number) increases, no overlaps of X
Fibre sequence as well as bundle order should be OK before gluing a ribbon
Max.
peak
Each X corresponds to peakSeven X in each bundle
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QA – scanning - iii Time interval of each peak checked as well Negative interval if there is fibre swapped
between bundles Mean = 4.24 frames => 212.17 micron
agrees with measured mold pitch of 426/2 micron
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Gluing Fix vacuum chuck, carbon-fibre station frame to gluing jig
Then glue them together
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Potting, cutting Pot fibres to connectors, then apply glue to stiffen fibres then cut
them before polishing
Apply glue Cut fibres
After cutting Ready for polishing
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Polishing Polish connector surface with diamond fly cutter We had problems not seen in prototype stations
Scratches Broken cladding layer
After applying optical grease, will not cause transmission problem Will use new diamond fly cutter
Cutter can degrade over time
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Plans
Test with cosmic ray Polish with new diamond fly cutter Measure uniformity of height (z) of station
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Summary Station 5 built with new manufacturing procedure, which proven to
work Ready to be tested
o view X
- mold4#X / 22 aug 206
- 1491 fibres
o view W
- moldX#X / 17 aug 2006
- 1491 fibres
o view V
- mold4#1 / 15 aug 2006
- 1492 fibres; one extra!
4474 350 micron fibres successfully bundled and connectorised by hand!