Takashi Matsushita

t.matsushita@imperial.ac.uk

Imperial College

T. Matsushita 1

Station 5 status

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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

T. Matsushita 3

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

T. Matsushita 4

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!