Barrel TRT Straw Wire Support Assembly and

InsertionK. McFarlane

Hampton UniversityDOE/NSF Review, BNL March 2001

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Wire Support Steps• Clean parts• Assemble parts with epoxy• Inspect a sample• Insert CWS in rough-cut straw, gluing in

place with epoxy• Inspect position and adhesion after curing• Inspect interior of final-cut straw.

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Ultem Part CleaningWe use a water-based ultra-sonic cleaning procedure, with multiple rinses in distilled water, and a final oven drying.

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Wire Support Assembly

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Center Wire Support Insertion

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CWS gluing method• A drop of epoxy is dispensed in the center

of a 1480mm straw• The CWS is then pushed down the straw,

over the drop.

Positioning rod

Dispenser

CWS

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Problems (1)• At the beginning of production, it often happened

that the drop was not dispensed, so the process was adjusted to ensure dispensing

• Problems were found in October, 2000 by Duke, coincidentally with our switching to a new batch of epoxy with less viscosity. There were glue spots in the straw, often very many

• CWS insertion was shut down for several weeks while the problem was studied and adjustments made.

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Problems (2)• Rejection was high, running above 50% for

some batches• About 700 straws were lost due to excessive

glue• As a result, a full interior inspection begun,

using an angioscope.

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Comparison of Interiors

Clean Small glue spots

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Changes• The problem seems to arise from an interaction

between glue viscosity, pressure and vacuum in the dispenser, and electrostatic forces between the glue and the straw.

• Changes were made in straw tip shape and spacing from the straw, pressure and vacuum used in dispensing, and the gluing fixture

• With rejection rates on interior inspection about 1%, the problem is being controlled

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More interiors

Twister

This ‘plow’ effect puts glue on wire-joint side

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Conclusions• Rejection rate is still high (~1%)• Work will continue to be done to reduce

this rate through changes in the process• May require additional changes, including

changing to inserting the CWS first; this will result in more glue in the straw at the wire joint side. This would affect the physics