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Barrel TRT Straw Wire Support Assembly and Insertion

Barrel TRT Straw Wire Support Assembly and Insertion. K. McFarlane Hampton University DOE/NSF Review, BNL March 2001. Wire Support Steps. Clean parts Assemble parts with epoxy Inspect a sample Insert CWS in rough-cut straw, gluing in place with epoxy

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Barrel TRT Straw Wire Support Assembly and Insertion

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  1. Barrel TRT Straw Wire Support Assembly and Insertion K. McFarlane Hampton University DOE/NSF Review, BNL March 2001

  2. 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. K. McFarlane BNL, 20-Mar to 22-Mar, 2001

  3. Ultem Part Cleaning We use a water-based ultra-sonic cleaning procedure, with multiple rinses in distilled water, and a final oven drying. K. McFarlane BNL, 20-Mar to 22-Mar, 2001

  4. Wire Support Assembly K. McFarlane BNL, 20-Mar to 22-Mar, 2001

  5. Center Wire Support Insertion K. McFarlane BNL, 20-Mar to 22-Mar, 2001

  6. 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. Dispenser Positioning rod CWS K. McFarlane BNL, 20-Mar to 22-Mar, 2001

  7. 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. K. McFarlane BNL, 20-Mar to 22-Mar, 2001

  8. 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. K. McFarlane BNL, 20-Mar to 22-Mar, 2001

  9. Comparison of Interiors Clean Small glue spots K. McFarlane BNL, 20-Mar to 22-Mar, 2001

  10. 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 K. McFarlane BNL, 20-Mar to 22-Mar, 2001

  11. More interiors This ‘plow’ effect puts glue on wire-joint side Twister K. McFarlane BNL, 20-Mar to 22-Mar, 2001

  12. 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 K. McFarlane BNL, 20-Mar to 22-Mar, 2001

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