CDC Construction Complications Tracking
From GlueXWiki
Endplates - resolved
- Problem noted during initial inspection of plates at CMU in early May, 2010.
- The problem was resolved by late June, 2010.
- A few of the holes in the Al endplate and almost all of those in the C fiber endplate were found to be undersized. They were reamed out at CMU.
Straw tubes - ongoing
- Problem identified at start of assembly on November 5, 2010.
- Most of the straw tubes in the first shipment from Lamina had a resistance along their length of 80-90 Ohms. Approximately 10% of the straws had a resistance of around 500 Ohms and the Al layer was noticeably more transparent.
- Procedure modified ob November 8, 2010.
- A measurement of the resistance of each straw was added to the checking procedure, before the stage where the straw is cut to size.
- Vendor was notified on November 8, 2010.
- Lamina was notified of this at the point of sending a second shipment. They retrieved the second shipment of straws and measured the resistance of over 50% of the straws. All of the straws which they checked had high resistance. All of the straws in the second shipment and some of those in the first shipment were made from the same roll of aluminized mylar. The rest of the straws in the first shipment were all made from another roll, which was finished first, presumably these were the low-resistance straws.
- QA to vendor modified on November 11, 2010.
- A requirement was made that the resistance along the length of the straw should not exceed 110 Ohms.
- Lamina have established contact with a second supplier of aluminized mylar and have asked for samples from them and the original supplier. It is possible that the layer of Al on the first good batch of straws was thicker than the 300A requested. They plan to inspect the samples and then contact Tim.
- Backup plan for construction made on 15 January, 2011.
- There is concern that CMU will install all straws on hand before new ones are received from Lamina and checked. At that time, sufficient straws will have been installed in the CDC that it will be possible to start string the straight layers.
