CDC Construction Complications Tracking

Magnetic Material

On April 27, 2012 it was discovered that much of the stainless hardware that we ordered to install the Swiss cheese plate was in fact magnetic. At the same time, we discovered that the the RG-316 coaxial cable that is to be used to connect the crimp pins to the transition board outside the gas plenum was also magnetic.
The alleviate the hardware issue, we have ordered silicon/brass bolts to replace the stainless ones. The are expected in on May 1, and will then allow us to proceed with the installation of the Swiss chesse plate.
We will try to quantify the force as a function of magnetic field acting on the hook-up wires to estimate what sort of issues this can cause. There will be roughly 1700 feet of this cable in the upstream plenum, so having a good handle on the force is crucial.
We are working to identify vendors who sale coaxial cable that is based on copper and aluminum conductors, rather than stainless. We will order samples from these and then test the material for suitability in construction. It needs to satisfy high-voltage, gas-tightness and size tests to be suitable for use in the CDC.

In late February, 2012 the Swiss cheese plate arrived at CMU and was found to not be clear enough to be able to perform electrical hook ups.
As of April 20, 2012, the plate has been polished and cleaned and is now suitable for electrical hook-up.

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.
Modified the straw insertion step, 5 November, 2010.
An extra step was added to the procedure for straw insertion to ensure that each hole in the Al endplate is dry-fitted with its designated feedthru. If necessary, the hole is reamed out and cleaned before the feedthru is glued into place.

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 on 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.

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 stringing the straight layers.

Status on 2 February, 2011: 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.

February 16, 2011: Tim reported that Lamina has still not received samples of new material. He also reported that Shedahl has the needed material available. He has communicated that information

to Lamina.