Tuesday, July 31, 2012

Mice are Moving

The big superconducting MICE coil was ready to move into the paint shop in preparation for vacuum potting. We will use the oven to preheat the 4400 lb coil to around 50C. The plan is to pull a vacuum on the cavity and basically suck epoxy into the mold from a reservoir. We use a special epoxy that performs at cryogenic temperatures called CTD-101 Its made by Composite Technology Development and is the gold standard impregnation epoxy for low temperature applications

It is imperative that the item being potted, or in this case the coil casing be vacuum tight with no leaks. We're not talking UHV type vacuum here just bubble tight. An example would be if we pressurized it to a few PSI and went around with  Snoop or soap bubbles looking for leaks. We actually did that on this coil but there were some pesky hard to find leaks so we brought in one of our Helium leak detectors. These are exquisitely sensitive leak testing tools. They are sensitized for helium and can actually detect even a few molecules. We pull a vacuum on the item to be checked and then go around the outside of the vessel or part spritzing helium gas with a wand. When we see a response from the detector we know we are near a leak. There are some special tricks for pinpointing leaks precisely which can be tricky if the vessel has multiple leaks or is out gassing internally and fogging the detector readings. 
Using the assembly shop bridge crane we plucked the coil off the assembly surface plate it was sitting on. The goal here was to place the coil almost vertical and mate it to a large steel support stand. The coil is then attached to the stand and the whole thing goes in the oven for a little bake.
The trick here is going from horizontal to vertical. The way we handled that was by re-rigging the coil on the floor with a manual chain fall in the lower side sling leg. As we pick it up from the blocks on the floor the side with the shorter fixed length slings goes up a little ahead of the adjustable side. Once the whole thing is suspended we lower the chain fall by hand until we get the angle we wanted to mate to the stand. Johnny and Jim guide the coil into final position behind the assembly shop.
  The rest was easy. We attached the coil to the stand with a large stud and then it took a little slow forklift ride to the easy bake oven in the paint shop. This oven is normally used for powder coating but we commandeered it for our potting operations. Tomorrow we start the potting process.

Right now is summer intern season. Tak, one of the technicians in the fusion research department is a barbeque master. He puts on probably four or five barbeques a year and usually cooks the Christmas party meal. Everybody chips in and helps with the prep but mysteriously have important meetings to go to when its time to clean up. The first and most important step is to get the necessary fire permit. Nothing can happen until we secure that important document. 
Tak never annouces the barbeque. Your on your own following the smell to figure it out. The scientific and engineering interns helped with the prep and he actually let them do some real cooking. I guess if you can cut the mustard for what it takes to get a PhD you can be trusted to not burn the Tri-tip.
 He still kept a close eye on them. Everything came out great as usual. Tri-tip, chicken, sausages, calamari, tater tots and chicken salad. For dessert, apple pie. Industrial barbequing at its best.

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