NCSX SHIM ISSUES NOV

Outer shim permeability (316L certified) Machining of the initial lot of shims increased the permeability from 1.02 to Going to a anneal-machine to fat shim (0.010 oversize)-grind to size- alumina coat would reduce the permeability significantly, but probably some would still be above –Zenex uses double disc grinder with ceramic abrasive. –Re-grinding costs ~$30/shim.~800 shims in total; $24K total cost. + $10K for annealing costs –Cannot anneal finished shims – they warp ”. Larry will try machining some 316L shims in house to gain some understanding about why these shims appear to work harden through the thickness. Will re-check Colin’s permeability measurements, also. –May need to set max. cut size for Zenex and may need to visit Zenex to observe how they machine the shims. General plan: proceed with 2 nd and 3 rd bullet –Art will consider results and then we will consider if we should change requirements or not. Art looks at field errors & tries to keep total field in sub-gauss range for permeability effects. ALARA is used for guidance. Alternative: Inconel, but $28/lb, and 30% COE mis-match. Alumina coating might have problems with adhesion.

Shim thickness spectrum adequacy 2 lots of 214 shims uncoated are here (the ones with permeability problems). Cost ~$180 each! –Need about 60 for the first 3 pack. –200 annealed by tomorrow. –Send 200 to Zenex in Patterson. –2-3 wks to grind –4 wks. For coating –2nd batch will follow by a few days. –Should have coated shims roughly by the Holidays. Spectrum of thicknesses per our spreadsheet – biased towards nominal thickness. –URGENT - MV requests A-B predictive gaps to get a handle on thicknesses needed. Tom sent info to Mark; he’s working on it. Art and Tom will review. What if we don’t have enough of the thickness needed? Time to get more is probably ~1 month. –MV thinks he could insert temporary shims and then wedge the castings apart locally to replace them. BUT would delay nose welding until shims are in place. –Larry suggests ordering a second batch after we analyze what we receive in the first batch. Time: probably 1 month.

Flex shim material Av. Sect. stress Peak sect. stress ksi ksi AA AB ~30 39 BC Allow The average section stress has an allowable of 2/3 yield -i.e. 39 ksi; the peak stress has an allowable of 1.5 of 2/3 yield, or yield, which is 58 ksi at 77k., so we're fine with 316L for the present operating scenarios. Also, Kevin is still refining the analyses so these are not absolutely firm numbers. The A-B doesn’t have the same margin – we should make the puck smaller or eliminate it where the local peak stress is. Shoot for matching with A-A.

PF/TF support material ~14,000 lbs. of SS used in structure Stellarator symmetric Current Al structure has insulating breaks. –Cost of fabrication is approx. equal. –Titus raised issue of “squirming” due to COE mismatch. Also listed in Constr. Report as an issue. Free stainless steel plate is available - we think it’s 304L – mu probably around 1.1, but this is “old” plate when Ni wasn’t so high in price – it might have lower mu. Measuring it tomorrow. –Need to check on quantity.