Cooling Loop Update ATLAS W4 Sheffield Richard French The University of Sheffield + all UK contributors

Stave Core Cooling Circuit Deliverable is 12 Stave Cores in total for 2yr bridge – deemed not enough to be useful (WP ). Is this a 1.3m or 1.4m long item? To mitigate the inevitable delay of a useful decision…….. Sticking with 1.3m – 2.275mm x 0.125mm CP2 Ti tube – Build only 2x new stave cores at 1.3m with isolators now ready for end Feb/March 2016 – This uses last remaining parts (isolators in short supply). NP nm Stave Cooling Assembly (Peter Sutcliffe 12/06/2014)

Stave Core Cooling Circuit 30x new electrical isolator assemblies arrives mid-end March to allow production of new stave cores. From reception of new isolators, produce and test all 12 cooling circuits in for July 2016 IN THE PERIOD MARCH – JULY 2015 Establish: Electrical Isolator development Begin capillary connection development + Trial new robust weld tooling Examine low cost fitting alternatives (pg8) Caveat = We still do not have any of the proposed thicker walled tube to work with!!

Prototype Electrical Break Final design iteration for test items 2 Titanium Caps & ID Alumina ceramic sleeve Vac Brazed into cap Cap vac brazed to tube Initial Evaluation Mechanically robust Standard component off the shelf for us to order Fast turnaround Leak rate high 10-9 mBar ls Pressure handling = 150 Bar Low statistics = 50 items only

Design / Costs: Prototype Isolator 2.2 to 1/8” OD Prototype short section: Note – no VCR fitting, this was brazed onto a short tube stub and then TIG welded to the isolator. This attracted both additional costs and labour. Only 20mm of useable tube was sticking out from the cap. This caused problems for TIG welding preparation and the weld head clamping. Weld prep allowed only one shot at welding correctly due to short tube length. Increasing tube length reduced “furnace optimisation” eg, we could not pack as many units into the oven per run therefore increasing cost. There was nothing wrong with this and it worked well but uses 2.275mm to 3.175mm OD NOT 2.275mm to 2.500mm OD Cp2 Ti tube. Costing based from quotation on 02/7/2013 ex vat ITEMQTYUNIT £Delivery£ Total Isolator w6, Brazing W Fitting W6, FTE Eng FTE Tech CoC25.00 Shipping25.00

Isolator production refinements in the 2year bridge Process not yet fully optimised for high volume production but with careful QA the physical items is acceptable, maybe not the cost (per unit cost has little reduction in high volume)? What do we look for? Main worry is embrittlement (2x furnace (or heat) cycles for 4 brazed joints) Furnace cycle #1 = Alumina Ceramic to Titanium cap (this is fine) Furnace cycle #2 = Tube to cap (needs better refinement (understood and will implement). WHY? = TEMPERATURE = ~780°C, which is borderline/just below Ti oxidisation temp. Statistics - 50 produced: 4 used for DT and NDA, 6 failed visual inspection = 40 GOOD components 3 Isolators now remain used but re-workable = 1 stave + ½ spare. Next batch will reduce the heat cycles from 2 to 1 (less oxidisation and contamination of Titanium). To refine and therefore reduce production costs we could explore: EB welding of the Ti tube to the Ti cap & VCRs then make only one ceramic vac brazed joint This means we can use a lower temperature braze alloy to avoid Ti oxidisation moving further away from “dangerous” temperature range (>800°C) for Titanium (new braze is at 580°C). This gives a better (unaltered) temper tube for the TIG welding operations & bending. This allows us to maximise furnace cycles for different ceramic OD’s (Strips and PIXEL EC’s). Refinement still needed: High braze alloy flow (aesthetics issue, not functionality)

Design / Cost Options : 4mm OD Ceramic (large) Full assembly inclusive of VCR fitting. Note – this U section and lengths are designed only for vacuum brazing of fittings and isolators. One weld to the stave core is possible. 16mm distance is too short to allow TIG welding as this would locate the weld in the HAZ of the tube. Position & accuracy of U bend must checked post brazing (annealing tube through heat cycle of furnace) as bend will relax. Could reduced unit cost by £30 ea with tests to braze full assembly in one shot. More trials needed = +£3/5k! Costing based from quotation on 02/12/2015 ex vat QTYUNIT £Delivery£ Total w16, w289, Optional Cert of Conf25.00 Tooling Cost <415, Tooling Cost >10007,500.00

Design / Cost Options : 4mm OD Ceramic (large) Part assembly excluding VCR fitting. Note – this U section and lengths are designed only for vacuum brazing of fittings and isolators. One weld to the stave core is possible. 16mm distance is too short to allow TIG welding as this would locate the weld in the HAZ of the tube. We could (if between a rock and a hard place) use cheaper 316L 2.5mm ID compression fittings then convert to a VCR or threaded adaptor only ~£1k less £ than full assembly = significant effort penalty Costing based from quotation on 13/11/2015 ex vat QTYUNIT £Delivery£ Total w15, w281, Cert of Conf25.00 Tooling Cost <415, Tooling Cost >10007, £3.60ea = Not economically viable