ATLAS Upgrade Meeting LBNL Sept 6 th 2012

1. ATLAS Upgrade Meeting LBNL Sept 6th 2012 Orbital Welding Development Richard French, Hector Marin-Reyes, Simon Dixon, Paul Kemp-Russell The University of Sheffield Martin Gibson, John Matheson, John Hill, John Noviss – RAL Ian Mercer - Lancaster

2. Correct technology/materials? • Started orbital welding in 2007 with the design methodology of: • 100% reliable connector-less system. • The tube will be galvanicallymore stable than the parts joined to it (e.g. grounding, supports). • The exceptions are joints, seals and connectors, these will have the same electro-potential as the tube. Step back and sanity check? • Tube material, diameter, wall thickness, equipment portability are all obvious factors of which joining method to adopt. There are hundreds of subtle influences that blur these definitions. • Assuming ideal tube is no longer 316L stainless steel of ~200um wall > Now CP2 Ti, 125um wall or thinner would I choose TIG orbital welding again without our knowledge of this technique? • On paper the equipment specifications say no – nothing other than laser, EB, microplasma diffusion bonding or brazing should work reliably at this wall thickness to make a welded joint in CP2 Ti. Non-specialist “experts” would also suggest no. • IGNORE SPECS – TIG WORKS WELL & IS PROVEN WITH HIGH REPEATABILITY as a result of the last 6 years R&D and work with specialists in industry. • I’ve learnt a significant amount about joining process for both 316L and CP2 Ti materials. • Get the material right - the joining process follows naturally. • Get the process correct and you have highly repeatable joint. • 6 years of materials development and refinement to make 2 bullet points!

3. Assuming we are still on the correct side of sane………… Achieving the correct material to work with in the first place. Titanium developments

4. Oxidation of the Ti tubes - complete Removal investigated through wet and dry etchants Dry etchants “Fun stuff” Plasma cleaning of ends –Looks like this might work, on short samples a reasonable result is achieved. For the full circuit mods to the plasma cleaning machine are required for a UHV seal to the tube. Shot blasting with glass bead – Works fine but requires very careful cleaning. NONE APPLICABLE TO IN-SITU REPAIR (Scotchbrite) HN03:HF concentrate Wet etchants “Nasty Chemistry” HF based solutions and trials carried out by, Martin Wilson – STFC. Repeat/refine Swantek – Jerry Lancaster. fin HTT/ Anipol?NDT ltd. fin SOLVED AND TRANSFERRED TO INSDUSTRY Attempting to remove this HN03:HF dilute

5. CP2 Ti well proven and now established in use, oxide issues solved in production using chemical etch solution (pickling) and cleaning process ok and proven, inspected & tested at CERN. Now need final CT images (125um wall) and evaluation from NAMTEC (freebie) to finalise reporting. # Still not made many items in this material Exhaust dimensions or on-Stave cooling tube guessed> 2.175 OD x 0.125mm wall (CP2 Ti), shared by IBL/PIXEL = sharing statistics and reporting. Tube developments • Need to begin pressure drop measurement component manufacture for realistic results of mass flow etc to refine tube dimensions (ex & cap). • 6Al4V Ti tube procured for alternative weld trials (is a better material all round) but impossible to obtain stock in our small dimensions because of low volume required. Could be made if we know a final quantity but our consumption is likely still to be too low. Will continue to gather joining data as will be done and published – an ideal but maybe not realistic • GETTING A LEAK TIGHT SEAL ON ODD SIZED TUBE FOR TESTING IS A PAIN IN THE A##. Everything is custom! Still a bad idea. 2 - 2.5mm OD please! • Can only manufacture in 3m lengths due to EU cleaning chemical rules – working on special dispensation but will need assistance as not much information available. 50um image of tube end – small edge defects

6. Ti tube capillaries AIMING TO REDUCE MASS OF WALL TO 0.125mm. Unlikely to be lower! • Capillaries – diameters and wall thicknesses now being prototyped. Initial problems, 3m length, 150um wall was difficult to get round (stock sizes). • Current capillary dimensions on offer (easy as drawn from stock) • MINIMUM BORE 0.3mm, MINIMUM WALL 0.150mm, MAXIMUM LENGTH 3000mm • 1.2mm OD x 0.90mm ID x 3000mm • 0.80mm OD x 0.50mm ID x3000mm • 0.60mm OD x 0.30 ID x 3000mm • Prototype capillary tubing fresh from the mill has now reduced wall to • 0.750mm OD x 0.490mm ID x 0.1300mm Wall. • 0.670mm OD x 0.405mm ID x 0.1325mm Wall. • 0.595mm OD x 0.330mm ID x 0.1325mm Wall. • 130um is about as low as sensible to pass pressure testing with headroom – we need good old fashioned measurements now to determine the ID. • 0.330mm ID is the smallest ID possible using this manufacturing process and UK factories. • Larger ID’s than 0.5mm possible through to 0.9mm ID. • Real testing is needed to enable further refinement, but it’s a start………..

7. Capillaries had too much mass in tube wall for optimal xo performance. • Looking at max burst pressure v watt thickness but large manufacturing constraint as stock sizes dictating final drawn sizeof ~130um wall • Can only purchase as international community to persuade Sandvik to supply stock in small enough volume. ~0.25 Tons. • I still doubt that we can achieve MOQ collectively so a rethink is needed. • Need to finalise a suitable joining solution as EU REACH preventing production longer than 3m – check if international shipping dispenses company from regsand store tube at CERN? VAT? Tube stock availability & lead time

8. This is not a serious proposal! Ti production currently limited to 3m lengths 10m PEEK capillaries purchased for fun with ingenious finger tight 500bar connectors PEEK capillaries • PEEK (polyetheretherketone) finger tight fitting are convenient, inert, and bio-compatible. • 1/16 inch O.D. PEEK, stainless steel, titanium, Tefzel, or PTFE tubing. • Compatible with most solvents (not concentrated sulfuric and nitric acids), • PEEK ferrules do not permanently lock into place on the tubing.

9. CP2 Ti weld joint Orbital TIG joint repeatability • CP2 Titanium1/8”OD x 0.20mm wall • 1042 repetitive welds • First 20 welds suffered from same lack of refinement as 316L process. • Testing at CERN for random batch samples – shipped. • OXIDE was a problem specific to this batch of Ti tubes only. • Regular cleaning is increasing repeatability. • More attention is paid to the joint preparation. And electrode. • WPS being written (best practice) • The process is highly repeatable for both materials (316L & CP2 Ti) and now highly optimised. • I need to check this again with a number of fixed tubes representing detector service connections then repeat the process for the CP2 Ti 2.275mm OD x 120um wall when happier with the weld itself. • Weld head angle. Electrode start position. Clearance for weld head • Internal gas purge pressure may be the tricky item to manage correctly during installation in the cryostat.

10. Welding of CP2 Titanium 120μm wall tube • Flare one end of the tube to bring extra material into the overlapped joint. = 120μm + 120μm give abulbous weld bead (now controlled to outside of tube by altering angle and depth of flaring tool) ~60μm Welded joint wall of ~220um wall at highest measured point straight tube flared tube • Can successfully join the 2.275mm OD x 120μm tube with orbital welding using the above process. Initial NDT results are underway (x-ray). Data returned (x-ray only) and have refined inclusions by • better cleaning methods. • This can be refined much further as not happy with visual results. ON THE LIMIT OF THE MACHINE • Gas purge issue is due to custom fittings not sealing correctly on tube OD. Refined but not fantastic. • Thrown fittings away and use soft Si tube (gas contamination) insert weld First butt weld joint in 2.275mm CP2 Ti – pin hole every time. Best welded joint to date using new tooling to create sleeve joint. Still have a indentation from post weld cooling [pressure or cleanliness] = Will now start high repeatability trials with this material. 1000 samples (Ti shortage)

11. Welding system evaluation Swagelok M200 COTTS From my 2007 market survey, the Swagelok M200 TIG Orbital welding system was the best priced system: CHEAP BY COMPARISON with other systems. EASY TO USE software removes operator knowledge WORKED OK FOR BASELINE 316L TUBE SERVICEABLE & SUPPORTED Has broken once, we’ve blown it up once or twice. Original system at Sheffield working fine 2nd System based at RAL. CAN NOT WELD 125um CP2 Ti FAILS TO WELD 180um wall tube. Weld heads all need to be modified to work well. Software all needed serious messing with. Effort v cost = not so good. Once the Ti wall went to 125um it caused me problems With enough time – most things work in the end. Biggest issue is high powered arc starting AV causing potential issues for damage to electronics Sheffield micro-weld head

12. Weld head mods at Sheffield – have tried UHP small weld head on loan from manufacturer. Have constructed digital IO to analogue module to interface to M200, unsure if was sensible use of effort as virtually removes all M200 useful functionality. • Modified version of the smaller scissor jawed weld head from Swagelok is working well but needs further refinement for joining 125um CP2 Ti. • Electronics damage – slowly understanding more with the system outputs and quirks, producing a best practice guide to avoid majority of misfires. • Reprogramming the system outputs (altering M200 welding software) for lower initial start arc – trade off with arc ramp down – may be a waste of time but worth a try. • Adding grounding system to drop initial arc start voltage – proving problematic so again, firmware needs altering inside machine to allow arc to start • Keep popping bits of the machine but it is easy to repair and quite robust. Future plans for M200 development Ultra pure gas purge system • Weld head internal temperature measurement is in progress. • Set up under construction for use with Tim’s FEIR camera. Tech effort dependent. • LASER WELDING – still on going investigations from Ian Mercer, we did expect some delay from SPI before final ideas placed on paper. Hopefully news soon.

13. Understanding system performance • Getting to grips with the M200 quirks. • Misfires mainly caused by bad practice, poor joint alignment and laziness. Correct procedure does solve this. • Occasionally there is a weird event. • 1000 welds on identical CP2 Ti stalks has seen 3 misfires = 3 failed joints. • 1000+ welds on 316L tube has seen 5 misfires = 5 failed joints. • WHY?Tmperature alters gas pressure so need to adjust as lab warms up • RH should not affect closed chamber welds – measured, undecided as low stats • We have no real way of measuring this. Right now I don’t believe the OSD/GUI showing A/V of the weld = RMS + fudge factor. • SO- measurements needed – HOW? • Looks nasty on first investigation but possible. • Swaglok M200 has reverse engineering protection in the system – connection of scopes and probes etc cause misfire or failure to start weld procedure. • It pretty simple in reality so we’ve figured out how to get round this & can now take measurements…………….. But before this……..

14. We made something new

15. New welding system development • Over the past 5 years in conjunction with our industrial partner Sheffield has developed an fully automatic TIG welding system that produces accurate low current narrow bead welds sourced from our partners aerospace joining knowledge. It was obvious that nothing like this was commercially available. • From the use of high frequency pulsing interposed within the pulsed weld current gives the system its unique characteristic and is capable of joining two razor blade edges together without distortion. • The benefit of this technique is that increased arc force or penetration is achieved with a lower input current which is crucial to thin wall Ti tube welding by allowing for improved heat management on critical welds whist still attaining full penetration. • Has additional grounding to prevent high arc start voltages through work piece • Production version fully tested in Sheffield available to ATLAS Upgrade for R&D. • Looks to be capable of joining >125 um Ti using minimal power– how thin? No idea at all (yet) • ~0.3A, 30v on 250um CP2 Ti tube (automatic weld)

16. Waveform arc v profile PLEASE DO NOT REPRODUCE

17. First weld set to offer the ability to weld single crystal and difficult to weld alloys such as Inconel 738, 713, MAR-M 247, PK33 and Titanium without a chamber or trailing gas shield. Pulsing switched off 60 Amps at 14 Volts (10 minutes welding 5 minutes cooling) Pulsing switched on 50 Amps (60 A Main, 40A Background) (10 minutes welding 1 minute cooling) System Details • Initial Current 0.1 – 60 Amps • Upslope time 0.0 – 20 Seconds • Downslope time 0.0 – 20 Seconds • Finish Current 0.1 – 60 Amps • Finish time 0.0 – 25 Seconds • Pre purge gas 0.0 – 100 Seconds • Post purge gas 0.0 – 100 Seconds • Main Current 0.1 – 60 Amps • Background Current 0.1 – 60 Amps • Main time 0.01- 5 Seconds • Background time 0.01- 5 Seconds • InterPulse Current 0.0 – 60 Amps • Time per level 0.01- 99.9 Seconds • Supply 230Volts 13 Amps 50Hz Current set up in old lab, 3 TIG weld systems 2 auto, 1 manual. 2.275mm OD tube weld cassette & head with arc start grounding 50 Amp Auto TIG version (130 Amp too big for ATU)

18. Weld head • Set up of electrode distance with shim – needs refining • Additional clamp for grounding during arc start • Remember start position and direction

19. New system programming/test Joints made with 0.4A & ~14v – no pulsing 2 years work in 6 hours!

20. Weld Parameter Sheet • By simplifying the weld build up as individual parameters, we can make accurate reproducible joints. • This approach is essential to automatic welding

21. Generic weld system measurements • Initial set up (principle so may refine) • Torch micro-positioner & rotary table • Can enclose in environmental chamber to match head conditions. FTIR window for arc profile • Some nice shunts for both A/V (plug and play to USB with some of our own software) monitoring both positive & negative outputs (electrode negative TIG system) • Power analyser measuring consumed power at 4 points in the system, mains input, pre start cap, pre main weld IC, ramping IC. Will refine as understood. • Using timestamp and data values linked via pc to both measurement systems we should see the variations. • We will then induce failure to measure and understand what happens. • We can then plug in the separate work-piece ground and remeasure. • Doubles up to measure electrode tip angle effects on arc profile and subsequent power / heat input to tube. Turntable Manual torch micro-positioner & fast scope USB shunts

22. System measurement schematic Input measured by power analyser Output by shunts Timestamp and data collected together in LabVIEW programme NOT tried out in anger

23. System measurements • Single & 3 phase measurement • Input voltage/current measurement • Output voltage/current measurement • Triggers at arc start • Configures to open and closed chamber weld heads or torch • Synchronised data taking • Hopefully learn nothing nasty!

24. Electrodes for TIG • Will drive you crazy…. • Swagelok items have to achieve CE certification. They are not fantastic for our use. Need to understand tip/length reproducibility v performance. • Custom electrodes made in-house at Sheffield outperform standard items. Measured by reduced heat damage, deeper penetration of weld = ~35% less arc power needed – need to work out how to cut tungsten to length accurately without shattering electrode (causes premature wear / arc failures) • Struggling for “clean” space – electrode prep contaminates area and reduces weld performance. New lab taking time – refurbishment very slow. TIG grinder (wet) • Tube/Electrode preparation area • Current issues are debris contamination so need some form of extraction – building does not permit ventilation to outside world (Dyson?) • Should store electrodes dry – drawers needed • Bake out before use – oven? • Separate grinding machines (or wheels) for different materials – final choice = 1 wheel only • Tube cutting proving laborious • Tube facing tool performance satisfactory • TOO MUCH STUFF FOR ONE PLACE Tube cutter Tube facing

25. Decision time • Theoretically there is only one of me, my time is split many ways and I need to be more efficient. • Assuming that 125um wall tube is desirable I’d sooner put effort into new system testing and give up with pushing the M200 past its limits and use this for tube wall >200um (services). • I reckon we have ~50 separate measurements to make for each weld to fully quantify and understand each. • I’ve not made the time to document this work but have reasonable notes. I’m in danger of forgetting as pace picks up. • Odd OD’s cause huge tooling costs in fittings, weld heads etc. • Pressure drop work is now ~ 1 year behind where we wanted to be. • We have many of the components but not enough to move forwards to allow us to decide on tube ID’s (EX &Cap). • Laser welding has gone very quiet – needs a push.

26. Next 12 months overviewAssuming we have minimal decisions made so rather vague or exceptionally obvious • Stave, Stavelet cooling circuits • Re-stock of cooling circuits and stavelet circuits. Include pressure testing > DATABASE entry. • Re-stocking of tube material and bending trials on capillary tubing • Pressure drop measurements – • Components part produced – design finalisation required • CO2 plant booking expired. This area has stalled and we are in trouble here. • TIG Orbital Welding. • Reprogramming M200 and using grounding system from new system • Gas purge over long distance and multiple manifold measurements/effects on weld quality. • Measurements of electrode tip angle – arc gap and power v weld quality • Finalised electrode – seeking mass production or tooling to make in house. • Continuing to refine Swagelok weld head for heat sinking and improved tube alignment. • Bring online the InterPulse system and test on 2.275mm OD 125um wall CP2 Ti. • Laser welding • Hopefully news soon. • Material reduction • Changing bulbous sleeve joint to butt weld on 125um tube with tooling from PIPE ltd. • Reducing mass in capillary tube wall – production limits. • Fittings • Vac brazed stubs full statistical trial. • CP2 ti fittings – material sourced from Sandvik. Need to check cost out v custom fitting from Swagelok or Fti plus the effort put in at QMUL. • Re-manufacture of 6LV VCR thin wall fittings as run out. • Thermal shock etc in the pipe line at some point– hardware almost completed at RAL. • Burst testing of circuits to see where calculated headroom is v actual – mass reduction maybe.

27. ADDITIONAL INFORMATIONAlternative joining techniqueVacuum Brazing of CP2 Ti to 316L Stave 250 drawings of cooling tubes at z=~1.3m

28. ATLAS Upgrade dissimilar metal joining activities • Overview • Stainless Steel to Titanium joining (temp connection) • Copper to Titanium (pressure drop measurements) • Richard French, Paul Kemp-Russell: Sheffield • Keith Birmingham: Aerobraze Europe • Neil Austin: VBC Group Ltd (brazing division) • Trevor Smith: Firmachrome Ltd • Peter Cookson: Bodycote

29. Connectors • Swagelok VCR in 316L works well as temporary fitting. Used 316L weld on VCR either with a TIG weld or Vac Brazed joint. • Mass of nut is an issue, also nuts are sliver plated inside to prevent galling which has proved problematic for vac brazing. • LOW mass fittings – VCR in CP2 Ti could be possible, can only find reasonable stock in Grade9 Ti to produce. QMUL CNC? Units of production too low for Swaglok MOQ • Vac brazed stubs work well – need statistics • Ideally remove the stub preferring tube-tube joint for low mass and increased reliability - relatively easy to do with a sleeve jointed TIG weld (common in nuclear reactors etc) – not ideal for dissimilar material joining • Can vac braze 316L stainless to CP2, Grade 9 and 6Al4V Ti without issues (other than getting the final ones back). • Vac brazing ceramic to Ti & 316L next (ideally write up so far before this)

30. Stainless VCR connector to Ti tubeUsed to make temporary test fitting stubs for cooling circuits………… Method A = cheap idea Method B = proven but expensive Vacuum Brazing using an aerospace proven method Using a silver copper eutectic braze alloy, coat the Ti with the alloy, assemble the Stainless VCR fitting to the tube (post electro-polishing) and place in furnace at a lower temperature somewhere around 850°C. http://www.vbcgroup.com/focus/Brazing-Division/Brazing-Alloy-selection-tables/BrazePrecious.htm Excellent joint, clean and pressure handling proven up to 250bar. 3.175mm Ti has heavy oxidisation that is proving difficult to remove. This is needed for the Cusil alloy to adhere to the Ti tube. Once tube is cleaned (glass bead blasting) good adhesion is found. • Electroless Nickel Plating. • Electroless Nickel coating is an alloy of nickel and phosphorous. Ability to work to close tolerances without post-plating grinding, whilst holding the original surface finish. • Electroless Nickel can improve corrosion resistance, wear resistance, lubricity, solderability or be used to rectify and recover close tolerance undersize parts. • The big advantage of elecroless (chemical) plating over electrolytic plating is it will adhere to Titanium, in a very controlled manner. We do not need to plate the entire circuit, just local areas as wherever the solution touches it will plate. • Both methods are the “active” or direct joining of dissimilar materials with a braze filler metal (BFM). This is ideal for Ti as the BFM forms a strong permanent joint with the base materials. • What we did not realise is that at certain temperatures the Ti can suddenly start taking on alloying abilities with the BFM. This should not have happened when correctly controlled. • Titanium is a strong oxygen-getter, and thus will react with any oxygen that it can as it is heated from room temperature up to brazing temperature, therefore, "reacting" too early. • This is with free oxygen or water-vapor in the furnace atmosphere, or with metal-oxides on the metal surfaces during heat-up (such as when the metals are not properly cleaned prior to brazing), then the so called “brazing” (joining/bonding) of alloy-to-metal may be completely prevented from happening.

31. Method A Stress cracking CTE mismatched • During this process, the bonding was be very successful but, the difference in the thermal expansion between the 6LV stainless steel – Nickel – Titanium which it is being joined caused premature cracking to develop in the brazed joint upon cooling. If we did not see the cracks at this stage they would present themselves during subsequent use in service. • It is very important to try to match the expansion characteristics of the metals to filler to metal joint, so that huge stresses in the joints are not built up. • During the furnace cycle (1100C) something really odd happened. High temp was down to a miscommunication. • The braze alloy has a initial melting temp of around 400C. The furnace temp was in the region of 1100C. Therefore we managed to alloy Ni with Ti: Ni-Ti alloyed tube As the Ti reaches 600C the oxygen in the Ti starts getting thirsty and in the resulting exchange drags the Ni into the microstructure. As the assembly cools, it falls apart as the CTE mismatch is beyond what the structure can cope with. GOOD NEWS – we don’t necessarily need to vac braze all our components and can do this with any induction furnace (have small tube furnace in lab ready). Ni plating works fine so will drop the cost of the heater block joining for pressure drop work.

32. Method B = OK! For mechanical tolerance, achieve a good push fit in the Ti tube to VCR fitting. Micropolish fitting. Using Cusil braze alloy from VBC simply clean components and plate the Stainless Steel component. Mechanically clean Ti, chemically clean the Ti, assemble components and remember your nuts. Place in furnace at 850C and cycle once allowing time to cool. Bingo – one joint. Items of weirdness to note: The VCR nut threads are silver plated to prevent gauling during assembly. This silver is reflowed during the furnace cycle. 1/8” Ti to VCR 2.275mm OD Ti to VCR 1/8” Ti to VCR NEW REFLOWED

33. What is length tube sticking out from stave end? Universal decision for 250. EOS – how does this shape up?

34. Image of z=1.3 Stave end