MICE Target Mechanical Design l Introduction - Issues with the current Target Assembly - Re-engineered Target with a ‘core’ based on stiff central housing to which critically aligned components fit then m/c as one. - Briefly cover coatings

MICE Target Mechanical Design l Issues with current design - Clearances between shaft and bearing allow lateral play - May cause hammering (shaft on bearing) - May contribute to lateral movement of target tip seen with HS camera - = Reduce clearance - Size and tolerance to give minimum clearance - Ensure good position and orientation between bearings

MICE Target Mechanical Design l Issues with current design - Ways to ensure good position & orientation - Bearing / assembly production Machine bearings & components very accurately (linear and geometric) to produce accurate assembly (relies on very tight tolerances and few components between bearings, currently 5 component between bearings and 6 ‘fits’) Machine parts separately and create assembly that allows adjustment on at least 1 bearing, e.g. an orientation + x,y adjustable mount. Assemble sub assembly and dowel together, fit bearings then final machine in ‘one-shot’ (dowel and bearing holes) (current assembly cannot be machined easily due to the protruding wires and cooling tubes)

MICE Target Mechanical Design l Issues with current design - Ways to improve on clearances + Alternative bearing hole shape that is easier to machine smooth and to tight tolerances (requires mating shaft shape change too). Ensure that the shaft is as accurate as possible (straight, smooth, tight tolerances) At least one bearing flexibly mounted to take up misalignment (even dynamic acting) Sprung follower to keep shaft in contact with bearing (causes extra force to ‘fire’ shaft) (Last 2 create side load and hence extra load on stator so not preferred)

MICE Target Mechanical Design l Issues with current design - Clamping of stator housing - Once welded = large unit. Risk of high stress / strain in vacuum tube (if knocked / screw tension lost / force when assembling optics) - = Alternative design Welded Vacuum Tube fixes flange separation Fixed height stator housing Possibility of placing uneven (skewed) load & not locked vertically

MICE Target Mechanical Design l Issues with current design - Resolving clamping issues Make the stator housing into central ‘core’ on which other parts are fixed (currently relatively complicated assembly of many parts) Core assembly to be fixed to bottom flange axially and supported radially at top (currently fixed axially at bottom and compressed vertically from top)

MICE Target Mechanical Design l Alternative core design - Extend stator housing and fit with end flanges - Machine - Assemble - Weld - Stress Relieve - Final machine Or make from solid? Should it be stainless steel?

MICE Target Mechanical Design l Alternative core design - Fit blank (cut-down) flanges - Align & dowel - M/C bearing bores - Fit blank bearings - Align & dowel - M/C shaft holes in bearings

MICE Target Mechanical Design l Stator assembly Collar welded on Stator and cooling jacket components added Tighten down stator stack with 3x bolts Fasten on cover

MICE Target Mechanical Design l Alternate core design - Remove bearings and upper flange and fit stator - Re-assemble upper flange with dowels - Fit vacuum tube & weld - Refit lower bearing & dowels

MICE Target Mechanical Design l Alternate core design - Insert shaft in lower bearing - Add upper bearing - Add bellows to protect lower shaft - Add optical housing to protect upper

MICE Target Mechanical Design l Alternate core design - Assemble the above ‘core’ assembly onto lower flange - Add stand-offs & fasten to bottom flange - Add top flange & fasten to stand-offs

MICE Target Mechanical Design l Alternative bearing design Wedge & dowel for full x,y,z location of clamp Anti rotation Feature (rounded or flat bearing face options) Single piece main body Wire cut from single piece for accurate wedge fit Full bearing merges into section for anti- rotation M/C with block in place to prevent tool wander Clearance for vane (potential risk if adding vane later otherwise simpler bearing)

MICE Target Mechanical Design l Other changes - Enclosed grating on vane for extra protection - Vane riveted on - Round tubular target end (nom 6mm OD 0.65mm wall, actual closest 0.7mm wall) l New assembly vs. current assembly - Issues - Thorough metrology required to determine relative position and orientation of bearing cups to decide on bearing clearances

MICE Target Mechanical Design l Tecvac Visit (PH, RN, E McC, & JT) - Possible cause of failure - Their DLC Expert thought probably adhesive failure - Polish left on from polishing (at Tecvac) - Silicon based chemicals for m/c - Excessive oxidisation from spark erosion

MICE Target Mechanical Design l Tecvac Visit - Recommendations for our design, as above + - Materials and hardness OK for this application - Improved surface finish (current 1.6 Ra, Ra pref) - No slots they cannot guarantee to coat the inside face - Differences in electro-potential can cause a build up (like electroplate) so relieve critical edges and corners - Other - The DLC hardness is 2000 Vickers not 4500 as quoted on the website (SP 2 SP 3 mix and hydrogen affect hardness, 20% H in Tecvac DLC)

MICE Target Mechanical Design l HIPIMS coatings (Talk to Professor P Hovsepian, Sheffield Hallam) - Multilayer TiAlCNi/VCNi alternating, each layer few nanometres thick, build up to 2.3-3um - Very strong adhesion, then delamination layer by layer so wear products are very fine (C diffuses at layer interface) - Vanadium implantation to adhere to substrate (adhesion of DLC know issue, Ar bombardment, Cr & CrNi coats help) - Wear in dry cutting machine tools better wear than DLC up to 2 orders of magnitude better - Comparable coefficient of friction in vacuum to DLC (DLC needs moisture! Both SP 2 & SP 3 ) - Temp as low degC but pref deg, affects density of coating but still better than other processes at low T - Industrial research standard rate £1000/run (10-20 pieces) Turn around in ~ 1week

MICE Target Mechanical Design l WS 2 coating (Dry lubricant) - Tungsten 0.5um thick (uniform) – 450degC & vacuum to Torr - Mil Spec DoD-L-85645A (inactive) - RoomT curing (can be accelerated with heat) - Can coat holes and slots dynamic and 0.07 static friction values - Can be over-coated on DLC - Limited to 698 MN/m 2

MICE Target Mechanical Design l Conclusions on re-engineered design l Decreased clearances bearing - shaft l Round bearing holes and round shaft (easier to m/c and finish) l Bearings & bearing recesses m/c in ‘one-shot’ & dowelled with core design, maximising alignment (position and orientation) l Minimum number of components between upper and lower bearings l Bearings main body = 1 piece l Bearing section and anti-rotation features separate but adjacent without a step / gap l ‘Safer’ assembly l Stator clamped in self contained unit, not rely on accurate alignment of larger flanged components l Solid location of flanges using pillars to eliminate potential skew stressing / straining delicate vacuum tube

MICE Target Mechanical Design l Conclusions on re-engineered design l Concerns l Anti-rotation feature & flat are relatively small, no idea presently of effectiveness l Ensuring shaft is straight and sections are concentric, especially where flat will be milled on upper section l Options l Go for it and get the new assemblies m/c & built…or l Use the alternate shaft and bearings in the present assemblies (need metrology) l Coatings l Try alternative?

MICE Target Mechanical Design l Schedule l Long lead items – identify now, into production immediately after a review (order materials now?) l Core tube = order materials, rough m/c, weld, stress relieve, final machine l Ti tube for target shaft = 0.7 has 4-6 wk delivery, 0.5 is 12 wk, then manufacture, weld, stress relieve, m/c / straightening, polishing, coating, assembly of magnet & vane l Timescale l Every attempt to achieve March assembly ready for offline testing