1. MICE Target l Jason Tarrant – STFC l Investigative work on T2 with plastic bearings »Stopped after >2 million cycles »Disassembly with photographic investigation »Microscopic investigation of bearing surfaces »Observations »Resolutions

2. l Disassembly – To upper Bearing MICE Target First look Little dust (polished flat) A lot of dust (rough flat) Polished flat Rough flat Amalgamated dust balls Dust On shaft, On bearing, On lock ring Survey point

3. l Disassembly – To shaft & vacuum tube MICE Target Coating on shaft Deposits on magnet In vacuum bore Bearing regionExternal to Target Dust to here

4. l Disassembly – To lower Bearing MICE Target Dust around bearing, lock ring removed Internal face External face

5. l Disassembly – To bellows MICE Target View into bellows

6. MICE Target l Observation – Dust »Amount –Most at upper bearing – esp. anti-rotate rough flat side –Amalgamated at bearings – scraped off »Location –Coated internal components, has escaped externally –How does it move against gravity? l Thrown off l Electrostatic attraction l Vibration movement »Attachment –Fixed – by what?

7. l Inspection - Upper bearing MICE Target No wear Tram lines Worn smooth

8. l Inspection – Lower bearing MICE Target No wear Longitudinal scratches Machining marks Worn smooth Wear regions 2 & 5 – Worn smooth 1 & 3 – Little wear, m/c marks 4 – Some wear, smooth + m/c marks

9. MICE Target l Observation – Wear orientation (lower bearing) Angle to vane Angle to stator power out Angle to anti- rotation

10. l Inspection – Anti-rotation component MICE Target Machining marks Rough flat wear Longitudinal scratches Longitudinal scratches Machined Surface Smooth flat wear

11. MICE Target l Observation – Wear on anti-rotation »Smooth side, machine marks in centre, longitudinal scratches on outside = rotation wear »Rough side, no machine marks, much longitudinal scratching = rotational + lateral wear »Wear region smoother than as machined

12. MICE Target l Reducing Dust »Smooth bearing interfaces –Polish shaft (both flats & cylindrical elements) –Burnish bearing faces (to size) »Harder wearing plastic –Duratron & Celazole alternatives to Vespel? »Target unit like T1? »Running less cycles l Managing Dust »Dust catcher

13. MICE Target l Conclusions »Plastic bearing is more tolerant to T2 running (DLC could not cope) »Wear does occur but bulk material tolerates wear (DLC too thin to do so, 3-5um thick) »Dust created –Fixed to unit (requires mechanical removal) –Will be reduced –Can be managed –Does not appear as ‘gritty’ as DLC