MICE MICE Target Mechanism Paul Smith University of Sheffield 8 th June 2010 (Based upon talk given by Chris Booth at CM26)

MICE History & Overview T1 – DLC bearings – running in ISIS (Installed Aug 2009) –> 215k + 50 k actuations - DLC on DLC T2 – nominally identical to T1 –Bearing failed rapidly - DLC on DLC T2.2 – like T1, improved QA –Failed after ~80k actuations - DLC on DLC T2.3 – same stator & shaft as T2.2 –New Vespel (polyimide) bearings – Vespel on DLC –Tested for >2.1M pulses in R78 Jan/Feb 2010 Results of T1 running, T2.3 tests, and plans 08/06/20102P J Smith - University of Sheffield

MICE Actuation 08/06/2010P J Smith - University of Sheffield3 Strike Beam Centre Distance (BCD)

MICE 08/06/2010P J Smith - University of Sheffield4 4 T2 distribution 3-4 times as broad Can be interpreted as a result of the target “sticking” due to adhesive pick-up of particulate DLC - wear. Confirmed when taking target apart – Mice note 269 MICE use the BCD histograms as a diagnostic to spot changes in target performance T1 T2 BCD (beam centre distance) DAQ Analysis (analysis by Paul Hodgson)

MICE Overlay of T1 Calibration Plots 08/06/2010P J Smith - University of Sheffield5 Represents 71K to 142K Actuations

MICE Summary for Target 1 Target continues to perform reliably (> 215k + 50 k actuations) No sign of significant change in BCD distributions No sign of dust production on view port – Latest photo 07/06/2010 – No Dust Target keeps running! 08/06/2010P J Smith - University of Sheffield6

MICE Status of Target 2.3 T2 Vespel installed in R78 Jan 25 th 2010 DLC coated shaft (from T2.2) – Vespel bearings Same stator body as previous T2 Pulsed target continuously for 2.15×10 6 pulses Approx. one month of operation at ~1 Hz Two short interruptions, chiller failed 1/2/2010, UPS failed 8/2/2010(!) Neither problem associated with target mechanical performance Target was deliberately stopped for inspection Very little dust on view-port (~ daily photos) 08/06/2010P J Smith - University of Sheffield7

MICE T2 BCD over month 08/06/2010P J Smith - University of Sheffield8 720k s1680k s Change over ~1 day Start up period DAQ gain changes 1×10 6 pulses EarlyMidLate

MICE T2 Acceleration over month 08/06/2010P J Smith - University of Sheffield9 Chiller failure Test power off UPS failure

MICE T2 Acceleration regions 08/06/2010P J Smith - University of Sheffield10 Steady decline 848 to 838 ms -2 Stable operation (838 ± 5) ms -2 Increased variability Early Mid Late 720k s 1680k s

MICE 08/06/2010P J Smith - University of Sheffield11 Questions and Comments How would the target have performed if we had carried on pulsing ?  Remember we arbitrarily stopped at 2.15 × 10 6 pulses. Does the early period correspond to the target “bedding in” ?  The mid period lasted approx. 1 million pulses where the target showed stable operation.  There was a reasonably rapid (1 day) change in performance after which the target parameters were (slightly) more variable. None of the variation seen above would compromise the normal target operation. The typical beam centre varies more than the target BCD. 11

MICE Disassembly & Inspection of Target 2 (Jason Tarrant) 08/06/2010P J Smith - University of Sheffield12 Target stopped after 2.16M actuations Optics block removed & upper bearing exposed Bellows removed & lower bearing exposed Significant amounts of Vespel dust, adhered to surfaces

MICE Disassembly – View of upper Bearing 08/06/2010P J Smith - University of Sheffield13 First look Little dust (polished flat) Most dust (rough flat) Polished flat Rough flat Amalgamated dust balls Dust On shaft, On bearing, On lock ring Survey point

MICE Disassembly – View of lower Bearing 08/06/2010P J Smith - University of Sheffield14 Dust around bearing, lock ring removed Internal face External face

MICE Observation – Dust Amount –Most at upper bearing – esp. anti-rotate rough flat side –(Only one flat on shaft polished) –Amalgamated at bearings – scraped off Location –Coated internal components, has escaped externally –How does it move / defy gravity? Thrown off? Electrostatic attraction? Vibration movement? When let up to air? Attachment –Fixed – by what? 08/06/2010P J Smith - University of Sheffield15

MICE Stator QA 08/06/2010P J Smith - University of Sheffield16 Is stator 2 different from stator 1? Stator field mapped with assistance of group at Diamond Indication of ~300um offset in magnetic axis. Note: This value is to be re-checked! Stator will be run in R78 with bearings aligned with the offset. Will this improve wear rate? An FE model of the stator has been built, the predicted forces match the observed forces very well. The model predicts strong lateral forces if shaft is not aligned with magnetic axis (for 500  m offset max lateral force = 10% thrust Force) The modelling and field measurements suggest that we need to improve the coil design/manufacture to ensure magnetic axis aligns with the geometric axis.

MICE Next Steps 08/06/2010P J Smith - University of Sheffield17 Reduce wear & dust production - Polished flats, burnished bearing faces - Continue using Vespel (but there are additional plastics that can be tried) - Align bearings with known magnetic offset Trap dust in catcher Further tests to start in June

MICE Summary Target 1 installed and operating well in ISIS Target 2 with plastic bearings performed reliably for >2M actuations –Stopped for inspection, not due to failure Test & measurement programme for reducing and trapping dust Stators have been magnetically mapped to improve QA – indication that there is a magnetic offset with stator 2. 08/06/2010P J Smith - University of Sheffield18