Target Operation and Status Report

1
Target Operation and Status Report

• Chris Booth for Target Team
• 13th January 2009

• Outline
• Current target performance
• Investigation of demonstrator failure
• New mechanical design
• Control monitoring issues
• Particle production vs. beam loss

2

• Current ISIS Target
• Target operation in ISIS for beam-line studies
  gt190K pulses by end December.
• Actuation control have operated flawlessly no
  target drops.
• Software (DAQ monitoring) run well, allows
  remote monitoring.
• System operated by non-experts.
• Target behaviour stable and reproducible.
• 29th November target accidentally parked in
  beam
• Interlock added to prevent parking with frame
  lowered
• 20th December target stopped actuating
• Apparent mechanical failure.
• No dust visible on inspection plate.
• Removed 10th January for examination. Awaiting
  news.
• (Any connection with previous incident?)

3

• Possible Demonstrator failure causes
• Misalignment of bearings and shaft. ()
• Partial demagnetisation of permanent magnets
  causing non-axial forces. ()
• Distortion of coils causing non-axial forces.
• Dynamic distortion of shaft.
• Poorer quality DLC coatings on shaft and/or
  bearings.
• () Already eliminated at last CM.
• Above are addressed in the following slides.
  Several experts from RAL, Sheffield Materials and
  outside companies (as well as MICE) have been
  consulted and provided valuable expertise.

4

• Stator Field Measurements Modelling
• Field measured (for DC current) by Craig
  MacWaters Paul Smith. FEA modelling by Paul.
  See following slides.
• Small azimuthal variation seen.
• Equivalent to coil offsets 0.2 mm.
• This is also the precision of the position
  reproducibility.
• Upper limit on coil misplacements is therefore
  0.2 mm.
• Further FEA in progress to determine how this
  maps onto transverse force on the shuttle
  magnets.

5
Stator field measurements

• B Field measured for every 0.2mm axially over a
  distance of 120mm. Repeated at 30 deg
  increments.

6
FEA Modelling
Repeated for AC Data Similar Match
7

• Dynamic distortion of shaft

• Distortion of shaft ?
• Stephanie Yang/Wing Lau modelled behaviour under
  acceleration.
• 30 Hz mode found (c.f. 30 ms acceleration period
  in operation.
• High speed camera data also shows wagging
  motion at similar frequency.
• (No evidence from camera that Sheffield
  shock-absorbing mounting is significant.)

8

• Dynamic distortion of shaft

• Distortion of shaft ?
• Stephanie Yang/Wing Lau modelled behaviour under
  acceleration.
• 30 Hz mode found (c.f. 30 ms acceleration period
  in operation.
• High speed camera data also shows wagging
  motion at similar frequency.
• (No evidence from camera that Sheffield
  shock-absorbing mounting is significant.)

9

• Surface coating problems
• Poor Diamond-Like Carbon (DLC) coatings ?
• Sheffield RAL team visited coating company
  (TecVac), who had examined failed parts.
• Likelihood of adhesive failure due to presence of
  cleaning or polishing materials, or oxidation due
  to wire erosion of bearings.
• Sharp edges give electropotential leading to
  uneven coatings.
• Surface quality pre-coating was also probably
  inadequate. (Recommend 0.1 to 0.02 Ra compared
  with current 1.6 Ra.)
• Adequate surface finish difficult to achieve with
  present machined cruciform shaft.

10

• New Mechanical Design
• Jason Tarrant producing revised mechanical
  design.
• Discussed at weekly target phone meetings.
• Details in Target Parallel this afternoon only
  summary here.
• Huge amount of work summarised in one slide!
• More rigid stator assembly.
• New flanges with bearings machined in situ.
• Improved alignment, reduced tolerances.
• Radically different shaft design to improve
  rigidity, ease of construction, surface finish.
• Tubular lower section (not cruciform)
• same mass/length as at present
• Flat on upper cylindrical section, with
  anti-rotation piece on bearing.
• Shorter shaft by reducing flange revised bearing
  positions.

11
Revised stator body
12
Upper Bearing Design
Single piece main body

• Alternative bearing design

Clearance for vane (potential risk if adding vane
later otherwise simpler bearing)
Wire cut from single piece for accurate wedge fit
Full bearing merges into section for anti-rotation
Wedge dowel for full x,y,z location of clamp
M/C with block in place to prevent tool wander
Anti rotation Feature (rounded or flat bearing
face options)
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• Conclusions of Target Workshop last week
• Timescale very tight.
• Drawing up documents for review.
• Key materials (Ti tube) should be ordered now.
• Baseline target is continued 6 mm tube
• Other geometries/materials may have particle
  production advantages
• Must not delay installation of next target
• Baseline coating is DLC
• Other coatings (HIPIMS, WS2, WS2 over DLC) may
  have advantages.
• Investigation will be left for subsequent
  targets.
• Informally, ISIS representatives are happy with
  design.
• Must have two drives ready for Demonstrator and
  installation in ISIS during April shutdown.

14

• Control Electronics Upgrade
• Present system stable, reliable but expert
  system, unfriendly to normal users!
• PIC processors at computational and I/O limits.
• Complete redesign planned with improved
  interfaces, PC configuration control,
  flexibility, enhanced feedback,
• FPGA-based system using USBDAQ board proposed.
• James Leaver (IC, FPGA experience) and Paul Smith
  (present target control designer) working
  together.
• 5 crates of electronics may come down to single
  FPGA plus few daughter cards (for A to D etc)!
• Requested input from MICE community over desired
  functionality.
• Major project expected to take 12 months.
• See talk this afternoon!

15
USBDAQ
4Mb PROM
1M Gate Spartan 3 FPGA
USB Mini-B
Cypress SX2 USB Interface
Single Ended User IO
1.2V Regulator
Differential / Single Ended User IO
2.5/3.3V Regulator
16

• DAQ Monitoring
• Change to new DAQ card has led to driver
  problems.
• Currently converting digital position to
  analogue! Unsatisfactory.
• DAQ code (James Leaver) dumps data to
  individual pulse files.
• Target depth, beam intensity, bam losses
  (various), frame status recorded
• Wish to include beam position, external delay
• Various monitoring codes (inc. EPICS based see
  Pierricks talk this afternoon).
• Hardware control upgrades will imply DAQ,
  monitoring control software redesigns.
• Again, input feedback requested from the
  community.
• For more details, see talk this afternoon!

17

• Beam-loss Particle Production
• Adam Dobbs ORBIT simulation of target ISIS
• Different target geometries orientations.
• Present orientation losses mainly near target
• 90? rotation losses near injection (see plots)
• Other angles, geometries considered.
• Marco Apollonio G4Beamline simulation of
  collection
• Pion acceptance into Q1 largely unaffected by
  target shape or orientation.
• Aluminium, Carbon, Beryllium also considered.
• Detailed study required to optimise collected
  pion to beam loss ratio.
• But must also consider mechanical and thermal
  properties! Aluminium could melt!
• For more details, see talk in beam-line session.

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Present orientation 90? rotated