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Target Specifications & History (to avoid reinventing a broken wheel!)

Target Specifications & History (to avoid reinventing a broken wheel!). 2 nd December 2009 Chris Booth The University of Sheffield. Original Specification (2003). Enter last 1-2 ms of beam Not disturb next injection Variable dip depth Required entry into beam unknown, but ~5 mm

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Target Specifications & History (to avoid reinventing a broken wheel!)

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  1. Target Specifications & History(to avoid reinventing a broken wheel!) 2nd December 2009 Chris Booth The University of Sheffield

  2. Original Specification (2003) • Enter last 1-2 ms of beam • Not disturb next injection • Variable dip depth • Required entry into beam unknown, but ~5 mm • Beam shrinkage 17.8 mm • Travel 25 mm • Reproducibility ~0.2 mm • Accurately synchronised to ISIS, drift/jitter < 0.2 ms • Frequency 1 Hz or faster • Target titanium 1 mm across beam, 10 mm along • Slit across beam pipe 2 mm wide max. • Radiation hard, UHV materials • Resonant system disfavoured. On-demand actuation preferred.

  3. Considered solutions1) Rotating arm A • Axis  beam (motion // beam) • Single arm (plus counterweight) • 5 mm and 2 ms entry into beam •  = 12.6 mrad •  = 2 (1 Hz) • Arm length R = 63 m (!) • Target velocity 396 ms-1 (!) • Multiple spokes makes R even greater • Target position & adjustability – see next slide  R 5 mm

  4. Considered solutions2) Rotating arm B • Axis // beam (motion across beam) • 1 (or n) spokes • Cross ~ 30 mm in 2 ms • V = 15 ms-1;  = 2/n; R = 2.4 n m • N.B. Slot across beam-pipe (not allowed!) • Source of particles moves significantly • Axis of rotation must be adjustable vertically (to control depth) • Rotary motion – bearings in vacuum R 30 mm

  5. Considered solutions3) Linear motor options • Fixed coils, moving magnet • Brushless, easier to cool coils, ... • Bearing-free design – shaft supported on diaphragm springs • Required travel  large springs (~150 mm diameter) • Designed fatigue-free • Tests: unstable. Did not align shaft when extended. • Non-lubricated bearings • Ceramic on titanium • Brass on titanium • Leaded bronze • DLC on DLC

  6. Considered solutions4) Linear motor variations • External linear drive • Transmission through diaphragm/bellows to vacuum region • Caburn designers/engineers could not guarantee lifetime • Linear drive + lever • Smaller amplitude drive + mechanical advantage • Fail-safe (falls out of beam) • Possibly combined with diaphragm? • Stiff enough lever (I-beam)  too much inertia for required acceleration • Bearing again (with lateral forces) drive target

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