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BI.BSW Chicane Magnets

BI.BSW Chicane Magnets. D. Aguglia, J. Borburgh , B. Balhan, C. Baud, C. Bracco, C. C arli, M. Cieslak, M. Hourican, D. Nisbet, W. Weterings. Chicane layout. Beta beating mitigation. S-bend Only effective for a fixed angle, not throughout the ramp

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BI.BSW Chicane Magnets

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  1. BI.BSW Chicane Magnets D. Aguglia, J. Borburgh, B. Balhan, C. Baud, C. Bracco, C. Carli, M. Cieslak, M. Hourican, D. Nisbet, W. Weterings

  2. Chicane layout Review on PSB 160 MeV H- injection

  3. Beta beating mitigation • S-bend • Only effective for a fixed angle, not throughout the ramp • More difficult to implement mechanically, in particular on short magnets • Combined function magnets • Only effective for a fixed angle, not throughout the ramp • R-bend and active compensation • Chosen as baseline solution Review on PSB 160 MeV H- injection

  4. Powering • Ramp down time ~ 5 ms. • Controlled ramp down to allow active compensation. • All four magnets per ring powered in series. • Each power converter will occupy either 2 or 3 19’’ standard racks. • 4 power converters + 1 spare = 10 to 15 racks. • Controllable switch mode power converter + current step-up transformer in the tunnel • Transformers to be placed near magnets, assuming 10μH margin (for cables + uncertainty on magnet inductance + transformer leakage inductance) → transformers must be placed not farther than ~5m from magnets! Review on PSB 160 MeV H- injection

  5. Power converters Topology : AC/DC conversion to 1kVDC & DC/DC conversion via two interleaved IGBTs H-Bridges. Interleaved topology allows using standard IGBTs (current share) and reduces current ripple. Magnetic energy regenerated into the capacitor banks (minimized losses & power consumption) Power converter output: 1kV - 1.5kA 1.5MW peak power Simulated primary voltage and current

  6. Bump closure flexibility • Following recommendation of “PS Booster with Linac4” review (January 2009), magnets are assumed to be powered in series per ring. →All magnets will have to provide same ∫B.dl/I. →Magnets should be aligned precisely at their position longitudinally. Would trim power supplies be desirable? Review on PSB 160 MeV H- injection

  7. Space constraints • Magnets must be removable from ring without breaking vacuum. • Permissible septum thickness limited. • Longitudinal space limited to 380 mm, to allow sufficient space for stripping foil mechanism. • Magnetic length maximised (↘β beating). Review on PSB 160 MeV H- injection

  8. Baseline magnet parameters Assumes ceramic vacuum chamber with a vertical beam acceptance ~ 65 mm. Review on PSB 160 MeV H- injection

  9. Parameters per magnet type Review on PSB 160 MeV H- injection

  10. How to describe field imperfections • What to calculate? • How to take into account field perturbations by dump and beam instrumentation? • Vacuum chamber coating neglected so far. • All calculations refer to By. Review on PSB 160 MeV H- injection Blue area within 1% of ∫Bnom.dl

  11. How to take into account field imperfections • Static field imperfection can be described as dipole with higher orders, but these are position dependant during the ramp. • Influence of eddy currents could be neglected if sufficiently low (dump, vacuum chamber coating). • Field maps could be used, but would have to be calculated for each turn. • Imposing a maximum limit on the field imperfections (in space and time)? May lead to unrealistic values for such short magnets (magnetic length is less than 4 gap heights). Review on PSB 160 MeV H- injection

  12. BSW1 leak field • Requirement not formalised. • Targeted leak field: 10-3∫Bnominal.dl. • External magnetic screen foreseen. • Count on injection steerers to compensate remaining leak field. Review on PSB 160 MeV H- injection

  13. Influence of dump on field in BS4 • 2D and 3D simulations performed. • Both solid as well as segmented dumps evaluated. Field distortion by dump eddy currents Review on PSB 160 MeV H- injection

  14. DUMP and its monitoring • BI equipment not taken into account for simulations as yet. • Dump specification defines a limit on the field disturbance due to presence of dump (1%). • Dump material suggested in specification: Carbon with resistivity in 1-510-5Ωm range. Review on PSB 160 MeV H- injection

  15. Magnetic field on stripping foil • Forces induced on the foil not evaluated yet, but J and B rather low. • How to track electrons escaping from the foil? Jmod < 0.7 μA rose coloured Bmod < 6 mT rose coloured areas. Review on PSB 160 MeV H- injection

  16. Mechanical integration (1/3) 2 turn coil, split-able magnets, outer dimensions, support development Interference with neighbouring equipment (BI, Stripping, Vacuum equipment).

  17. Mechanical integration (2/3) • 2 turn coil, split-able magnets. • 0.35 mm thick laminations, glued magnets blocks. • Glued end plates, same material as yoke. • Is the use of glued laminated magnets a reliable over time? • Fixation to be studied. • Outer dimensions limited in height and length. • Magnet support and bus bars to be developed and integrated. • Transformers to be integrated in vicinity: dimensions to be evaluated, but rough estimation 80cmx80cmx80cm! • Interference with neighbouring equipment (BI, stripping foils, vacuum equipment). • Ease of maintenance required (RP ALARA)! Review on PSB 160 MeV H- injection

  18. Mechanical integration (3/3) • Mechanical concept design started • Coil and yoke design to be completed at CERN • Coil and yoke manufacture to be subcontracted to industry • Mechanical support and installation jig to be designed and built in house Review on PSB 160 MeV H- injection

  19. What if we adopt Inconel vacuum chambers? (1/2) + Mechanically more robust + Less costly + Potentially less activation Field deformation due to induced eddy currents: - delay (depending on vacuum chamber width) - deformed field shape Approximate field delays vary from 47μs (BSW1) to 90 μs (BSW4). Current distribution in race track shaped vacuum chamber. Review on PSB 160 MeV H- injection

  20. What if we adopt Inconel vacuum chambers? (2/2) • Field quality deterioration. • Introduction of higher order field components, magnetic centre not on the central orbit. • Sextupolar components manageable, but quadrupolar component potentially dangerous (needs precise compensation to avoid resonance). • Field delay depends on width of vacuum chamber! • 3 field delays implies three power supplies per ring -> space for transformers (12!) ? • Try to design all magnets same gap and vacuum chamber width (inductance ↗, BS1 may become too tall or even more non-linear)? Review on PSB 160 MeV H- injection

  21. Summary of outstanding questions • Would trim power supplies be recommended when powering all BSW per ring in series? • What to calculate to simulate the impact of field imperfections? • How to add the field deformation provoked by dump and its measurement systems? • Would imposing a limit on the absolute field imperfections (in space and time) be realistic? • Is septum (BSW1) leak field critical? • Is it necessary and how to track the electrons escaping from the stripping foil? • Are glued laminated yoke reliable over time in a radioactive environment? • What should be the preferred vacuum chamber material? • Have we overlooked anything else? Review on PSB 160 MeV H- injection

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