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Beam Dump

Beam Dump. The existing LHC beam dump is described, together with the relevant design aspects, technological and operational limitations. The issues and challenges presented by the various LHC luminosity upgrade options are detailed, together with some possible upgrade paths.

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Beam Dump

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  1. Beam Dump The existing LHC beam dump is described, together with the relevant design aspects, technological and operational limitations. The issues and challenges presented by the various LHC luminosity upgrade options are detailed, together with some possible upgrade paths. Thanks to V.Mertens, E.Vossenberg. Brennan GODDARD CERN AB/BT HHH 2004 Workshop, CERN

  2. Outline of talk • Existing LHC beam dumping system • overview, parameters, design aspects and limitations; • Issues and challenges of LHC luminosity upgrades • Extraction, dilution, absoption, protection; • Possible beam dump upgrade paths • Conclusion HHH 2004 Workshop, CERN

  3. Present system - concept extract  dilute  dump • Loss-free fast extraction system • Laminated steel kickers; DC Lambertson septum; • Dilution system • Laminated steel kickers; passive ~650m drift length. • Beam dump (absorber) block • Graphite cylinder, steel and concrete shielding • Protection devices • Graphite protection (dilution) for septum and LHC machine HHH 2004 Workshop, CERN

  4. Present design - schematic layout 10 x MKB kickers TDE dump block 15 x MSD septa TCDS protection 15 x MKD kickers TCDQ protection Total ‘beamline’ length : 975m from kicker MKD to dump TDE HHH 2004 Workshop, CERN

  5. Present design - tunnel layout Total ‘beamline’ length : 975m from kicker MKD to dump block TDE Dump cavern 40 m HHH 2004 Workshop, CERN

  6. Present design – main parameters HHH 2004 Workshop, CERN

  7. Present system – TDE absorber  0.7m  7.7 m C cylinder HHH 2004 Workshop, CERN

  8. Present system – TDE absorber • Density is graded to minimise DT: graphite with r = 1.8 - 1.1 - 1.8 g/cc • Full sweep DT = 1250OC in the dump block (LHC ultimate 0.86 A, 7 TeV) HHH 2004 Workshop, CERN

  9. Present system - protection • Unsynchronised dump would destroy septum and downstream elements • 2 long (6m), low density (carbon) absorbers to intercept undiluted bunches HHH 2004 Workshop, CERN

  10. Present system - limitations • Extraction system • Intensity : not limited • Energy : 7.5 TeV by kicker and septum strength • Filling scheme : not limited (need 3 ms abort gap) • Dilution system • Intensity : not limited; • Energy : limited to 7.5 TeV by kicker strength • Filling scheme : fails for superbunch (sweep length) HHH 2004 Workshop, CERN

  11. Present system - limitations • Beam dump absorber block • Intensity : 1 A (at 7 TeV) with DT max of ~1500OC • Energy : 7.5 TeV (at 0.7 A) with DT max of ~1500OC • Filling scheme : not limited (if adequate dilution). • Protection devices • Intensity : 1 A at 7 TeV by DT in septum and Q4 • Energy : 7.5 TeV (at 0.7 A) by DT in septum and Q4 • Filling scheme : protection fails for superbunch. HHH 2004 Workshop, CERN

  12. Increasing Intensity to 1.7 A - issues • Extraction system • Kicker - no problems (unless RF heating??). Feasible • Septum – no problems. Feasible • Dilution system • x2 sweep length. Feasible • Beam dump Absorber block • Reduce DT max by reduced C density. Feasible • Protection devices • Reduce DT max by reduced C density. Feasible HHH 2004 Workshop, CERN

  13. Increasing Energy to 14 TeV - issues • Extraction system • Kicker x2 B.dl – x2 length or x2 rise-time (6ms). Feasible • Septum x2 B.dl – x2 length. Feasible • Dilution system • x4 sweep  x4 kicker f0; plus x2 B.dl x8length. Difficult • Increase dump tunnel length Difficult • Beam dump Absorber block • Reduce DT max by reduced C density – x4 length. Difficult • Protection devices • Reduce DT max by reduced C density – x4 length. Difficult HHH 2004 Workshop, CERN

  14. Superbunch with 0.86 A - issues • Extraction system • Kicker - no problems.Feasible • Septum – no problems. Feasible • Dilution system • x100 sweep length. Impossible • Beam dump Absorber block • Reduce DT max with C density – increase length. Feasible • Protection devices • Dilute full beam current without damage. Impossible HHH 2004 Workshop, CERN

  15. Upgrades – Higher I at 7 TeV • Total intensity in distributed bunches • Upgrades required for dump system • Increase sweep length (higher f0 more dilution kickers) • Upgrade dump block (longer, lower density C); • Upgrade protection devices (longer, lower density C, more lr). • Feasible for 1.7 A with ‘modest’ upgrades (e.g. avoiding civil engineering) HHH 2004 Workshop, CERN

  16. Upgrades – 14 TeV • Intensity in distributed bunches • Considerable upgrades required for dump system • Increase kicker and septum strength (6ms kicker rise time OR x2 kickers; x2 septa) • Increase dilution sweep length higher f0, more kickers OR SC dilution quadrupole OR longer beam dump tunnel • Upgrade dump block (longer, lower density) • Upgrade protection devices (longer, sacrificial elements) • Main Challenges • Beam dilution and energy deposition in dump block (small spot) • Machine protection for failure cases (slower rise time bad) HHH 2004 Workshop, CERN

  17. Upgrades – superbunch • All intensity in 1 ms superbunch at 7 TeV • Major dump system upgrades required • Dilution with SC quadrupole • Upgrade dump block (longer, lower density C, larger diameter) • Lengthen (+500m) and possibly widen dump tunnel; new cavern • Sacrificial protection devices OR 100% reliable ‘active’ machine protection… • Main challenges • Achieving sufficient dilution (sweeping beam impossible) • Machine protection against synchronisation error HHH 2004 Workshop, CERN

  18. Dilution with spiral sweep • Increase dilution kicker frequency and sweep length • 14 to 56 kHz… would require ~4 times more kicker length 108 cm sweep length 400 cm sweep length • At 7 TeV would allow currents of ~3 A in distributed bunches • At 14 TeV would allow ~0.8 A in distributed bunches HHH 2004 Workshop, CERN

  19. Dilution with SC quadrupole 20 m quad @ 200 T/m Dilution quad b max ~1000km, s ~20mm Present optics b max ~5km, s ~1.5mm • Works for any filling pattern : s constant at ≈ 20 mm (need ‘squeeze’) • Need extra 500 m beam dump tunnel…. • Quad design ~OK : L 20 m @ 200 T/m, ~70mm aperture • Very orbit sensitive : 2 mm  0.35 mrad  ~0.4 m at dump (1150m drift). • Absorber block size :  ≈ 1.5 m (±0.5 m orbit, ±0.25 m for 8 s beam) HHH 2004 Workshop, CERN

  20. Protection – difficult with increasing E • Low material density essential to avoid material damage • More total material required to dilute energy density • Very long objects as a result… Peak GeV/cc in Cu vs beam size at 450 GeV and 7 TeV • 107 dilution factor, need ~16 lr of C 1.8 g/cc, or ~6 m at 7 TeV. • For 107at 14 TeV, ~0.8 g/cc to avoid damage  14 m. • Some optimisation with graded density to get more lr 3.31 4.5 1.77 1.4 1.77 DT and density in LHC diluter for 7 TeV sweep (47 bunches) HHH 2004 Workshop, CERN

  21. Conclusion • Dump upgrade for ~1.7 A at 7 TeV looks feasible • Some changes to dilution, absorption and protection • Upgrading for 0.8 A superbunch is more difficult: • Achieving sufficient dilution to allow safe absorption (SC quadrupole dilution, absorber, tunnel, cavern, orbit…) • Machine protection (use sacrificial elements? depends on reliability…) HHH 2004 Workshop, CERN

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