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Requirements of the LHC on its injectors What are the nominal & already achieved beams at PS exit?

THE LHC PROTON BEAM. E&G Métral PS-OP shut-down lectures, 1/02/2002. Requirements of the LHC on its injectors What are the nominal & already achieved beams at PS exit? How is it obtained in the PS complex? General aspects PSB PS LHC beam in 2001 Future work.

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Requirements of the LHC on its injectors What are the nominal & already achieved beams at PS exit?

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  1. THE LHC PROTON BEAM E&G MétralPS-OP shut-down lectures, 1/02/2002 • Requirements of the LHC on its injectors • What are the nominal & already achieved beams at PS exit? • How is it obtained in the PS complex? • General aspects • PSB • PS • LHC beam in 2001 • Future work

  2. Requirements of the LHC on its injectors Choice of the nominal LHC parameters

  3. Requirements of the LHC on its injectors • LHC project leader  L. Evans •  Major upgrade needed • all along the injector chain

  4. What are the nominal & already achieved beams at PS exit?  The specifications are met in the PS complex

  5. How is it obtained in the PS complex? General aspects • Main challenges • High brightness & very short bunches • Solutions • Double-batch filling of the PS  Lowers the space charge effects at PSB • Increase of the PS injection energy  Lowers the space charge effects at PS injection • Multi splittings=> bunch number, bunch spacing & emittance • Bunch rotation to produce the desired bunch length

  6. PSB • General aspects for PSB • 2 consecutive cycles (LHC, TSTLHC) • 1 bunch per ring (H1)Different possibility to fill the 6 buckets of the PS 2 PSB rings + 4 PSB rings, 2 times 3 PSB rings, 4 PSB rings + 2 PSB rings • Multi-turn injection : 3 turns exactly (for homogeneous longitudinal distribution) • Special tune due to large tune shift • Double harmonics operation (bunch flattening) => decreases the space charge tune shift at injection • Available controlled blow-up  C16 (H9) • No coupling between the transverse planes • Standard settings of multipoles for resonance compensations

  7. Transfer PSB PS C805 • Synchronization • Non-standard bunch spacing at ejection to fit the PS H7 RF system • Adjustment with the phase offsets : BAx.PSYNCOFFSET (ring 3 is always used as the reference) • Remember that the Timing used in that process is in H8 • more difficulties to adjust the timing for the synchronization & for the instrumentation • Ejection at 1.4 GeV • fast extraction towards the PS through the BT/BTP transfer line

  8. PSB Beam parameters at PSB extraction

  9. PS • General aspects • Double-batch injection : separated by 1.2 s  6 bunches out of 7 buckets • Longitudinal beam slicing  complicated RF gymnastics • High brightness conservation  careful control of collective effects, injection oscillations, working point, chromaticity, non-linearity at extraction… PSB exit PS exit ~ 300 ns

  10. PS 1.4 GeV kinetic energy • At low energy • 1st injection => 2 or 3 bunches (H7) • Transverse matching between PSB and PS, orbit correction... • RF phase adjustment (PA.PDISC-H7)adjusted from the CB if the PSB extraction phase is correct • Working point during the long flat-bottom  Qh ~ 6.21 and Qv ~ 6.23 • RMS current on low energy power supply • 2nd injection => 3 or 4 bunches (after the first batch ) • Momentum adaptation PSB-PS => PSB synchro. made with PS beam • Same frequency sent to the PSB for the same MRP as the first injection one & same PS magnetic field • RF phase adjustment (PA.PDISC-H7) Inj42 at C170 Inj42 at C1370

  11. PS 1.4 GeV kinetic energy Head-Tail resistive-wall instability Beam-Position Monitor (20 revolutions superimposed) R signal Time (20 ns/div)

  12. PS Remember that the Timing of the second injection can also be adjusted by the Timing_f_t program

  13. PS 1.4 GeV kinetic energy • 1.4 Gev after second injection • Triple splitting 6 × 3 = 18 bunchesH7 to H21

  14. PS Acceleration C1563 • At transition : -jump + change of the chromaticity sign • Longitudinal coupled-bunch instabilities between 6 and 20 GeV/c cured by controlled longitudinal blow-up • From 20 to 26 GeV/c,horizontal orbit correction => PR.GSDHZ15,60-OC • At high energy (26 GeV/c momentum) • Synchronization H1 => the worst • 1stdouble splitting => 18 × 2 = 36 bunches (H42) • 2nddouble splitting => 36 × 2 = 72 bunches (H84) Cavities 200MHz 1cavity 20MHz 1 cavity 40MHz

  15. PS ejection • Orbit correction during the Bump • New ABS interface with virtual GFAs • Bump compensation in the RF phase loop system • Without, the phase loop is not strong enough • Bunch compression by a step voltage => longitudinal mismatch => bunch rotation and ejection after 1/4 of synchrotron period • Ejection at 26 GeV/c  fast extraction towards the SPS through the TT2/TT10 transfer line 1 cavity 40 MHz (H84) 2 cavities 80 MHz Ej 16 at C2395  with

  16. Inj at C169.8 Inj2 at C1369.8 Ej at C2395 PS 1011Gauss at C160 B up at C1450 Transition at C1563 12576Gauss at C2120 Blow up2 C1725=>C1825 Triple split. C1375 =>C1400 Blow up1 C1400=>C1440

  17. PS Start PL H84 C2363 Start fine sync Synchro H21 PAX.SD2SYNCSPS C2365 Lock of a frequency source on the BEAM PAX.SSYNCH1INT C2141 Start sync SPS Synchro H1 PAX.SD1SYNCSPS C2155 Start PL H42 C2318 Ej at C2395 Start first Double split. Start cavity 20MHz C2258 End cavity 10Mhz Start cavity 40mhz C2338 End cavity 20Mhz Start GFA cavity 80mhz C2388

  18. PS Start of the bunch rotation process Synchro with The extraction

  19. PS Ej at C2395 Start of the bump16 Start of PA.GSCOMP-BSW16 Ej –7.5ms = C2387.5 External restart For PA.GSV40 & PA.GSV80 By PAX.SBRH84 Ej –5.3ms = C2389.7 End cavity 20Mhz Start GFA cavity 80mhz C2388 Start cavity 80mhz ~ej –100us

  20. PS RF signals during extraction process Phase discri H21 Phase discri H42 • Other important signals on NAOS • PA.PDISC-H84 • PA.SYNCDISC-H21 • PA.GSCOMP-BSW16

  21. PS Longitudinal beam structure in the last turn of the PS

  22. PS Only 1 measurement is still missing the transverse emittances in TT2 in the presence of bunch rotation Emittance measurements using the Semfils in TT2 without bunch rotation H - plane V - plane

  23. Also observed in the PS PS Baseline drift on electrostatic pick-ups in TT2 Without solenoid With solenoid ~ 50-100 G Apparently the beam is not affected  this is only a measurement problem for the PS (contrary to the SPS and LHC)

  24. SPS and LHC filling LHC Proton Injection Cycle (21.6 s) This cycle is repeated 12 times for each LHC ring. 3 or 4-batch cycles will be interleaved in the form 334 334 334 333 to fill each ring with a total of 2808 bunches. The LHC filling time will be 12  21.6 s = 4.3 minutes per ring

  25. SPS and LHC filling Bunch disposition in the LHC, SPS and PS

  26. LHC Beam in 2001 • Blow up on the PSB machine • Better low energy process in the PS machine • New synchronization at extraction implemented • Bunch stability better than 0.5ns at ejection (only measurable in CB) • Better splitting at 26GeV/c (phase loop) • Bunch to bunch intensity fluctuations <10% as required • Coupling measurements at different energies • H/V coupling at transition (tune crossing) • H/V coupling at 26GeV/c • 50 ns bunch spacing done • Ultimate beam done

  27. LHC Beam in 2002 • New B train (at the start up) • Magnetic cycle to be reviewed • LHC beam must be the first operation • Working point at low energy • Suppress the ripple on the PFW GFAs • TTSM (type EPTTSM) to monitor the phase stability at extraction • Test of a fast LHC cycle in the PS

  28. Fast LHC cycle

  29. To find documentation • This file • N:\Psop\Doc\PS\Presentation\LHCBeam2002.ppt • All the MD measurements • N:\Psop\Archives\data\PS\&MDs\Lhc • Beam reference on the WEB • http://srv1ps/psop/cps/BeamRef/lhc/

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