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Pb for LHC: requirements summary D.Manglunki. Why upgrade?. ALICE Upgrade approved: Request for peak luminosity “higher tha n L=6x10 27 cm -2 .s -1 ” after LS2 Programme in coming years: HL Pb-Pb (today) Ar & Xe.

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Presentation Transcript
why upgrade
Why upgrade?
  • ALICE Upgrade approved: Request for peak luminosity “higher than L=6x1027cm-2.s-1” after LS2
  • Programme in coming years:
    • HL Pb-Pb (today)
    • Ar & Xe
slide3

Luminosity increaseNote: current brightness performance is already 2 x design

  • b functions at IP (/2 to 0.5m)
  • Transverse emittances (/2 by energy )
  • Intensity per bunch (=)
  • Number of bunches (by reducing spacing)
    • Influence of LHC injection kicker (0.9ms) & abort gap (3ms)
    • Increase nr of injections in SPS (present limits = 12 due to ROCS; 15 due to RF)
  • One can shoot for L=7x1027cm-2.s-1
100 50 ns scheme

Harmonic number

Nb of bunches

6 injections

2

2

16–18-21-169

4653…4620

2

35640

48

~912

100/50 ns scheme

Pbions/bunch

5.5 108

LEIR

(1.1 109 Pb ions / 3.6 s)

PS batch compression + rebucketingBunch spacing = 100ns

3.8 108

100ns

2.2 108

100ns

50ns

SPS at extraction,after 24 transfers from PS,

Batch spacing = 50 ns

1.7 108

LHC at injection,after 19 transfers from SPS

b* =0.4 m -> L = 7x1027 cm-2s-1

route to 100 50ns
Route to 100/50ns
  • Linac3 / LEIR produce similar performance as in 2013:
    • 2 bunches of ~5.5 108Pb54+
  • PS gymnastics
    • Batch compression to 100ns h = 16 -> 18 -> 21(no need for new cavities, 10MHz system exists)
    • 2 bunches > 2 x108 Pb82+ into SPS
  • 24 SPS injections spaced by 50ns
    • Similar bunch quality as present beam
    • 48 bunches of ~1.7x108Pb82+
    • Transverse emittances ~0.85mm
    • Alternating 100/50ns spacing
  • 19 injections / LHC ring -> 912 bunches /ring
plan b in case no sps injection upgrade
Plan B (in case no SPS injection upgrade)
  • Double current from Linac 3 (~50mA)
  • LEIR
    • Produce 2 bunches of ~1.1 109Pb54+ in same emittance(i.e. twice today)
  • PS gymnastics
    • As “old nominal scheme” 4bunches > 1.4 x108 Pb82+
    • OR Batch compression to 100ns h = 16 -> 18 -> 21Splitting to 50 ns; 4 bunches > 1.4 x108 Pb82+ into SPS
  • Issues:
    • splitting to 50ns at high energy imposes some gamma-transition distortion
    • splitting to 50ns at low energy imposes acceleration at 20MHz
actions issues since 2012 brainstorm
Actions/Issues since 2012 “Brainstorm”
  • Is the ECR source the bottleneck?
  • RFQ rematching
  • Multiple charge acceleration: Study still to be reactivated
  • Faster repetition rate
    • OK for source and Linac
    • Power supplies & magnets in ETL, planned for consolidation
    • LEIR injection to be checked

Source & LINAC

slide9
LEIR
  • Study loss at beginning of ramp (different Bdot, tunes,…)
  • Intensity limits (tests with longer flat bottom until higher intensity from Linac)
  • Vacuum (limit loss by cleaner dump)

PS

  • Longitudinal acceptance for suggested RF gymnastics
  • Alternate schemes (Gamma-t jump at flat top, acceleration on 20MHz)
  • Vacuum

SPS

  • Issues on flat bottom
    • RF noise
    • Space charge & IBS (Q20)
  • Increase number of injections
  • Injection kicker rise time 50ns