Pb for lhc requirements summary d manglunki
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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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Pb for LHC: requirements summary D.Manglunki

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Pb for lhc requirements summary d manglunki

Pbfor LHC: requirements summaryD.Manglunki


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


Pb for lhc requirements summary d manglunki

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


Luminosity scaling vs sps injection kicker rise time ns 24 ps injections into sps

Luminosity scaling (%) vs SPS injection kicker rise time (ns), 24 PS injections into SPS


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


Pb for lhc requirements summary d manglunki

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


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