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Overview of LHC Machine Upgrade Plans from an LHCb Perspective - . Frank Zimmermann LHCb Upgrade Meeting CERN, 5 August 2008. We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6

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overview of lhc machine upgrade plans from an lhcb perspective

Overview of LHC Machine Upgrade Plans from an LHCb Perspective-

Frank Zimmermann

LHCb Upgrade Meeting

CERN, 5 August 2008

We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6

"Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395)

  • (1) general LHC upgrade plan
  • (2) shutdown plans for the machine, i.e. time- windows with longer than normal shutdown detector access
  • (3) luminosity scenarios in point 8 after phase 2 (“and maybe phase 1 - if there is a change?”).
two strong reasons for lhc upgrade
Two Strong Reasons for LHC Upgrade

J. Strait 2003

hypothetical luminosity


1) after few years, statistical error hardly decreases

2) radiation damage limit of IR quadrupoles(~700 fb-1) reached by ~2016

 time for an upgrade! 3) extending physics potential!


staged approach to LHC upgrade

“phase-1” 2013:

new triplets, D1, TAS, b*=0.25 m in IP1 & 5,

reliable LHC operation at ~2-3x luminosity;

beam from new Linac4

“phase-2” 2017:

target luminosity 10x nominal,

possibly Nb3Sn triplet & b*~0.15 m

complementary measures 2010-2017:

e.g. long-range beam-beam compensation,

crab cavities, new/upgraded injectors, advanced

collimators, coherent e- cooling??, e- lenses??

longer term (2020?): energy upgrade, LHeC,…

+ injector


phase-2 might be just phase-1 plus complementary measures


constraint crossing angle

“Piwinski angle”


luminosity reduction factor


effective beam

size s→s/Rf

other constraints:


e- cloud



LHC upgrade paths for IP1 & 5

early separation (ES)

full crab crossing (FCC)

L. Evans,

W. Scandale,

F. Zimmermann

J.-P. Koutchouk

stronger triplet


stronger triplet


D0 dipole


crab cavity


crab cavity

  • ultimate beam (1.7x1011 protons/bunch, 25 spacing), b* ~10 cm
  • early-separation dipoles in side detectors , crab cavities
  • → hardware inside ATLAS & CMS detectors,
  • first hadron crab cavities; off-d b
  • ultimate LHC beam (1.7x1011 protons/bunch, 25 spacing)
  • b* ~10 cm
  • crab cavities with 60% higher voltage
  • → first hadron crab cavities, off-d b-beat

larger-aperture triplet magnets

large Piwinski

angle (LPA)

  • 50 ns spacing, longer & more intense bunches
  • (5x1011 protons/bunch)
  • b*~25 cm, no elements inside detectors
  • long-range beam-beam wire compensation
  • → novel operating regime for hadron colliders, beam generation



F. Ruggiero,

W. Scandale.

F. Zimmermann


large Piwinski angle (LPA)

full crab crossing (FCC)

early separation (ES)


luminosity leveling

initial luminosity

peak may not

be useful for


(set up &


ES or



experiments prefer ~constant luminosity, less pile up at start of run, higher luminosity at end



how can we achieve this?

ES or FCC: dynamic b squeeze, or dynamic q change (either IP angle bumps or varying crab voltage)

LPA: dynamic b squeeze, or dynamic change of bunch length

reasons for injector upgrade
reasons for injector upgrade
  • Need for reliability:
    • Accelerators are old [Linac2: 1978, PSB: 1975, PS: 1959, SPS: 1976]
    • They operate far from their design parameters and close to hardware limits
    • The infrastructure has suffered from the concentration of resources on LHC during the past 10 years
  • Need for better beam characteristics

Roland Garoby, LHCC 1July ‘08

present and future injectors
present and future injectors

Proton flux / Beam power



50 MeV

160 MeV



1.4 GeV

4 GeV

(LP)SPL: (Low Power) Superconducting Proton Linac (4-5 GeV)

PS2: High Energy PS

(~ 5 to 50 GeV – 0.3 Hz)

SPS+: Superconducting SPS

(50 to1000 GeV)

SLHC: “Superluminosity” LHC

(up to 1035 cm-2s-1)

DLHC: “Double energy” LHC

(1 to ~14 TeV)


26 GeV


50 GeV

Output energy



450 GeV

1 TeV




7 TeV

~ 14 TeV

Roland Garoby, LHCC 1July ‘08

layout of the new injectors
layout of the new injectors






R. Garoby, CARE-HHH BEAM07, October’07; L. Evans, LHCC, 20 Feb ‘08

injector upgrade schedule synchronized with lhc ir upgrades
injector upgrade schedulesynchronized with LHC IR upgrades

R. Garoby,

LHCC 1 July 2008

LHC IR phase 1


phase 2

staged upgrade peak luminosity in ips 1 5 vs year
staged upgrade: peak luminosity in IPs 1 & 5 vs year

new injectors + IR upgrade phase 2

linac4 + IR upgrade phase 1

Roland Garoby, LHCC 1July ‘08

early operation

extended shutdowns:

2012/13 & 2017

collimationphase 2

r egular annual shutdown
regular annual shutdown

minimum duration of the annual accelerator shutdown

(analysis for 2007 by Simon Baird,ATC mtg. 4 May‘07)

basic  needs:

  • 6 weeks for mandatory maintenance (legal obligation),
  • 3 weeks for hardware tests/cold check-out,
  • 3 weeks for setting-up of the accelerators,
  • adding up to incompressible minimumduration of 12 weeks
  • of interruptionof LHC beam every year, without any major
  • intervention/modification

information from R. Garoby

t ime slots with 6 months access
time slots with >6 months access

in present upgrade schedule:

4th quarter 2012 – 2nd quarter 2013

~7.5 months

for PSB cooldown, PSB modifications,

PSB commissioning with LINAC4

→ LHC peak luminosity in IP1&5 ~ 2x1034 cm-2s-1

(1-2) ATLAS [& CMS] may need 18 months downtime as

early as 2015 (N. Hessey, LHCC 1 July 2008)

(2) mid-November 2016 – end June 2017:

~7.5 months

for SPS cooldown, SPS modifications,

SPS commissioning with SPL+PS2

→ LHC peak luminosity in IP1&5 ~ 1x1035 cm-2s-1


from 2001 upgrade feasibility study


2006 nominal

and ultimate


are slightly



from 2001 upgrade feasibility study





tune footprint up to 6s

with 2 IPs

tune footprint up to 6s

with 2 IPs at ultimate


nominal tune footprint

up to 6s with 4 IPs

L=1034 cm-2s-1

L=2.3x1034 cm-2s-1

SPS, Tevatron, RHIC experience: beam-beam limit ↔ total tune shift DQ~0.01

going from 4 to 2 IPs we can increase ATLAS&CMS luminosity by factor 2.3

this and all following upgrade studies were based on assumption of only 2 IPs

can we make upgraded lhcb compatible with upgraded lhc
can we make (upgraded) LHCb compatible with upgraded LHC?!
  • aim to minimize contribution to beam-beam tune shift (note: DQ is independent of b*)
  • aim to provide optimum LHCb luminosity of 2x1033 cm-2s-1/2808 per bunch crossing, or 1/50th of luminosity in IP1 & 5

bunch structures


25 ns


& 25-ns upgrade

(ES & FCC)

25 ns

50-ns upgrade (LPA),

no collisions in LHCb!

50 ns

50-ns upgrade

with 25-ns


in LHCb

50 ns

25 ns


LHCb recipe for 50-ns scenario

  • add satellites at 25 ns spacing
  • these can be produced by highly asymmetric bunch
  • splitting in the PS (possibly large fluctuation)
  • in LHCb satellites collide with main bunches
  • satellite intensity should be lower than 3x1010 p/bunch
  • to add <5% to beam-beam tune shift and to avoid
  • e-cloud problems;
  • 3x1010 ~ 1/16th of main-bunch charge
  • b function of ~3 m would result in desired
  • luminosity equivalent to 2x1033 cm-2s-1;
  • easily possible with present IR magnets & layout
  • [simpler alternative with lower rate: collide displaced
  • 50-ns bunch trains in LHCb @ b*~ 25 m (R. Garoby)]
lhcb schemes for 25 ns scenario
LHCb schemes for 25-ns scenario
  • here head-on collisions add to beam-beam tune shift of bunches colliding in ATLAS & CMS
  • potential ways out:
    • collisions withtransverse offset
    • collide at LHCb only in later part of each store, when the beam-beam tune shift from IP1 & 5 has decreased (H. Dijkstra)

more “exotic” / advanced (need studies):

    • “electron lenses” for tune-shift compensation
    • flat-beam “crab-waist” collisions for DQx~0

LHCb collisions with transverse offset d


L = L0exp (-d2/(4s2))

tune shift:

DQ LHCb = 2 DQIP1or5 / (d/s)2

suppose tune shift from LHCb should be less

than 10% of that from CMS or ATLAS →d>4.5 s ;

then luminosity L ~ 0.006 L0

if we wish LLHCb~0.01 LIP1or5 (~1-2x1033 cm-2s-1)

we need b* ~0.08 m → IR triplet upgrade!

offset collisions w/o IR upgrade LLHCb ~ 4x1031 cm-2s-1


other concerns for 4-5s offset collisions:

  • offset stability
  • interference with LHC collimation
  • effect on beam lifetime
  • effect on detector background
  • experience at RHIC, SPS, HERA and Tevatron was
  • discouraging (see slides with examples presented
  • at LHCB Upgrade Workshop of January 2007);
  • but interpretation of past results and their application
  • to LHC is a bit controversial

LHCb luminosity for 25 ns with offset & 50 ns

25 ns


4.5s offset,

b*~0.08 m

50 ns



LHCb 50-ns luminosity decays 2x more slowly

than 25-ns luminosity or that at ATLAS and CMS

PAF/POFPA Meeting 20 November 2006


tune shift during store for 25-ns & 50-ns spacing

50 ns



DQ ~


25 ns


LHCb 25-ns collisions from middle of each store?! b*~3 m

(5 h turnaround time is assumed)

PAF/POFPA Meeting 20 November 2006


LHCb luminosity for 25-ns late collisions & 50 ns

25 ns


b* ~ 3 m,

no transverse


50 ns


b*~3 m,


(5 h turnaround time is assumed)

PAF/POFPA Meeting 20 November 2006

lhcb collision parameters
LHCb collision parameters

rms length of luminous region:

(in cases w/o transverse offset)

PAF/POFPA Meeting 20 November 2006

  • time slots for LHCb upgrade: annual shutdown: > 3 months; phase-1 2012/13: > 7 months; ATLAS/CMS upgrade: 2015/16/17? ~18 months; phase-2 2016/17: > 7 months
  • three paths to 10x higher luminosity in IP1&5: 25-ns or 50-ns bunch spacing; early LHC experience may decide
  • original upgrade plans did not consider LHCb, however LHCb can be made compatible
  • 50-ns upgrade: satellite bunches at 25 ns could yield desired LHCb luminosity nearly transparently
  • 25-ns upgrade:LHCb collisions with transverse offset + LHCb IR upgrade not too promising; better: late collisions with b*~3 m; e- lenses & crab-waist option to be studied

PAF/POFPA Meeting 20 November 2006