i-lhc project overview and statuslhc-collimation.web.cern.ch/lhc-collimation/files/...2006/04/03...

J.M. Jowett, Collimation Working Group, 3/4/2006 1

II--LHC ProjectLHC ProjectOverview and StatusOverview and Status

John JowettJohn Jowett


Heavy Ion Physics ParametersHeavy Ion Physics Parameters

With increasing energy, more partons are available, interact more effectively. Thermalized high-T phase established more quickly and lasts longer.

SPS RHIC LHCCM energy nucleon s u GeV 17 200 5500 μ 28

Charged multiplicity dNchdy 400 800 > 3000 challenge

Energy density e GeV fm3 3 5 15- 60 denserFreeze- out volume Vf fm3 º 103 º 104 º 105 larger

QGP lifetime tQGP fm c b 1 1.5- 4 > 10 longerThermalization time t0 fm c r 1 º 0.2 b 0.1 faster

tQGP t0 1 6 r 30


II--LHC LongLHC Long--Term PlanningTerm Planning

Baseline: LeadBaseline: Lead--Lead collisionsLead collisions–– ““Early Early PbPb SchemeScheme”” –– much easier to achieve much easier to achieve –– for for

2008 (and 2009?)2008 (and 2009?)Allows study of performance limitations.Allows study of performance limitations.

–– ““Nominal Nominal PbPb SchemeScheme”” by 2009 by 2009 PbPb--PbPb is perceived as posing the most difficult is perceived as posing the most difficult accelerator physics problemsaccelerator physics problems

Future Future ““upgradesupgrades”” not in Baseline: not in Baseline: –– pp--PbPb collisions under studycollisions under study

Effects of revolution frequency difference at injection Effects of revolution frequency difference at injection expected to be expected to be muchmuch weakerweaker than at RHICthan at RHIC

–– lighter ionlighter ion--ion collisions (e.g. Ca, ion collisions (e.g. Ca, ArAr, O, , O, ……) appear ) appear possible without major upgrades, to be studied.possible without major upgrades, to be studied.


Nominal Nominal vsvs Early Ion Beam in LHCEarly Ion Beam in LHC

Why Early Beam?Why Early Beam?– Easier for injectors, shorter LHC filling time (4

min/ring)– Keep nominal bunch population (7 107 ions/bunch) to

study limitations without risks– A Luminosity of L=5. 1025 cm-2 s-1 (lower by a factor

20) by fewer bunches (1/10) and β* =1 m (factor 1/2) useful for physics (early results)

– Improved Luminosity lifetime because of larger β*


Nominal vs. Early Ion Beam: Key ParametersNominal vs. Early Ion Beam: Key Parameters

ParameterParameter UnitsUnits Nominal Nominal Early BeamEarly Beam

Energy per nucleonEnergy per nucleon TeV/nTeV/n 2.762.76 2.762.76

Initial Luminosity LInitial Luminosity L00 cmcm--22 ss--11 1 101 102727 5 105 102525

No. bunches/bunch harmonicNo. bunches/bunch harmonic 592/891592/891 62/6662/66

Bunch spacingBunch spacing nsns 99.899.8 13501350

ββ** mm 0.5 (same as p)0.5 (same as p) 1.01.0

Number of Pb ions/bunchNumber of Pb ions/bunch 7 107 1077 7 107 1077

Transv. norm. RMS emittanceTransv. norm. RMS emittance μμmm 1.51.5 1.51.5

Longitudinal emittanceLongitudinal emittance eVeV s/charges/charge 2.52.5 2.52.5

Luminosity halfLuminosity half--life (1,2,3 life (1,2,3 exptsexpts.).) HH 8, 4.5, 38, 4.5, 3 14, 7.5, 5.514, 7.5, 5.5


Lead Ion Schedule (postLead Ion Schedule (post--Chamonix 2006)Chamonix 2006)


Electromagnetic Interactions of Heavy ionsElectromagnetic Interactions of Heavy ions

QED effects in the peripheral collisions of heavy ions Rutherford scattering:

++γ++ +⎯→⎯+ 82208822088220882208 PbPbPbPb Copious but harmless

Free pair production:

−+++γ++ +++⎯→⎯+ eePbPbPbPb 82208822088220882208 Copious but harmless

Electron capture by pair production (ECPP)

+++γ++ ++⎯→⎯+ ePbPbPbPb 81208822088220882208 Electron can be captured to a number of bound states, not only 1s.

Secondary beam out of IP, effectively off-momentum”

Pbfor 012.01

1=

−=δ

Zp

Electromagnetic Dissociation (EMD)

Secondary beam out of IP, effectively off-momentum:

Pbfor 108.41

1 3−×−=−

−=δAp

nPb

*)Pb(PbPbPb

82207

82208822088220882208

+

↓

+⎯→⎯+

+

++γ++

(Numerous other changes of ion charge and mass state happen at smaller rates.)


Nuclear cross sectionsNuclear cross sections

CrossCross--section for section for PbPb totally totally dominated by electromagnetic dominated by electromagnetic processesprocessesValues for nonValues for non--PbPb ions may ions may need upward revision need upward revision

HHe O Ar Kr In Pb

sH

sEMD

sECPP

stot0

200

400

sêbarn

HHe O Ar Kr In Pb

sH sEMD sECPP s tot

Hydrogen 0.105 0 4.25μ 10-11 0.105Helium 0.35 0.002 1.μ 10-8 0.352Oxygen 1.5 0.13 0.00016 1.63016Argon 3.1 1.7 0.04 4.84Krypton 4.5 15.5 3. 23.Indium 5.5 44.5 18.5 68.5Lead 8 225. 280.756 513.756

ECPPEMDHtot

beamfromremovalion for section -crossTotalσ+σ+σ=σ

BFPP(=ECPP) from Meier et al, Phys. Rev. A, 63, 032713 (2001), calculation for Pb-Pbat LHC energy

BFPP(=ECPP) from Meier et al, Phys. Rev. A, 63, 032713 (2001), calculation for Pb-Pbat LHC energy

Need to update


Luminosity Limit from BFPPLuminosity Limit from BFPP

3700

3705

3710sêm

-0.02-0.0100.010.02

xêm

-0.010

0.01

yêm 3700

3705

3710sêm

00.010.0

0

100

200

300

400

sêm

-0.02 0 0.02

xêm

-0.03

-0.02

-0.01

0

yêm

100

200

300

400

m

Beam screen in one magnetBeam screen in one magnet

IP2IP2

Longitudinal Pb81+ ion distribution on screen

Longitudinal Pb81+ ion distribution on screen

Beam screen

Beam screen

Main Pb82+ beamMain Pb82+ beam

9.5 10 10.5 11 11.5 12

0.2

0.4

0.6

0.8

Secondary Pb81+ beam emerging grom IP and impinging on beam screen

Secondary Pb81+ beam emerging grom IP and impinging on beam screen

82 8 208208 208 82 82 2 8 10 PP Pb Pb ebb ++γ ++ ++ ⎯⎯→ + +

Energy deposition by ion flux may exceeds quench limit of superconducting magnets at nominal luminosity.

Calculations being refined with new ion-matter interaction models in FLUKA

See LHC Project Note 379,

New estimates for dipole quench limit


Operational Parameter Space for Operational Parameter Space for PbPb IonsIons

0.01 0.05 0.1 0.5 1 5 10

Ib μ

1. × 10 22

1. × 10 23

1. × 10 24

1. × 10 25

1. × 10 26

1. × 10 27

cm 2 s − 1

Visibility threshold on FB

CT

Nominal

Visible o

n BCTDC

Early

-1-2scm/L

A/μbI

Visibility threshold on arc B

PM

BFPP Quench limits ?N

ominal single bunch current

Visible o

n BCTDC

Thresholds for visibility on BPMs and BCTs.

Collimationlimit?


Optical Parameters at the Optical Parameters at the IPsIPs (Nominal)(Nominal)

= IPopticsTable@"CollisionIons", "LHCB1"D

]//NumberForm=

IP1 IP2 IP5 IP8 IP1.L1βxêm 0.55 0.5 0.55 10. 0.55βyêm 0.55 0.5 0.55 10. 0.55

xcêmm 1.1× 10−9 −3.59× 10−9 0.5 −3.18× 10−9 1.1× 10−9

ycêmm −0.5 5.77× 10−9 2.08× 10−9 −0.5 −0.5pxcêμrad −2.95× 10−6 2.63× 10−6 142. −210. −2.95× 10−6

pycêμrad 143. −10. −7.9× 10−6 −1.81× 10−7 143.

= IPopticsTable@"CollisionIons", "LHCB2"D

]//NumberForm=

IP1 IP2 IP5 IP8 IP1.L1βxêm 0.55 0.5 0.55 10. 0.55βyêm 0.55 0.5 0.55 10. 0.55

xcêmm 4.11× 10−9 3.94× 10−9 0.5 −2.43× 10−8 4.11× 10−9

ycêmm −0.5 −6.01× 10−9 −2.72× 10−9 0.5 −0.5pxcêμrad −2.79× 10−6 5.5× 10−6 −142. 210. −2.79× 10−6

pycêμrad −142. 10. −0.0000107 −2.69× 10−6 −142.


Optical Parameters at the Optical Parameters at the IPsIPs (Early)(Early)

IPopticsTable@"EarlyCollisionIons", "LHCB1"D

/NumberForm=

IP1 IP2 IP5 IP8 IP1.L1βxêm 2. 1. 2. 10. 2.βyêm 2. 1. 2. 10. 2.

xcêmm −1.11× 10−9 2.29× 10−9 0.322 1.78× 10−9 3.08× 10−9

ycêmm −0.322 2.78× 10−9 3.61× 10−10 −2. −0.322pxcêμrad 2.37× 10−6 −1.83× 10−6 92. −170. 1.86× 10−6

pycêμrad 92. −2.13× 10−6 −1.98× 10−6 8.67× 10−7 92.

IPopticsTable@"EarlyCollisionIons", "LHCB2"D

/NumberForm=

IP1 IP2 IP5 IP8 IP1.L1βxêm 2. 1. 2. 10. 2.βyêm 2. 1. 2. 10. 2.

xcêmm 3.94× 10−9 3.09× 10−9 0.322 −8.36× 10−9 3.94× 10−9

ycêmm −0.322 −4.5× 10−9 −5.35× 10−9 2. −0.322pxcêμrad −1.74× 10−6 1.11× 10−8 −92. 170. −1.74× 10−6

pycêμrad −92. −3.55× 10−7 −1.07× 10−6 −1.13× 10−6 −92.


Beams crossing inside LHC aperture, Nominal, IR2Beams crossing inside LHC aperture, Nominal, IR2

IRcrossingPlot3D@"CollisionsIons", "IR2", 2, 0.25D

CollisionsIons, IR2

3250

3300

3350

3400

3450

sêm

-0.2-0.1

00.1

0.2

xêm

-0.2

-0.1

0

0.1

0.2

yêm

3250

3300

3350

3400

3450

sêm

-0.2-0.1

00.1


Beams crossing, Beams crossing, Nominal+EARLYNominal+EARLY, IR2 (2, IR2 (2σσ beam)beam)IRcrossingPlot3D@"CollisionIons", "IR2", 2, 0.02D

CollisionIons, IR2

32503300

33503400

3450

sêm

-0.02-0.0100.010.02

xêm

-0.02

-0.01

0

0.01

0.02

yêm

32503300

33503400

3450

EarlyCollisionIons, IR2

32503300

33503400

3450

sêm

-0.02-0.0100.010.02

-0.02

-0.01

0

0.01

0.02

yêm

32503300

33503400

3450


RFRF

Larger frequency swing than with protons, no problem Larger frequency swing than with protons, no problem Different bunch filling schemesDifferent bunch filling schemesRF noise to be clarified (SPS MD to test continuous use)RF noise to be clarified (SPS MD to test continuous use)Needed to blowNeeded to blow--up longitudinal emittance at collision energy (IBS)up longitudinal emittance at collision energy (IBS)

1 2 3 4 5 6 7Proton momentum TeVê H êcL

400.78

400.782

400.784

400.786

400.788

400.79

fFRê

zHM

1 2 3 4 5 6 7Proton momentum ê HTeVêcL

400.78

400.782

400.784

400.786

400.788

400.79

fFRê

zHM 208Pb82+

p

RFRF 2

ion

ion p

On central orbit:

1

chfm cC

Q p

=⎛ ⎞

+ ⎜ ⎟⎜ ⎟⎝ ⎠


Optics for the Early and Nominal Ion SchemesOptics for the Early and Nominal Ion Schemes

Same Same geometricalgeometrical transverse beam size and emittancetransverse beam size and emittance–– Optics, dynamic aperture, mechanical acceptance, etc. similar toOptics, dynamic aperture, mechanical acceptance, etc. similar to

protons.protons.Injection and ramp done with Injection and ramp done with exactly the sameexactly the same optics, orbits, optics, orbits, corrections, etc. as for protonscorrections, etc. as for protons–– Should shorten ion commissioning time considerably!Should shorten ion commissioning time considerably!

Colliding in ATLAS, CMS Colliding in ATLAS, CMS ⇒⇒ same squeeze as protonssame squeeze as protonsLeave IR8 in injection configurationLeave IR8 in injection configurationMain difference is that IR2 is squeezed to Main difference is that IR2 is squeezed to –– May May -- or may not or may not -- be operationally convenient to commission be operationally convenient to commission

the ion optics first with lowthe ion optics first with low--intensity protons.intensity protons.Crossing angle at IP2 (1,5?) may be small (includes ALICE muon Crossing angle at IP2 (1,5?) may be small (includes ALICE muon spectrometer, details in Design Report)spectrometer, details in Design Report)–– Aperture requirements somewhat relaxed Aperture requirements somewhat relaxed w.r.tw.r.t. protons. protons–– Operational time for polarity reversalsOperational time for polarity reversals

* 2.,1.,0.5 mβ =


Plan for Commissioning LHC Rings with Lead Ions (1) Plan for Commissioning LHC Rings with Lead Ions (1)

Assume that protons can be collidedAssume that protons can be collided–– Injection, ramp, squeeze (where applicable) are Injection, ramp, squeeze (where applicable) are

set upset upReRe--commission injection and first turns with single ion commission injection and first turns with single ion ““pilotpilot”” bunch (close to nominal intensity)bunch (close to nominal intensity)–– Adjust BSTAdjust BST–– Energy matching to different SPS cycle, each ringEnergy matching to different SPS cycle, each ring–– Should go quickly (magnetic reproducibilityShould go quickly (magnetic reproducibility……))–– Deal with any difference of geometric beam size from Deal with any difference of geometric beam size from

protons (collimator settings, etc.)protons (collimator settings, etc.)Set up RF and capture (Set up RF and capture (““few shiftsfew shifts””), instrumentation), instrumentation


Plan for Commissioning LHC Rings with Lead Ions (2) Plan for Commissioning LHC Rings with Lead Ions (2)

ReRe--commission rampcommission ramp–– Should also go quickly (magnetic reproducibility again)Should also go quickly (magnetic reproducibility again)–– Deal with any difference of geometric beam size from protons Deal with any difference of geometric beam size from protons

(collimator settings, etc.)(collimator settings, etc.)Commission squeeze of IP2 (if applicable) Commission squeeze of IP2 (if applicable) –– Including crossing angle with ALICE spectrometer bump Including crossing angle with ALICE spectrometer bump –– (Alignment of IR2 triplet quadrupoles?)(Alignment of IR2 triplet quadrupoles?)–– Could take a few days (see experience with IP1 and IP5)Could take a few days (see experience with IP1 and IP5)

Collide Collide PbPb--PbPb–– ReRe--optimise collimation (how?), measurements, etc.optimise collimation (how?), measurements, etc.

Need to review time requirements with proton experience.Need to review time requirements with proton experience.Provide > 4 weeks of physics with Early Scheme for ALICE, ATLAS,Provide > 4 weeks of physics with Early Scheme for ALICE, ATLAS,

CMS.CMS.DonDon’’t forget MD time (t forget MD time (→→ Nominal SchemeNominal Scheme) with ) with PbPb ions ions


Synchrotron RadiationSynchrotron Radiation

LHC is the first proton storage ring in which synchrotron radiation plays a noticeable role, (mainly as a heat load on the cryogenic system) It is also the first heavy ion storage ring in which synchrotron radiation has significant effects on beam dynamics. – Surprisingly, perhaps, some of these effects are

stronger for lead ions than for protons.– Nucleus radiates coherently:

pp

p EAZE

mAcErZ

mcErU =

ρ

π=

ρπ

= ion346

4ion

2

3ion

6

4ionion ,

34

34

per turnlossradiation n Synchrotro


Synchrotron RadiationSynchrotron Radiation

Scaling with respect to protons Scaling with respect to protons in same ring, same magnetic in same ring, same magnetic fieldfield

–– Radiation damping for Radiation damping for PbPb is is twice as fast as for protonstwice as fast as for protons

Many very soft photonsMany very soft photonsCritical energy in visible Critical energy in visible spectrumspectrum

20 40 60 80Z

0.5

1

1.5

2

tpÅÅÅÅÅÅÅÅÅÅÅtion

Radiation damping enhancement for all stable isotopes

Lead is (almost) best, deuteron is worst.


Evolution during a fillEvolution during a fill

( ) ( ) ( )

( ) ( )( ) ( )( )

( )

( ) ( )( ) ( ) ( )( )

( )

= −

ε = −ε

ε

ε =

ε

ε

ε

ε

τ

ε

τ

⎛ ⎞ σ− σ⎜ ⎟

−

πβ

ε

⎠ ε⎝∑

radi

2

tot exp 0

*

luminosi

IBS

IBS

Bj-M in MAD, full lattic

ty b

a

beam-gas

tioe

urn-of

n

f

, ,

,

4

,

2

4

g bg b b

x

x b x l

x

x

l

bg

x

lx

b

b

l x l

x

x

t

T

t

t

N t

t

n f N

N t t

t

T N t tt

n v N tt

t( )+ RF

Injected RF noise

damping

D t

0 2 4 6 8 10têh

1μ10-10

2μ10-10

3μ10-10

4μ10-10

5μ10-10

6μ10-10

7μ10-10

e xêm

No radiation damping, DRF=0

Radiation damping, DRF>0

=expNo. of experiments: 0, 31,2,n0 2 4 6 8 10

têh

2μ1026

4μ1026

6μ1026

8μ1026

1μ1027

Lêmc-2

s-1

0 2 4 6 8 10têh

1μ10-10

2μ10-10

3μ10-10

4μ10-10

5μ10-10

6μ10-10

e xêm

Nominal initial εx

=expNo. of experiments: 0, 31,2,n

Nominal initial εx

Blown-up initial εx

Blown-up initial εx

=expNo. of experiments: 0, 31,2,n


Luminosity evolution during a fill: Early schemeLuminosity evolution during a fill: Early scheme

0 2 4 6 8 10têh

1μ10-10

2μ10-10

3μ10-10

4μ10-10

5μ10-10

e xêm

0 2 4 6 8 10têh

1μ107

2μ107

3μ107

4μ107

5μ107

6μ107

7μ107

N b

expNo. of experiments: 0, 3,1,2n =Assuming good vacuum conditions, but including all effects.

Particles per bunch

Transverse emittance

0 2 4 6 8 10têh

1μ1025

2μ1025

3μ1025

4μ1025

5μ1025

Lêmc-2

s-1

Luminosity

Increasing number Increasing number of experiments of experiments reduces beam and reduces beam and luminosity lifetime luminosity lifetime butbut we can still we can still keep fills for a long keep fills for a long time (useful if turntime (useful if turn--round time is long).round time is long).

Arc BPM visibility threshold

* 1 mβ =


0 2 4 6 8 10têh

1μ107

2μ107

3μ107

4μ107

5μ107

6μ107

7μ107

N b

0 2 4 6 8 10têh

1μ10-10

2μ10-10

3μ10-10

4μ10-10

5μ10-10

e xêm

Luminosity evolution: Nominal schemeLuminosity evolution: Nominal scheme

expNo. of experiments: 0, 3,1,2n =

An “ideal” fill, starting from design parameters giving nominal luminosity.

Particles per bunch

Transverse emittance

0 2 4 6 8 10têh

2μ1026

4μ1026

6μ1026

8μ1026

1μ1027

Lêmc-2

s-1

Luminosity

Increasing number Increasing number of experiments of experiments reduces beam and reduces beam and luminosity lifetime.luminosity lifetime.

BPM visibility threshold


SummarySummary

II--LHC Project remains on track for LHC Project remains on track for PbPb--PbPb collisions with collisions with ““Early SchemeEarly Scheme”” at end 2008at end 2008–– See talk by S. See talk by S. MauryMaury at Chamonix 2006at Chamonix 2006–– No serious performance limits expectedNo serious performance limits expected

Move towards Move towards PbPb--PbPb nominal parameters from 2009nominal parameters from 2009–– Various performance limits, including collimationVarious performance limits, including collimation

This is just the first step in the ion programmeThis is just the first step in the ion programme


ConclusionsConclusions

US DOE/NSAC Review 2004: US DOE/NSAC Review 2004: –– ““LHC will open up a new regime of ultraLHC will open up a new regime of ultra--relativistic relativistic

heavyheavy--ion physics with significant opportunities for ion physics with significant opportunities for new discoveries.new discoveries.””

AddedAdded--value for the worldvalue for the world--wide investment in LHC.wide investment in LHC.Operation of LHC with lead ions limited by new effects, Operation of LHC with lead ions limited by new effects, qualitatively different from protons qualitatively different from protons –– Several effects important around design luminosity. Several effects important around design luminosity. –– Challenge to achieve design luminosity.Challenge to achieve design luminosity.

Extensive future programme, colliding Extensive future programme, colliding pp--PbPb, , ArAr--ArAr, O, O--O, O, pp--ArAr, p, p--O, O, …… with further challenges.with further challenges.

i-lhc project overview and statuslhc-collimation.web.cern.ch/lhc-collimation/files/...2006/04/03...

Documents