Lead Ions in the LHC · 2004-03-12 · 208 Pb82+ +208 Pb82+ →γ 208 Pb82+ +208 Pb81+ +e+ Electron...
Transcript of Lead Ions in the LHC · 2004-03-12 · 208 Pb82+ +208 Pb82+ →γ 208 Pb82+ +208 Pb81+ +e+ Electron...
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 1
Lead Ions in the LHC Lead Ions in the LHC
Contributors to this talk Contributors to this talk (re(re--run of run of ChamonixChamonix plus some extras): plus some extras):
H. Braun, H. Braun, J.M. Jowett, J.M. Jowett, E. E. MahnerMahner, , K. K. SchindlSchindl, , E. E. ShaposhnikovaShaposhnikova (CERN)(CERN)M. Gresham (Reed College, Portland), M. Gresham (Reed College, Portland),
I. I. PschenichnovPschenichnov (INR, Moscow) (INR, Moscow)
Thanks to: many other CERN colleagues, Thanks to: many other CERN colleagues, I. I. BaishevBaishev, S. , S. StriganovStriganov (FNAL)(FNAL)
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 2
Ions for LHC (IIons for LHC (I--LHC) ProjectLHC) Project
�� New INew I--LHC Project Web pages: LHC Project Web pages: –– http://carli.home.cern.ch/carli/ILHC_website/http://carli.home.cern.ch/carli/ILHC_website/
�� Members of the IMembers of the I--LHC Steering Group: LHC Steering Group: –– KarlheinzKarlheinz SchindlSchindl : : Chairman Chairman –– Hans Braun Hans Braun : : Ion collimation in LHC Ion collimation in LHC –– Christian Christian CarliCarli : : Scientific Secretary Scientific Secretary –– Michel Michel ChanelChanel : : Deputy Chairman, LEIR Deputy Chairman, LEIR –– Steven Hancock Steven Hancock : : RF aspects in LEIR and PS RF aspects in LEIR and PS –– Charles Hill Charles Hill : : LinacLinac 3, ECR ion source 3, ECR ion source –– John Jowett John Jowett : : LHC, linkman to experiments LHC, linkman to experiments –– DjangoDjango ManglunkiManglunki : : SPS, operational aspects SPS, operational aspects
Michel Martini Michel Martini : : PS, line to SPS PS, line to SPS –– Stephan Maury Stephan Maury : : Linkman to AC Linkman to AC –– FlemmingFlemming Pedersen Pedersen :: Low level RF all machines Low level RF all machines –– Elena Elena ShaposhnikovaShaposhnikova:: RF aspects SPS and LHC RF aspects SPS and LHC
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 3
Plan of talkPlan of talk
�� The IThe I--LHC ProjectLHC Project�� Review new ion parameters Review new ion parameters �� SmallSmall--angle separation schemeangle separation scheme�� Quench limit and ECPPQuench limit and ECPP�� CollimationCollimation�� Vacuum AspectsVacuum Aspects�� Luminosity and beam lifetimeLuminosity and beam lifetime�� Conclusions, implicationsConclusions, implications
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 4
Parameters for Lead Ions in LHCParameters for Lead Ions in LHC
�� Revision/verification of all parametersRevision/verification of all parameters–– Started at Started at ChamonixChamonix Workshop 2003Workshop 2003–– SummarisedSummarised in LHC Design Report in LHC Design Report VolVol I, Chapter 21I, Chapter 21
�� Recent changes:Recent changes:–– Introduction of “Early Ion Scheme”Introduction of “Early Ion Scheme”–– Optics update, smallOptics update, small--angle crossing scheme for ALICEangle crossing scheme for ALICE–– Revised lifetimes, IBS, etc.Revised lifetimes, IBS, etc.–– No 200 MHz RF system for capture at injection nowNo 200 MHz RF system for capture at injection now
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 5
Nominal scheme parametersNominal scheme parameters
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 6
Nominal scheme, lifetime parametersNominal scheme, lifetime parameters
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 7
Early scheme ParametersEarly scheme Parameters
Only show parameters that are different from nominal schemeOnly show parameters that are different from nominal scheme
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 8
Some things are straightforward Some things are straightforward
�� Beam current and stored energy 100 times lowerBeam current and stored energy 100 times lower–– Many limits to performance of proton beams are not a Many limits to performance of proton beams are not a
problem for lead ion beamsproblem for lead ion beams�� impedanceimpedance--driven collective effectsdriven collective effects�� beambeam--beambeam�� electron cloud (?)electron cloud (?)�� activation and maintenance of collimators activation and maintenance of collimators
�� Same Same geometricalgeometrical transverse beam size and emittance transverse beam size and emittance ⇒⇒ ssome aspects are similarome aspects are similar–– Optics, dynamic aperture, mechanical acceptance, Optics, dynamic aperture, mechanical acceptance,
etc. more or less carry over from protons.etc. more or less carry over from protons.
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 9
OpticsOptics
�� Ion optics at injection/ramp Ion optics at injection/ramp –– assumed to be essentially same as protonsassumed to be essentially same as protons
�� Lead ion optics in collisionLead ion optics in collision–– Update for move of Q3 magnets (part of V6.5)Update for move of Q3 magnets (part of V6.5)–– Focus on IR2 (ALICE, Focus on IR2 (ALICE, specialisedspecialised ion experiment)ion experiment)
�� Maintain Maintain ββ*=0.5 m (unlike protons which have *=0.5 m (unlike protons which have ββ*=0.55 m *=0.55 m for reasons of aperture)for reasons of aperture)
–– Ion collisions for ATLAS/CMS may use proton optics Ion collisions for ATLAS/CMS may use proton optics �� Or also squeeze furtherOr also squeeze further
–– Main issue is separationMain issue is separation
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 10
Separation in IR2: three illustrative casesSeparation in IR2: three illustrative cases
3100 3200 3300 3400 3500 3600fIP2bump= 17%, fALICE= 100%, qc= 82.2 mrad
-0.005
0
0.005
0.01
y cêm sêm
3100 3200 3300 3400 3500 3600fIP2bump= 42%, fALICE= 100%, qc= -2.8 mrad
-0.005
0
0.005
0.01
y cêm sêm
3100 3200 3300 3400 3500 3600fIP2bump= -65%, fALICE= -100%, qc= 81. mrad
-0.005
0
0.005
0.01
y cêm sêm
Two ways of getting a crossing angle of 80 µrad; one way to get zero crossing angle.
Total separation is superposition of ALICE spectrometer bump and “external” vertical separationBeam 1 / Beam 2
Animation!
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 12
Parasitic beamParasitic beam--beam encountersbeam encounters
3200 3250 3300 3350 3400 3450fIP2bump= 17%, fALICE= 100%, qc= 82.2 mrad
-7.5
-5
-2.5
0
2.5
5
7.5
10
Yês 1y sêm
3200 3250 3300 3350 3400 3450fIP2bump= -65%, fALICE= -100%, qc= 81. mrad
-7.5
-5
-2.5
0
2.5
5
7.5
10
Yês 1y sêm
3200 3250 3300 3350 3400 3450fIP2bump= 42%, fALICE= 100%, qc= -2.8 mrad
-7.5
-5
-2.5
0
2.5
5
7.5
10
Yês 1y sêm
Show only vertical separation in units of vertical RMS beam size of Beam 1.
Red lines are possible (ion) encounters (Sb/2)
Zero crossing angle is just about achievable with minimum 3σ separation (strictly need 20 µrad).
Bad!
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 13
Aperture (APL program)Aperture (APL program)
All meet the canonical aperture requirements with β*=0.5m
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 14
Electromagnetic Interactions of Lead ionsElectromagnetic Interactions of Lead 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=
−=δZp
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.)
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 15
Nuclear cross sectionsNuclear cross sections
�� CrossCross--section for section for PbPb totally totally dominated by electromagnetic dominated by electromagnetic processesprocesses
�� Values 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
ECPP values from Meier et al, Phys. Rev. A, 63, 032713 (2001), calculation for Pb-Pbat LHC energy
ECPP values from Meier et al, Phys. Rev. A, 63, 032713 (2001), calculation for Pb-Pbat LHC energy
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 16
Involved topic, numerous references …
Extrapolation from SPS measurements at lower energy in Grafström et al, PAC99
Meier et al, Phys. Rev. A, 63, 032713 (2001), calculation for Pb-Pb at LHC energy
Involved topic, numerous references …
Extrapolation from SPS measurements at lower energy in Grafström et al, PAC99
Meier et al, Phys. Rev. A, 63, 032713 (2001), calculation for Pb-Pb at LHC energy
CrossCross--sectionsectionfor ECPPfor ECPP
Electron can be captured to a number of bound states, not only 1s.
Electron can be captured to a number of bound states, not only 1s.
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 17
C.f. 204 barn used in previous discussions
[ ]
[ ]
[ ]
barn 281
barn 533.076.9)1()3(
barn 533.076.92.88.28.225
)2()2()3()2()1(
ECPP
2/3ECPP2/1ECPP
ECPPECPPECPPECPP
≈
+++σζ≈
++++++≈
+σ+σ++σ+σ+σ=σ
L
L
L
L
L
s
ppsss
Use Meier et al’s result for Pb-Pb at LHC energy:
CrossCross--section for ECPPsection for ECPP
3ECPP
ECPP)1()(
nsns σ
≈σ
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 18
Main and ECPP secondary beamsMain and ECPP secondary beams
0
100
200
300
400
sêm
-0.02
0
0.02
xêm-0.03
-0.02
-0.01
0
yêm0.02
0
5σ beam envelopes, emerging to right of IP2
Collimation of secondary beam seems difficult.
Beam screen
Uncorrected strong chromatic effects of low-b insertion⇒ cannot use linear beam sizes for Pb71+ beam
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 19
Secondary beam spotSecondary beam spot
3700
3705
3710
sêm
-0.02-0.01
00.01
0.02
xêm
-0.01
0
0.01
yêm 3700
3705
3710
sêm
0.0100.01
0.02
m/s
m/y
m/x
9.5 10 10.5 11 11.5 12
0.2
0.4
0.6
0.8
Energy deposition by ion flux from ECPP exceeds nominal quench limit of superconducting magnets by factor 2 at nominal luminosity. DIRECT LIMIT ON LUMINOSITY.
m 4.1m 1length shower with quadratureIn m, 1over Dilution
≈≈dl Beam screen in a
dispersion suppressor dipole
Pb/m/s 108 is ive)(conservatlimit Quench 4×
Plan to improve heat deposition estimate with FLUKA calculations.
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 20
Collimation for Collimation for PbPb ionsions
�� 208208PbPb82+82+ ionion--graphite interactions compared with pgraphite interactions compared with p--graphite interactions.graphite interactions.
From Hans Braun
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 21
FLUKA calculations from Vasilis Vlachoudisfor dump kicker single module prefire
Robustness of collimator against mishapsRobustness of collimator against mishaps
–The higher Ionisation loss makes the energy deposition at the impact side almost equal to proton case, despite 100 times less beam power.
–Similar damage potential.
From Hans Braun
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 22
The probability to convert a 208Pb nucleus into a neighboring nucleus. Impact on graphite at LHC collision energy.
Cleaning efficiencyCleaning efficiency
From Hans Braun
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 23
Simulation of collimation (Hans Braun)Simulation of collimation (Hans Braun)
� Model of ion fragmentation, linear optics, collimators and beam aperture
� Suppose beam lifetime is down to 12 min– due to non-luminosity processes, e.g., IBS, beam-gas,
resonances, … � Collimators tend to put ion fragments on trajectories
with large momentum errors and small betatron amplitude –– but the secondary collimators are designed to cut
betatron amplitudes� Acts like one-stage system� Worrying results at collision energy (following slides)
– Various hot-spots around ring� Seems OK at injection energy
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 24
570 580 590 600 610 620 630
0
5
10
15
20P' (W
/m)
distance from TCP.D6L7.B1 (m)
Fractional heat load in dispersion suppressor, τ=12min
MQ
.10R
7.B1
MQ
TLI.1
0R7.
B1
MB.
A11
R7.B
1
MB.
B11
R7.B
1
MQ
.11R
7.B1
MQ
TLI.1
1R7.
B1
Maximum for continous loss,corresponds to local collimation inefficiency of 1.61 10-3m-1
Pb208
Pb207
Pb206
Pb205
Pb204
Pb203
Tl204
Tl203
Tl202
Tl201
Tl200
Tl199
Tl198
Hg201
Hg200
Hg199
Nominal ILHC beam at collision
From Hans Braun
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 25
0 5 10 15 20 25
0
10
20
30
IP1 IP2 IP3 IP4 IP5 IP6 IP7 IP8 IP1
P' (W/m
)
Distance from IP1 (km)
Loss map
0
500
1000
1500
TCP
.6L3
.B1
TCS
.5L3
.B1
TCS
.A4R
3.B
1
TCS
.B4R
3.B
1
TCS
.A5R
3.B
1
TCS
.B5R
3.B
1
TCS
.C5R
3.B
1
TCP
.D6L
7.B
1
TCP
.C6L
7.B
1
TCP
.B6L
7.B
1
TCP
.A6L
7.B
1
TCS
.C6L
7.B
1
TCS
.B6L
7.B
1
TCS
.A6L
7.B
1
TCS
.B5L
7.B
1
TCS
.A5L
7.B
1
TCS
.B4L
7.B
1
TCS
.A4L
7.B
1
TCS
.A4R
7.B
1
TCS
.B4R
7.B
1
TCS
.C4R
7.B
1
TCS
.D4R
7.B
1
TCS
.E4R
7.B
1
TCS
.F4R
7.B
1
TCS
.G4R
7.B
1
TCS
.A5R
7.B
1
TCS
.B5R
7.B
1
P CO
LL (W
)Collimator load distribution
0 20 40 60 80 100 120 140 1600
2
4
6x 10
4
NTURN
Time development after first impact on collimatorparticles lost on collimatorsparticles lost elsewhereparticles in beam
Nominal ILHC beam at collision
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 26
Interaction of Interaction of PbPb ions with residual gasions with residual gas
�� Losses due to nuclear scattering on residual gasesLosses due to nuclear scattering on residual gases–– Atoms in residual gases (6 usual suspects in Design Atoms in residual gases (6 usual suspects in Design
Report for protons) have Z≤8. Report for protons) have Z≤8. –– For simplicity, discuss only the dominant inelastic For simplicity, discuss only the dominant inelastic
nuclear scattering (leave out elastic and nuclear scattering (leave out elastic and electromagnetic contributions, EMD, ECPP which are electromagnetic contributions, EMD, ECPP which are smaller). Somewhat optimistic!smaller). Somewhat optimistic!
–– Dominant beamDominant beam--gas lifetime:gas lifetime:is independent of intensity is independent of intensity
–– Multiple Coulomb scattering on residual gas also Multiple Coulomb scattering on residual gas also causes emittance growth (similar to protons, not causes emittance growth (similar to protons, not treated here).treated here).
–– Lost ions are a heat load:Lost ions are a heat load:
ii
i nc ∑∈
σ=τ gasesbg
1
bgτ=Zec
EIkP bbbg
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 27
Inelastic nuclear cross sectionsInelastic nuclear cross sections
�� CrossCross--sections of protonsections of proton--nucleus and nucleusnucleus and nucleus--nucleus inelastic interactions nucleus inelastic interactions at ~10 GeV/n, assumed similar at 2.75 TeV/n (as is the case for at ~10 GeV/n, assumed similar at 2.75 TeV/n (as is the case for protons)protons)–– Simple formula, V.S. Barashenkov, 1993Simple formula, V.S. Barashenkov, 1993
( )
( ) ( )
barn. 038.0 where
215.285.1,,, :AA
1215.21
85.1, :pA
0
2
2
2
1
13/1
23/1
1
3/1213/1
23/1
102211in21
2
3/1
3/13/1
0in
=σ
−
−−+
+++σ=σ
−
−+
++σ=σ
AZ
AZ
AAAAAAAZAZ
AZ
AAAAZ
Comparison with earlier Hard-sphere overlap model (Bradt & Peters 1950)
20 40 60 80Z
2
4
6
8
σêbarnPb, Barashenkov
Pb, Hard-sphere
pA, BarashenkovpA, Hard-sphere
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 28
Required gas pressuresRequired gas pressures
Gas σin nêm−3 τbgêh PbgêHWêmLH2 3.75 1.03× 1015 2.4 0.0165He 2.48 8.2× 1014 4.55 0.00872CH4 10.9 2.14× 1014 3.96 0.01H2O 7.52 2.33× 1014 5.28 0.00752CO 7.22 1.65× 1014 7.76 0.00512CO2 11. 1.07× 1014 7.89 0.00503
Gas σin nêm−3 PH300KLênTorr PH5KLêPa PbgêHWêmLH2 0.09 1.03× 1015 32. 7.11× 10−8 0.0377He 0.113 8.2×1014 25.5 5.66× 10−8 0.0377CH4 0.433 2.14× 1014 6.65 1.48× 10−8 0.0377H2O 0.397 2.33× 1014 7.24 1.61× 10−8 0.0377CO 0.56 1.65× 1014 5.14 1.14× 10−8 0.0377CO2 0.868 1.07× 1014 3.32 7.37× 10−9 0.0377
Protons with lifetime 100h
Lead ions with pressure that gave proton lifetime 100h
Gas σin nêm−3 PH300KLênTorr PH5KLêPa PbgêHWêmLH2 3.75 2.47× 1013 0.768 1.71× 10−9 0.000397He 2.48 3.73× 1013 1.16 2.58× 10−9 0.000397CH4 10.9 8.47× 1012 0.263 5.85× 10−10 0.000397H2O 7.52 1.23× 1013 0.383 8.5× 10−10 0.000397CO 7.22 1.28× 1013 0.399 8.86× 10−10 0.000397CO2 11. 8.43× 1012 0.262 5.82× 10−10 0.000397
Lead ions with lifetime 100h
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 29
0.1 1 10 100 1000 10000 100000101
102
103
104
105
106
107
108
Pb27+
BNL (AGS) BNL (RHIC) CERN (LINAC 3) CERN (SPS) GSI (HLI) GSI (HLI) GSI (SIS 18)
PRELIMINARY
In49+
Au79+
U28+Pb53+
Zn10+
Au31+
η eff [
mol
ecul
es/io
n]
Ion energy [MeV/u]
HeavyHeavy--ion induced ion induced desorptiondesorption data:data:New OverviewNew Overview
15 From Edgar Mahner
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 30
Electron Cloud effect with ions ?Electron Cloud effect with ions ?
�� Key parameters are charge/bunch and bunch spacingKey parameters are charge/bunch and bunch spacing–– We do not expect electron cloud effects with We do not expect electron cloud effects with PbPb ions. ions.
0.01 0.02 0.03 0.041êSb
2µ 1010
4µ 1010
6µ 1010
8µ 1010
1µ 1011
NbQion
Pb nominalPb early
RHIC with ecloud
LHC p nominal
LHC p no electron cloud (FZ simulation)
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 31
Longitudinal parametersLongitudinal parameters
Longitudinal emittance at injection from SPS has been reduced since we no longer have 200 MHz RF system for capture.
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 32
IntraIntra--beam scatteringbeam scattering
Injection Collision
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 33
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 photons�� Critical 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.
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 34
Damping partition number variationDamping partition number variation
�� Allows us to switch some radiation damping from Allows us to switch some radiation damping from longitudinal into horizontal motionlongitudinal into horizontal motion–– Heavily used at LEP, PETRA, TRISTAN, … Heavily used at LEP, PETRA, TRISTAN, … –– Overcome IBS, shrinking horizontal emittance to Overcome IBS, shrinking horizontal emittance to
maximisemaximise integrated luminosityintegrated luminosity–– Price of a few mm negative closed orbit in arc Price of a few mm negative closed orbit in arc QFsQFs ––
needs further studyneeds further study
( ) ( )
( ) ( )( ) dssDsKI
III
ff
II
II
dUdJ
x
sss
ss
2
18
23
42
RF
RF
2
8
2
4
,10 ,2
1 ,22log:orbitclosedofdeviation momentumh number witpartition dampingallongitudin ofVariation
∫=
≈ρπ
≈
∆η
−=δδ++≈δδ
=δ
−
ε
( ) ( ) ( ) ( )( ) ( )030motionbetatron horizontalfor rateDamping
xsxsxsx JJ αδ−=αδ=δα ε
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 35
Luminosity and beam lifetimeLuminosity and beam lifetime
�� InitialInitial beam (intensity) lifetime due to beambeam (intensity) lifetime due to beam--beam beam interactions (noninteractions (non--exponential decay) exponential decay)
–– where where nnexpexp is the number of experiments illuminatedis the number of experiments illuminated�� But luminosity may be limited by experiment or quench But luminosity may be limited by experiment or quench
limitlimit
ββ**--tuning during collision to tuning during collision to maximisemaximise integrated integrated luminosity luminosity –– especially if especially if NNbb can be increased.can be increased.
Pb-Pbwith scm 10 nominalfor hour4.22 1-2-27
exptotexp
==σ
=τ LnLn
Nk bbNL
2
02
20
2
* by varying luminosity same havecan
*4*4
b
n
bbbb
N
fNkfNkL
∝β⇒
γεβπ
=σπ
=
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 36
Nominal scheme, lifetime parameters (again)Nominal scheme, lifetime parameters (again)
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 37
Operational parameter space Operational parameter space with lead ionswith lead ions
0.01 0.05 0.1 0.5 1 5 10Ib µ
1. × 1022
1. × 1023
1. × 1024
1. × 1025
1. × 1026
1. × 1027
cm 2s−1
Visibility threshold on FB
CT
Nominal
Visible o
n BCTDC
Early
-1-2scm/L
A/µbI
Visibility threshold on arc B
PM
ECPP Quench limitN
ominal single bunch current
Visible o
n BCTDC
Thresholds for visibility on BPMs and BCTs.
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 38
ConclusionsConclusions
�� Operation of LHC with lead ions limited by diverse effects, ofteOperation of LHC with lead ions limited by diverse effects, often n qualitatively different from protonsqualitatively different from protons
�� ECPP leading to magnet quench limits luminosityECPP leading to magnet quench limits luminosity�� Poor collimation efficiency, large particle losses in dispersionPoor collimation efficiency, large particle losses in dispersion
compressor, limit on total currentcompressor, limit on total current–– Either keep > 40 min lifetime for nominal Ion parameters in Either keep > 40 min lifetime for nominal Ion parameters in
collision (!) or reduce beam currentcollision (!) or reduce beam current�� “Early scheme” will allow relatively safe commissioning, access “Early scheme” will allow relatively safe commissioning, access good good
initial physicsinitial physics–– Reduced risk of magnet quenches from ECPPReduced risk of magnet quenches from ECPP–– Reduced heat deposition related to collimationReduced heat deposition related to collimation
�� But But PbPb ions require much lower vacuum pressure than protonsions require much lower vacuum pressure than protons–– Independent of beam intensity! Independent of beam intensity!
�� Restricted to a small range of operational parameters below the Restricted to a small range of operational parameters below the nominal luminositynominal luminosity–– Do everything possible to expand it!Do everything possible to expand it!
J.M. Jowett, LHC Experiment Accelerator Data Exchange Working Group, 9/2/2004 39
ImplicationsImplications
�� Some effects (collimation,…) limit Some effects (collimation,…) limit total beam current total beam current but but there are no hard limits on single bunch currentthere are no hard limits on single bunch current–– More luminosity by distributing current in fewer More luminosity by distributing current in fewer
bunchesbunches–– Optimum filling scheme may be somewhere between Optimum filling scheme may be somewhere between
Early (kb=62) and Nominal (kb=592)Early (kb=62) and Nominal (kb=592)–– Possibility of running with, Possibility of running with, e.ge.g, 100, 100--300 bunches 300 bunches
should be kept in mind by injectors, all LHC systems should be kept in mind by injectors, all LHC systems and the experiments.and the experiments.
�� Do everything possible to increase singleDo everything possible to increase single--bunch currentbunch current–– Push all limits in injector chainPush all limits in injector chain
�� Many uncertainties to be resolved with further workMany uncertainties to be resolved with further work–– ECPP heating, EMD losses, vacuum, collimation, RF ECPP heating, EMD losses, vacuum, collimation, RF
noise, …noise, …