a first look at the performance for pb-pb and p-pb collisions in fcc-hh michaela schaumann (cern,...
DESCRIPTION
General FCC-hh Parameters 2014/02/14 M. Schaumann, Pb-Pb and p-Pb performance of FCC 3 UnitsInjectionCollision Circumference[km]80 Main dipole strength[T]1.220 Bending radius[m] Proton equivalent energy[TeV]350 Lead ion energy[TeV] Lead ion energy/nucleon[TeV] [TeV] Based on a working p-p collider exists.TRANSCRIPT
A First Look at the Performance for Pb-Pb and p-Pb collisions in FCC-hh
Michaela Schaumann (CERN, RWTH Aachen)
In collaboration with J.M. Jowett and R. Versteegen (CERN)14th February 2014
FCC Study Kickoff Meeting, Geneva
M. Schaumann, Pb-Pb and p-Pb performance of FCC 2
Outline
2014/02/14
• General assumptions (Pre-accelerator chain, ring and beam parameters)
• Estimates for: • IBS and radiation damping• Luminosity and beam evolution• Beam-beam tune shift• Power in secondary beams emerging from collision
point
• Parameter table• Conclusions
M. Schaumann, Pb-Pb and p-Pb performance of FCC 3
General FCC-hh Parameters
2014/02/14
Units Injection Collision
Circumference [km] 80 80
Main dipole strength [T] 1.2 20
Bending radius [m] 8339.1 8339.1
Proton equivalent energy [TeV] 3 50
Lead ion energy [TeV] 246 4100
Lead ion energy/nucleon [TeV] 1.2 19.7
C.M. energy [TeV] 2.4 39.4
Based on a working p-p collider exists.
M. Schaumann, Pb-Pb and p-Pb performance of FCC
Heavy Ion Pre-Accelerator Chain
42014/02/14
Straw-man assumption to estimate (conservative) beam parameters and luminosity: LHC, as it is today, but cycling to 3 Z TeV, is assumed to be the injector for FCC-hh.
The requirements and performance of the pre-accelerator chain for FCC are not studied yet.
Present heavy-ion pre-injectors
LEIRHI source + Linac 3
Inject one LHC beam into 1/3 FCC, no waiting. Will see later that injector cycle time is similar to time taken to burn-off all beam in FCC.
PS
SPS
LHCFCC
R&D
M. Schaumann, Pb-Pb and p-Pb performance of FCC 5
Pb Beam Parameters in LHC and FCC-hh
LHCDesign
LHC 2011
LHC 2013
FCC-hh
Beam Energy [Z TeV] 7 3.5 4 50
β-function at the IP [m] 0.5 1.0 0.8 1.1
No. Ions per bunch [] 0.7 1.4
Transv. normalised emittance [] 1.5 1.5
RMS Beam Size at IP [] 15.9 33.9 26.6 8.8
RMS bunch length [] 7.94 10
Number of bunches 592 358 358 432
Peak Luminosity [] 1 (Pb-Pb) 110 (p-Pb) ?
2014/02/14
Best injector performance achieved in 2013 p-Pb run.
Average beam parameters from 2013 are assumed as VERY conservative baseline for FCC-hh!
→ Improvements are already under study for HL-LHC!
M. Schaumann, Pb-Pb and p-Pb performance of FCC 6
Effects on the Emittance – a new regime
2014/02/14
Intra-Beam Scattering (IBS) Radiation DampingEmittance Growth Emittance Shrinkage
twice as fast as for protons!!Growth rate dynamically changing with beam properties: Damping rate is constant for a given energy:
Damping Times
Unit FCCcollision
[h] 0.16
[h] 0.31
[h] 0.31
Growth Times
Unit FCC collision
[h] 144.7
[h] 39.1
[h]
IBS is weak for initial beam parameters, but increases with decreasing emittance .
Fast emittance decrease at the beginning of the fill, until IBS becomes strong enough to counteract the radiation damping.
M. Schaumann, Pb-Pb and p-Pb performance of FCC 7
Beam Evolution in Pb-Pb Collisions (1 Experiment)
2014/02/14
• “Analytical calculation” considers only burn-off and radiation damping , becomes unrealistic as !
• In simulation horizontal IBS counteracts radiation damping for small emittances:o Without betatron coupling .o With coupling, horizontal IBS growth is
transferred to vertical plane.o Equilibrium emittance in both planes.
Horizontal Emittance Vertical Emittance
Intensity
M. Schaumann, Pb-Pb and p-Pb performance of FCC 8
Pb-Pb Luminosity Evolution (1 Experiment)
2014/02/14
• “Analytical calculation” neglects IBS, so over-estimates luminosity peak and burn-off speed
• Simulation with coupling is most realistic case.
• Emittances and bunch length become very small instabilities and artificial blow-up may have to be studied.
Unit per Bunch whole Beam
[Hz/mb] 0.0075 3.2
[Hz/mb] 0.029 12.7
[] 0.2 83
• Very high • Is detector able to take hadronic rates >
100 kHz ?• Levelling required? → Evolution with varying see back-up slides
1 experiment in collisions
R&D
R&D
M. Schaumann, Pb-Pb and p-Pb performance of FCC 9
Beam-Beam Tune Shift
2014/02/14
Beam-Beam Parameter per Experiment
Unit LHC Designp-p
LHC DesignPb-Pb
FCCPb-Pb
Initial [ 3.7 0.18 0.37
Peak [ 3.7 0.18 2.0
Beam-beam tune shift per experiment.For round beams :
The tune shift due to beam-beam interactions remains well below assumed limit.
M. Schaumann, Pb-Pb and p-Pb performance of FCC 10
p-Pb Luminosity Evolution (1 Experiment)
2014/02/14
“Analytical calculation” only! – Neglecting IBS
Initial conditions:• Pb-beam as for Pb-Pb operation.• Equal geometric beam sizes for p and Pb.• 2 = const.• = const.
→ Fast Pb burn-off: Fill Length
Maximum integrated luminosity is achieved, when all Pb ions are converted into luminosity
Unit per Bunch whole Beam[Hz/mb] 0.6 267
[Hz/mb] 13 5477
[] 70 30240
M. Schaumann, Pb-Pb and p-Pb performance of FCC 11
BFPP Beam Power
2014/02/14
Main: 208-Pb-82+
BFPP1: 208-Pb-81+BFPP2: 208-Pb-80+
EMD1: 207-Pb-82+EMD2: 206-Pb-82+
LHC
Example: LHC Pb beam right of IP2
Countermeasures (e.g., DS collimators) have to be considered in initial lattice & hardware design.
Main contribution to fast Pb-Pb burn-off:
R&D
FCC-PbPb
peak
M. Schaumann, Pb-Pb and p-Pb performance of FCC 12
Summary Table (1)
2014/02/14
Unit LHC Design FCCInjection
FCCCollision
FCCCollision
Operation mode - Pb-Pb Pb Pb-Pb p-Pb
Particle type - Pb Pb Pb p
Beam Energy [TeV] 574 246 4100 50
Lead ion energy/nucleon [TeV] 2.76 1.2 19.7 50
Relativistic γ-factor - 2963 1270 21168 53290
Number of bunches - 592 432 432 432
No. Ions per bunch [] 0.7 1.4 1.4 115
Transv. normalised emittance [] 1.5 1.5 1.5 3.75
RMS bunch length [] 7.94 10 10 10
Synchrotron frequency [Hz] 23.0 5.5 1.9 1.9
Longitudinal emittance (4σ) [eVs/charge] 2.5 4 23 23
RMS energy spread [ 1.1 3.3 1.1 1.1
Circulating beam current [mA] 6.12 3.0 3.0 3.0
Stored beam energy [MJ] 3.81 2.4 40 40
Longitudinal IBS emit. growth time [h] 7.7 16.9 144.7 1
Horizontal IBS emit. growth time [h] 13 8.5 39.1 3
Longitudinal emit. rad. damping time [h] 6.3 725 0.16 0.32
Horizontal emit. rad. damping time [h] 12.6 1451 0.31 0.63
M. Schaumann, Pb-Pb and p-Pb performance of FCC 13
Summary Table (2)
2014/02/14
Unit LHC Design FCCInjection
FCCCollision
FCCCollision
Operation mode - Pb-Pb Pb Pb-Pb p-PbPeak RF voltage [MV] 16 11 22 22
RF frequency [MHz] 400 400 400 400Harmonic number - 35640 106740 106740 106740Power loss per ion [W]Energy loss per ion per turn [MeV] 1.12 0.01 969.1 5.8Synchrotron radiation power per ring [W] 83.9 0.7 53732 26587Critical photon energy [eV] 2.77 0.07 336.7 5376β-function at the IP [m] 0.5 - 1.1 1.1RMS beam size at IP [] 15.9 - 8.8 8.8 Initial luminosity [] 1 - 3.2 267Peak luminosity [] 1 - 12.7 5477Integrated luminosity per fill [] <15 - 83 30240Beam-beam tune shift [] 1.8 - 3.7 3.7Total cross-section [b] 515 - 597 2Peak BFPP beam power [W] 26 - 2947 0Initial beam current lifetime (1 exp.) [h] <11.2 (2 exp.) - 8.7 24Initial luminosity lifetime [h] <5.6 (2 exp.) - 3.7 3.2
M. Schaumann, Pb-Pb and p-Pb performance of FCC 14
Peak and Integrated Luminosity per Month
2014/02/14
https://indico.cern.ch/event/288576/material/1/0
Luminosity values discussed with the Ion Physics Working Group for FCC-hh.
M. Schaumann, Pb-Pb and p-Pb performance of FCC 15
Conclusions and Outlook
2014/02/14
Conservative assumptions based on existing injector-chain:• High peak luminosity
( nominal LHC) – consider levelling?
• Max. int. luminosity: ~100% of particles converted into luminosity as fast as injectors can produce them.
• N.B. Two experiments would share approx. same integrated luminosity.
Strong rad. damping, small emittances and effective intensity burn-off.
• High potential for luminosity improvement from injectors:• Luminosity is rather insensitive to the
initial emittance coming from the injectors, due to rad. damping.
• New ion source and injector chain to deliver higher beam current (higher smaller bunch spacing).
• Faster cycling of injectors; more injections to increase the number of bunches.
• Small emittances and bunch lengths might require artificial blow-up to prevent instabilities; could be used as levelling method.
R&D
Watch compatibility of evolving hadron collider design with nuclear beams.
M. Schaumann, Pb-Pb and p-Pb performance of FCC 16
THANK YOU FOR YOUR ATTENTION
2014/02/14
M. Schaumann, Pb-Pb and p-Pb performance of FCC 17
Bunch-by-Bunch Differences after Injection in the LHC
• Structure within a train (1st to last bunch):
• increase: - intensity - bunch length
• decrease: emittance.
• IBS, space charge, RF noise … at the injection plateau of the SPS:• while waiting for the 12 injections from the PS to construct a LHC train.
• First injections sit longer at low energy strong IBS, emittance growth and particle losses.
Intensity
Design
Horizontal / VerticalEmittance
Design
2014/02/14
1 train
E = 450 Z GeV
M. Schaumann, Pb-Pb and p-Pb performance of FCC 18
Smooth Lattice Approximation
2014/02/14
A lattice design does not yet exist!Approximations for smooth lattice functions are used where necessary.
Cell Length from aperture constraints
Unit LHC Design FCC
Arc Filling Factor - 0.78 0.78
Average β-function [m] [66, 71] [100, 125]
Average Dispersion (hor.) [m] 1.4 [1.3, 2.0]
Gamma Transition - 55.7 [78, 100]
Assume FODO cell with
M. Schaumann, Pb-Pb and p-Pb performance of FCC
Intra-Beam Scattering
2014/02/14 19
Handbook of Accelerator Physics and Engineering, 1st Edition, 3rd Print, pp. 141
A. Piwinski Formalism for IBS growth rates: Particle Type
Energy Beam properties
Lattice and beam sizes
IBS strength changes dynamically with beam properties.
M. Schaumann, Pb-Pb and p-Pb performance of FCC 20
Intra-Beam Scattering
2014/02/14
Growth Times
Unit LHC Design
FCC injection
FCC collision
[h] 7.7 16.9 144.7
[h] 13 8.5 39.1
[h] -75000 -6604
Variation of IBS growth times for initial beam conditions with FODO cell length.
Effect of long. (hor.) IBS decreases (increases) with increasing cell length.At collision energy, IBS is weak for initial beam parameters.
Injection Energy Collision Energy
Expected Range
Expected Range
M. Schaumann, Pb-Pb and p-Pb performance of FCC 21
Radiation Damping
2014/02/14
Radiation Integrals
Energy Particle Type Ring
Constant depending on particle’s mass and charge
Isomagnetic ring with separated
function magnets &
Damping Rates
Handbook of Accelerator Physics and Engineering, 1st Edition, 3rd Print, pp. 210
M. Schaumann, Pb-Pb and p-Pb performance of FCC 22
Luminosity Evolution
2014/02/14
Consider burn off and radiation damping:IBS is weak at top energy and dominated by radiation damping: → approximate constant emittance damping time.
System of two differential equations to be solved:
M. Schaumann, Pb-Pb and p-Pb performance of FCC 23
Beam Evolution Simulations
2014/02/14
Evolution of 3 typical Pb-bunches in collisions.
HeadCoreTail
Dashed lines: without couplingSolid lines: with coupling
M. Schaumann, Pb-Pb and p-Pb performance of FCC 24
Pb-Pb Luminosity for varying β*
2014/02/14
CTE simulation assuming full IBS coupling.
Red curve corresponds to solid red curve on slide 8.
M. Schaumann, Pb-Pb and p-Pb performance of FCC 25
p-Pb Beam Evolution
2014/02/14
is assumed to be constant at approximately 100
Pb emittance damps twice as fast as p emittance; assuming exponential emittance damping with constant rad. damping rate and no IBS.
M. Schaumann, Pb-Pb and p-Pb performance of FCC 26
Longitudinal Beam Parameters
2014/02/14
Unit LHC Design FCC
Synchrotron frequency [Hz] 23.0 1.9
Momentum spread [ 1.1 1.1
Longitudinal emittance [eVs/charge] 2.5 23
S.Y.Lee, Accelerator Physics, 3rd edition
at top energy
M. Schaumann, Pb-Pb and p-Pb performance of FCC 27
Circulating Beam Current and Stored Beam Energy
2014/02/14
Circulating beam current:
Stored beam energy:
Unit LHC Design
FCC injection
FCC collision
[mA] 6.12 2.98 2.98
[MJ] 3.81 2.38 39.73
M. Schaumann, Pb-Pb and p-Pb performance of FCC 28
Energy Loss per Turn
2014/02/14
Radiated power per ion:
Radiated power per beam:
Energy loss per ion per turn:
Damping Times
Unit LHC Design FCC injection
FCC collision
[W]
[MeV] 1.12 0.01 969.1
[W] 83.9 0.7 53732
[eV] 2.77 0.07 336.7
Critical photon energy:
Handbook of Accelerator Physics and Engineering, 2nd Edition, pp. 215
M. Schaumann, Pb-Pb and p-Pb performance of FCC 29
Initial Beam Current Lifetime
2014/02/14
Lifetime due to burn-off only!
Unit LHC Design(2 experiments)
FCC (1 experiment)
FCC(2 experiments)
[h] 11.2 8.7 4.3
Total cross-section at 50Z TeV:H. Meier et al, Phys. Rev. A, vol. 63, 032713. 02/2011
M. Schaumann, Pb-Pb and p-Pb performance of FCC 30
Cycle with LHC as Last Injector
2014/02/14
3h LHC turn around time = time between 2 injections to FCC. Luminosity lifetime FCC
→ Refill LHC during physics in FCC.→ No waiting time for FCC due to cycling
in LHC.
If 2 experiments are considered, they have to be placed at opposite positions in the ring to be provided with luminosity!
Intensity Evolution in FCC with 1 exp. in collisions
M. Schaumann, Pb-Pb and p-Pb performance of FCC 31
Smaller Z Ions – Impact on Luminosity
2014/02/14
• New ions source & injectors possibly higher are available. No studies on improved heavy ion injectors done yet!
• Contribution of ultra-peripheral electromagnetic processes to the total cross-section would be reduced:
Increased luminosity lifetime, more particles available for hadronic interactions.
Reduced secondary beam power emerging from collision point.
• Radiation damping rate does not change much for Z>60:o