Title: Status of Beam-Beam Task
1Status of Beam-Beam Task
US LHC Accelerator Research Program
BNL - FNAL- LBNL - SLAC
- Valishev, FNAL
- W. Fischer, Y. Luo BNL
- H.-J. Kim, A. Makarevich, V. Shiltsev, G.
Stancari, X.Zhang FNAL - A. Kabel SLAC, A. Romanov BINP
- 04 November 2009
- LARP CM13, Port Jefferson, NY
2FY09 LARP Beam-Beam Task
The Goal Evaluate the possible benefit to LHC
(RHIC) luminosity from HO beam-beam compensation.
- Experimental studies at the Tevatron
- Installation of the Gaussian profile gun was
planned - To experiment with beam to beam alignment
tolerances - Attempt tune footprint suppression
- Identify operational problems
- Provide data for comparison with simulations
- Numerical simulations
- Develop and validate codes/machine models using
existing experimental data - Provide predictions for RHIC and LHC to support
E-Lens installation - Theoretical analysis
- Effect of dispersion and chromaticity on RDTs,
finite e-beam rigidity
3Outline of the Talk
- Status of Gaussian Tevatron electron lens
- Beam-beam codes development, validation
- Simulations of head-on compensation at RHIC
- Effect of imperfections
- Simulations of head-on compensation at LHC
- Summary
4Beam-Beam Effects and BBC at the Tevatron
- Head-on tune spread in proton bunches is larger
due to 3/1 p/a emittance ratio - Bunches have different working points due to
Long-Range BBI
Gaussian TEL can generate dQ0.01
xa0.019
xp0.018
Na
Np
5Gaussian TEL Progress(A. Romanov, V. Shiltsev,
G. Stancari, A. Valishev, X. Zhang)
- Gaussian gun was installed in TEL-2 on June 20
(Tevatron shutdown 6/15 9/11). Peak current up
to 1A (Ne2x1011) - New TEL-2 BPM software
- Java, faster than old LabView
- Measures positions of individual proton,
antiproton, e- bunches - New software for high resolution Tev BPM
- Established electron beam timing, started
alignment with proton bunches
6TEL-2 BPMs
- One channel with strong reflections
- Frequency dependence
- Different calibrations and different offsets for
(anti)protons and electrons
7Next Steps and Tevatron Beam Time Requirements
- Calibrate BPMs with electrons and protons
- 1 hour end-of-store
- Align electron beam with protons
- 4-6 hours proton-only
- Measure tune-spread changes, effect on beam life
time - 2 hours end-of-store, 4-6 parasitic in-store
studies - Awaiting Run Coordinators approval for beam time
8Simulation Tools
- Weak-strong (some codes have strong-strong
capabilities) - Essential features
- Linear machine lattice with all IPs and
separations - Chromaticity
- Nonlinear elements
- Short-term measures
- tune footprint
- diffusion coefficients, tune diffusion
- resonance driving terms
- short-term dynamic aperture
- 103 turns - fast
- Interpretation of results is not
straightforward.
- Long-term tracking
- intensity life time
- emittance growth
- 106 107 turns - slow
- The main parameters for evaluation are
measurable quantities
9Simulation Tools Continued
- BBSIM (T. Sen, H.-J. Kim FNAL)
- RHIC head-on compensation
- LIFETRAC (D.Shatilov BINP, A. Valishev FNAL)
- RHIC head-on compensation
- LHC head-on compensation (LR collisions also
included) - PLIBB (A. Kabel SLAC)
- Configured to run LHC head-on compensation. No
new results in FY09 - SIXTRACK (F. Schmidt CERN, G. Robert-Demolaize,
Y. Luo BNL) - RHIC head-on compensation
10Benchmarking BBSIM vs. LIFETRAC, RHIC BBC (H.-J.
Kim, A. Valishev FNAL)
- Model differences
- Initial distribution
- BBSIM hollow Gaussian
- Lifetrac weighted Gaussian
- Aperture
- Lattice chromaticity (sextupoles)
- Model similarities
- Machine optics
- Includes multipoles
- Beam parameters
- 3D beam-beam
NO BBC
1/2 BBC
11Benchmarking BBSIM vs. SimTrack, RHIC BBC (H.-J.
Kim FNAL, Y. Luo BNL)
Also compared Lifetrac and SixTrack in 2D good
agreement
12RHIC BBC Simulations with SixTrack(Y. Luo, W.
Fischer, G. Robert-Demolaize, R. De Maria BNL)
t5 h
t20 min
Also did phase and Beam mismatch scans (see Yuns
talk)
nonlinear IR errors and arc sextupoles included,
4D BB at IP6 and IP8, zero length elens at IP10,
core tunes at (0.67,0.68) and chromaticities of
1 for all cases, 250 GeV, 6400 macroparticles in
Gaussian distribution
With Nb2e11 losses are less than 3/hour
13RHIC BBC Simulations with BBSIM(H.-J. Kim, T.
Sen FNAL)
- SEFT Electron Lens
- Flat top edge is 4sigma
- Small Ne reduces beam loss much
- Gaussian Electron Lens
- Same beam size as IP10's
- Small Ne reduces beam loss
- Ne lt 0.5 Nip Np
NO BBC
- 1x bbc beam-beam compensation with Ne Nip
Np 22E11
Is this a tune effect?
14RHIC BBC Simulations with BBSIM Continued
Np3e11 Np2e11
BBCon BBCoff
BBC off Intensity loss in /hour vs. lattice
tunes
Np2e11, se2sp, full compensation Intensity loss
in /hour vs. lattice tunes
15RHIC BBC Simulations with BBSIM Continued
BBCon BBCoff
Np2e11, se1sp, half compensation Intensity loss
in /hour
Np2e11, se1sp Relative intensity loss over 106
turns
16RHIC BBC Simulations with BBSIM Continued
BBCon BBCoff
BBCon BBCoff
Np2e11, SEFT, full compensation Intensity loss
in /hour vs. lattice tunes
Np2e11, SEFT, half compensation Intensity loss
in /hour vs. lattice tunes
17Effect of Imperfections - Misalignment
- Length of interaction region in the EL is much
smaller than beta-function - consider ELs as
short kick element. - Model of imperfect alignment - split the EL beam
into several slices and sum the kicks.
Proton orbit
Electron beam
Slices
Nslice 1 2 3 4 5
Difference between exact numerical integral and
slice kicks for -1s pitch
18Tune Spread Compensation with Misalignment shift
in X-Z plane scan
Gaussian
SEFT
- Full compensation.
- xi, xf varied from 0 to 2s
- yi 0, yf 0
19RHIC BBC Simulations with Misalignment(A.
Valishev FNAL)
Dx/sp
Np2e11, sp0.3mm, se0.45mm Parallel offset in
horizontal plane, 3 slices
20LHC BBC Simulations with Lifetrac(A. Valishev
FNAL)
t200 h
t130 h
- Np2.3x1011
- 4 IPs
- No FF nonlinearities
t80 h
Shiltsev
20
LHC Electron Lenses FNAL 06/04/08
21LHC BBC Simulations with Lifetrac Continued
BBCon BBCoff
BBCon BBCoff
Np2.3e11, sesp half compensation Intensity loss
in /hour vs. lattice tunes
Np2.3e11, se1.5x sp half compensation Intensity
loss in /hour vs. lattice tunes
Shiltsev
21
LHC Electron Lenses FNAL 06/04/08
22LHC BBC Simulations with Lifetrac Continued
BBCon BBCoff
Min. loss (/hour) EL off 27 EL on 8
Np3.45e11, se sp half compensation Intensity
loss in /hour vs. lattice tunes
From Tevatron experience losses lt 10/hour are
tolerable
Shiltsev
22
LHC Electron Lenses FNAL 06/04/08
23Summary
- Gaussian gun in TEL-2 (finally!), beam studies
started. First results may become available in
2009 - 3 simulation codes (BBSIM, Lifetrac, SixTrack)
well developed and demonstrated good agreement in
test cases. Expecting some results from PlibB
shortly. - Simulations of head-on BBC at RHIC predict
significant beam life time improvement at
Npgt2.5e11. Very little beam-beam effect at
Nplt2e11. - Simulations of beam-beam effects at the LHC show
that - At Np2.3e11 (2x nominal) losses do not exceed
1/hour upgrade path? - At Np3.45e11 (3x nominal) head-on BBC with a
single EL placed at bbc (wire) location is
efficient and losses can be kept under 10/hour - Need to ramp up collaboration with CERN