X-Band Linear ColliderPath to the Future
Stanford Linear Accelerator Center
International Technology Recommendation PanelApril 26-27, 2004
NLC Luminosity and Accelerator Physics
Tor Raubenheimer
Tor RaubenheimerSlide 2 of 46SLAC ITRP Meeting
Outline
Talk will focus on luminosity designChris Adolphsen will discuss the rf hardware
1. Lessons from the SLC2. Performance for peak luminosity
Beam emittance generation and preservationBeam power issues
3. Design headroom and luminosity upgrade potential
All aspects of the GLC/NLC design have been studiedHeavily based on experience (good and bad) from the SLCConservative design rapid commissioning and luminosity
Tor RaubenheimerSlide 3 of 46SLAC ITRP Meeting
First Linear Collider: SLC
Built to study the Z0and demonstrate linear colliderfeasibility
Energy = 92 GeVLuminosity = 3e30
Had all the featuresof a 2nd gen. LCexcept both e+and e- shared thesame linac
Much more than a 10% prototype
Tor RaubenheimerSlide 4 of 46SLAC ITRP Meeting
SLC LuminosityMany Lessons Learned
Flexible design toallow parameteroptimization
Extensive diagnostics fortroubleshootingand tuning
Reliable and stableoperation
Well designed collimation to limit backgrounds
Provides the basis for the next generation LC
1992 - 1998 SLD Luminosity
0
5000
10000
15000
20000
18-Apr
13-Jun
8-Aug
6-Mar
1-May
26-Jun
2-Jul 27-Aug
22-Oct
17-Dec
11-Feb
26-May
21-Jul
27-Jul
21-Sep
16-Nov
11-Jan
8-Mar
3-May
1992 -- 1993 -- --1994-----1995 1996 ---1997-----1998---
Zs p
er w
eek
0
50000
100000
150000
200000
250000
300000
350000
Inte
grat
ed Z
s
SLD Z/weekSLD Z total
Tor RaubenheimerSlide 5 of 46SLAC ITRP Meeting
Peak Luminosity~7,000 times larger than SLC
Focusing (βx ∗ βy)−1/2 NLC/SLC 3Demonstrated at FFTB
Disruption HD NLC/SLC 0.7Demonstrated at SLC
Emittance (γεx ∗ γεy)−1/2 NLC/SLC 85Low Emittance Transport and Damping rings
Beam power term (Pb ∗ N) NLC/SLC 35Bunch trains, Particle sources, Collimation and MPS
Integrated luminosity Tom Himel this afternoon
2/12/12 )()(4 yxyxDb H
πmcNPL
γεγεββ =D
yx
brep HNnf
Lσσπ
2
4 =
Tor RaubenheimerSlide 6 of 46SLAC ITRP Meeting
Luminosity Comparison with SLCEnhancement Factors
UNITS SLC GLC/NLC TESLA NLC/SLC TESLA/SLC NLC/SLC TESLA/SLCE_cm GeV 92 500 500 5.43 5.43f_rep Hz 120 120 5n_b 1 192 2820N 4.10E+10 7.50E+09 2.00E+10 0.18 0.49H_d 2 1.43 2.1 0.72 1.05
sqrt(e+ x e-)Inj_Inv_Emit_x 10^-8 m-rad 3834.1 300 800 0.08 0.21 3.57 2.19Inj_Inv_Emit_y 10^-8 m-rad 259.8 2 2 0.01 0.01 11.40 11.40
IP_Inv_Emit_x 10^-8 m-rad 6144.3 360 1000IP_Inv_Emit_y 10^-8 m-rad 1715.2 4 3Dilution-X 1.60 1.20 1.25 0.75 0.78 1.16 1.13Dilution-Y 6.6 2.00 1.50 0.30 0.23 1.82 2.10BetaX mm 3.3 8 15 2.42 4.55 0.64 0.47BetaY mm 2.6 0.11 0.4 0.04 0.15 4.86 2.55IP Divergence-x urad 454.8 30.3 36.9IP Divergence-y urad 270.7 27.3 12.4sig_x nm 1500.8 242.6 553.7 1.62E-01 3.69E-01 3.77E-01 8.60E-01sig_y nm 703.8 3.0 5.0 4.26E-03 7.04E-03 9.93E-03 1.64E-02SigX*SigY nm^2 1056321.0 727.6 2742.3 6.89E-04 2.60E-03
P_b MW 0.036 6.921 11.294 190.88 311.51I uA 0.788 27.683 45.176 35.12 57.32I*N A 32315.5 207619.2 903528.0 6.42 27.96
L 3.04E+30 2.03E+34 3.44E+34 6668.90 11308.32CrossSection nb 30 "Free"=Energy, Beam Power, Q/bunch 34.92 151.95Event Rate Z/hr 328 Disruption 0.72 1.05
Damping Ring 40.75 24.95Emittance Preservation 2.10 2.38
Aggressive FF 3.12 1.20Total 6668.90 11308.32
Tor RaubenheimerSlide 7 of 46SLAC ITRP Meeting
Bunch TrainsAccelerator Structure Long-Range Wakefield
Goal: reduce transverse coupling between bunches to ~0Alignment and emittance issues are dominated by single bunch
Requires suppressing the accelerator structure long-range wakefield to
Tor RaubenheimerSlide 8 of 46SLAC ITRP Meeting
Structure Long-Range WakefieldTheory and Measurements
Time of Next Bunch
Time After Bunch (ns)
Wak
efie
ld A
mpl
itude
(V/p
C/m
/mm
)
Measurements
Ohmic Loss Only
Damping and Detuning
Detuning Only
Tor RaubenheimerSlide 9 of 46SLAC ITRP Meeting
Bunch TrainsLong-Range Wakefields Have Small Effect
Accelerator structure wakefield is suppressed by ~100Use combination of detuning and weak dampingSets requirements on dipole frequency distribution and structurefabrication – discussed by Chris Adolphsen
Long-range wakefield has minimal effect on bunch trainBunch train behaves like single bunch alignment tolerances driven by short-range wakefield
Damping rings: Beam current is smaller than in B-factoriesKicker stability is required to keep well aligned bunch train
Intra-train feedback can remove pulse-to-pulse jitterDemonstrated IP-style feedback with 60~70 ns latency (FONT)Intra-train feedback requires well aligned bunch train
Tor RaubenheimerSlide 10 of 46SLAC ITRP Meeting
Peak Luminosity~7,000 times larger than SLC
Focusing (βx ∗ βy)−1/2 NLC/SLC 3Demonstrated at FFTB
Disruption HD NLC/SLC 0.7Demonstrated at SLC
Emittance (γεx ∗ γεy)−1/2 NLC/SLC 85Low Emittance Transport and Damping rings
Beam power term (Pb ∗ N) NLC/SLC 35Bunch trains, Particle sources, Collimation and MPS
2/12/12 )()(4 yxyxDb H
πmcNPL
γεγεββ =D
yx
brep HNnf
Lσσπ
2
4 =
Tor RaubenheimerSlide 11 of 46SLAC ITRP Meeting
Emittance PreservationPreserve Small Emittances from DR IP
1. Parameters chosen to make wakefields manageable
2. Make extensive use of demonstrated BBA techniquesAlign magnets and structures for complete flexibilitySuite of BBA and tuning techniquesNecessary instrumentation and controls demonstrated
3. Multiple paths to ensure stable beams for tuning and luminosity
4. Completely modeled transport from DR IP DumpAccurately represent operational tuning techniquesGenerous emittance budgets through system
Tor RaubenheimerSlide 12 of 46SLAC ITRP Meeting
Transverse WakefieldsWakefields in TESLA are 1000x Smaller
Transverse wakefields in TESLA are 1000x smaller True but incomplete statement Effect of wakefields depends on charge, bunch length, and focusing
Real comparison is effect of wakefields on the beam Best quantified with the “BNS autophasing” energy spread δAuto
Tor RaubenheimerSlide 13 of 46SLAC ITRP Meeting
Transverse wakefields in TESLA are 1000x smaller True but incomplete statement Effect of wakefields depends on charge, bunch length, and focusing
Real comparison is effect of wakefields on the beam Best quantified with the “BNS autophasing” energy spread
⇒ X-band LC wakefield control already demonstrated at FFTB
SLC Design parameters too difficult Operation with lower charge
FFTB operation with still lower chargevery stable beam – easy operation
Transverse WakefieldsAlready demonstrated NLC wakefield control at FFTB
0.11%TESLA Design1.1%X-band LC Design1.1%FFTB5.8%SLC Operation9.9%SLC DesignδAuto
Tor RaubenheimerSlide 14 of 46SLAC ITRP Meeting
TolerancesLesson from the SLC: Beam-Based Alignment
All linear collider designs have small ε tight tolerancesAll LC designs require Beam-Based Alignment (BBA)SLC used BBA to align quadrupoles but could not align structuresX-band LC will use BBA for both quadrupoles and structures
Linac tolerancesAlign quadrupoles BPMs to magnetic center with 5 µm rmsAlign the structures to the beam with a 6 µm rmsAlign with high performance diagnostics and controls
Tolerances achievableRequired diagnostics and controls demonstratedMultiple BBA techniques demonstrated
Tor RaubenheimerSlide 15 of 46SLAC ITRP Meeting
Beam Based AlignmentAll Necessary Techniques have been Demonstrated
X-band uses beam-based techniques to align the magnets and structures
Pre-AlignmentInstall 50 ~100 µm level
Beam-based alignmentDetermine Q-BPM-to-quadoffsets using quad-shunting
Align structures to orbitUse S-BPMs to center struct.
Establish ‘Gold’ OrbitUse DF Steering (if nec.)to find low dispersion orbit
Establish BeamSteer to post-linac dump
Tune Emittance bumpsUse ε-wires to opt. ε
Steer to Gold OrbitUse quad movers to steer
Lock Beam-based Fbck.Maintain orbit with feedback
YearlyConventional methods
MonthlyMethods from SLC & FFTB
Invasive to Luminosity
HourlyMethods from SLC & ASSETNon-invasive to Luminosity
Tor RaubenheimerSlide 16 of 46SLAC ITRP Meeting
Quadrupole Beam-Based AlignmentUtilize Robust, Local Alignment of Magnets
Multiple quadrupole BBA alignment techniquesQuad-shunting (used many places; FFTB demonstrated
Tor RaubenheimerSlide 17 of 46SLAC ITRP Meeting
BBA: Quadrupole ShuntingRobust, Local Alignment of Magnets
Quadrupole shunting: find the magnetic center by varying the quad strength and measuring the resulting deflection
Determine BPM-quad offsetNulling meas; good sensitivityMain systematic error: magnetic center shift with excitationPrototype is measured to be2~3x better than spec.
Tor RaubenheimerSlide 18 of 46SLAC ITRP Meeting
Structure Straightness and PositioningAlign Structures to the Beam using Wakefield Signal
Four 60 cm structures per girder S-BPMs
RF Girder
CellCenterline
Best-LineFit to Centerline
Beam
X-Y Mover2.5 m
1) Before installation, straighten and align structures on rf girder such that deviation of cell centers from best-line fit is 100 µm peak-to-peak
2) During operation, use S-BPM measurements (purple dots) to determine optimal beam trajectory and move girder to the beam with remote movers – want average offset less than 3µm
Tor RaubenheimerSlide 19 of 46SLAC ITRP Meeting
Structure BPMHigh Performance Diagnostic
HOM Manifold can beused to measure wakefields
Tor RaubenheimerSlide 20 of 46SLAC ITRP Meeting
Can also sweep LO frequency to map entire structure
Test of Structure-BPM in ASSETDemonstration of Alignment Technique
Achieved 11µm alignment – limited by beam jitter
Tor RaubenheimerSlide 21 of 46SLAC ITRP Meeting
Vibration and DriftsStability is Necessary for Beam Tuning
Extensive measurements of natural ground motionMany measurements of ‘cultural’ sources and transmission
Isolated measurements of modulators, accelerator structures withcooling, quadrupole magnets with cooling all look acceptableTransmission between tunnels is large so must be careful in utility tunnel as well as the main tunnel
Developing prototypes of main linac girder and utility clusters to measure vibration of full system
Can always use active suppression for further improvementMagnets and supports easily accessedStabilization systems developed at DESY, CERN, KEK, and SLAC
Tor RaubenheimerSlide 22 of 46SLAC ITRP Meeting
IP StabilizationThree Approaches
Three different approaches being pursued:1. Quiet site and IR/Detector engineering (many suitable sites identified)2. Active (inertial) stabilization3. Fast intra-train feedback (FONT at NLCTA and FEATHER at ATF)
Inertial stabilizationDeveloping compact non-magnetic sensors (in-house and commercial)Stabilizing an extended object that models a PM final quadrupoleand cantilevered support tube
Feedback On Nanosecond Timescales (FONT) at NLCTA2003 run demonstrated ~15x reduction of intra-train offsetsLatency was about 60 ns ⇒ Significant effect on 75% of train
Tor RaubenheimerSlide 23 of 46SLAC ITRP Meeting
IP Stabilization SummaryMultiple Paths to Stabilize Collisions
IP collisions can be stabilized using any two out of the three approaches with >90% of peak luminosity
FONTActiveStabilization
QuietDetector
YesNo20 nm
NoYes4 nm
NoYes*~20 nm*
YesNo4 nm
Yes*Yes*~20 nm*
NoNo4 nm
NoNo20 nm
* based on measurements in NLCTA. 20 nm vibration measured on SLD.
Tor RaubenheimerSlide 24 of 46SLAC ITRP Meeting
Realistic Simulation StudiesExample: Emittance Bumps
Emittance bumps are the classic ‘global’ correction methodEmittance bump technique used in SLC operation and TESLA sims.100% effective if used or studied with a single primary ∆ε source
Performance less optimal in LC with many ∆ε sourcesTechniques in simulation based on SLC operational proceduresAlternate approaches may yield better performance but ….
37% → 21%25% → 19%Nominal Errors
US Cold ∆ε
US Warm ∆ε
Still useful technique to ‘finish’ emittance tuning and achievebest performance
Bumps with combined wakefield and dispersive errors after nominal tuning are 30% effective
Tor RaubenheimerSlide 25 of 46SLAC ITRP Meeting
DR IP SimulationsExtensive Studies Refined for over 10 Years
Tools developed and benchmarked against SLCDifferent codes compared against each other during TRCReasonable agreement between simulations
Studied many different techniques and many different effectsComplete simulations including ‘all’ static errors and many dynamic errors while modeling operational tuning procedures
About 20,000 cpu-hrs in simulations of NLC, TESLA, US Warm, and US Cold over the last two years
Emittance budgets based on detailed DR IP simulationsDilution budget has 100% ∆εy/εy in BC, BDS, and linacsBudget does not assume use of ε-bumps
Tor RaubenheimerSlide 26 of 46SLAC ITRP Meeting
Emittance Preservation SummaryPreserve Small Emittances from DR IP
1. Parameters chosen to make wakefields manageable
2. Make use of demonstrated BBA techniquesAlign both magnets and structures for complete flexibilityCorrect emittance dilution sources locally for stable solutionDemonstrated necessary instrumentation and controls
Most prototypes are better than spec see poster
3. Multiple paths to ensure stable beams for tuning and luminosity
4. Completely modeled transport from DR IP DumpAccurately represent operational tuning techniquesGenerous emittance budgets through DR IP system
Tor RaubenheimerSlide 27 of 46SLAC ITRP Meeting
Peak Luminosity~7,000 times larger than SLC
Focusing (βx ∗ βy)−1/2 NLC/SLC 3Demonstrated at FFTB
Disruption HD NLC/SLC 0.7Demonstrated at SLC
Emittance (γεx ∗ γεy)−1/2 NLC/SLC 85Low Emittance Transport and Damping rings
Beam power term (Pb ∗ N) NLC/SLC 35Bunch trains, Particle sources, Collimation and MPS
2/12/12 )()(4 yxyxDb H
πmcNPL
γεγεββ =D
yx
brep HNnf
Lσσπ
2
4 =
Tor RaubenheimerSlide 28 of 46SLAC ITRP Meeting
Emittance GenerationDamping rings have most accelerator physics in LC
Required to:1. Damp beam emittances and incoming transients2. Provide a stable platform for downstream systems3. Have excellent availability ~99% (best of 3rd generation SRS)
Mixed experience with SLC damping rings:Referred to as the “The source of all Evil”Collective instabilities; Dynamic aperture; Stability
X-band damping ring designs based on KEK ATF, 3rd generation SRS, and high luminosity factories
Experimental results provide high confidence in design
Tor RaubenheimerSlide 29 of 46SLAC ITRP Meeting
KEK ATFLargest LC Test Facility
World’s lowest emittance beam:εy = 4 pm-radbelow X-band LC requirements
Used to verify X-bandDR concepts
Detailed measurementsof emittance tuning, lattice properties, IBS, ions, collective effects,and instrumentation
1.3 GeV Damping Ring and S-band linacCommissioning started in 1997
Tor RaubenheimerSlide 30 of 46SLAC ITRP Meeting
Collective InstabilitiesDownstream Systems Sensitive to Rings
Bursting quadrupole instability in SLC DR redistributed 3% of charge
Correlation between DR instability and linac BPM – 20 µm of motion
Example: bursting microwave quadrupole instability in the SLC ring caused µm’s of jitter at end of the linac
Complicated effect that involved interplay of the instability, damping ring feedback systems and linac beam dynamics
Tor RaubenheimerSlide 31 of 46SLAC ITRP Meeting
Electron CloudActive R&D Program Aimed at Suppression
Electron cloud is a known limitation in PEP-II and KEK-B positron rings
Electrons from photo-emission, ionization, or secondary emission are trapped in the potential well of the positron beam
Thresholds for cloud formation are very similar in both X-band and TESLA damping ring designs
Low densities can cause large tune shifts, single, or multi-bunch collective instabilities Address cloud everywhere in all rings
Active R&D effort on vacuum surfaces and treatmentsNo single vacuum material sufficient
Plan to test treated coupons in PEP-II and install treated chamber in ~ 2 years
Tor RaubenheimerSlide 32 of 46SLAC ITRP Meeting
Wiggler NonlinearitiesRing Designed with 15σinj Dynamic Aperture
X-band damping ring dynamic aperture >15x injected beamHigh power injector (55 kW) – cannot allow injection lossesDetailed modeling of dynamic aperture with wiggler field map
15σx
15σ y
Dynamic aperture with nonlinear wiggler
Dynamic aperture with wiggler and octupole correction
ln νx,y
Tor RaubenheimerSlide 33 of 46SLAC ITRP Meeting
X-band Damping RingsDesigned with Care of 3rd Generation SRS
ATF and the ALS at Berkeley have demonstrated the specified vertical emittanceTolerance sensitivities require the care of 3rd generation SRSCollective effects are more important than in 3rd generation SRSNonlinear dynamics enter new regime with long wiggler
2.00.750.90.60.5Bunch Charge [1010]
Tor RaubenheimerSlide 34 of 46SLAC ITRP Meeting
Emittance Generation SummaryKEK ATF is a full scale prototype for the X-band DR
Demonstrated at ATF: X-band DR alignment tolerances and emittance generationX-band DR kicker rise/fall times and required stabilitySingle bunch collective effects in desired regime for X-band DRRequired instrumentation for LC
Demonstrated at luminosity factories:High current multi-bunch operation (B-factories)Dynamic aperture with large wigglers (CESR-C)
Outstanding:Ongoing studies on electron cloud and ion instabilities for all LC damping rings
To ensure stability and availability future damping rings will require engineering like 3rd generation light sources
Tor RaubenheimerSlide 35 of 46SLAC ITRP Meeting
Peak Luminosity~7,000 times larger than SLC
Focusing (βx ∗ βy)−1/2 NLC/SLC 3Demonstrated at FFTB
Disruption HD NLC/SLC 0.7Demonstrated at SLC
Emittance (γεx ∗ γεy)−1/2 NLC/SLC 85Low Emittance Transport and Damping rings
Beam power term (Pb ∗ N) NLC/SLC 35Bunch trains, Particle sources, Collimation and MPS
2/12/12 )()(4 yxyxDb H
πmcNPL
γεγεββ =D
yx
brep HNnf
Lσσπ
2
4 =
Tor RaubenheimerSlide 36 of 46SLAC ITRP Meeting
Polarized Electron SourceBased on Cathode R&D for SLC and E-158
Tor RaubenheimerSlide 37 of 46SLAC ITRP Meeting
Positron Source ConfigurationIndependent Positron Source
SLC Positron source used 30 GeV electron beam from shared electron linacThree operational problems:1. Difficult to commission and develop
Unable to commission or perform machine development on positron system without tuned 30 GeV electrons
2. Low yieldFactor of 2 in yield lost due to aperturesCould not recover by increasing electron beam current
3. Coupled system sensitive to cross talkFluctuations in either the electron or positron current would couple into other beam
Design positron source with independent drive e- beam
Tor RaubenheimerSlide 38 of 46SLAC ITRP Meeting
Positron Source TargetDesign is Based on SLC Experience with WRe
SLC e+ target failed after 5 years at stress levels ~2x lower than previously measured and predicted for WRe targets
Radiation damage problem is thought worse for the Ti targets planned for undulator based sources
SLC e+ target Beam direction • SLC target studied atLANL and modeledat LLNL
• Problem due to embrittlement fromradiation damage
• NLC source is basedon multiple targets to reduce stress
Tor RaubenheimerSlide 39 of 46SLAC ITRP Meeting
Positron Target Options
Conventional target is not more difficult than undulator targetNC Conv. NC Und. SC Conv. SC Und.
E beam [GeV] 6.2 153 6.2 153Ne-/bunch [1e10] 0.75 0.75 2.00 2.00Undulator Len. [m] - 150 - 150Energy/pulse [J] 477 1130 28000 44300Target Mat. W Re Ti W Re TiTarget Thick. [rl] 4 0.4 4 0.4Absorption 14.0% 8.6% 14.0% 8.6%Spot size [mm] 1.6 0.75 2.5 0.75# targets/spares 3 / 1 1 / 1 2 / 1 1 / 1Target radius [m] 0.125 0.125 0.8 0.8Rotation [rpm] 46 46 1500 1200∆T [C] 189 422 256 410Yield 1.5 1.5 1.5 1.5
Tor RaubenheimerSlide 40 of 46SLAC ITRP Meeting
Beam CollimationSLC Luminosity was Frequently Background Limited
Collimation system is integral to design and is part of Machine Protection System
Collimation system designed for beam tails 1000x that expected Passive energy collimation and consumable betatron collimationMany advantages over SLC
No synchrotron radiation in IRBeam tails from damping rings collimated at low energy
Tor RaubenheimerSlide 41 of 46SLAC ITRP Meeting
Beam CollimationTRC Task-force Reviewed Basic Design
Excellent performance in length of 800 metersAll tail particles removed 500 meters upstream of IP
Frac
tion
of b
unch
cha
rge
outs
ide
squa
re re
gion
K=1
K>1
Final Doublet aperture
SR passes through IR K
Tor RaubenheimerSlide 42 of 46SLAC ITRP Meeting
Beam CollimationOctupoles Ease Collimator Wakefields
Collimator wakefields measured in SLAC test facilityMeasured collimators with Cu and Ti (and C from DESY)OK at 250 GeV but impact low E luminosity
Octupole tail-folding opens gaps reducing Ay
Collimator wakefield jitter amplification from TRC Study 20 1 yAyy +=∆
2.841.202.26Total Ay
--0.530.38FF absorbers0.32--0.73FF spoilers0.330.0140.51β absorbers1.670.590.55β spoilers0.370.0160.034δ absorbers0.160.0450.054δ spoilers
CLICNLCTESLAγ/1∝yA
Tor RaubenheimerSlide 43 of 46SLAC ITRP Meeting
Peak Luminosity Summary
Low Emittance TransportParameters chosen to make wakefields manageableExtensive use of demonstrated BBA techniquesMultiple paths to ensure stable beams for tuning and luminosityCompletely modeled transport from DR IP Dump
Damping ringsPerformance demonstrated at ATF and 3rd generation SRS
Beam powerLong-range wakefields and coupled bunch instabilities not limitationsParticle sources based on SLC experienceRobust collimation design
Tor RaubenheimerSlide 44 of 46SLAC ITRP Meeting
Design HeadroomFaster Commissioning and Higher Luminosity
Most sub-systems have substantial headroom For example: E− Source emittance – Simulations predict γε half of design spec γε=10x10-5; DR acceptance and damping for γε=15x10-5
Sources 50% beam power3x emittance (described above)10x damping (injected beam 10% of extracted)20% bunch length (σz > 90µm; spec=110µm)
RF system 10% energy (allocation for trips, phasing, repair)Dilutions 100% vertical emittance
4x horizontal IP beta function
Provide stable operation and flexibility to optimize luminosityFast commissioning and higher luminosity with time
Tor RaubenheimerSlide 45 of 46SLAC ITRP Meeting
Potential for Luminosity Upgrades
Design margins allow parameter optimizationExample 1: if low emittance transport component specs are met⇒ ∆εy < 50% and L = 3x1034
Example 2: if damping ring alignment can attain and maintain the TESLA DR specs ⇒ γεy
Tor RaubenheimerSlide 46 of 46SLAC ITRP Meeting
Summary
The X-band design is based on: 20 years of linear collider development including:SLC, NLCTA, ASSET, CollWake, ATF, FFTB, Stabilization, …Extensive beam tuning experience with SLC, FFTB, and ATFProven principles of structure wakefield suppression and S-BPMs
The design luminosity is possible because:Luminosity performance has been a focus of the design and R&D
Performance goals verified with in depth DR IP simulationsResults from prototype testing support the performance goalsEssential experience from SLC, FFTB, and ATF included
Headroom in design ensure luminosity goals are attained quickly
X-band LC is the LC design which has been studied in depth
Tor RaubenheimerSlide 47 of 46SLAC ITRP Meeting
Extra Slides
Tor RaubenheimerSlide 48 of 46SLAC ITRP Meeting
Energy SpectrumNarrow Energy Spectrum for Special Measurements
Adjusting BNS phases allows control of energy spectra
-4 -2 0 2 4x 10-4
244
246
248
250
252
254
256
z position (m)
Ener
gy (G
eV)
E-z Distributions for Assorted BNS Final Switch Points
170 GeV (nominal)150 GeV100 GeV75 GeVBunch Shape
244 246 248 250 252 254 256 2580
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16Energy Spectrum for Assorted BNS Final Switch Points
Energy, GeV
Cha
rge,
nC
170 GeV (nominal)150 GeV100 GeV75 GeV
Energy spectrum for different BNS configurations
Longitudinal phasespace for differentBNS configurations
80 100 120 140 160 180250
255
260
265
270
275Total Voltage Needed to Reach 250 GeV/Beam
Energy of Final BNS Switch (GeV) [Nominal = 170 GeV]
Tota
l Vol
tage
, GeV
80 100 120 140 160 1800.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1FWHM Energy Spread for Assorted BNS Final Switch Points
Energy of Final BNS Switch (GeV) [Nominal = 170 GeV]
FWH
M (%
)
Total voltage requiredfor different BNS configurations
FWHM energy spreadfor differentBNS configurations
TESLA∆E/EFWHM
Tor RaubenheimerSlide 49 of 46SLAC ITRP Meeting
Energy SpectrumLuminosity Energy Bias 0
New BNS configuration has small Ebias
Nominal spectrum Low Ebias spectrum
z [µm] z [µm]
E G
eV
Luminosity energy biasNominal
Low Ebias
Luminosity rms spectrumNominal
Low Ebias
NLC Luminosity and Accelerator PhysicsOutlineFirst Linear Collider: SLCSLC LuminosityMany Lessons LearnedPeak Luminosity~7,000 times larger than SLCLuminosity Comparison with SLCBunch TrainsAccelerator Structure Long-Range WakefieldBunch TrainsLong-Range Wakefields Have Small EffectPeak Luminosity~7,000 times larger than SLCEmittance PreservationPreserve Small Emittances from DR ? IPTransverse WakefieldsWakefields in TESLA are 1000x SmallerTransverse WakefieldsAlready demonstrated NLC wakefield control at FFTBTolerancesLesson from the SLC: Beam-Based AlignmentBeam Based AlignmentAll Necessary Techniques have been DemonstratedQuadrupole Beam-Based AlignmentUtilize Robust, Local Alignment of MagnetsBBA: Quadrupole Shunting Robust, Local Alignment of MagnetsStructure BPMHigh Performance DiagnosticVibration and DriftsStability is Necessary for Beam TuningIP StabilizationThree ApproachesIP Stabilization SummaryMultiple Paths to Stabilize CollisionsRealistic Simulation StudiesExample: Emittance BumpsDR ? IP SimulationsExtensive Studies Refined for over 10 YearsEmittance Preservation SummaryPreserve Small Emittances from DR ? IPPeak Luminosity~7,000 times larger than SLCEmittance GenerationDamping rings have most accelerator physics in LCKEK ATFLargest LC Test FacilityCollective InstabilitiesDownstream Systems Sensitive to RingsElectron CloudActive R&D Program Aimed at SuppressionWiggler NonlinearitiesRing Designed with 15sinj Dynamic ApertureX-band Damping RingsDesigned with Care of 3rd Generation SRSEmittance Generation Summary KEK ATF is a full scale prototype for the X-band DRPeak Luminosity~7,000 times larger than SLCPolarized Electron SourceBased on Cathode R&D for SLC and E-158Positron Source ConfigurationIndependent Positron SourcePositron Source TargetDesign is Based on SLC Experience with WRePositron Target OptionsBeam CollimationSLC Luminosity was Frequently Background LimitedBeam CollimationTRC Task-force Reviewed Basic DesignBeam CollimationOctupoles Ease Collimator WakefieldsPeak Luminosity SummaryDesign HeadroomFaster Commissioning and Higher LuminosityPotential for Luminosity UpgradesSummaryExtra SlidesEnergy SpectrumNarrow Energy Spectrum for Special MeasurementsEnergy SpectrumLuminosity Energy Bias ? 0