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Intra-Beam Scattering and Electron Cloud for the Damping Rings Intra-Beam Scattering and Electron Cloud for the Damping Rings

Intra-Beam Scattering and Electron Cloud for the Damping Rings - PowerPoint Presentation

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Intra-Beam Scattering and Electron Cloud for the Damping Rings - PPT Presentation

Mauro Pivi CERNSLAC CLIC Collabortion Meeting CERN 911 May 2012 Thanks to F Antoniou Y Papaphilippou CERN T Demma LAL A Chao SLAC ID: 798577

clic cloud ibs electron cloud clic electron ibs beam mitigations evaluation vertical bunch pivi clearing simulations lattice damping mitigation

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Slide1

Intra-Beam Scattering and Electron Cloud for the Damping Rings

Mauro Pivi CERN/SLAC

CLIC Collabortion Meeting CERN 9-11 May 2012

Thanks

to:

F

. Antoniou,

Y. Papaphilippou

(

CERN) T. Demma (LAL), A. Chao (SLAC)

and the ILC

electron cloud Working

Group, i.p.

M. Furman (LBNL), J. Crittenden (Cornell U.) , L. Wang (SLAC).

Slide2

Intra-Beam Scattering (IBS) Simulation Algorithm: CMAD

CMAD parallel code:

C

ollective effects &

MADLattice read from MADX files containing Twiss functions and transport matricesAt each element in the ring, the IBS scattering routine is called. At each element:Particles of the beam are grouped in cells.Particles inside a cell are coupledMomentum of particles is changed because of scattering.Particles are transported to the next element.Radiation damping and excitation effects are evaluated at each turn. Vertical dispersion is included Code physics: Electron Cloud + IBS + Radiation Damping & Quantum Excitation

IBS applied at each element of the Ring

M.

Pivi

, T. Demma (SLAC, LAL), A. Chao (SLAC)

Mauro Pivi, CERN, CLIC

May 9-11, 2012

Slide3

For two particles colliding with each other, the changes in momentum for particle 1 can be expressed as:

with the equivalent polar angle

eff and the azimuthal angle  distributing uniformly in [0; 2], the invariant changes caused by the equivalent random process are the same as that of the IBS in the time interval tsIBS - Zenkevich-Bolshakov AlgorithmMauro Pivi, CERN, CLIC collaborationSIRE code uses similar implementation (A. Vivoli Fermilab, Y. Papaphilippou CERN)May 9-11, 2012

Slide4

IBS modeling: animation

http://www-user.slac.stanford.edu/gstewart/movies/particlesimulation_animation/

Slide5

IBS - SuperB LER

Parameter

Unit

Value

EnergyGeV4.18Bunch population10106.5

 

Circumference

m

1257

 

Emittances (H/V)

nm/pm

1.8/4.5

 

Bunch Length

mm

3.99

 

Momentum spread

%

0.0667

 

Damping times (H/V/L)

ms

40/40/20

 

N. of macroparticles

-

10

5

 N. of grid cells-64x64x64 

Bane PiwinskiIBS-Track

M. Pivi, T. Demma

Mauro Pivi CERN, CLIC collaboration

May 9-11, 2012

IBS-Track

C-MAD

Slide6

IBS - Swiss Light Source (SLS)

IBS_Track

(T.

Demma

) See: Fanouria talk for SLS experimental resultsEvolution of the emittances obtained by tracking with IBS for different bunch populations. Horizontal lines: Piwinski (full) and Bane (dashed) models for the considered bunch populations.-- 6×109 ppb-- 60 ×109 ppb-- 100 ×109 ppb

Slide7

A.

Vivoli

, Y.

Papaphilippou

Previous work: SIRE Benchmarking (Gaussian Distribution) CLIC DRF. Antoniou, IPAC10

Slide8

IBS - CLIC DR

Ideal lattice

One turn evolution

of emittance in the CLIC DR. Energy (GeV)2.86emitx (m)5.554e-11emity (m)

5.8193 e-13Deltap

1.209209e-3sigmaz (m)

0.001461

Slide9

CLIC DR parameters

optimization

: IBS and bunch length

Ideal lattice, no magnet misalignments or rotation

One turn emittance evolution for different bunch lengthsC:\Physics CLIC\2012 SIMULATIONS\CLIC_IBS_1GHz_ideal_latticeCMAD

Slide10

Next step: include vertical Dispersion in CLIC DR

In the vertical plane, IBS is much stronger in the presence of vertical dispersion. Then, it is crucial to include vertical dispersion in simulations to estimate the evolution of vertical emittance.

We wish to generate a lattice with Vertical Dispersion but no Coupling to benchmark theoretical models that include the 1

st

but not the 2nd. Thus, in MADX we create quadrupole misalignments to generate vertical dispersion. In the CLIC DR (not in SLS), this generates also coupling due to Sextupoles. Then for now, turned off Sextupoles.

Slide11

Lattice with vertical quadrupole

misalignments

Vertical dispersions in DR lattice with misaligned

quadrupoles dy=1um (Left) and dy=4.5um (Right)One turn matrix: large coupling terms for misalignment dy=4.5um

Slide12

Single particle tracking in lattice with misaligned quadrupoles

Quad misalignment:

dy

=1um

dy=4.5um dy=1um and sextupole offPhase spaces of single particle, 1000 turnsHVZ

Slide13

Review: RF parameters in CLIC DR lattice

Issue:

MADX computes Qs = 5.6782E-003 from RF cavity parameters

By the One-Turn-Matrix, computed Qs

= 7.183E-003Tracking (below) shows a synchrotron tune Qs = 7.183E-003Thus  reviewing the RF parameters and matchingBeam tracking: Longitudinal centroid of the bunch (Left) oscillates with Qs=7.18E-3 (139 turns) and sigmaz oscillates twice faster (Right) confirming Qs=7.18E-3 (period ~70 turns)

Slide14

IBS evaluation: Long Term Plans

Code validation: benchmark recent experiments made at

CesrTA

and SLS with simulations

Code predictions: long term beam evolution in CLIC Damping RingsFix RF systemUse ideal MAD lattice (no errors)Include magnet vertical misalignments and vertical dispersionInclude magnet rotation and coupling also to closely benchmark experimental data (CesrTA, SLS)M. Pivi, F. Anotniou, Y. Papaphilippou (CERN)

Slide15

Code use to optimize CLIC DRs:Optimize ring parameters and IBS: beam energy, bunch length, optics

Improve code speed: Merge

wiggler elements in

simulationsStudy the evolution of the bunch shape during IBS: generation of non-Gaussian tailsIBS theoretical models: include

betatron couplingM. Pivi, F. Anotniou, Y. Papaphilippou (CERN)IBS evaluation: Long Term Plans

Slide16

Electron cloud in the Linear Colliders

Global Design Effort

16

SLAC is coordinating the ILC electron cloud Working Group (WG)

WG milestones: evaluations and recommendations on electron cloud mitigations that lead to reduction of ILC DR circumference from 17km to 6km (2006) and from 6km to 3km (2010)2012 goal is to evaluate electron cloud effect with mitigations implemented in each DR region, in preparation for the ILC Technical Design Report 2012.

Slide17

Recommendation of Electron Cloud Mitigations

17

Clearing Electrodes

KEKB

Grooves w/TiN coatingClearing ElectrodeCESRTAGrooves on Cu

Stable Structures

Reliable Feedthroughs

Manufacturing Techniques

& Quality

amorphous-Carbon

Slide18

Preliminary C

ESR

TA results and simulations suggest the possible presence of

sub-threshold

emittance growthFurther investigation requiredMay require reduction in acceptable cloud density a reduction in safety marginAn aggressive mitigation plan is required to obtain optimum performance from the 3.2km positron damping ring and to pursue the high current option ILC Working Group Baseline Mitigation RecommendationDrift*DipoleWigglerQuadrupole*Baseline Mitigation ITiN CoatingGrooves with TiN coatingClearing ElectrodesTiN CoatingBaseline Mitigation IISolenoid Windings

Antechamber

AntechamberAlternate Mitigation

Carbon coating/ NEG CoatingTiN Coating

Grooves with TiN CoatingClearing Electrodes or Grooves*Drift and Quadrupole chambers in arc and wiggler regions will incorporate antechambers

Summary of Electron Cloud Mitigation PlanGlobal Design Effort

18

Mitigation Evaluation conducted at ILC DR Working Group Workshop meeting

M. Pivi, S

.

Guiducci

, M. Palmer,

J

. Urakawa on behalf of the ILC DR

Electron Cloud Working

Group

Slide19

Mitigations: Wiggler Chamber with Clearing Electrode

Thermal spray tungsten electrode and Alumina insulator

0.2mm thick layers

2

0mm wide electrode in wigglerAntechamber full height is 20mmJoe Conway – Cornell U.

Slide20

Mitigations: Dipole Chamber with Grooves

20 grooves (19 tips)

0.079in (2mm) deep with 0.003in tip radius

0.035in tip to tip spacing

Top and bottom of chamberJoe Conway – Cornell U.

Slide21

Electron cloud assessment for 2012 TDR: P

lans

Photon generation and distribution

PI: Cornell U.

In BENDs with groovesPI: LBNLIn WIGGLERS with clearing electrodesPI: SLACIn DRIFT, QUAD, SEXT with TiN coatingPI: Cornell U.Input cloud density from build-upPI: SLACElectron cloud Build-up Photon distribution Beam Instability

Slide22

Photon rates, by magnet type and region

dtc03

Use

Synrad3d

a 3D simulation code that includes the ring lattice at input and chambers geometry (photon stops, antechambers, etc.)G. Dugan Cornell U.

Slide23

Electron Cloud in Drift Regions, with Solenoid field (40 G)

Solenoid fields in drift regions are very

effective

at eliminating the central density

J. Crittenden, Cornell U.

Slide24

Quadrupole in wiggler section

The calculated

beampipe

-averaged cloud densities does not reach equilibrium after 8 bunch trains.

J. Crittenden, Cornell U.

Slide25

Quadrupole in wiggler section

Electron cloud density (e/m

3

) Electron energies (eV

) J. Crittenden, Cornell U.

Slide26

Sextupole in TME arc cell

Electron cloud density (e/m

3

) Electron energies (eV

) J. Crittenden, Cornell U.

Slide27

Clearing electrode in wiggler magnet

Modeling of clearing electrode: round chamber is used

Clearing Field (left) & potential (right)

L. Wang, SLAC

Slide28

detail

+600V

0v

+600V

+400V+100V-300V-600VL. Wang, SLAC

Electrodes with negative (above) or positive (below) potential

Slide29

Completing evaluation for ILC

Next steps:

1) Simulations to include grooves in Bends

2) Beam instability simulations using electron cloud densities from build-up simulations.

At this stage, with recommended mitigations, the ring-average cloud density is 4×1010 e/m3 (a factor 3 lower than the instability threshold evaluated in 2010 ...)

Slide30

CLIC DR: Electron Cloud R&D program

2008 simulations: electron cloud strongly destabilize the beam and deposit excessive heat load in SC wigglers.

2008 studies are currently the latest results.

Electron cloud effect is high priority issue for the CLIC

DRs.In 2009, CLIC has been re-designed with several changes in the DR parameters: beam energy, circumference, all othersNeed for an up-to-date R&D program to:systematically evaluate the electron cloud build-up and instabilities in the present DR configurationproperly select mitigation techniques to be implemented in each of the DR regionsovercome the beam instability and excessive heat loads

Slide31

Summary

Intra-Beam Scattering codes in agreement with theoretical models

Estimations for Super-B and SLS,

CesrTAPlans for methodical evaluation of IBS in CLIC Damping Rings

Evaluation of electron cloud in ILC ongoing for Technical Design Report (2012)Need for re-evaluation of electron cloud in CLIC Damping Rings

Slide32

Back up slides

Slide33

Computation in parallel - pipeline

Each processor deals with the bunch-slice, then send information to the next in the pipeline. The last processor print out the beam information. At each turn, 1 processor gathers all particles and compute Radiation Damping and Quantum Excitation.

Bunch-slice parallel decomposition

M. Pivi (SLAC)

Slide34

Computational speed

(CMAD)

IBS simulations: computing time per turn,

Super-B lattice

(1582 ring elements)Mauro Pivi, CERN, CLIC collaboration341 processor64 processors100,000 macroparticle200 sec18.5 sec300,000 macroparticle540 sec24.4 secideal

e- cloud simulations

IBS:

Super-B, 100,000 macrop

IBS: Super-B, 300,000 macrop

Room for code optimization

CMAD

Slide35

Intra-Beam Scattering – CLIC DR

Overview

Previous work with SIRE simulation code

Evaluation of IBS with CMAD during one turn in ideal lattice (no errors) to compare with theory

Vertical dispersion and couplingPlans for IBS evaluation

Slide36

Previous

work

: SIRE

IBS Distribution study D: IBSParameterValueEq. ex (m rad)2.001e-10Eq. ey (m rad)2.064e-12Eq. sd 1.992e-3Eq. sz (m)1.687e-3Parameterc2999

Confidence

Dp/p3048.7

<1e-15X1441.7<1e-15

Y1466.9<1e-15

A.

Vivoli

, Y.

Papaphilippou

Slide37

Structured Evaluation of EC Mitigations

Nov 3-4, 2011 CLIC coll. meeting

Global Design Effort

37

Criteria for the evaluation of mitigations: Working Group ratingEfficacy of MitigationCostsRisksImpact on MachineRating10144Normalized Weighting0.530.050.210.21

Slide38

EC Mitigation Evaluation – 4 Criteria

Global Design Effort

38

Efficacy

Photoelectric yield (PEY)Secondary emission yield (SEY)Ability to keep the vertical emittance growth below 10%CostDesign and manufacturing of mitigationMaintenance of mitigationEx: Replacement of clearing electrode PSOperationalEx: Time incurred for replacement of damaged clearing electrode PS

Risk

Mitigation manufacturing challenges:

Ex: ≤1mm

or less in small aperture

VCEx: Clearing electrode in limited space or in presence of BPM buttons

Technical uncertainty

Incomplete evidence of efficacy

Incomplete experimental studies

Reliability

Durability

of mitigation

Ex:

Damage of clearing electrode

feed-through

Impact on Machine Performance

Impact on vacuum

performance

Ex:

NEG pumping can have a positive effect

Ex

: Vacuum outgassing

Impact on machine impedance

Ex: Impedance of grooves

and

electrodesImpact on opticsEx: x-y coupling due to solenoidsOperationalEx: NEG re-activation after saturationNov 3-4, 2011 CLIC coll. meetingDedicated ILC DR Working Group Workshop Meeting to evaluate technologies and give recommendation on electron cloud mitigations

Slide39

Bends: Overall average EC density: all cases

(QE=0.05)

M. Furman, LBNL

Slide40

Methodical Electron Cloud evaluation for CLIC DR: Major Research Goals.

Phase

I. Simulation R&D effort.

 

Characterize the photon generation and details of the photoelectron distribution in the whole damping ringCharacterize the electron cloud (EC) effect in field free regions, dipole, quadrupole, sextupole and wiggler regionsEstimate effect of antechamber and photon stop designs on EC build-upPerform parameter space studies: vacuum chamber radii, base vacuum pressure, scan of the secondary electron yield and beam parameters, antechamber and photon stop designEstimate the single-bunch instability threshold by simulations and for a realistic CLIC damping ring latticeInvestigate coupled-bunch instability by simulations: quantify growth rate and address feedback systemDefine the maximum acceptable secondary electron yield SEY level, above which the beam would be unstable

Slide41

Phase II. R&D on mitigations and recommendation: 

Estimate

beneficial effect of solenoid field in field free

regionsInvestigate efficacy of technical mitigations on suppressing electron cloud build-up by simulationsE

xperimental R&D effort on mitigations tailored to the CLIC DR : amorphous Carbon, NEG and TiN coating, clearing electrodes, groovesEvaluate impact on impedance for possible mitigations: all coating options, clearing electrodes, grooves and photon stopsGive recommendation for technical mitigations for each machine regionGive recommendation on the design and specifications of mitigationsMethodical Electron Cloud evaluation for CLIC DR: Major Research Goals.

Slide42

Change energy: scale H emittance (

epsxnew

=

epsold*newgamma^2/gamma^2), energy spread deltapnew=deltapold

*energynew/energyold, tau to be updated (not needed 1 turn); Optics scale the magnets …

Slide43

CLIC DR meetings

It is important to continuously and dynamically, i.e. critically, review our work

Goal is to communicate during informal meetings about beam dynamics and technical issues and/or progress

In the these meetings,

you are encouraged to ask openly several questions to favour exchange of information and a deeper understanding of beam instabilities, collective effects and technical systems, as a group.M. Pivi, Y. Papaphilippou and F. Antoniou

Slide44

CLIC DR meetings

The

format of the new

meetings:Every month meet with all DR group including Technical Systems and Beam Dynamics

Every 2 weeks meet with Beam Dynamics group  M. Pivi, Y. Papaphilippou and F. Antoniou

Slide45

CLIC DR Meetings Schedule

Date

Meeting

Wednesday 23

rd MayBDWednesday 6th JuneTS and BDTentative: Wednesday 13th JuneBDTentative: Wednesday 27th JuneTS and BD(BD = Beam Dynamics , TS = Technical Systems)Join us on the next DR meeting!