CESR as a Vehicle for ILC Damping Rings R&D Mark Palmer Cornell Laboratory for Accelerator-Based...

CESR as a Vehicle for ILC Damping Rings R&D

Mark Palmer

Cornell Laboratory for

Accelerator-Based Sciences and Education

April 24, 2007 LBNL Center for Beam Physics Seminar 2

Outline

• International Linear Collider Overview– Preparing for the Engineering Design Report (EDR)– ILC R&D at Cornell

• CesrTA Proposal– ILC Damping Rings Overview– Damping Rings R&D Using CESR

• Concept and Goals• Ring Modifications• Parameters and Experimental Reach• Collaborators• Damping Rings Projects• Schedule

• Synergies with Other Parts of the CLASSE Program• Acknowledgments and Conclusion


The ILC

• Basic Numbers– 500 GeV – upgradeable to 1 TeV– 14 kHz Collision Rate– Luminosity: 2x1034 cm-2s-1

– 31 km end-to-end length– 31.5 MV/m SRF cavities

• 16K Cavities• 2K Cryostats

• Machine Configuration– Helical Undulator polarized e+ source– Two 6.7 km damping rings in central

complex– RTML running length of linac– 11.2 km Main Linac– Single Beam Delivery System– 2 Detectors in Push-Pull

Configuration


ILC Program

• ICFA Release of Reference Design Report (RDR)– Release Date: February 8, 2007– Draft available at: http://www.linearcollider.org

– Press Release: http://www.interactions.org/cms/?pid=1024912

– RDR Cost Estimate (accelerator complex):• $1.8bn site costs (eg, tunneling)

• $4.9bn technology and component costs

• 13K person-years of effort (personnel costs not in above numbers)

• Start of the Engineering Design Phase– Engineering Design Report (EDR) in early 2010

– Complete critical R&D (eg, SRF cavity gradient yield for ML, electron cloud and fast kicker technology for DR)

– Basic engineering design


ILC R&D at Cornell

• R&D Efforts– Helical Undulator Polarized

Positron Source

– Ring-to-Main Linac

– Low Emittance Transport (RTML and Main Linac)

– Damping Rings

– SRF

– Detector (TPC)

• Also management contributions


ILC Damping Rings R&D Overview

J. Urban

• Damping Rings– Simulation– Electron Cloud and Ion Effects– Technical Systems (wigglers, kickers, instrumentation…)– CesrTA Development– BCD and RDR Support

• J. Alexander, M. Billing, G. Codner, J. Crittenden, G. Dugan, M. Ehrlichman, D. Hartill, R. Helms, R. Holtzapple, J. Kern, Y. Li, R. Meller, M. Palmer, D. Rice, D. Rubin, D. Sagan, L. Schachter, J. Shanks, E. Tanke, M. Tigner, J. Urban (note: 5 students)


Outline

• International Linear Collider Overview– Preparing for the Engineering Design Report (EDR)– ILC R&D at Cornell

• CesrTA Proposal– ILC Damping Rings Overview– Damping Rings R&D Using CESR

• Concept and Goals• Ring Modifications• Parameters and Experimental Reach• Collaborators• Damping Rings Projects• Schedule

• Synergies with Other Parts of the CLASSE Program• Acknowledgments and Conclusion


The ILC Damping Rings

Beam energy 5 GeV

Circumference 6695 m

RF frequency 650 MHz

Harmonic number 14516

Injected (normalised) positron emittance

0.01 m

Extracted (normalised) emittance

8 μm × 20 nm

Extracted energy spread <0.15%

Average current 400 mA

Maximum particles per bunch 2×1010

Bunch length (rms) 6 mm 9mm

Minimum bunch separation 3.08 ns

2 pm-rad geometric emittance

OCS v6TME Lattice

Circled items play a key role in our local R&D plans…

250 km main linac bunch trainis “folded” into the DRs


RDR Version of ILC DR Layout

e- ring circulates in opposite direction in same central tunnel


RDB S3 Very High Priorities

• Lattice design for baseline positron ring• Lattice design for baseline electron ring• Demonstrate < 2 pm vertical emittance• Characterize single bunch impedance-driven instabilities• Characterize electron cloud build-up• Develop electron cloud suppression techniques• Develop modelling tools for electron cloud instabilities• Determine electron cloud instability thresholds• Characterize ion effects• Specify techniques for suppressing ion effects• Develop a fast high-power pulser


Moving to a Single Positron DR

Cloud density near (r=1mm) beam (m-3) before bunch passage, values are taken at a cloud equilibrium density. Solenoids decrease the cloud density in DRIFT regions, where they are only effective. Compare options LowQ and LowQ+train gaps. All cases wiggler aperture 46mm.

M. PiviILCDR06

No additionalsuppression techniques assumed in dipoles andwigglers!


Suppressing Electron Cloud in Wigglers

0 20 40 60 80 100 12010

9

1010

1011

1012

1013

1014

Bunch ID

e (

m-3

)

average density, long traincentral density, long trainaverage density, bunch train, -100Vcentral density, bunch train, -100Vaverage density, bunch train, 200Vcentral density, bunch train, 200V

stripline position

Strip-line typeWire type

Strip-line type Wire type

Calculation of the impedance ( Cho, Lanfa)

Design & test of impedance is under the way, test in PEPII Dipole & CESR Wiggler

Submitted to PRSTAB

Suetsugu’s talk

L. WangILCDR06


ILCDR R&D Issues and CesrTA

• Some High and Very High Priority R&D Items that Can Be Addressed at CesrTA…– Electron Cloud

• Growth in quadrupoles, dipoles, and wigglers• Suppression in quadrupoles, dipoles, and wigglers• Instability thresholds and emittance growth in the positron damping ring• This issue has become more significant due to the decision to employ a single

positron damping ring– Ion Effects

• Instability thresholds and emittance growth in the electron damping ring– Ultra-low Emittance Operation

• Alignment and Survey• Beam-based Alignment• Optics Correction• Measurement and Tuning

– Fast (single bunch) high voltage kickers for injection/extraction• >100 kV-m of stripline kick required• <6 ns wide pulse into a 0.3 m long stripline so as not to perturb neighboring bunches

in the damping ring– Development of 650 MHz SRF System


CesrTA Concept

• Reconfigure CESR as a damping ring test facility– Move wigglers to zero dispersion regions for low emittance

operation– Open up space for insertion devices and instrumentation

• Provide an R&D program that is complementary to work going on elsewhere (eg, KEK-ATF)

• Provide a vehicle for: – R&D needed for EDR decisions (EDR R&D completion by end of

2009 is ILC target)– Operating and tuning experience with ultra-low emittance beams– DR technical systems development

• Provide significant amounts of dedicated running time for damping ring experiments


CesrTA Operating Model

• Experimental Model– Collaboration among international researchers (similar to

HEP collaborations)– Cornell provides machine infrastructure and support– Cornell provides operations staff

• Scheduling Model– Provide multiple dedicated experimental periods each

year– Provide sufficient scheduled down time to flexibly

upgrade machine and install experimental apparatus– Alternate running periods with CHESS


CesrTA Ring Modifications

• Place all wigglers in zero dispersion regions– Wigglers in L1 and L5 straights can remain in place– Emittance scaling for wiggler dominated ring:

• Vacuum system modifications– Electron cloud and ion diagnostics– Synchrotron x-ray dump for high energy operation of part of the

wiggler complement• Remove 4 of 6 electrostatic separators• Upgrade instrumentation and diagnostics for planned

experiments• Feedback system modifications for 4 ns bunch spacing

32

2

15

8

wp

x

xqx kJ

C


CESR Modifications• Move 6 wigglers from the CESR

arcs to the South IR (zero dispersion region around CLEO)– NOTE: this is a recent change in

plans

• Instrumentation and feedback upgrades


The South IR

South IR Modifications:• Remove CLEO drift chambers• Instrumented vacuum chambers for local electron cloud diagnostics• Eventual test location for prototype ILC damping wiggler and vacuum chambers


Instrumentation for Ultra-Low Emittance Measurement

• Typical Beam Sizes– Vertical: y~10-12 m

– Horizontal: x ~ 80 m (at a zero dispersion point)

• Have considered laserwire and X-ray profile monitors– Fast X-ray imaging system (Alexander)

• Core diagnostic for CesrTA – high resolution and bunch-by-bunch capability

• Plan for integrating systems into CHESS lines

• First pinhole camera tests were successful! (see next slide)

– Laserwire• CESR-c fast luminosity monitor offers window suitable for laserwire use

• Detector potentially could be used for fast segmented readout of Compton photon distribution


GaAs Detector for X-ray Imaging

Sig

nal

(A

DC

Cou

nts

)

Position (m)Fast enough for single bunch resolution

First bunch-by-bunch beam size data in CHESS conditions Significant CHESS support

= 142 +/- 7 mDifferent symbolsrepresent differentbunches

Pinhole camerasetup at B1 hutch

NEW: GaAs arrays from Hamamatsu• 1x512 linear array• 25 m pitch• 1st sample has recently arrived


CesrTA Beamsize Monitor Concept

• Simple optics– High transmission– 2 keV operation (works for both 2 GeV and 5 GeV)– Hundreds (2 GeV) to thousands (5 GeV) of photons per bunch

passage

• Explore other detector possibilities (eg, InSb arrays)• Collaboration with CHESS colleagues for optics and device

development as well as integration with existing Xray lines

p q

25um Be

detectorzone plate

Multilayer W/C mirrors;


CESR Modifications Summary

• How extensive are the modifications?– Significant changes to the South IR (however, certainly

no more difficult than a detector and IR magnet upgrade)

• Conversion is relatively modest– Core ring modifications will take place in a single down

period• Mid-2008

• <3 months duration

– Carry out key preparation work between now and April 2008


Experimental Reach

Parameter Value

E 2.0 GeV

Nwiggler 12

Bmax 2.1 T

x 2.25 nm

Qx 14.59

Qy 9.63

Qz 0.075

E/E 8.6 x 10-4

x,y 47 ms

z (with VRF=8.5MV) 9 mm

c 6.4 x 10-3

Touschek(Nb=2x1010) >10 minutes

Baseline Lattice


Tune scans• Tune scans used to identify suitable working points

Qx~14.59 Qy~9.63


Alternate Optics

• Have explored a range of optics for machine transition and physics studies

Layout Energy

(GeV)

Bpeak

(T)

No. Wigglers Zero current x (nm-rad)

CesrTA 2.0 2.1 12 1.8

CESR-c 2.0 2.1 6 6.5

CesrTA 2.0 1.9 12 1.9

CesrTA 2.5 2.1 12 3.2

CesrTA 1.5 1.4 12 1.3

CesrTA 5.0 2.1 6 26


Lattice Evaluation

Misalignment Nominal Value

Quadrupole, Bend and Wiggler Offsets

150 m

Sextupole Offsets 300 m

Quadrupole, Bend, Wiggler and Sextupole Rotations

100 rad

• Dynamic aperture– 1 damping time– Injected beam fully coupled

• x = 1 mm• y = 500 nm

• Alignment sensitivity and low emittance correction algorithms– Simulations based on achieving

nominal CESR alignment resolutions


Vertical Emittance Sensitivities(Selected Examples)


Low Emittance Operations

• Have evaluated our ability to correct for ring errors with the above lattice– Goal: y~5-10 pm

at zero current

– Simulation results indicate that we can reasonably expect to meet our targets

Correction Type Average Value 95% Limit

Orbit Only 10.2 pm 21.4 pm

Orbit+Dispersion 3.9 pm 8.2 pm

Nominal Values


IBS Evaluation (2 GeV Baseline Lattice)

• Transverse emittance growth for different contributions of coupling and dispersion to the vertical emittance– Baseline lattice– Compare different corrected optics assumptions– 9 mm bunch length

• Energy flexibility of CESR and -4 IBS dependence offers a flexible way to study, control and understand IBS contributions to emittance relative to other physics under consideration


CesrTA Research Directions

• Core Efforts– Electron Cloud Growth Studies – particularly in the CESR-c

wigglers• Bunch trains similar to those in the ILC DR• Vacuum chambers with mitigation techniques and diagnostics

– Ultra low Emittance Operation• Alignment and Survey• Beam-based Alignment• Optics Correction• Measurement and Tuning

– Beam Dynamics Studies• Detailed inter-species comparisons (use to distinguish electron cloud, ion

and wake field effects)• Characterize emittance growth in ultra-low emittance beams (electron cloud,

ion effects, IBS, …)– Test and Demonstrate Key Damping Ring Technologies

• Wiggler vacuum chambers, optimized wigglers, diagnostics, …


Proposal Collaborators

Collaborators Institution Topic

M. Pivi and L. Wang SLAC Electron cloud studies, wiggler chambers for electron cloud suppression

Y. Cai and PEP-II Beam Physics Group SLAC Machine correction and ultra-low emittance tuning

A. Reichold and D. Urner Oxford Alignment and survey requirements and upgrades

S. Marks and R. Schlueter and M. Zisman LBNL Wiggler chambers for electron cloud suppression

C. Celata, M. Furman and M. Venturini LBNL Simulation of electron cloud in wigglers

A. Molvik LLNL Electron cloud measurements

J. Byrd, S. de Santis, M. Venturini, and M. Zisman

LBNL Wiggler and electron cloud and FII studies

K. Harkay ANL Electron cloud measurements

J. Flannagan, K. Ohmi, N. Ohuchi, K. Shibata, Y. Suetsugu, and M. Tobiyama

KEK Electron cloud measurements and simulation

P. Spentzouris, J. Amundsen and L. Michelotti

FNAL Beam dynamics simulations and measurements

A. Wolski Cockcroft Inst. Machine correction and ultra-low emittance tuning

R. Holtzapple Alfred Univ. Instrumentation and beam measurements

J. Urakawa KEK R&D program coordination

L. Schächter Technion-Haifa Electron cloud measurements and analysis

Letters of intent from ~30 collaborators for direct work on CesrTA


CESR-c Wiggler Modifications

• Initial vacuum tests in CesrTA • Remove Cu beam-pipe• Replace with beam-pipe having ECE suppression and diagnostics hardware• CU/SLAC/LBNL Collaboration

• Prototype Optimized ILC Wiggler and Vacuum Chamber

• Cornell/LBNL Collaboration


Wiggler Design

• Basic Requirements– Large Aperture

• Physical Acceptance for injected e+ beam

• Improved thresholds for collective effects – Electron cloud

– Resistive wall coupled bunch instability

– Dynamic Aperture• Field quality

• Wiggler nonlinearities

• Have carried out a series of physics studies with an eye towards the engineering develop an optimized wiggler design which we hope will lead to an ILC prototype– Dynamic aperture studies using OCS2


Optimized Wiggler

• Superferric ILC-Optimized CESR-c Wiggler– 12 poles (vs 14)– Period = 32 cm (vs 40)– Length = 1.68 m (vs 2.5)

– By,peak = 1.95 T (vs 1.67)

– Gap = 86 mm (vs 76)– Width = 238 mm– I = 141 A damp = 26.4 ms

x,rad = 0.56 nm·rad

= 0.13 %

Misses nominal target (25 ms)


Engineering Issues

• Cryogenics Modifications– Indirect cooling for cold mass– Switch to cold He gas for cooling thermal shields– 42% of manpower for inner cryostat and stack assembly significant cost

reduction expected

• Shorter Unit– Simplified and more robust yoke assembly– Significant cost reduction

• 14 % fewer poles• 30% reduction in length

• Larger aperture– Relaxed constraints on warm vacuum chamber interface with cryostat

• Estimated cost savings relative to RDR value: ~25%• Wiggler Information:

https://wiki.lepp.cornell.edu/ilc/bin/view/Public/CesrTA/WigglerInfo


EC in Wiggler Vacuum Chamber

-30 -20 -10 0 10 20 300

1

2

3

4

5

6x 10

13

X (mm)

(m-3

)-10 -5 0 5 100

0.5

1

1.5

2

2.5

3x 10

13

X (mm)

Wiggler Dipole, B=0.194T

The multipacting strips of electron cloud in the wigglers is more close to the beam

L. Wang, ILCDR06


Wiggler Trajectory

• Note that CESR beam trajectory significant relative to stripe spacing at 2GeV

• Diagnostics– Ideally should be capable

of roughly millimeter transverse resolution

– Longitudinal segmentation to cleanly sample stripe 4mm


Diagnostic Wiggler Chamber Concept

• Expect to make several variants to explore– Electrodes– Grooves– Coatings

• Modify existing extrusions

RFA sections 31mmx38mm sampling central fields of wiggler

Clearing Electrode

1.5mm slot spacing

Clearing Electrode

Integral RFA


Survey and Alignment

collider component

Rapid Tunnel Reference Surveyor (RTRS) ConceptProposal submitted for ILC DR alignment and survey studies using CesrTA

Tunnel Wall

Reconstructed tunnel shapes(relative co-ordinates)

wall markers internal FSI external FSISM beam

LiCAS technologyfor automated stake-out process

A. Reichold

D. Urner


Electron Cloud (and Ion) Studies

• Electron Cloud and Ion Studies Underway• Utilize multi-bunch turn-by-turn instrumentation

– Beam profile monitors

– Beam position monitor

• Collaborator

Participation– Sept. 2006: M. Pivi

– Jan. 2007:

K. Harkay (ANL),

J. Flanagan (KEKB),

A. Molvik (LLNL)


e+ Beam Size vs Bunch Current

• 2 GeV vertical bunch-by-bunch beam size for 1x45 pattern, positrons


Theory and measurement of instability onset

0.35 mA

0 10 20 30 40 500.1

0.15

0.2

0.25

0.3

0.35

0.4

b

103

0.11

0.4

[ ]b mm

0.5

60

pf MHz

a m

1/2 4

221 y

bb

c

Qualitative comparison: if the transverse eigen-frequency of the electron cloud

becomes comparable with the corresponding betatron frequency (xc), then the transverse motion becomes

unstable. Need to take into account the horizontal motion as well.

See ILCDR06 Talk by L. Schachter – https://wiki.lepp.cornell.edu/ilc/pub/Public/DampingRings/CornellWorkshopTalks/Schachter.Wake-Field_in_eCloud.ppt


Witness Bunch Studies –e+ Vertical Tune Shift

• Initial train of 10 bunches generate EC• Measure tune shift and beamsize for witness bunches at various spacings

1 kHz e ~ 1.5 x 1011 m-3

Ohmi, etal, APAC01, p.445

Positron Beam, 0.75 mA/bunch, 14 ns spacing, 1.9 GeV Operation

Preliminary ResultsError bars represent scatter observed during a sequenceof measurements


Witness Bunch Studies –e- Vertical Tune Shift

• Same setup as for positrons• Negative vertical tune shift and long decay consistent with EC

Electron Beam, 0.75 mA/bunch, 14 ns spacing, 1.9 GeV Operation

Preliminary ResultsNegative vertical tune shift along train consistent with ECMagnitude of shift along train is ~1/4th of shift for positron beamNOTE: Shift continues to grow for 1st 4 witness bunches!


Witness Bunch Studies –Comparison of e-/e+ Tunes

• Magnitude of tune shift for electron beam is ~1/4th of shift observed for positron beam


Fast Ion Instability?

- 45 bunch train- Electrons- 14ns spacing- 1.2e10/bunch

Qh

0.6 kHz full scale

Instability?Linear theory predicts100 turn growth rate for45th bunch

Qv

0.5 kHz full scale

Vertical beam size

Measurements underway to characterize mode spectra


CesrTA Schedule

• Initial Focus– Electron cloud growth and suppression in wigglers– Improvements for low emittance operations through 2009

• ILC EDR needs drive research program until early 2010– Expect re-evaluation of program at that point– Potential for prototype testing after the EDR period

• At NSF request, we have resubmitted (3 weeks ago) the CesrTA proposal jointly to DOE and NSF


Now Until April 1, 2008

• Implement 4ns transverse feedback (transverse now operating)– R. Meller, M. Billing, G. Codner, J. Sikora

• Install North IR Retarding Field Analyzers (RFA) for electron cloud measurements during May down

• Preparatory machine studies program– Continue electron cloud and ion studies– Start exploration of low emittance operations

• CESR-c (existing machine layout) optics have been designed: x ~ 6.5 nm

• Early work on beam-based alignment• Prepare for wiggler vacuum chamber studies

– Collaboration: SLAC, LBNL– Design and construction of new vacuum chambers is a

critical path item– Segmented RFA for high field operation

• General infrastructure preparation– Feedback– Cryogenics– Vacuum– Other…

RFA Assembly


• International Linear Collider Overview– Preparing for the Engineering Design Report (EDR)– ILC R&D at Cornell– ILC Damping Rings R&D in Detail

• CesrTA Proposal– Overall Scope– Damping Rings R&D Using CESR

• Concept and Goals• Ring Modifications• Parameters and Experimental Reach• Schedule• Collaborators and Projects

• Synergies with Other Parts of the CLASSE Program• Conclusion and Acknowledgments


Synergies

• Modifications that will benefit ERL@CESR– BPM system upgrade provides electronics that will be

reused for the ERL– Improvements in low emittance diagnostics– Improvements in survey and alignment capabilities– Development of machine correction methods at ultra low

emittance

• Potential new regimes for CHESS operations– 5 GeV low emittance lattice

• 6 wiggler operation with x ~ 26 nm• Requires a ~100kW x-ray dump• Goal is 100 mA single beam operations


Unique Features of R&D at CESR

CESR offers:– The only operating wiggler-dominated storage ring in the world– The CESR-c damping wigglers

• Technology choice for the ILC DR baseline design– Physical aperture: Acceptance for the injected positron beam– Field quality: Critical for providing sufficient dynamic aperture in the damping rings

– Flexible operation with positrons and electrons– Flexible bunch spacings suitable for damping ring tests

• Presently operate with 14 ns spacing• Can operate down to 4ns (or 2ns) spacings with suitable feedback system upgrades

– Flexible energy range from 1.5 to 5.5 GeV• CESR-c wigglers and vacuum chamber specified for 1.5-2.5 GeV operation• An ILC DR prototype wiggler and vacuum chamber could be run at 5 GeV

– Dedicated focus on damping ring R&D for significant running periods after the end of CLEO-c data-taking

– A useful set of damping ring research opportunities…• The ability to operate with positrons and with the CESR-c damping wigglers offers a

unique experimental reach


Conclusion

• CesrTA conceptual design work is ongoing– Program offers unique features for critical ILC damping

ring R&D– Simulations indicate that the emittance reach is suitable

for a range of damping ring beam dynamics studies– The experimental schedule will allow timely results for

ILC damping ring R&D!


Acknowledgments

• CesrTA Studies and CESR Machine Studies– J. Alexander

– M. Billing

– G. Codner

– J. Crittenden

– M. Ehrlichman (Minn)

– M. Forster

– D. Hartill

– R. Helms

– D. Rice

– D. Rubin

– D. Sagan

– L. Schachter

– J. Shanks (REU)

– E. Tanke

– M. Tigner

– J. Urban

CESR as a Vehicle for ILC Damping Rings R&D Mark Palmer Cornell Laboratory for Accelerator-Based...

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