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

2. International Linear Collider Overview
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
April 22, 2019
CesrTA Seminar

3. The ILC Basic Numbers Machine Configuration
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
April 22, 2019
CesrTA Seminar

4. ICFA Release of Reference Design Report (RDR)
ILC Program
ICFA Release of Reference Design Report (RDR)
Release Date: February 8, 2007
Draft available at:
Press Release:
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
April 22, 2019
CesrTA Seminar

5. ILC R&D at Cornell R&D Efforts Also management contributions
Helical Undulator Polarized Positron Source
Ring-to-Main Linac
Low Emittance Transport (RTML and Main Linac)
Damping Rings
SRF
Detector (TPC)
Also management contributions
April 22, 2019
CesrTA Seminar

6. ILC Damping Rings R&D Overview
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)
J. Urban
April 22, 2019
CesrTA Seminar

7. International Linear Collider Overview
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
April 22, 2019
CesrTA Seminar

8. 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
OCS v6
TME Lattice
2 pm-rad geometric emittance
250 km main linac bunch train
is “folded” into the DRs
Circled items play a key role in our local R&D plans…
April 22, 2019
CesrTA Seminar

9. RDR Version of ILC DR Layout
e- ring circulates in opposite
direction in same central tunnel
April 22, 2019
CesrTA Seminar

10. 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
April 22, 2019
CesrTA Seminar

11. Moving to a Single Positron DR
M. Pivi
ILCDR06
No additional
suppression
techniques
assumed in
dipoles and
wigglers!
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.
April 22, 2019
CesrTA Seminar

12. Suppressing Electron Cloud in Wigglers
Submitted to PRSTAB
Design & test of impedance is under the way, test in PEPII Dipole & CESR Wiggler
Strip-line type
Wire type
Suetsugu’s talk
Calculation of the impedance ( Cho, Lanfa)
Wire type
L. Wang
ILCDR06
Strip-line type
April 22, 2019
CesrTA Seminar

13. 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
April 22, 2019
CesrTA Seminar

14. Reconfigure CESR as a damping ring test facility
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
April 22, 2019
CesrTA Seminar

15. 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
April 22, 2019
CesrTA Seminar

16. 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
April 22, 2019
CesrTA Seminar

17. 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
April 22, 2019
CesrTA Seminar

18. 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
April 22, 2019
CesrTA Seminar

19. Instrumentation for Ultra-Low Emittance Measurement
Typical Beam Sizes
Vertical: sy~10-12 mm
Horizontal: sx ~ 80 mm (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
April 22, 2019
CesrTA Seminar

20. GaAs Detector for X-ray Imaging
First bunch-by-bunch beam
size data in CHESS conditions a
Significant CHESS support
Signal (ADC Counts)
= 142 +/- 7 mm
Different symbols
represent different
bunches
Pinhole camera
setup at B1 hutch
Fast enough for single bunch resolution
Position (mm)
NEW: GaAs arrays from
Hamamatsu
1x512 linear array
25 mm pitch
1st sample has recently arrived
April 22, 2019
CesrTA Seminar

21. 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
detector
zone plate
Multilayer W/C mirrors;
April 22, 2019
CesrTA Seminar

22. 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
April 22, 2019
CesrTA Seminar

23. Experimental Reach Baseline Lattice Parameter Value E 2.0 GeV Nwiggler12
Bmax
2.1 T ex
2.25 nm Qx
14.59 Qy
9.63 Qz
0.075
sE/E
8.6 x 10-4
tx,y
47 ms
sz (with VRF=8.5MV)
9 mm ac
6.4 x 10-3
tTouschek(Nb=2x1010)
>10 minutes
April 22, 2019
CesrTA Seminar

24. Tune scans used to identify suitable working points
Qx~ Qy~9.63
April 22, 2019
CesrTA Seminar

25. Zero current ex (nm-rad)
Alternate Optics
Have explored a range of optics for machine transition and physics studies
Layout
Energy
(GeV)
Bpeak
(T)
No. Wigglers
Zero current ex (nm-rad)
CesrTA
2.0
2.1 12
1.8
CESR-c 6
6.5
1.9
2.5
3.2
1.5
1.4
1.3
5.0 26
April 22, 2019
CesrTA Seminar

26. Lattice Evaluation Dynamic aperture
1 damping time
Injected beam fully coupled
ex = 1 mm
ey = 500 nm
Alignment sensitivity and low emittance correction algorithms
Simulations based on achieving nominal CESR alignment resolutions
Misalignment
Nominal Value
Quadrupole, Bend and Wiggler Offsets
150 mm
Sextupole Offsets
300 mm
Quadrupole, Bend, Wiggler and Sextupole Rotations
100 mrad
April 22, 2019
CesrTA Seminar

27. Vertical Emittance Sensitivities (Selected Examples)
April 22, 2019
CesrTA Seminar

28. Low Emittance Operations
Have evaluated our ability to correct for ring errors with the above lattice
Goal: ey~5-10 pm at zero current
Simulation results indicate that we can reasonably expect to meet our targets
Nominal Values
Correction Type
Average Value
95% Limit
Orbit Only
10.2 pm
21.4 pm
Orbit+Dispersion
3.9 pm
8.2 pm
April 22, 2019
CesrTA Seminar

29. 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 g-4 IBS dependence offers a flexible way to study, control and understand IBS contributions to emittance relative to other physics under consideration
April 22, 2019
CesrTA Seminar

30. 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, …
April 22, 2019
CesrTA Seminar

31. Proposal 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
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
Simulation of electron cloud in wigglers
A. Molvik
LLNL
Electron cloud measurements
J. Byrd, S. de Santis, M. Venturini, and M. Zisman
Wiggler and electron cloud and FII studies
K. Harkay
ANL
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.
R. Holtzapple
Alfred Univ.
Instrumentation and beam measurements
J. Urakawa
R&D program coordination
L. Schächter
Technion-Haifa
Electron cloud measurements and analysis
Letters of intent from ~30 collaborators for direct work on CesrTA
April 22, 2019
CesrTA Seminar

32. 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
April 22, 2019
CesrTA Seminar

33. 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
April 22, 2019
CesrTA Seminar

34. Superferric ILC-Optimized CESR-c Wiggler
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
tdamp = 26.4 ms
ex,rad = 0.56 nm·rad
sd = 0.13 %
Misses nominal target (25 ms)
April 22, 2019
CesrTA Seminar

35. Engineering Issues Cryogenics Modifications Shorter Unit
Indirect cooling for cold mass
Switch to cold He gas for cooling thermal shields
42% of manpower for inner cryostat and stack assembly a 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:
April 22, 2019
CesrTA Seminar

36. EC in Wiggler Vacuum Chamber
The multipacting strips of electron cloud in the wigglers is more close to the beam
L. Wang, ILCDR06
Wiggler
Dipole, B=0.194T
April 22, 2019
CesrTA Seminar

37. 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
April 22, 2019
CesrTA Seminar

38. Diagnostic Wiggler Chamber Concept
Integral RFA
Expect to make several variants to explore
Electrodes
Grooves
Coatings
Modify existing extrusions
Clearing Electrode
Clearing Electrode
1.5mm slot spacing
RFA sections 31mmx38mm sampling central fields of wiggler
April 22, 2019
CesrTA Seminar

39. Survey and Alignment
Rapid Tunnel Reference Surveyor (RTRS) Concept Proposal submitted for ILC DR alignment and survey studies using CesrTA
wall markers
internal FSI
SM beam
external FSI
Tunnel Wall
Reichold
D. Urner
LiCAS technology
for automated
stake-out process
Reconstructed
tunnel shapes
(relative co-ordinates)
collider component
April 22, 2019
CesrTA Seminar

40. 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)
April 22, 2019
CesrTA Seminar

41. e+ Beam Size vs Bunch Current
2 GeV vertical bunch-by-bunch beam size for 1x45 pattern, positrons
April 22, 2019
CesrTA Seminar

42. Theory and measurement of instability onset
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.
0.35 mA
See ILCDR06 Talk by L. Schachter –
April 22, 2019
CesrTA Seminar

43. Witness Bunch Studies – e+ Vertical Tune Shift
Initial train of 10 bunches a generate EC
Measure tune shift and beamsize for witness bunches at various spacings
Positron Beam, 0.75 mA/bunch, 14 ns spacing, 1.9 GeV Operation
Error bars represent scatter
observed during a sequence
of measurements
1 kHz a Dn=0.0026
re ~ 1.5 x 1011 m-3
Ohmi, etal, APAC01, p.445
Preliminary Results
April 22, 2019
CesrTA Seminar

44. 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
Negative vertical tune shift along train a consistent with EC
Magnitude of shift along train is ~1/4th of shift for positron beam
NOTE: Shift continues to grow for 1st 4 witness bunches!
Preliminary Results
April 22, 2019
CesrTA Seminar

45. Witness Bunch Studies – Comparison of e-/e+ Tunes
Magnitude of tune shift for electron beam is ~1/4th of shift observed for positron beam
April 22, 2019
CesrTA Seminar

46. Fast Ion Instability? Qh Qv 0.5 kHz full scale - 45 bunch train
- Electrons
- 14ns spacing
- 1.2e10/bunch Qh
0.6 kHz full scale
Instability?
Linear theory predicts
100 turn growth rate for
45th bunch
Vertical beam size Qv
0.5 kHz full scale
Measurements underway to characterize mode spectra
April 22, 2019
CesrTA Seminar

47. ILC EDR needs drive research program until early 2010
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
April 22, 2019
CesrTA Seminar

48. Now Until April 1, 2008 RFA Assembly
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: ex ~ 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
April 22, 2019
CesrTA Seminar

49. 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
April 22, 2019
CesrTA Seminar

50. Modifications that will benefit ERL@CESR
Synergies
Modifications that will benefit
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 ex ~ 26 nm
Requires a ~100kW x-ray dump
Goal is 100 mA single beam operations
April 22, 2019
CesrTA Seminar

51. 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 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
April 22, 2019
CesrTA Seminar

52. CesrTA conceptual design work is ongoing
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!
April 22, 2019
CesrTA Seminar

53. CesrTA Studies and CESR Machine Studies
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
April 22, 2019
CesrTA Seminar