1. Damping Ring R&D Kwang-Je Kim Argonne Accelerator Institute
Argonne National Laboratory
ILC Americas Regional Team Review
April 4-6, 2006
Fermi National Accelerator Laboratory

2. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 2
ILC General Layout DR
5-GeV
Linac
Electrons
Positrons
Undulator
Main Linac
(500 GeV C.M. , L = 2×1034 cm-2s-1)
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

3. Challenges for ILC Damping Ring
Compress 1 ms linac bunch train in to a “reasonable size” ring
Fast kicker (ns)
Damping of gx,y= m-rad positron beams to
(gH, gv)=(8  10-6,2  10-8) m-rad
Low emittance, diagnostics
Cycle time 0.2 sec (5 Hz rep rate) =25 ms
Damping wiggler
2820 bunches, 21010 electrons or positrons per bunch, bunch length= 6 mm
Instabilities ( classical, electron cloud, fast ion)
Beam power >220 kW
Injection efficiency, dynamic aperture
What does dynamic aperture <10 sig means? Sig=beamsize at injection?
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

4. Design &Beam Dynamics Tools
Lattice design procedure
TME or FODO, damping wiggler, symmetry,..
L. Emery, Stanford thesis ( Aug. 1990)
P. Emma and T. Raubenheimer, PRSTAB (2001)
Tracking codes for DA and instabilities
LEGO (Cai, SLAC), ELEGANT (Borland, ANL), Merlin (Walker, DESY), BMAD (Sagan, Cornell), SAD (Hirata, KEK), MARYLIE (Dragt, U of Md), COSY (Berz, U Michigan), …
Experiences at HEP & BES machines
SLC, KEK-ATF, B-Factories, CESR-c, ALS, APS,..
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

5. Coordinated Progress in ILC Damping Ring Research & Design
Workshops:
ILC-Americas WS (SLAC, October, 2004)
First ILC WS (KEK, November 2004)
Wiggle-05 (Frascati, February 2005)
Second ILC WS ( Snowmass, August 2005)
Damping Rings Meeting at CERN, 9-11 November 2005
Teleconferences:
US: Bi-Weekly ( December 04-July 05)
International ( October 05- )
Coordinated by Andy Wolski
Configuration Studies and Recommendations for the ILC Damping Rings (LBNL-59449, Feb. 4, 2006)
Editors: A. Wolski, J. Gao, S. Guiducci
Damping Ring R&D Tasks List (Feb. 2006)
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

6. Comparative Study of Possible ILC Configurations
A major activity in 2005
Explore different configuration options (including lattice styles) for the damping rings.
16 km FODO ‘dogbone’ (LBNL)
6 km TME ‘circular’ (ANL/FNAL)
3 km TME ‘racetrack’ (KEK)
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

7. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 7
Dynamic Aperture in the Reference Lattices with Ideal Nonlinear Wiggler Model and 15 Seeds of Multipole Errors, computed with BMAD ( from Config Studies& Recomm Report)
(a) PPA (b) OTW (c) OCS
(d) BRU (e) MCH (f) DAS
Good agreement between results by different groups using different codes; elegant, Merlin, LEGO
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/
(g) TESLA

8. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 8
Tracking a ‘realistic’ distribution ( from Configuration Studies& Recommendations Report)
A physical aperture of at least 16 mm radius is needed in the wiggler, to ensure adequate injection efficiency. The average injected beam power is 226 kW.
Distribution of injected positrons in phase space (top) and coordinate space (left). W. Gai, ANL.
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

9. DR Baseline Recommendations
Essentially the “OCS” lattice proposed by Cornell-FNAL and studied in ANL
Energy: 5 GeV
Circumference:
Electron: one 6 km circular ring/one tunnel
Positron: two 6 km circular rings/one tunnel
Injection/extraction kicker: striplines with fast pulsers
Damping wiggler: superconducting
RF cavity: 500/650 MHz superconducting
Bunch length: 6 mm
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

10. FY06 Damping Ring Work PackagesWP
Work package name
Lab / Univ*
Contact
Labor (K$)
M&S (K$)
Total (K$)**
2.5.1
Ring design
SLAC
Cai
378
2.5.2
Accelerator physics
FNAL
Spentzouris
150 58
208
2.5.3
Injection & Extraction Beamline
LBNL
Zisman 2
2.5.4
Dynamic Aperture 81 3 84
2.5.5
Collective Effects
Venturini
227 4
231
2.5.6
Ring design and optimization
ANL
Xiao
3.5.1
Electron PEP-II
Pivi
140
116
256
3.5.2
ATF Ring BPM electronics
Ross
271
246
517
3.5.3
Damping Rings Studies at LBNL-ALS 10
3.5.4
Novel Schemes for Inj/Ext Kickers
UIUC
Gollin 17
3.5.5
Prototyping of fast kicker options
Cornell
Palmer 75
3.5.6
Experimental, simulation, and design
Sagan
47***
3.5.7
Fast Synchrotron Radiation Imaging
Alexander
24***
*University projects are for FY05
**The budget sometimes is augmented by base program and/or internal fundings
***NSF
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

11. SLAC: Impedances and Instabilities
(WP: 2.5.1)
SLAC: Impedances and Instabilities
Single bunch threshold for electron cloud for the OCS lattice may be lower than expected with new effects included (dispersion in bends, 12 superperiods, damping ) ( Cai)
ne=1E11 m-3
Analytic and numerical estimates of Impedance for grooved surfaces ( Stupakov, Bane)
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

12. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 12
(WP: 2.5.1)
SLAC: Trans. coupled bunch instability due to resistive wall and narrow band impedance G. Stupakov, S. Heifets, K. Bane
The conventional instabilities will in general have little impact on the ring performance if the impedance is minimized with careful design.
The transverse coupled bunch instability would have threshold current above nominal if the aperture in the wigglers is increased from 8 mm to 16 mm.
The microwave instability needs more studies.
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

13. Fermilab: Modeling Effort in FY06 (Spentzouris)
(WP: 2.5.2)
Fermilab: Modeling Effort in FY06 (Spentzouris)
Ring modeling
Use Synergia: 3D parallel code developed by Spentzouris and Amundson 
Accurate wiggler representation using CHEF: arbitrary order Lie algebra code developed by Michelotti
Electron cloud modeling in collaboration with ANL, LBNL, UCLA, and USC, focusing on utilizing PIC codes, such as QuickPIC
Simulations to be performed on the Fermilab Computational Physics for Accelerators parallel cluster
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

14. LBNL: Beam Dynamics (Zisman )
(WP: )
LBNL: Beam Dynamics (Zisman )
DR: Injection and Extraction Beamlines
Optics design for injection and extraction lines for the damping rings
Tracking studies to characterize dynamics in lines (particle loss and sensitivity to errors)
April 2006: Preliminary lattice design for lines
June 2006: Complete optics design
August 2006: Complete characterization
DR: Dynamic Aperture Studies
Characterization of dynamic aperture in ring lattices including studies of injection efficiency
April 2006: Preliminary characterization
September 2006: Complete studies including injection efficiency
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

15. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 15
(WP: 2.5.5)
LBNL: “Other” Collective Effects: IBS, Space Charge, CSR (M. Venturini)
Overall of lesser concern than other instabilities
Space charge:
Shouldn’t be a problem for 6 km’s rings at 5GeV
Progress has been made in developing a model to account for the interplay of space charge, lattice coupling, and radiation in determining equilibrium emittance.
IBS:
Likely not a problem for the positron rings. For the electron ring IBS will be a factor to be considered before deciding the damping time needed
CSR:
A program for experimental studies has been started at ATF by LBLN (next slide)
Collaborators: LBNL (S. DeSantis, I. Reichel, M.Venturini),
Harvard (S. Mtingwa), FNAL (P. Spentzouris)
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

16. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 16
(WP: 2.5.5)
LBNL: “Other” Collective Effects ( cont’d)
CSR Studies at KEK-ATF
extraction
injection
stored beam
- Measurements were made in May and December 2005, using an infrared bolometer borrowed from ALS.
- Signal at injection can be explained in terms of transient behavior. However, signal from stored beam is unexpected since currents should be below CSR instability threshold.
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

17. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 17
(WP: 2.5.6)
ANL: Ring Design and Optimization (L. Emery, A. Xiao, Y.C. Chae, V. Sajaev )
Create a detailed lattice based on “OCS” of the baseline report
including inj/extr, RF cavities, wiggler, orbit & coupling corrections
Add to elegant
vertical emittance calculation, space charge effects, SVD (singular value decomposition) for orbit correction, etc
Impedance and instabilities
Single bunch limit with particle tracking with wakefield modeled from 3D codes
Application of multi-objective evolutionary optimizer for trade-off curves of different objectives
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

18. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 18
* May be reduced by 1/2
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

19. ANL: DR Baseline – Linear Lattice
(WP: 2.5.6)
ANL: DR Baseline – Linear Lattice
Arc designed for required mom. compaction
RF/Wiggler sections are designed to satisfy the requirement of equilibrium emittance and damping time.
Wiggler RF
On-Axis Injection
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

20. ANL: Multi-Objective Evolutionary Optimizer*
(WP: 2.5.6)
ANL: Multi-Objective Evolutionary Optimizer*
A software tool to reveal trade-offs of objectives in complex design*
Initialize random sets of variables (eg., # of arc cells & lengths, dipole filling factor, wiggler period, ..)
Compute violation of constraints (emittance, damping time, circumference,..) and objectives ( performance &cost such as non-linear kick, magnet count, ..)
Select best subsets of variables for mutation and crossingevaluate new population and repeat
Simplified application to a 6 km FODO ring
Example of decision: select variables corresponding to sextupole strength of 10:
Each point correspond to a
different set of variables
92 arc cell arc cell length 58 m, 6 wiggler cells, 10 m wiggler cell (fixed), m wiggler period
stronger wiggler stronger damping
weaker focusing weaker sextupole
*“A Fast and Elitist Multi-objective Genetic Algorithm: NSGA-II” , K. Deb, 2002
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

21. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 21
(WP: 3.5.1)
SLAC: E-cloud R&D Program ( M. Pivi)
Project 1: Installation of chambers with rectangular longitudinal fins (grooves) surface profile. ILC, PEP-II collaboration.
Project 2: Installation of chambers with coated samples in PEP-II. Extraction and measurements of samples SEY in the laboratory. ILC, PEP-II collaboration.
Project 3: Installation of chambers with clearing electrodes (+Voltage) in bends in PEP-II LER.
Laboratory R&D: SEY measurements and surface analysis.
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/
M. Pivi, SLAC. Mar 2006

22. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 22
(WP: 3.5.1)
SLAC: E-cloud R&D Program (Cont’d)
Curved clearing electrodes
M. Pivi – L. Wang – T. Raubenheimer - P. Raimondi, SLAC. Mar 2006
Layout of the clearing electrodes in ILC DR BEND vacuum chamber
Electric field lines for positively biased +100V clearing electrodes
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

23. Experimental Study of Fast Ion Instability at LBNL
(WP: 3.5.3)
Experimental Study of Fast Ion Instability at LBNL
People involved: J. Byrd, C. Steier, M. Venturini, A. Wolski et al.
First experimental evidence of FII at ALS in the 90’s
The ALS has made recent improvements in beam quality and instrumentation, and now offers some of the best prospects of making quantitative comparisons with theory.
One ALS machine session has already been devoted to FII. No data yet. Results expected for later this year.
Beam size in the ALS as a function of the number of bunches. J. Byrd et al, Phys. Rev. Lett. 79, (1997).
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

24. UIUC: Kicker Study at the FNAL-A0 (G. Gollin)
(WP: 3.5.4)
UIUC: Kicker Study at the FNAL-A0 (G. Gollin)
Understand properties of the 16 MeV A0 beam (underway)
Test the stripline kicker built at FNAL with fast pulsers from Cornell
Investigate possible use of a Fourier Series Kicker at the ILC, using the A0 beam to test a prototype module (simulations nearly finished)
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

25. Cornell: Prototyping of Fast Kicker Options (Palmer)
(WP: 3.5.5)
Cornell: Prototyping of Fast Kicker Options (Palmer)
Present focus is on obtaining a suitable high voltage pulser
Pulser width: wmax= 2tbunch-2tstripline ~ 4 ns, for tbunch~ 3 ns and tstripline ~ 1 ns
Have acquired a FID Technology F5201 Pulser for evaluation:
Dual channel: +/-1 kV with 0.5% - 0.7% amplitude stability
0.7 ns rise time / 2.0 ns top of pulse / 1.2 ns fall time
3 MHz max. burst rate with 15 kHz max. average rate with <20 ps timing jitter
Up to 10 kV devices available with similar specifications
Initial tests at A0 Photoinjector
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

26. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 26
(WP: 3.5.6)
Cornell: Experimental, Simulation, and Design G. Dugan, R. Helms, M. Palmer, D. Rubin, *D. Sagan, J. Smith, J. Urban, Cornell University. M. Ehrlichman, R. Poling, A. Smith, University of Minnesota.
BMAD: simulation and modeling tools
Software toolkit expanded to include spin tracking, space charge, parallelized version
Studies of space charge effects
Development of high--quality beam diagnostics systems
Prototype turn-by-turn multi-bunch vertical beam profile monitor installed and operational in CESR
Superferric option for damping wiggler
Alternate injection scheme: RF deflectors and multiple lines to separate the bunches
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

27. Cornell: Fast SR Imaging of Beam Size (J. Alexander)
(WP: 3.5.7)
Cornell: Fast SR Imaging of Beam Size (J. Alexander)
Fast detector,
Fast switch,
Slow amplifiers
Image synchrotron radiation from damping rings
Snapshots of transverse bunch shape
Measure sx, sy, distortions, rotations, etc.
Bunch-by-bunch: single bunch resolution
Possibility for CESR as test bench
Availability of nano fabrication facility
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

28. RDR and Cost Estimate Procedure (Courtesy: A. Wolski)
Priority for ILC is to produce RDR and cost estimate by end 2006
Area Systems (e.g. Damping Rings) will develop designs, and produce lists of component quantities and specifications.
Component specifications will be passed to the appropriate Technical Systems or Global Systems group (e.g. Magnets, Cryogenics), who will provide unit costs back to the Area System group.
Area Systems group will be responsible for maintaining their section of a database of component quantities, specifications and costs.
When complete, detailed costs information can be obtained easily from the database.
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

29. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 29

30. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 30
FY07 and Beyond; A Partial List (in addition to continuation of some FY06 topics)
ANL
Detailed specification: diagnostics, alignment, orbit and coupling correction, kicker reproducibility, stripline field uniformity,..
Time resolved photon diagnostics and imaging using OTR, ODR, XSR, UR & streak camera to monitor injection, emittance damping, bunch-by-bunch beam sizes
Emittance tuning study at the APS
LBNL
Electron cloud in wiggler via 3D self-consistent BD codes, WARD/POSINST
FII simulation with WARP and observation at the ALS
Technical system: vacuum, mechanical system, FB for transverse, broadband, multi-bunch instability
SLAC
High-availability fast kickers in collaboration with LLNL
Electron cloud measurement at PEP-II
BPM electronics and test at ATF-KEK
Cornell
CESR-c plan for test facility (NSF)
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

31. CESR as a Damping Ring Test Facility (Courtesy: M. Palmer)
A proposal for the NSF to convert CESR to an ILC damping ring test facility in mid-2008 at the end of CESR-c/CLEO-c
A facility to study critical beam dynamics issues:
Electron cloud
Positron operation (complementary to ATF at KEK), Wiggler-dominated, Amelioration techniques ( particularly in wigglers)
Fast ion instability
Ultra-low emittance operation
Emittances; horizontal= GeV & Vertical <10 pm
A large insert region for testing damping ring hardware with cryogenics support
A possible extraction line
All members of ILC DR community are welcome to collaborate
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/

32. Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/06 32
Summary
Several groups from national laboratories and universities in the Americas Region have been actively pursuing the damping ring R&D
Cross-comparison of results from different groups gives confidence to the conclusions
The effort has been coordinated intra-regionally via frequent teleconferences and inter-regionally via teleconferences and workshops
Most of the challenges of the DR issues have been addressed
A baseline configuration has been developed, providing a solid foundation for RDR and cost estimate
R&D tasks in the rest of FY06 and beyond are:
Detailed study and remedy of some beam dynamics issues, such as the electron cloud instabilities
Hardware development of critical technical components, such as kickers, vacuum chambers, diagnostics & control systems
Kwang-Je Kim, ILC ART Review, Fermilab, 4/4-6/