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

2. 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

3. April 24, 2007 LBNL Center for Beam Physics Seminar 3 The ILC Basic Numbers –500 GeV – upgradeable to 1 TeV –14 kHz Collision Rate –Luminosity: 2x10 34 cm -2 s -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

4. April 24, 2007 LBNL Center for Beam Physics Seminar 4 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

5. April 24, 2007 LBNL Center for Beam Physics Seminar 5 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

6. April 24, 2007 LBNL Center for Beam Physics Seminar 6 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)

7. April 24, 2007 LBNL Center for Beam Physics Seminar 7 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

8. April 24, 2007 LBNL Center for Beam Physics Seminar 8 The ILC Damping Rings Beam energy5 GeV Circumference6695 m RF frequency650 MHz Harmonic number14516 Injected (normalised) positron emittance 0.01 m Extracted (normalised) emittance8 μm × 20 nm Extracted energy spread<0.15% Average current400 mA Maximum particles per bunch2×10 10 Bunch length (rms)6 mm 9mm Minimum bunch separation3.08 ns 2 pm-rad geometric emittance OCS v6 TME Lattice Circled items play a key role in our local R&D plans… 250 km main linac bunch train is “folded” into the DRs

9. April 24, 2007 LBNL Center for Beam Physics Seminar 9 RDR Version of ILC DR Layout e- ring circulates in opposite direction in same central tunnel

10. April 24, 2007 LBNL Center for Beam Physics 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

11. April 24, 2007 LBNL Center for Beam Physics Seminar 11 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. Pivi ILCDR06 No additional suppression techniques assumed in dipoles and wigglers!

12. April 24, 2007 LBNL Center for Beam Physics Seminar 12 Suppressing Electron Cloud in Wigglers Strip-line type Wire type Strip-line typeWire 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. Wang ILCDR06

13. April 24, 2007 LBNL Center for Beam Physics 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

14. April 24, 2007 LBNL Center for Beam Physics Seminar 14 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

15. April 24, 2007 LBNL Center for Beam Physics 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

16. April 24, 2007 LBNL Center for Beam Physics 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

17. April 24, 2007 LBNL Center for Beam Physics 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

18. April 24, 2007 LBNL Center for Beam Physics 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

19. April 24, 2007 LBNL Center for Beam Physics Seminar 19 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

20. April 24, 2007 LBNL Center for Beam Physics Seminar 20 GaAs Detector for X-ray Imaging Signal (ADC Counts) Position (  m) Fast enough for single bunch resolution First bunch-by-bunch beam size data in CHESS conditions  Significant CHESS support  = 142 +/- 7  m Different symbols represent different bunches Pinhole camera setup at B1 hutch NEW: GaAs arrays from Hamamatsu 1x512 linear array 25  m pitch 1 st sample has recently arrived

21. April 24, 2007 LBNL Center for Beam Physics 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;

22. April 24, 2007 LBNL Center for Beam Physics 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

23. April 24, 2007 LBNL Center for Beam Physics Seminar 23 Experimental Reach ParameterValue E2.0 GeV N wiggler 12 B max 2.1 T xx 2.25 nm QxQx 14.59 QyQy 9.63 QzQz 0.075  E /E 8.6 x 10 -4  x,y 47 ms  z (with V RF =8.5MV) 9 mm cc 6.4 x 10 -3  Touschek (N b =2x10 10 ) >10 minutes Baseline Lattice

24. April 24, 2007 LBNL Center for Beam Physics Seminar 24 Tune scans Tune scans used to identify suitable working points Q x ~14.59 Q y ~9.63

25. April 24, 2007 LBNL Center for Beam Physics Seminar 25 Alternate Optics Have explored a range of optics for machine transition and physics studies LayoutEnergy (GeV) B peak (T) No. WigglersZero current  x (nm-rad) CesrTA2.02.1121.8 CESR-c2.02.166.5 CesrTA2.01.9121.9 CesrTA2.52.1123.2 CesrTA1.51.4121.3 CesrTA5.02.1626

26. April 24, 2007 LBNL Center for Beam Physics Seminar 26 Lattice Evaluation MisalignmentNominal 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

27. April 24, 2007 LBNL Center for Beam Physics Seminar 27 Vertical Emittance Sensitivities (Selected Examples)

28. April 24, 2007 LBNL Center for Beam Physics Seminar 28 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 TypeAverage Value95% Limit Orbit Only10.2 pm21.4 pm Orbit+Dispersion3.9 pm8.2 pm Nominal Values

29. April 24, 2007 LBNL Center for Beam Physics 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  -4 IBS dependence offers a flexible way to study, control and understand IBS contributions to emittance relative to other physics under consideration

30. April 24, 2007 LBNL Center for Beam Physics 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, …

31. April 24, 2007 LBNL Center for Beam Physics Seminar 31 Proposal Collaborators CollaboratorsInstitutionTopic M. Pivi and L. WangSLACElectron cloud studies, wiggler chambers for electron cloud suppression Y. Cai and PEP-II Beam Physics GroupSLACMachine correction and ultra-low emittance tuning A. Reichold and D. UrnerOxfordAlignment and survey requirements and upgrades S. Marks and R. Schlueter and M. ZismanLBNLWiggler chambers for electron cloud suppression C. Celata, M. Furman and M. VenturiniLBNLSimulation of electron cloud in wigglers A. MolvikLLNLElectron cloud measurements J. Byrd, S. de Santis, M. Venturini, and M. Zisman LBNLWiggler and electron cloud and FII studies K. HarkayANLElectron cloud measurements J. Flannagan, K. Ohmi, N. Ohuchi, K. Shibata, Y. Suetsugu, and M. Tobiyama KEKElectron cloud measurements and simulation P. Spentzouris, J. Amundsen and L. Michelotti FNALBeam dynamics simulations and measurements A. WolskiCockcroft Inst.Machine correction and ultra-low emittance tuning R. HoltzappleAlfred Univ.Instrumentation and beam measurements J. UrakawaKEKR&D program coordination L. SchächterTechnion-HaifaElectron cloud measurements and analysis Letters of intent from ~30 collaborators for direct work on CesrTA

32. April 24, 2007 LBNL Center for Beam Physics 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

33. April 24, 2007 LBNL Center for Beam Physics 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

34. April 24, 2007 LBNL Center for Beam Physics Seminar 34 Optimized Wiggler Superferric ILC-Optimized CESR-c Wiggler –12 poles (vs 14) –Period = 32 cm (vs 40) –Length = 1.68 m (vs 2.5) –B y,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)

35. April 24, 2007 LBNL Center for Beam Physics Seminar 35 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

36. April 24, 2007 LBNL Center for Beam Physics Seminar 36 EC in Wiggler Vacuum Chamber Wiggler Dipole, B=0.194T The multipacting strips of electron cloud in the wigglers is more close to the beam L. Wang, ILCDR06

37. April 24, 2007 LBNL Center for Beam Physics 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

38. April 24, 2007 LBNL Center for Beam Physics Seminar 38 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

39. April 24, 2007 LBNL Center for Beam Physics Seminar 39 Survey and Alignment collider component Rapid Tunnel Reference Surveyor (RTRS) Concept Proposal 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 technology for automated stake-out process A.Reichold D. Urner

40. April 24, 2007 LBNL Center for Beam Physics 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)

41. April 24, 2007 LBNL Center for Beam Physics Seminar 41 e+ Beam Size vs Bunch Current 2 GeV vertical bunch-by-bunch beam size for 1x45 pattern, positrons

42. April 24, 2007 LBNL Center for Beam Physics Seminar 42 Theory and measurement of instability onset 0.35 mA Qualitative comparison: if the transverse eigen-frequency of the electron cloud becomes comparable with the corresponding betatron frequency ( x c), 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

43. April 24, 2007 LBNL Center for Beam Physics Seminar 43 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 10 11 m -3 Ohmi, etal, APAC01, p.445 Positron Beam, 0.75 mA/bunch, 14 ns spacing, 1.9 GeV Operation Preliminary Results Error bars represent scatter observed during a sequence of measurements

44. April 24, 2007 LBNL Center for Beam Physics 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 Preliminary Results Negative vertical tune shift along train  consistent with EC Magnitude of shift along train is ~1/4 th of shift for positron beam NOTE: Shift continues to grow for 1 st 4 witness bunches!

45. April 24, 2007 LBNL Center for Beam Physics Seminar 45 Witness Bunch Studies – Comparison of e-/e+ Tunes Magnitude of tune shift for electron beam is ~1/4 th of shift observed for positron beam

46. April 24, 2007 LBNL Center for Beam Physics Seminar 46 Fast Ion Instability? - 45 bunch train - Electrons - 14ns spacing - 1.2e10/bunch Q h 0.6 kHz full scale Instability? Linear theory predicts 100 turn growth rate for 45 th bunch Q v 0.5 kHz full scale Vertical beam size Measurements underway to characterize mode spectra

47. April 24, 2007 LBNL Center for Beam Physics Seminar 47 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

48. April 24, 2007 LBNL Center for Beam Physics Seminar 48 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

49. April 24, 2007 LBNL Center for Beam Physics 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

50. April 24, 2007 LBNL Center for Beam Physics Seminar 50 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

51. April 24, 2007 LBNL Center for Beam Physics 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 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

52. April 24, 2007 LBNL Center for Beam Physics Seminar 52 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!

53. April 24, 2007 LBNL Center for Beam Physics Seminar 53 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