1. November 6, 2007-Beijing (Zisman) Global Design Effort 1 Perspective on LBNL-IHEP Damping Ring EDR Activities Michael S. Zisman Center for Beam Physics Accelerator & Fusion Research Division Lawrence Berkeley National Laboratory

2. November 6, 2007-Beijing (Zisman) Global Design Effort 2 Introduction (1) LBNL has a long history of participating in storage ring designs for HEP –PEP, PEP-II, NLC-DR, ILC-DR Main LBNL activity in ILC is DR work –this is where we wish to focus LBNL participated in global DR planning effort via S3 task force –M. Zisman  A. Jackson –M. Venturini LBNL is providing DR leadership for ART also –M. Zisman  A. Jackson; also M. Palmer (Cornell)

3. November 6, 2007-Beijing (Zisman) Global Design Effort 3 Introduction (2) Tasks of interest for DR EDR effort –magnet design, vacuum system design, feedback system design, diagnostics design, mechanical integration, kicker design, injection/extraction, RF cavity design Also interested in beam dynamics R&D efforts –e.g., e-cloud, fast ions, impedance-related issues Some non-DR ILC tasks also of interest –overall timing/synchronization system of relevance to linac –general magnet and vacuum system design of relevance to RTLs and BDS

4. November 6, 2007-Beijing (Zisman) Global Design Effort 4 Introduction (3) We have a history of successful collaboration with IHEP –PEP-II quadrupoles fabricated and measured here –PEP-II dipole fabrication supervised by IHEP and these magnets also measured here We have an MOU with IHEP in place to facilitate collaborative activities And...we like Chinese food!

5. November 6, 2007-Beijing (Zisman) Global Design Effort 5 People & Resources ILC-ART resources –$795k in FY07 2.2 scientist FTEs 0.4 engineer FTEs –$1751k in FY08 2 scientist FTEs 1 engineer FTE Additional manpower support from “core” program People contributing: –J. Byrd, D. Bates, C. Celata, S. DeSantis, M. Furman, A. Jackson (program leader), S. Marks, D. Plate, G. Penn, I. Reichel, R. Schlueter, M. Venturini, J-L Vay, M. Zisman FY09 support will likely increase if overall ILC R&D budget does –unfortunately, this is not a given

6. November 6, 2007-Beijing (Zisman) Global Design Effort 6 Responding to R&D Priorities We continue to contribute to critical areas of DR EDR needs by developing new capabilities and leveraging existing LBNL expertise and resources Already engaged in, or plan to start, activities in the following very high-priority R&D areas: –Electron cloud (ongoing) –Fast ion instability (measurements at ALS planned later this year) –Single-bunch instabilities (ongoing) –Low-emittance tuning –650 MHz cavity design Additional activities include –Lattice optimization, single particle dynamics, wiggler modeling (ongoing) –Characterization of space-charge effects (mostly completed) –Design of prototype kicker meeting DR specification (to be tested at ATF/KEK); characterization of CSR at ATF/KEK (ongoing) –Multi-bunch instability, feedback systems, transients Vacuum design and mechanical integration (RDR  EDR)

7. November 6, 2007-Beijing (Zisman) Global Design Effort 7 Suppression of e-cloud Change of baseline has elevated rank of e-cloud R&D –must demonstrate that e-cloud build-up can be suppressed to the level where it is harmless Suppression techniques being investigated include grooved chambers and clearing electrodes (+ more “conventional” surface coatings) –measurements conducted at PEP-II will test both proposed remedies. Design of chamber w/ CE for experiment at PEP-II by D. Plate, LBNL Proposed design of grooved chamber for PEP-II experiment Electrode, Copper 0.04” x 1.0” x 50.0” (49.606” between feedthrough centers) Electrode, Copper 0.04” x 1.0” x 50.0” (49.606” between feedthrough centers)

8. November 6, 2007-Beijing (Zisman) Global Design Effort 8 e-cloud in Grooved Chambers Simulations show that triangular groove geometry with a sufficiently steep angle can suppress e-cloud effectively To mitigate impedance, rounding the tips would be desirable … … but it spoils the effectiveness of grooves Max. longitudinal density of e – accumulated through a 111 e+ bunch train in DR dipoles drops by 100 for  =75 o Simulations done w/ augmented version of POSINST (Venturini, Furman)  max =1.75

9. November 6, 2007-Beijing (Zisman) Global Design Effort 9 Wiggler Modeling and Simulations Progress in e-cloud experiments/measurements and simulations must go hand in hand Making a substantial investment in characterizing e-cloud in wigglers, a significant issue for DRs –use/expand integrated code suite WARP/POSINST (already successfully tested for HCX heavy ion experiment here at LBNL) –study both e-cloud build-up and e-cloud induced instabilities –ultimate-goal, a fully self-consistent simulation, very challenging but within reach LBNL to –model e-cloud measurements in wigglers –design wiggler vacuum chamber with clearing electrodes Wigglers installed at CESR-c have inspired the technology choice for current DR baseline Proposed e-cloud experiment at CesrTA

10. November 6, 2007-Beijing (Zisman) Global Design Effort 10 3D e-Cloud Code Development Using WARP-POSINST code –beam and cloud evolve self-consistently (PIC) –refined mesh gives efficient calc. of beam evolution –calculates in moving frame (~ 1000x speedup) proton bunch radius vs. z CPU time: lab frame: >2 weeks frame with  2 =512: <30 min CPU time: lab frame: >2 weeks frame with  2 =512: <30 min J.-L. Vay, PRL 98, 130405 (2007) 2D benchmark shows excellent agreement

11. November 6, 2007-Beijing (Zisman) Global Design Effort 11 Wiggler Vacuum Chamber Concept Wiggler vacuum chamber is a warm-bore insert –not integral to cryostat Design assumptions: –machined, welded aluminum with antechamber –photon power absorbed within chambers by copper absorber –pumping: NEG wafers mounted on heater for regeneration –integral cooling to minimize thermal load during regeneration –NEG coating for reduction of secondary electrons LBNL provided mechanical integration for the DRs S. Marks, D. Plate, R. Schlueter Vacuum chamber for quads in wiggler section Wiggler vacuum chamber

12. November 6, 2007-Beijing (Zisman) Global Design Effort 12 Fast Ion Instability Experimental validation of present fast ion instability models essential for DRs but largely unaccomplished New set of measurements planned for ALS promises to provide the required validation (Byrd, Steier) Use grow/damp techniques to measure growth rate under varying machine conditions and bunch train structure. First experimental evidence of Fast Ion Instability produced at ALS (ca. 1996, J. Byrd et al.) No. of bunches in bunch train y-rms size  m with He nominal pressure

13. November 6, 2007-Beijing (Zisman) Global Design Effort 13 Single-bunch Longitudinal Instabilities To avoid unacceptable emittance degradation down the linac, collective instabilities can’t be tolerated –otherwise, DRs can be “source of all evil” (Anonymous from SLAC) Collaboration w/SLAC for characterization of single- bunch dynamics based on detailed modeling of impedance sources –goal: benchmark available tools and methods Mode analysis of linearized Vlasov Eq. for longitudinal Motion may fail to give accurate Characterization of instability Venturini, ILC-DR06 Workshop Mode analysis of linearized Vlasov Eq. for longitudinal motion may fail to give accurate characterization of instability Venturini, ILC-DR06 Workshop Mode analysis Vlasov Eq. solution in time domain Vlasov Eq. solution in time domain Good agreement No agreement Mode analysis

14. November 6, 2007-Beijing (Zisman) Global Design Effort 14 Influence of Space-Charge Equilibrium emittance in a non-ideal lattice modified by space charge –radiation envelope formalism extended to account for effective modification of linear lattice due to space charge ( Venturini et al. ) Formalism being extended to include IBS Equilibrium vertical emittance for 200 random realizations of sext. displacement w/o space charge … Equilibrium vertical emittance for 200 random realizations of sext. displacement w/o space charge … … with space charge. Effect is small (current lattice) … with space charge. Effect is small (current lattice)

15. November 6, 2007-Beijing (Zisman) Global Design Effort 15 Dynamic Aperture Studies Frequency maps indicate presence of harmful resonances and suggest ways for lattice optimization OCS6 lattice suffers from reduced degree of symmetry –different working point and harmonic sextupoles improve dynamic aperture Nominal DR lattice Improved lattice regular motion chaotic motion x =52.40 y =49.31 x =52.30 y =49.275 I. Reichel, LBNL x (mm) y (mm) e + at injection x (mm)

16. November 6, 2007-Beijing (Zisman) Global Design Effort 16 Kicker Technology ATF/KEK is test bench for DR kicker technologies (pulsers, striplines, loads, feedthroughs,…) with specification close to or exceeding DR requirements Contributing to design of ATF striplines kicker structures: –demonstrate 5 mrad deflection, 2.8/5.6 ns bunch separation; stringent requirements on field decay time (DR specs: 3.1/6.2 ns; 0.6 mrad) –transform voltage pulse into a deflecting field efficiently w/o introducing undesired beam impedance –produced a kicker design; estimated impedance; transients analyzed trailing bunch enters module Time transient analysis z (m) Snapshot of field when trailing bunch Is in the middle 0.7% fluct.. S. De Santis Energy stored vs. time 9 ns Detail of the mesh (with coax for modeling bench measurement of impedance

17. November 6, 2007-Beijing (Zisman) Global Design Effort 17 Meeting Kicker Specifications variation < 1% over 5 mm Longitudinal impedance (loss factor ~ 0.1 V/pc) Analysis of deflecting field uniformity Bunch at kicker’s mid-length x (mm) Specifications likely to be met for 5.6 ns –no pulser currently available with required rise/fall time characteristics at 2.8 ns Residual uncertainty mainly connected with the development of high-voltage, high-repetition rate feedthroughs Minimizing impedance and high-order modes Z (  ) High Order Mode localized by the feedthrough

18. November 6, 2007-Beijing (Zisman) Global Design Effort 18 Universal Accelerator Parser: Undoing the Tower of Babel Different accelerator analysis programs use different input formats to describe a lattice The UAP library will provide a way to translate input files between various accelerator codes Fred designs a complicated beamline using MAD Format: SIF Eric wants to simulate this using PLACET Format: SIF doesn’t work Need to translate deck to PLACET’s native dialect! Brian wants cross-check the result using ELEGANT Algernon wants to do some BDSIM work A Tower of Babel: D. Bates in collaboration with D. Sagan, A. Wolski Ease the way of using multiple platforms to study a complex accelerator system

19. November 6, 2007-Beijing (Zisman) Global Design Effort 19 Instrumentation and Feedback Transverse feedback [Barry, Byrd] –develop model to assess noise, gain, phase margins –design prototype low-noise receiver Injection noise [Byrd, Penn] –characterize sources of jitter and develop tools for transient analysis –assess implications for feedback system design

20. November 6, 2007-Beijing (Zisman) Global Design Effort 20 LLRF Activities (1) Continued work on LLRF design for HINS –suitable for ILC also Objectives –determine stability with multiple loads (HINS) –characterize state-of-the-art components (HINS) –examine scalability + high-volume production capability In collaboration with SNS 4 14-bit 80 MS/s digitizers 2 14-bit DACs Xilinx Spartan-3 FPGA USB interface Bench tested and working

21. November 6, 2007-Beijing (Zisman) Global Design Effort 21 LLRF Activities (2) Initial test results –2.5 bits rms wideband noise –clock jitter < 0.5 ps rms Modeling –goal: to improve understanding of single klystron with multiple cavities study microphonics noise at klystron and cavity understand feedback configuration and system stability

22. November 6, 2007-Beijing (Zisman) Global Design Effort 22 Areas of Mutual Interest Recent completion of BEPC-II has greatly enhanced IHEP’s technical strengths Areas where collaboration seems natural include –hardware vacuum, magnets, power supplies, feedback, diagnostics, LLRF –simulations lattice design, dynamic aperture, low-emittance tuning instabilities –impedance-driven, e-cloud, fast-ion Both areas could include a joint experimental program at BEPC-II and ALS

23. November 6, 2007-Beijing (Zisman) Global Design Effort 23 How To Work Together Assign contact persons from each institution –suggest Jie Gao (IHEP); Alan Jackson (LBNL) Next, we should together select a few key areas and technical problems on which to collaborate –e.g., vacuum, lattice/dynamic aperture, feedback choose topics already funded either by ART or core program Selected collaborators should meet initially in person –followed by phone conferences to continue the technical interactions propose overall deliverables –define milestones and dates

24. November 6, 2007-Beijing (Zisman) Global Design Effort 24 Summary LBNL has made significant contributions to the DR design found in Baseline Configuration Document and RDR We wish to continue a strong role in ILC-DR design and focus on critical R&D areas needed to complete the EDR: –Beam dynamics Electron cloud (characterization of e-cloud in wigglers; assistance with design of experiments and data analysis) Fast Ions (measurements and validation of theory) Collective effects (space-charge effects for RTML lines; estimate of single-bunch threshold instabilities based on numerical impedance modeling) Low-emittance tuning Study of transients at injection/extraction –Engineering, design of technical systems Kickers, feedback, LLRF, vacuum, mechanical integration An LBNL-IHEP collaboration will increase technical strength of DR EDR effort –and enhance contributions of both institutions