1. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi Accelerator Working Group summary Many thanks to all WG3 chairpersons, speakers and participants and for the poster presentations

2. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi Organization 9 sessions –Proton drivers chair M. Zisman –Capturechair K. Yoshimura –Muon source - end to end simulation - chairE. Keil Target (part 1) –Target (part 2)chair J. Pozimski –Front-endchairB. Palmer –AccelerationchairY. Mori –Experiences from operating facilitieschair T. Nakaya –Beta beamschairM. Lindroos –Beta beams and NF optimizationchairE. Wildner

3. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi Organization 2-5 talks per session Favor discussion time 6 Joint sessions (WG1 or WG4) Not a summary of all talks (apologies to speakers) Emphasize new results / ideas, possible changes in baseline requirements and possible future steps (To-Do list)

4. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi Proton Driver Session Challenging! 4 MW ->2500 Amps in 1 ns bunch Issues: Beam chopper, injection, bunch compression ->To-Do list Injection Foil issues. Use of painting techniques. Inject energy varying beam in dispersion region to change transverse positions: gives free painting! Laser stripping: Promising work at SNS - may be solution for the future. C. Prior

5. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi Proton Driver – Neutrino Factory PD updates? Mean beam power4 MW Pulse repetition rate50 Hz Proton kinetic energy5-10-15 GeV Bunch duration at target1-3 ns rms Number of bunches per pulse1-3 Separated bunch extraction delay  17 µ s Pulse duration: –liquid mercury target≤ 40 µ s –Solid metal target> 70 µ s Should we update the baseline parameters? Too premature: Require first to study consequences in each system and perform end- to-end assessment. To-Do list ≤ 150  s ? NF- IDS 01-08 C. Prior J. Pozimski M. Aiba

6. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi Proton Driver – Super Beam Baseline proton driver scenario for Super Beam –Primary proton beam energy FULLY USED THE RECENT HARP RESULTS to crosscheck simulation. And better understand the low energy behavior around 5 GeV. -> To-Do list –Main challenge: TARGET -power dissipation, thermal stress, radiation damage and COLLECTOR To-Do list M. Zito

7. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi A muon collider would likely need ~4 MW of proton power –Should plan for a further upgrade potential of factor ~2 to cover shortfalls in cooling efficiency and future luminosity upgrades Bunch rep rate on target ranges from 12-65 Hz –Not necessarily the same as linac rep rate. Flexibility can be achieved with intermediate fixed energy rings. PD energy is a design choice, not a requirement, but at least at Fermilab 8 GeV seems most attractive –Need more detailed study of intensity limitations. –Need to weigh cost of new 50 GeV ring(s) against cost of Project X linac upgrades Considerable Do-To list Proton Driver - muon collider A. Jansson Early stage of design, specifications being assessed: Design Flexibility highly desirable MC needs are much more demanding than NF

8. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi Capture Session- Horns v.s. Solenoids M. Yoshida Solenoid in Neutrino FactoryHorn in Neutrino Factory Solenoid option: lifetime limited by radiation damage -> R&D on radiation damage of insulator up to 10 MGy To-Do list Horn option: Lifetime limited by mechanical fatigue -> Need to overcome ~10 9 pulses/yr at 50 Hz To-Do list Beam dump and radiation dose in target station are an issue -> Maintenance scenario To-Do list

9. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi CAPTURE – Baseline updates? K. Yoshimura Performance, cost, maintenance should be considered to decide on the capture system Horn and solenoid: Part of handling of 4 MW facilities Experiences from operating facilities are crucial inputs One sign desired: horn is cheaper Both signs are wanted simultaneously: Solenoid is needed No need to have a common design goal for both NF and SB Neutrino Factory: Keep solenoid as baseline Super Beam: horn is probably the best option SB horn studies very active through EURO (multiple horns in p-beam – cryogenic horn) M. Dracos

10. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi Muon source – End-to-End simulation Can we share a muon source among NF, MC and low energy muon programs ? S. Geer No definitive answer but subjects for thought - Flexible proton beam structure - Cost effective solution for staging & the minimal (& possibly upgradable) Muon Collider R&D Test Facility – Updates on requirements for a low energy muon experiment facility delivering ~10 13 μ/secTo-Do list Important to not complicate an already very challenging NF/MC design Sharing muons perhaps in periods when NF, MC, or detectors are not yet available, or in fraction of the machine cycles devoted to muon physics. End to End simulation: tools ready! Simulations on To-Do list Simulation codes are now available. Codes must have an input-output compatibility to make sure we can compare results. Start point: after the target – End point: decay ring Perform simulation in sections with re-generation of beam distribution at each stage. Verify that matching regions between the sections are possible: must be done! C. Prior

11. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi Cross-sections to be fed into neutrino factory studies to find optimum design: Ta and Pb x-sections at large angle (see Eur. J. Phys C51 (2007) 787) yield/E kin ++ p+p+ M. Bonesini 1.How simulation results match experimental results? Target sessions

12. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi HARP results below 15 GeV are essential for future neutrino facilities To-Do list: Take advantage of the HARP data Revisit the estimates made in the past Any other questions from new facility designers which need to be answered? Requests for more experiments? Organize a mini-workshop dedicated to this subject to promote close collaboration between the two communities

13. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi Static Solid Targets - Graphite (or carbon composite) cooled by water/gas/radiation [CNGS, NuMI, T2K] - Tungsten or Tantalum (discs/rods/beads) cooled by water/gas [PSI, LANL] Moving Solid Targets - Rotating wheels/cylinders cooled (or heated!) off to side [SLD, FNAL, Bennett] - Continuous or discrete belts/chains [King] - Flowing powder [Densham] Solid targets To-Do list: failure tests with beam, engineering and lab. studies Flowing liquid in a vessel with beam windows [SNS, ESS] Free liquid jet [Neutrino Factory Study 2] 2- Can solid target vs. liquid target survive 4 MW? 3- What additional experimental results are needed? K. McDonald R. Edgecock Much progress J. Backand ongoing S. Brookswork reported

14. NuFact08, WG3 Valencia, 30 June-5 July D. Li, M. Meddahi To-do List: More R&D to improve the jet quality and to advance understanding of systems design issues Baseline updates? Keep Liquid Jet target as baseline for Neutrino Factories and Muon Colliders For Superbeams that will be limited in beam power to less than 2 MW –TBC- static solid targets continue to be appealing. Results to be followed-up closely Free Liquid Jet Targets H. Kirk MERIT: The Neutrino Factory/Muon Collider target concept of a free liquid jet has been validated for 4 MW operation

15. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain Summary of WG3 on Accelerator Physics and Machine Design R & D (Part 2) M. Meddahi* and D. Li Center for Beam Physics Lawrence Berkeley National Laboratory *CERN, Switzerland

16. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain Front-End & Muon Cooling PresentationsPresentations –Pros and cons of existing cooling schemes? (D. Neuffer) –Experimental tests of cooling: expected results and what else should be done? (M. Zisman) –RF issues for muon ionization cooling channels (D. Li & R. Palmer) DiscussionsDiscussions –Discussion session joint with WG4: Updates on the front end specification (if any) and endorsement

17. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain Cooling and Cooling Experiment Cooling studies and experiment:Cooling studies and experiment: –Muon Ionization Cooling is the most promising –Demonstration of ionization cooling experiment: MICE at RAL, UK

18. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain Muon Ionization Cooling: MICE Spectrometer Solenoid 2 Liquid Hydrogen Absorber and Focusing Coil (AFC) Module RF Cavity and Coupling Coil (RFCC) Module Spectrometer Solenoid 1 Trans. Emittance reduction (cooling) ~ 10% for 200-MeV/c muons Emittance measurement absolute precision ~ 0.1% (2011) M. Zisman

19. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain Technical Challenges of Cooling –Achievable accelerating gradient drops in magnetic fields 805-MHz test results 201-MHz for MuCool 19-MV/m without B19-MV/m without B 14-MV/m with stray magnetic field of 0.75-T14-MV/m with stray magnetic field of 0.75-T Experiments with high B ~ one year for SC CCExperiments with high B ~ one year for SC CC

20. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain New Model to Understand the RF Breakdown Problem Fixes discussed: HP gas, magnetic Insulation, canceling fields Fixes discussed: HP gas, magnetic Insulation, canceling fields By R. Palmer

21. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain Beta-beams Production:Production: –Neutron converters with low energy deuteron drivers (20-40 MeV) can produce copious amount of 6 He and 8 Li. Sufficient for even the more ambitious beta-beam scenarios (Micha Hass, Weizmann Inst.) R&D on the transport, bunching and ionization of ionsR&D on the transport, bunching and ionization of ions –R&D on (radiation hard) 60 GHz ECR source and duo- plasmatron source at LPSC (Thomas Thuillier, LPSC, IN2P3)

22. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain Beta-beams (cont’d) Acceleration:Acceleration: –RCS design well advanced (A. Lachaize, IPNO) (A. Lachaize, IPNO) –Could also be used for “ions for LHC” Decay Ring:Decay Ring: –Detailed design which can be used as starting point for higher energy rings and more exotically shaped rings (Antoine Chance, CEA) –Collimation: an important challenge, but simulations in progress (Pierre Delahaye, CERN) Next step:Next step: –New studies on production, ionization and magnet protection (collimation) starting in EURONU DS (Pierre Delahaye, CERN) Schematic layout of RCS ring

23. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain Beta Beams (cont ’ d) Fluxes vs Lorentz gamma issues:Fluxes vs Lorentz gamma issues: –Production of He/Ne is worked on at several laboratories with encouraging results. Li/B Production will be studied imminently and rates of 1014ions/s have been calculated. Gamma 350 needs for example 5 1013 /s out of the source. –LHC upgrades of the SPS permits Lorentz gamma 350 also for 6He Half-life increased: Higher intensity needed in decay ring, space charge problems, annual rates decrease by a factor two.Half-life increased: Higher intensity needed in decay ring, space charge problems, annual rates decrease by a factor two. Higher field magnets in decay ring or larger ring (civil engineering cost)Higher field magnets in decay ring or larger ring (civil engineering cost) If the duty cycle (needed for background suppression), can be relaxed (0.1), methods to inject into decay ring with less losses possible (barrier bucket injection)If the duty cycle (needed for background suppression), can be relaxed (0.1), methods to inject into decay ring with less losses possible (barrier bucket injection) Activation and energy deposition studies of PS, SPS and the storage ring show that losses can be mastered for annual rates of 1018, Pushing to 1019 needs additional shielding and absorption studies, including new magnet design. Open midplane magnets exist to cope with decay loss.Activation and energy deposition studies of PS, SPS and the storage ring show that losses can be mastered for annual rates of 1018, Pushing to 1019 needs additional shielding and absorption studies, including new magnet design. Open midplane magnets exist to cope with decay loss. Go stepwise, 8Li and 6He can give good intensities, then follow with 8B and 18Ne ! Then go for higher Lorentz gamma!Go stepwise, 8Li and 6He can give good intensities, then follow with 8B and 18Ne ! Then go for higher Lorentz gamma!

24. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain Horns PresentationsPresentations –Horn operational experience in K2K, NuMI and CNGS (PARDONS, Ans) –Radiation protection lessons (VINCKE, Heinz) –Delivering high intensity proton beam: lessons for the next beam generations (CHILDRESS, Sam) DiscussionsDiscussions –Challenges to deal with hot radiation environments + MW beam power –Previous operational experience: beam trips –Protection, maintenance and repair Need to be thought through even during the design phaseNeed to be thought through even during the design phase Automatic protection controls, reliable (redundant) hardware + spares (vacuum windows, BPM, monitors, …) are necessary and essentialAutomatic protection controls, reliable (redundant) hardware + spares (vacuum windows, BPM, monitors, …) are necessary and essential Use remote control and operation + robotsUse remote control and operation + robots

25. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain Acceleration: IDS Baseline Linear Pre-acceleratorLinear Pre-accelerator –244 MeV to 900 MeV RLA IRLA I  4.5 pass, 0.6 GeV/pass, (0.9 GeV to 3.6 GeV ) RLA IIRLA II – 4.5 pass, 2 GeV/pass (3.6 GeV to 12.6 GeV ) Non scaling FFAGNon scaling FFAG –12.6 GeV to 25 GeV Towards Engineering Design Foundation By A. Bogacz Acceleration Goals – Large acceptance acceleration to 25 GeV + beam ‘ shaping ’Acceleration Goals – Large acceptance acceleration to 25 GeV + beam ‘ shaping ’ Various fixed field accelerators at different stagesVarious fixed field accelerators at different stages IDS Acceleration scenario optimized to take maximum advantage of appropriate acceleration scheme at a given stageIDS Acceleration scenario optimized to take maximum advantage of appropriate acceleration scheme at a given stage Laying out engineering design foundationLaying out engineering design foundation Carry out end-to-end tracking study  Machine AcceptanceCarry out end-to-end tracking study  Machine Acceptance

26. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain FFAG Acceleration FFAG activities in JapanFFAG activities in Japan –PRISM (Osaka Univ.) phase rotation for muon physicsphase rotation for muon physics –p-FFAG (Kyusyu Univ.) 150MeV proton FFAG developed at KEK for versatile applications150MeV proton FFAG developed at KEK for versatile applications –e-FFAG (NHV corp.): 500keV 10mA e-FFAG for industrial applications500keV 10mA e-FFAG for industrial applications –ADSR study (Kyoto Univ. RRI): p- FFAGs cascade + Nuclear Critical Assemblyp- FFAGs cascade + Nuclear Critical Assembly –Neutron source (Kyoto Univ. RRI): ERIT (emittance/energy recovery internal target) with FFAGERIT (emittance/energy recovery internal target) with FFAG by Y. Mori

27. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain FFAG-ERIT Ring Beam Energy: 11-MeV Circ. Beam Current: 70-mA Beam Life-time (# of turns): 500-1000-Turns Acceptance Av > 3000-mm.mrad dp/p>+-5% (Full) dp/p>+-5% (Full)

28. Summary of WG3 – M. Meddahi & D. Li (July 5, 2008) Valencia, Spain FFAG (cont ’ d) Two-beam scaling FFAGTwo-beam scaling FFAG –Uni-directional for Mu+/Mu- Strong focusing in HNJ acceleration with multi-cavityStrong focusing in HNJ acceleration with multi-cavity –Constant RF voltage along ring radius –Large enough acceptance : Good longitudinal matching with the next non-scaling FFAG IssuesIssues –Large aperture magnet (B=2.9T) : super ferric magnet? –Wide aperture RF cavity –Increase number of turns New idea (to-do-list): Small dispersion and long straight section in (semi-) scaling FFAG?New idea (to-do-list): Small dispersion and long straight section in (semi-) scaling FFAG?