1. September 23, 2005ISS Plenary Meeting - Zisman International Scoping Study Accelerator Working Group: Tasks and Plans Michael S. Zisman Center for Beam Physics Accelerator & Fusion Research Division Lawrence Berkeley National Laboratory ISS Plenary Meeting–CERN September 22-24, 2005

2. September 23, 2005ISS Plenary Meeting - Zisman2 Introduction This marks the first time the ISS Accelerator Group has met together —welcome to all of you who will help us complete this task in the upcoming year —please continue to encourage your colleagues to join the effort We have a full agenda! —any interested members of the ISS are welcome to attend and contribute to the Accelerator Group o in particular, we welcome input from Detector Group on requirements that impact our design specifications Accomplishments here and plans for next meeting will be summarized tomorrow by Chris Prior

3. September 23, 2005ISS Plenary Meeting - Zisman3 Yesterday’s Agenda

4. September 23, 2005ISS Plenary Meeting - Zisman4 Today’s Agenda Palmer talk

5. September 23, 2005ISS Plenary Meeting - Zisman5 Neutrino Factory Ingredients Proton Driver —primary beam on production target Target, Capture, Decay —create , decay into  Bunching, Phase Rotation —reduce  E of bunch Cooling —reduce transverse emittance Acceleration —130 MeV  20 GeV Storage Ring —store for ~500 turns; long straight section 1-4 MW Proton Source Hg-Jet Target Decay Channel Linear Cooler Buncher Pre Accel -erator Acceleration Storage Ring ~ 1 km 5-10 GeV 10-20 GeV 1.5-5 GeV

6. September 23, 2005ISS Plenary Meeting - Zisman6 FFAG-Based Neutrino Factory Alternative design concept based on FFAG rings for phase rotation and acceleration is under study in Japan —this approach will be evaluated and compared with other designs as part of our task

7. September 23, 2005ISS Plenary Meeting - Zisman7 NF Design: Driving Issues Constructing a muon-based NF will be challenging —muons have short lifetime (2.2  s at rest) o puts premium on rapid beam manipulations –requires high-gradient NCRF for cooling (in B field) –requires presently untested ionization cooling technique –requires fast acceleration system —muons are created as a tertiary beam (p  ) o low production rate  –target that can handle multi-MW proton beam o large muon beam transverse phase space and large energy spread  –high acceptance acceleration system and storage ring

8. September 23, 2005ISS Plenary Meeting - Zisman8 Challenges Challenges go well beyond those of standard beams —developing solutions requires substantial R&D effort o R&D should aim to specify: –expected performance, technical feasibility/risk, approximate cost

9. September 23, 2005ISS Plenary Meeting - Zisman9 History (1) There have been 4½ previous NF “feasibility” studies —1 in Japan —1 in Europe —2½ in the U.S. o studies I, II, IIa

10. September 23, 2005ISS Plenary Meeting - Zisman10 History (2) Most studies focused on feasibility and performance —cost optimization was secondary, or ignored U.S. Study IIa attempted to maintain performance while reducing costs —succeeded in keeping both sign muons and substantially lowering hardware cost estimate o ISS needs to build on this philosophy (i.e., high performance, optimized cost)

11. September 23, 2005ISS Plenary Meeting - Zisman11 Why Another Study? Many different approaches have been considered —we must compare them to assess which features are optimal o in terms of performance o in terms of cost —we must include the detector in such optimizations o and the latest understanding of the physics requirements To select best approaches, must study and understand what the different regions have done —partly a team-building exercise o number of facilities likely to be built worldwide  1 –voluntarily working together toward a single design increases odds of some facility being built Prepares the way for WDS in 2007

12. September 23, 2005ISS Plenary Meeting - Zisman12 Lessons Learned Do “local” optimizations first Work as partners with engineers to converge on buildable design —scoping study does need some engineers as “consultants” Simulate entire concept before developing detailed engineering approaches —develop self-consistent solution —complete this step by the end of scoping study Facility is costly, O(€1B)

13. September 23, 2005ISS Plenary Meeting - Zisman13 Accelerator WG Organization Accelerator study program managed by “Machine Council” —R. Fernow, R. Garoby, Y. Mori, R. Palmer, C. Prior, M. Zisman Aided by Task Coordinators —Proton Driver: R. Garoby, H. Kirk, Y. Mori, C. Prior —Target/Capture: J. Lettry, K. McDonald —Phase Rotation/Bunching/Cooling: R. Fernow, K. Yoshimura —Acceleration: S. Berg, Y. Mori, C. Prior —Storage Ring: C. Johnstone, G. Rees All these people serve as “assistant pests” —recruiting people to help —assigning and coordinating tasks o we could not hope to succeed if this were a “one person show”

14. September 23, 2005ISS Plenary Meeting - Zisman14 Accelerator Study Phase 1 Study alternative configurations; arrive at baseline specifications for a system to pursue —examine both cooling and no-cooling options Develop and validate tools for end-to-end simulations of alternative facility concepts —correlations in beam and details of distributions have significant effect on transmission at interfaces (muons have “memory”) —simulation effort will tie all aspects together Goal is to complete this work within 6 months —then reach consensus on which option(s) to pursue further Making choices requires (“top-down”) cost evaluation —ISS will require engineering resources knowledgeable in accelerator and detector design

15. September 23, 2005ISS Plenary Meeting - Zisman15 Accelerator Study Phase 2 Focus on selected option(s) —as prelude to subsequent World Design Study o WDS will have more of an engineering aspect than the ISS Must develop R&D list as we proceed —identify activities that must be accomplished to develop confidence in the community that we have arrived at a design that is: o credible o cost-effective —until construction starts, R&D is what keeps the effort alive

16. September 23, 2005ISS Plenary Meeting - Zisman16 Accelerator Study Comments Must ensure common understanding of, and buy- in for, the results —best if trade-off studies include those from all regions Goal is to examine possibilities to choose the best ones —not easily done if each group “defends its own choices” Study leadership needs to foster this “regional mixing”

17. September 23, 2005ISS Plenary Meeting - Zisman17 Proton Driver Questions Optimum beam energy —depends on choice of target o consider C, Ni, Ta, Hg Optimum repetition rate —depends on target and downstream RF systems Bunch length trade-offs —need (and approaches) for bunch compression —performance implications for downstream systems Hardware options —FFAG, linac, synchrotron o compare performance, cost

18. September 23, 2005ISS Plenary Meeting - Zisman18 Proton Driver Phase 1 Examine candidate machine types for 4 MW operation —FFAG (scaling and/or non-scaling) —Linac (SPL and/or Fermilab approach) —Synchrotron (J-PARC and/or AGS approach) o consider –beam current limitations (injection, acceleration, activation) –bunch length limitations and schemes to provide 1-3 ns bunches –repetition rate limitations (power, vacuum chamber,…) –tolerances (field errors, alignment, RF stability,…) –optimization of beam energy Compare and contrast Superbeam and Neutrino Factory requirements —required emittance and focusing —how do we migrate from one to the other?

19. September 23, 2005ISS Plenary Meeting - Zisman19 Target/Capture/Decay Questions Optimum target material —solid or liquid o low, medium, or high Z Intensity limitations —from target Superbeam vs. Neutrino Factory trade-offs —horn vs. solenoid capture o can one solution serve both needs? —is a single choice of target material adequate for both?

20. September 23, 2005ISS Plenary Meeting - Zisman20 Target/Capture/Decay Phase 1 Production rates as f(E) for C, Ni, Hg —do reality check with HARP data if possible Target limitations for 4 MW operation —use guidance from FEA and experiments o consider bunch intensity, spacing, repetition rate Implications of 1 vs. 3 ns bunches on delivered beam —for various downstream rf systems Superbeam vs. Neutrino Factory comparisons —horn vs. solenoid —selected targets

21. September 23, 2005ISS Plenary Meeting - Zisman21 Bunching/  Rotation/Cooling Questions Practical accelerating gradient and cost per GeV at several frequencies (5, 88, 201 MHz) —include power sources as well as cavities Relative performance of existing schemes (KEK, CERN, U.S.-FS 2b) Optimization of cooling vs. acceleration acceptance

22. September 23, 2005ISS Plenary Meeting - Zisman22 Bunching/  Rotation/Cooling Phase 1 (1) Compare performance of existing schemes (KEK, CERN, U.S.-FS 2b) —use common proton driver and target configuration(s) —consider possibility of both signs simultaneously —conclusions will require cost comparisons, which will come later Evaluate implications of reduced V RF for each scheme —take V max = 0.75 V des and 0.5 V des o re-optimize system based on new V max, changing lattice, absorber, no. of cavities, etc. Optimize U.S.  Rotation/Bunching scheme with lower gradients and/or fewer frequencies —evaluate performance —costs will come later

23. September 23, 2005ISS Plenary Meeting - Zisman23 Bunching/  Rotation/Cooling Phase 1 (2) Evaluate trade-offs between cooling efficacy and downstream acceptance —consider several values of downstream acceptance (longitudinal and transverse) o small, medium, and large (or extra-large?) o see how much cooling channel can be simplified —develop agreed-upon figure-of-merit (e.g.,  /P prot ) —consider need/merits of longitudinal cooling —costs will come later Evaluate performance issues and limitations —absorbers (LH 2, LiH, Be or plastic) o consider implications of both sign muons —RF gradient (e.g., due to windows) —interactions with Target group recommended for this topic

24. September 23, 2005ISS Plenary Meeting - Zisman24 Acceleration Phase 1 Compare different schemes on an even footing —RLA, scaling FFAG, non-scaling FFAG, linac o consider implications of keeping both sign muons o consider not only performance but relative costs Prepare scenarios for different values of acceptance —transverse and longitudinal o small, medium, large (or extra-large?) —identify cost drivers o these will be used later to assess cost vs. acceptance Consider matching between acceleration subsystems —are there simplifications in using fewer types of machines?

25. September 23, 2005ISS Plenary Meeting - Zisman25 Storage Ring Phase 1 Design implications of final energy (20 vs. 50 GeV) Optics requirements vs. beam emittance —arcs, injection and decay straight sections Implications of keeping both sign muons —can there be both injection and decay optics in this case? Implications of two simultaneous baselines Radiation issues at 10 21 useful neutrinos per year —liner vs. open-midplane magnets Cost implications of design will be dealt with later

26. September 23, 2005ISS Plenary Meeting - Zisman26 Detector Not our responsibility…but —need to understand cost trade-offs of higher neutrino intensity vs. bigger detector —need to understand issues related to simultaneous use of both sign muons

27. September 23, 2005ISS Plenary Meeting - Zisman27 Summary Challenge is to try to reach consensus on a single optimized Neutrino Factory scheme —if we can do this ourselves, without requiring an uninvolved panel of “wise persons” to do it for us, we have truly accomplished a lot as an international community Even if we don’t quite succeed in selecting a single design, whatever convergence we attain will improve the probability of having a future international facility Developing optimal design requires an adequately- funded accelerator R&D program —we need to articulate this need and define the ingredients of the program