April 25, 2006ISS Plenary Meeting: RAL - Zisman International Scoping Study Accelerator Working Group: Status and Plans Michael S. Zisman Center for Beam Physics Accelerator & Fusion Research Division Lawrence Berkeley National Laboratory ISS Plenary Meeting–RAL April 25-27, 2006

April 25, 2006ISS Plenary Meeting: RAL - Zisman2 Introduction Fourth time ISS Accelerator Group has met together —at CERN, September 2005 (Plenary meeting) —at BNL, December 2005 (Accelerator Group workshop) —at KEK, January 2006 (Accelerator Group workshop + Plenary meeting) —at RAL, April 2006 (Accelerator Group workshop + Plenary meeting) o we welcome BENE colleagues to join the effort –subscribe to NF-SB-ISS-ACCELERATOR list We have already completed 2.5 days of workshop —aiming to reach consensus on the features of a baseline configuration Accomplishments here and plans for next meeting summarized Thursday by Bob Palmer

April 25, 2006ISS Plenary Meeting: RAL - Zisman3 Workshop Agenda (1) Accelerator Group began meeting last Friday in “Workshop mode” —try to reach consensus on baseline configuration  more discussion, fewer talks Session 1 (Friday 4/21, 14:00-18:00) —Planning and Status Reports [Convener: Zisman] Session 2 (Saturday 4/22, 09:00-13:00) —Bunch Structure [Conveners: Berg, Rees] o summarize issues for Driver, Target, Front End, Acceleration, Decay Ring o Goal: agree on bunch structure (assume simult. need for  + and  – )

April 25, 2006ISS Plenary Meeting: RAL - Zisman4 Workshop Agenda (2) Session 3 (Saturday 4/22, 14:00-18:00) —Proton Driver and Target (1) [Conveners: Bennett, Kirk] o Proton Driver –compare alternatives and trade-offs –Goal: agree on optimal configuration; assess compromises from non-optimal choices o Target –compare solid vs. liquid target and solenoid vs. horn scenarios –Goal: decide on baseline target configuration Session 4 (Monday 4/24, 09:00-13:00) —Decay Ring [Conveners: Johnstone, Rees] o compare alternatives and trade-offs, in context of desired bunch structure o Goal: decide on racetrack vs. triangle, no. of rings needed, RF requirements

April 25, 2006ISS Plenary Meeting: RAL - Zisman5 Workshop Agenda (3) Session 5 (Monday 4/24, 14:00-18:00) —Cooling [Conveners: Fernow, Mori, Palmer] o compare cooling and non-cooling options, compare specific cooling implementations for optimal configuration o Goal: decide on need for cooling; if yes, pick baseline configuration

April 25, 2006ISS Plenary Meeting: RAL - Zisman6 Today’s Agenda Session 6 (Tuesday 4/25, 14:00-15:30) —Proton Driver and Target (2) [Conveners: Bennett, Kirk] o discussions aimed toward reaching target goals –liquid vs. solid target issues –collection of both sign muons “Plenary Parallel” (Tuesday 4/25, 16:00-18:00) —Conveners: Blondel, Nagashima, Zisman o Baseline bunch structure, repetition rate, baseline issues (Rees) o Siting considerations update (Prior) o Emittance measurement issues (Johnstone) Change from printed program

April 25, 2006ISS Plenary Meeting: RAL - Zisman7 Tomorrow’s Agenda Accelerator-Physics (Wednesday 4/26, 09:00-10:30) —Conveners: Nagashima, Zisman o NF-SB Proton Driver and Target comparison (Kirk) Proton Driver revisited (Wednesday 4/26, 14:00-15:30) —Convener: Bennett, Kirk o SPL update (Garoby) o RAL/Imperial linac front-end R&D (Pozimski) o Discussion of optimal proton driver parameters Accelerator Summary (Wednesday 4/26, 16:00-18:00) —Convener: Zisman o Further discussion of bunch structure issues (Rees, Berg) o Preview of Accelerator Summary talk (Palmer)

April 25, 2006ISS Plenary Meeting: RAL - Zisman8 Thursday’s Agenda Accelerator Planning (Thursday 4/27, 09:00-10:30) —Convener: Zisman o Planning for NuFact06 meeting (all) o Life after ISS (all)

April 25, 2006ISS Plenary Meeting: RAL - Zisman9 Accelerator WG Organization Accelerator study program managed by “Accelerator Council” —R. Fernow, R. Garoby, Y. Mori, R. Palmer, C. Prior, M. Zisman o meet (roughly) biweekly by phone conference –less often than this recently Aided by Task Coordinators —Proton Driver: R. Garoby, H. Kirk, Y. Mori, C. Prior —Target/Capture: J. Lettry, K. McDonald —Front End: R. Fernow, K. Yoshimura —Acceleration: S. Berg, Y. Mori, C. Prior —Decay Ring: C. Johnstone, G. Rees

April 25, 2006ISS Plenary Meeting: RAL - Zisman10 NF Design: Driving Issues Constructing a muon-based NF is 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 —neutrinos themselves are a quaternary beam o even less intensity and “a mind of their own”

April 25, 2006ISS Plenary Meeting: RAL - Zisman11 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  GeV Decay Ring —store for ~500 turns; long straight section Decay Channel Linear Cooler Buncher 1-4 MW Proton Source Hg-Jet Target Pre-Accelerator Acceleration Decay Ring ~ 1 km 5-10 GeV GeV GeV

April 25, 2006ISS Plenary Meeting: RAL - Zisman12 FFAG-Based Neutrino Factory Alternative design concept based on FFAG rings for phase rotation and acceleration is under study in Japan —this approach is being evaluated and compared with other designs as part of our task o implications of keeping both sign muons need evaluation

April 25, 2006ISS Plenary Meeting: RAL - Zisman13 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: complete this work within 6 9 months —this has going more slowly than I had initially hoped 

April 25, 2006ISS Plenary Meeting: RAL - Zisman14 Accelerator Study Phase 2 Focus on selected option(s) —as prelude to subsequent International Design Study o IDS will have more of an engineering aspect than the ISS Making choices ideally requires cost evaluation —ISS needs engineering resources knowledgeable in accelerator and detector design o not clear we’ll have the luxury of this 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

April 25, 2006ISS Plenary Meeting: RAL - Zisman15 Proton Driver Questions Optimum beam energy√ —depends on choice of target o consider C, Ta, Hg Optimum repetition rate √ —depends on target and downstream RF systems Bunch length trade-offs √ Hardware options (in progress) —FFAG, linac, synchrotron o compare performance, cost

April 25, 2006ISS Plenary Meeting: RAL - Zisman16 Optimum Energy Optimum energy for high-Z targets is broad, but drops at low-energy  – : 6 – 11 GeV  + : 9 – 19 GeV C peaks at lower energies, GeV

April 25, 2006ISS Plenary Meeting: RAL - Zisman17 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, RAL, 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?

April 25, 2006ISS Plenary Meeting: RAL - Zisman18 Target/Capture/Decay Questions Optimum target material —solid or liquid o low, medium, or high Z Intensity limitations —from target o or from beam dump, which is no easy task either 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?

April 25, 2006ISS Plenary Meeting: RAL - Zisman19 Target/Capture/Decay Phase 1 Production rates as f(E) for C, Hg, Ta √ —do reality check with HARP data if possible Target limitations for 4 MW operation (in progress) —use guidance from FEA and experiments o consider bunch intensity, spacing, repetition rate Implications of 1 vs. 3 ns bunches on production efficiency √ Superbeam vs. Neutrino Factory comparisons —horn vs. solenoid —selected targets

April 25, 2006ISS Plenary Meeting: RAL - Zisman20 Target Material Comparisons (1) Studied by Fernow, Gallardo, Brooks, Kirk —targets examined: C; Cu; Hg; Ta, all with r = 1 cm o target aligned with solenoid axis o re-interactions included —accelerator normalized acceptance o transverse: 30 mm o longitudinal: 150 mm o momentum range: 100–300 MeV/c —compared: C (5, 24 GeV); Hg (10, 24 GeV) o Hg (24 GeV) is nominal Study 2/2a “benchmark” case —proton bunch length 1 ns o performance decreases 12% for 3 ns bunch

April 25, 2006ISS Plenary Meeting: RAL - Zisman21 Target Material Comparisons (2) Results from H. Kirk

April 25, 2006ISS Plenary Meeting: RAL - Zisman22 Target Material Comparisons (3) Results —Hg at 10 GeV looks best thus far Power handling capabilities of solid target materials is still an issue —C at 4 MW still looks hard o would require frequent target changes Can required short bunches be produced at E ~ 5 GeV? Results all based on MARS predictions —need experimental data to validate

April 25, 2006ISS Plenary Meeting: RAL - Zisman23 Bunch Length Dependence Investigated by Gallardo et al. using Study 2a channel —decrease starts from zero bunch length o 1 ns is preferred, but 2-3 ns is acceptable –such short bunches harder to achieve at low beam energy —sensitivity to bunch length higher than seen in Study 2 o not yet understood in detail

April 25, 2006ISS Plenary Meeting: RAL - Zisman24 Front-End 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 (in progress) —practicality of very large acceptance for non-scaling FFAGs has been called into question o looking into this now

April 25, 2006ISS Plenary Meeting: RAL - Zisman25 Front End 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 √ 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 √ —present scheme seems reasonably well optimized

April 25, 2006ISS Plenary Meeting: RAL - Zisman26 Front End Phase 1 (2) Evaluate trade-offs between cooling efficacy and downstream acceptance —consider several values of downstream acceptance (longitudinal and transverse) (in progress) o small, medium, and large o see how much cooling channel can be simplified —large acceptance looks difficult for non-scaling FFAGs o working to understand this Evaluate performance issues and limitations —absorbers (LH 2, LiH, Be or plastic) (in progress) o consider implications of both sign muons —RF gradient (e.g., due to windows) √

April 25, 2006ISS Plenary Meeting: RAL - Zisman27 Cooling Channel Comparisons (1) Palmer has looked at all current designs — FS2, FS2a, CERN, KEK channels o more details in Accelerator summary on Thursday Performance of FS2a channel is best —includes benefits of both sign muons

April 25, 2006ISS Plenary Meeting: RAL - Zisman28 FS2a-CERN Comparisons (2) Intensity predictions —only FS2a (with both signs) meets initial Lyon goal of useful decays per year

April 25, 2006ISS Plenary Meeting: RAL - Zisman29 Acceleration Phase 1 Compare different schemes on an equal footing —RLA, scaling FFAG, non-scaling FFAG, isochronous FFAG (started) o consider implications of keeping both sign muons —need to bring scaling and non-scaling FFAG designs to same level o requires tracking codes adequate to this parameter regime Prepare scenarios for different values of acceptance —transverse and longitudinal o small, medium, large –some acceptance issues have arisen in non-scaling case (Machida) Consider matching between acceleration subsystems —are there simplifications in using fewer types of machines? o requires specific designs –not available in all cases

April 25, 2006ISS Plenary Meeting: RAL - Zisman30 Decay Ring Phase 1 Design implications of final energy (20 vs. 50 GeV) √ —can accommodate both in one ring Optics requirements vs. beam emittance √ —arcs, injection and decay straight sections Implications of keeping both sign muons (under way) —do we need two rings? o probably yes –reasons different in triangle and racetrack configurations Implications of two simultaneous baselines √ Radiation issues at useful neutrinos per year —liner vs. open-midplane magnets

April 25, 2006ISS Plenary Meeting: RAL - Zisman31 R&D Progress (1) There are two international experiments in progress —MERIT and MICE MERIT successfully tested its 15-T pulsed solenoid to full field on March 30

April 25, 2006ISS Plenary Meeting: RAL - Zisman32 R&D Progress (2) MICE has —begun preparations for muon beam line at RAL —making plans to test production target this summer (Sheffield/RAL) —obtained decay solenoid from PSI —passed external review on LH 2 R&D system —tested prototype tracker detector at KEK —sent out bid request from LBNL for two spectrometer solenoids —made preparations to test detector modules at Frascati this summer —successfully tested 201-MHz RF cavity to 16 MV/m (without magnetic field) at Fermilab MTA

April 25, 2006ISS Plenary Meeting: RAL - Zisman33 R&D Progress (3)

April 25, 2006ISS Plenary Meeting: RAL - Zisman34 Summary Making progress toward goal of reaching consensus on a single optimized Neutrino Factory scheme Must continue to articulate need for an adequately- funded accelerator R&D program —and define its ingredients Considering additional workshop —at Princeton, during week of July 24 All are welcome to participate