Neutrino Factory Accelerator Complex

1. Neutrino Factory Accelerator Complex Overview Michael S. Zisman, 5 March, 2011

2. Introduction • Muon-based accelerator facilities would be powerful tools in the experimentalist’s arsenal • storage ring is intense neutrino source (NF) • gives best physics reach and precision for CP violation and mass hierarchy • even if sin2 213 is large • collider explores energy frontier with leptons • complementary to LHC • likely needed to sort out the science • small footprint • would fit on existing Lab site • potential advantage of muon approach is possibility of NF  MC • Design of such facilities is challenging! NF overview - Zisman

3. Baseline Accelerator Design Goals • Intensity • 1 x 1021 neutrinos per 107-s year aimed at far detectors • that is, ~5 x 1020 of each sign • Angular divergence in production straights • ≤ 0.1/ • Muon beam energy • 25 GeV • influenced by detector threshold • and possibly by magnitude of sin2 213 • Detector baselines ( tilt angle of rings) • intermediate: 2500–5000 km • far: 7000–8000 km NF overview - Zisman

4. Neutrino Factory Ingredients • Neutrino Factory comprises these sections • Proton Driver • primary beam on production target  HARP • Target, Capture, and Decay • create ; decay into   MERIT • Bunching and Phase Rotation • reduce E of bunch • Cooling • reduce transverse emittance  MICE • Acceleration • Ek 130 MeV  25 GeV with RLAs or FFAGs  EMMA • Decay Rings • store for ~100 turns; long straight sections IDS-NF Baseline Layout NF overview - Zisman

5. Muon Accelerator Advantages • Muon-beam accelerators address several outstanding accelerator-related particle physics questions • neutrino sector • Neutrino Factory beam properties • decay kinematics well known • minimal hadronic uncertainties in the spectrum and flux • e oscillations give easily detectable “wrong-sign”  (low background) • energy frontier • point particle makes full beam energy available for particle production • couples strongly to Higgs sector • Muon Collider has almost no synchrotron radiation or beamstrahlung • narrow energy spread at IP compared with e+e– collider • reuses expensive RF equipment (circular  fits on existing Lab sites) Produces high energy e, above  threshold Unmatched sensitivity for CP violation,  mass hierarchy, and unitarity NF overview - Zisman

6. Muon Beam Challenges • Muons created as tertiary beam (p    ) • low production rate • need target that can tolerate multi-MW beam (+ source to provide it!) • large energy spread and transverse phase space • need emittance cooling • high-acceptance acceleration system and collider/decay ring • Muons have short lifetime (2.2 s at rest) • puts premium on rapid beam manipulations • high-gradient RF cavities (in magnetic field) for cooling • presently untested ionization cooling technique • fast acceleration system • decay electrons give rise to heat load in magnets and backgrounds in collider detector • R&D program aims to turn these challenges into opportunities If intense muon beams were easy to produce, we’d already have them! NF overview - Zisman

7. Precursor Studies (1) • There have been six previous NF studies • Study 1 (Fermilab + NFMCC) [2000] • showed feasibility but performance low and costs high • Study 2 (BNL + NFMCC) [2001] • acceptable performance but cost remained high • NuFact-J study [2001] • CERN Neutrino Factory study [2002] • Study 2a (APS Multidivisional Neutrino Study) [2004] • maintained performance and reduced cost by ~1/3 • ISS (first international study; ISS group) [2006] • not site-specific • examined details of alternatives and further optimized • also served as international “team-building” exercise • All emphasized physics (as opposed to engineering) design NF overview - Zisman

8. Precursor Studies (2) • IDS-NF study aims at more rigorous engineering and costing • also will carry out end-to-end simulations • all matching and transitions between sections will be defined, simulated, and costed • simulation tools will be upgraded as needed • EU members of the IDS-NF accelerator working group participate as members of EUROnu WG3 • the IDR is a only a step along that path • “big pieces” defined • little pieces (matching and transition regions) in many cases remain to be specified • Plenty of work remains before RDR is ready! NF overview - Zisman

9. Progress Since ISS (1) • Starting point was ISS baseline • since then: • several example proton driver approaches developed • reflect site-specific constraints (Section II-B and Appendices A & B of IDR) • Fermilab; RAL; CERN • add realism for future costing exercise • target concept refined • MERIT experiment showed that bunches separated by <350 s maintain pion yield • geometry of beam and Hg jet was optimized • production yield vs. Ebeam has been studied • HARP results showed initial simulations were incorrect • muon front-end systems optimized (shortened) • made initial energy deposition studies for muon front-end region • these indicate that some redesign is needed (esp. target area) NF overview - Zisman

10. Progress Since ISS (2) • explored alternative cooling lattices with more forgiving RF parameters • performed more realistic linac tracking studies • improved RLA designs • reflection symmetric focusing optics • initial chromatic correction scheme • arc-crossing chicanes • developed improved FFAG design • higher RF gradient to reduce transverse-to-longitudinal coupling • injection/extraction schemes (and hardware concepts) defined • studied decay ring diagnostics • beam energy; beam divergence • Updated design looks similar to ISS version but is more robust and better defined in most areas NF overview - Zisman

11. RDR Goals • Next big task: move toward RDR • three main goals • develop complete and technically feasible NF design having the required performance • carry out end-to-end tracking of entire facility to validate performance estimate • develop cost estimate for facility • requires component designs adequate for this purpose NF overview - Zisman

12. Steps Toward RDR (1) • AWG leaders have identified main work needed for each subsystem • Target • redesign target/capture region to permit more shielding, better cooling, and improved mechanical supports (forces) • define target station infrastructure, incl. outer shielding, remote handling, Hg cooling loop, beam windows, and beam dump • also needed for later costing exercise NF overview - Zisman

13. Steps Toward RDR (2) • Muon front end • determine (MuCool) realistic operational RF gradient limit • impacts front end design and performance • assess and mitigate energy deposition from particle losses • optimize lattice (esp. matching sections) • develop engineering design (magnets, RF, absorbers,…) • knowledge gained from MICE will inform this task • Linac and RLAs • complete lattice design (matching sections; injection; overall layout) • track through all subsystems with realistic errors • engineering design of components (magnets, RF,…) NF overview - Zisman

14. Steps Toward RDR (3) • FFAG • finalize chromatic correction scheme • determine optimal longitudinal phase space matching • design matching to upstream and downstream systems • complete 6D tracking with errors • design main components (magnets, RF, injection/extraction,…) • hardware tests of injection/extraction magnets desirable • make cost comparison with equivalent RLA solution • Decay Ring • design injection system • assess need for chromatic correction and beam abort schemes (design abort scheme if needed) • design diagnostics (polarimeter, OTR,…) • define means to determine neutrino flux spectrum at far detectors (critical for physics normalization) NF overview - Zisman

15. RDR Accelerator Task Schedule • Overall schedule consistent with physics effort • engineering effort remains a concern NF overview - Zisman

16. Accelerator Agenda • In what follows we will present • target design and alternatives • J. Back (U.-Warwick) • muon front end • C. Rogers (STFC/ASTeC) • acceleration and decay ring • J. S. Berg (BNL) N.B. Work presented in these talks includes substantial contributions from EUROnu WG3 NF overview - Zisman

17. Summary • Design of NF is well along • major subsystem designs defined (following talks) • Substantial progress has been made since completion of previous study (ISS) • work documented in IDR • Goals for RDR defined • tasks needed to achieve them identified • initial schedule for work prepared NF overview - Zisman