Muon Acceleration Who Ordered That? *

1. Muon AccelerationWho Ordered That?* Alan Bross Introduction & Limiting Technologies Accelerator Physics Center Fermilab *With apologies to I. Rabi

2. Introduction My Talk • Why Muon Accelerator Facilities? Inspirational • Nature of possible future facilities based on ultra-high intensity muon beams • What technologies are crucially central to making the above a reality. Technical R&D Overview • Where’s The Beef?* In the Next Two Talks: • Neutrino Factory to Muon Collider R. Palmer • Experiments & a Look to the Future H. Kirk *With apologies to Clara Peller & Wendy’s NuFact08 – Alan Bross

3. Who Needs Muons? • Super Beams Facilities? • No – need to be absorbed • b Beam Facilities? • Obviously not NuFact08 – Alan Bross

4. Who Needs Accelerators? With a big enough Detector – Just turn it on and let Nature do the rest Or, If we build it – It (SuperNova) will happen* *With apologies to Kevin Costner NuFact08 – Alan Bross

5. 5 MT Water Cerenkov – Big Enough? Under Ground Under Water Under ICE It’s Not a Job, Its an Adventure* *With apologies to the US Navy NuFact08 – Alan Bross

6. Muon Accelerator Facilities

7. Evolution of a Physics Program • Intense Low-energy muon physics • m e conversion experiment • Neutrino Factory • Low Energy 4 GeV • High Energy 25 GeV • Energy Frontier Muon Collider • 1.5 - 4 TeV+ PRSTAB 2002 NuFact08 – Alan Bross

8. Possible Evolution of Muon Facility Not to scale in size or cost! NuFact08 – Alan Bross

9. m e N N LFV - m to e conversion - Mu2e • Sensitive tests of Lepton Flavor Violation (LFV) • In SM occurs via n mixing • Rate well below what is experimentally accessible • Places stringent constraints on physics beyond SM • Supersymmetry • Predictions at 10-15 • Requirement – Intense low energy m beam • FFAG application • Cooling improves stopping efficiency in target of experiment • Test bed for Muon Ionization Cooling for NF and MC with intense m beam NuFact08 – Alan Bross

10. NF Motivation - Physics Reach (ISS) • The NF still gives the best Physics Reach in 3n mixing model • And NF presents best opportunity to exploit New Physics Sin22q13 Hierarchy d CP SPL: 4MW, 1MT H2OC, 130 km BL T2HK: 4 MW, 1MT H2OC, 295 km BL WBB: 2MW, 1MT H2OC, 1300 km BL NF: 4MW, 100KT MIND, 4000 & 7500 BL BB350: g=350, 1MT H2OC, 730 km BL NuFact08 – Alan Bross

11. Muon Collider - Motivation Reach Multi-TeV Lepton-Lepton Collisions at High Luminosity Muon Colliders may have special role for precision measurements. Small DE beam spread – Precise energy scans Small Footprint - Could Fit on Existing LaboratorySite NuFact08 – Alan Bross

12. The Gospel According to Snowmass NuFact08 – Alan Bross

13. But, There are always Heretics Strong Case for considering Multi-TeV Lepton Collider Stephen Martin hep-ph/0703097 March, 2007 A typical sample “compressed” Higgs and superpartner mass spectrum with WDMh2 = 0.11 An unfortunate feature, quite common to this scenario for dark matter, is that no visible superpartners would be within reach of a linear collider with √s = 500 GeV NuFact08 – Alan Bross

14. Neutrino Factory and Muon Collider Facilities

15. NF & MCAlthough Very Different – Front End Can be the Same • Neutrino Factory • IDS Baseline (FS1, FS2(a)(b), ISS) • 25 GeV m storage ring • MC: One Concept • 4 TeV Center-of-Mass • Rapid-Cycling Synchrotron Acceleration SMALL FOOTPRINT NuFact08 – Alan Bross

16. Needs Common to NF and MC Facility • Proton Driver • Project X • PD for MC likely can work for NF but not necessarily vice versa • Target, Capture, and Decay • create ’s; decay into ’s • Phase Rotation • reduce E of bunch • Cooling • reduce emittance of the muons • Cost-effective for NF • Essential for MC • Acceleration • Accelerate the Muons • Storage Ring • store for ~1000 turns 80% Overlap in initial R&D NuFact08 – Alan Bross

17. But there are Key Differences Neutrino Factory Muon Collider • Cooling • Reduce transverse emittance • ε┴ ~ 7 mm • Acceleration • Accelerate to 25 GeV • May be as low as 5-7 GeV • Storage Ring • No intersecting beams • Cooling • Reduce 6D emittance • ε┴ ~ 3-25 μm • εL ~ 70 mm • Acceleration • Accelerate to 1-2 TeV • Storage Ring • Intersecting beams NuFact08 – Alan Bross

18. Limiting Technologies andthe R&D Program

19. Key R&D Issues • High Power Targetry – NF & MC (MERIT Experiment) • Initial Cooling – NF & MC (MICE (4D Cooling)) • 200 MHz RF - NF & MC (MuCool and Muon’s Inc) • Investigate operation of vacuum RF cavities in presence of high magneticfields • Investigate Gas-Filled RF cavities • Operation in B field and Beam-Induced Effects • While obtaining high accelerating gradients (~16MV/m) • Intense 6D Cooling – MC • RFOFO “Guggenheim” • Helical Channel Cooling (MANX Proposal) • Parametric Resonance Ionization Cooling • Bunch Recombination • Acceleration– A cost driver for both NF & MC, but in very different ways • FFAG’s –( Electron Model Muon Accelerator - EMMA Demonstration) • Multi-turn RLA’s • Storage Ring(s) – NF & MC • Theoretical Studies NF & MC • Analytic Calculations • Lattice Designs • Numeric Simulations Note: Almost all R&D Issues for a NF are currently under theoretical and experimental study NuFact08 – Alan Bross

20. Muon Cooling: MuCool • MuCool • Component testing: RF, Absorbers, Solenoids • With High-Intensity Proton Beam • Uses Facility @Fermilab (MuCool Test Area –MTA) • Supports Muon Ionization Cooling Experiment (MICE) • 10 institutions from the US, UK and Japan participate MuCool Test Area 50 cm ÆBe RF window MuCool 201 MHz RF Testing MuCool LH2 Absorber Body NuFact08 – Alan Bross

21. Fundamental Focus Of RF R&D • Study the limits on Accelerating Gradient in NCRF cavities in magnetic field • It has been proposed that the behavior of RF systems in general can be accurately described (predicted) by universal curves • Electric Tensile Stresses are important in RF Breakdown events • This applies to all accelerating structures • Fundamental Importance to both NF and MC • Muon capture, bunching, phase rotation • Muon Cooling • Acceleration NuFact08 – Alan Bross

22. The Basic Problem – B Field Effect805 MHz Studies • Data seem to follow universal curve • Max stable gradient degrades quickly with B field • Remeasured • Same results >2X Reduction @ required field Gradient in MV/m Peak Magnetic Field in T at the Window NuFact08 – Alan Bross

23. 805 MHz Imaging NuFact08 – Alan Bross

24. RF R&D – 201 MHz Cavity Test • The 201 MHz Cavity – 19 MV/m Gradient Achieved (Design – 16MV/m) • At 0.75T reached 14MV/m (multipactoring observed) NuFact08 – Alan Bross

25. RF Breakdown Models Jim Norem B=0 Bob Palmer B ¹ 0 NuFact08 – Alan Bross

26. Addressing the RF Problem in Magnetic Field • Eliminate field emission • Processing Cu cavities with SCRF techniques • Atomic Layer Deposition • A CVD-like process that produces almost perfectly smooth surfaces • Prevent the magnetic focusing • Addition of coils in lattice to modify B field direction • Introduces performance loss at some level • Open cell – more power (X2) • Operate RF cavities filled with high pressure gas – H2 • Suppress breakdown with Paschen effect NuFact08 – Alan Bross

27. ALD to eliminate field emission? NuFact08 – Alan Bross • Single-cell cavity ALD coated by Jerry Moore, Jim Norem, Mike Pellin, Jeffrey Elam at Argonne • Alumina barrier layer plus niobium oxide coating • Cavity prepared and tested at JLab by Peter Kneisel • Result equaled best previous performance with no FE

28. High Pressure H2 Filled Cavity Work - Muon’s Inc • High Pressure Test Cell • Study breakdown properties of materials in H2 gas • Operation in B field • No degradation in M.S.O.G. up to » 3.5T • Next Test – Repeat with beam No Difference B=0 & B=3T NuFact08 – Alan Bross

29. Beam Test of HP Gas Filled Cavity Test of Muons Inc High Pressure H2 805 MHz test cell Beam tests will be done in collaboration with Muons Inc First test will use the existing Muons Inc test cell Will indicate direction of follow-ups experiments Linac 400MeV proton beam can generate ionization levels similar to muon beam. About 50% of protons make it into cavity, at ~100MeV/c Each proton ~5 MIPs 6e12 protons ~1.2e13 muons If successful, next step is to build realistic 805 MHz test cavity Note: Calc. Indicate severe drop in Q with beam beam Muons Inc test cell NuFact08 – Alan Bross

30. 4D Cooling for Neutrino Factory • Basically MICE (Harold will cover in detail) • 201 MHz RF • LiH or LH2 Absorbers • Solenoidal Lattice NuFact08 – Alan Bross

31. Absorber Design Issues • 2D Transverse Cooling and • Figure of merit: M=LRdEm/ds M2 (4D cooling) for different absorbers H2 is clearly Best - Neglecting Engineering Issues Windows, Safety LiH and LH2 to be studied in MICE NuFact08 – Alan Bross

32. Additional Technologies Needed for a Muon Collider • Although a great deal of R&D has been done (or is ongoing) for a Neutrino Factory and is applicable to a MC, the Technological requirements for a Muon Collider are Much More Aggressive • Bunch Merging is required • MUCH more Cooling is required ( MAKE OR BREAK FOR MC ! ) • 1000X in each transverse dimension, » 10X in longitudinal • Acceleration to much higher energy (20-40 GeV vs. 1.5-3 TeV) • Storage rings • Colliding beams • Energy loss in magnets from muon decay (electrons) is an issue Muons Inc. High pressure gas-filled cavities Helical Cooling Channel Reverse Emittance Exchange Parametric Resonance Induced Cooling Palmer et al: RFOFO Ring Guggenheim 50-60T Solenoid Channel NuFact08 – Alan Bross

33. 6 Dimensional Cooling RFOFO Ring Guggenheim “Ring” NuFact08 – Alan Bross

34. Helical Cooling Channel – Muons Inc • Magnetic field is solenoid B0+ dipole + quad • System is filled with H2 gas • Cools 6-D (large E means longer path length) • But, incorporating RF is Engineering challenge! NuFact08 – Alan Bross

35. HCC Magnet design – Fermilab TD Helical solenoid (HS): Smaller coils than in a “snake” design Smaller peak field Lower cost Field components in HS determined by geometry Over constrained Coil radius is not free parameter 4 Coil Demonstration Model Validate mechanical structure and fabrication methods Study quench performance and margins, field quality, quench protection Use SSC conductor Outer bandage rings Inner bobbin Superconducting coils (one layer, hard bend wound) NuFact08 – Alan Bross

36. MCTF Conductor Program: Extreme-High-Field Magnets • Several schemes for the final stage(s) of muon cooling for the MC require 30-50T solenoids ÞHigh Temperature Superconductor R&D (Covered by Bob) • We are working to form a National HTS R&D Program • Address very-high magnet R&D in general • Emphasis on HTS strands, tapes and cables • Nb3Sn and Nb3Al strand and cable R&D is supported by other programs (DOE, LARP, NIMS/FNAL/KEK, CARE, etc.) • Fermilab R&D infrastructure • Two Oxford Instrument Teslatron stations with 16T and 17T solenoids, and test temperatures from 1.9K to 70K • 42-strand cabling machine • Probes to measure • Ic of HTS strands and tapes as a function of field, temperature, and field orientation • Transverse pressure sensitivity of strand Ic in a cable • 28 kA SC transformer to test cables at self-field in LHe NuFact08 – Alan Bross

37. m+ m+ m- m- Acceleration - NF NuFact08 – Alan Bross

38. 201 MHz SCRF • Test results for the first cavity are Test results for the first cavity are Eacc = 11 • Making good progress on understanding the Q-slope. Making good progress on understanding the Q-slope. • Confident that we can build 200 MHz SCRF cavities with Confident that we can build 200 MHz SCRF cavities with Eacc > 17 MV NuFact08 – Alan Bross

39. 201 MHz SCRF Cryo-Modules NuFact08 – Alan Bross

40. Acceleration – Muon Collider • Many technologies are being considered • Rapid-Cycling Synchrotron (Don Summers) • RLAs based on ILC accelerating structures • Viability • Final muon beam emittance • Beam loading Bob will cover in his talk NuFact08 – Alan Bross

41. Other Issues • NF • Storage ring depth • At 30 degree dip angle presents problems at many sites to depth (certainly at Fermilab) • Not a limiting technology, but may impose significant engineering constraints and possible significant cost increasese • MC • Collider ring • Interaction region optics • Beam-induced background NuFact08 – Alan Bross

42. Conclusions • There are many strong physics cases for facilities utilizing intense muon beams • Fundamentally different from other facilities addressing the n sector • The Neutrino Factory is a natural first step towards a Muon Collider • The Muon Collider is an exciting option to reach Multi-TeV COM Lepton-Lepton Collisions • Muon Cooling is the crucial technological challenge for the Muon Collider • Muon Cooling is also important for the NF, but what is needed for the NF is technically much less challenging • Muon Cooling may extend be able to extend the reach of future LFV experiments • One of the most (the most?) critical technical issues facing both facilities is high gradient operation of RF cavities in a magnetic field • There are a number of potential solutions being pursued in parallel NuFact08 – Alan Bross