1. Rol - July 21, 2009 NuFact09 1 Muon Cooling for a Neutrino Factory Rolland P. Johnson Muons, Inc. (http://www.muonsinc.com/)http://www.muonsinc.com/ More muon cooling in NF designs would improve synergy between NF and MC R&D. Present designs of MC front-ends would fill NF storage rings very well. 6D muon cooling progress has been encouraging. It may well be ready for prime time when a NF is to be built. Muons, Inc.

2. Rol - July 21, 2009 NuFact09 2 Muons, Inc. Scenario for: High-Energy High-Luminosity Muon Colliders precision lepton machines at the energy frontier precision lepton machines at the energy frontier achieved in physics-motivated stages that require developing inventions and technology, e.g. achieved in physics-motivated stages that require developing inventions and technology, e.g. intense proton driver (CW Linac, H- Source, Laser Stripping)intense proton driver (CW Linac, H- Source, Laser Stripping) stopping muon beams (HCC, EEX w Homogeneous absorber)stopping muon beams (HCC, EEX w Homogeneous absorber) neutrino factory (HCC with HPRF, RLA in CW Proj-X)neutrino factory (HCC with HPRF, RLA in CW Proj-X) Z’ factory (low Luminosity collider, HE RLA)Z’ factory (low Luminosity collider, HE RLA) Higgs factory (extreme cooling, low beta, super-detectors)Higgs factory (extreme cooling, low beta, super-detectors) Energy-frontier muon collider (more cooling, lower beta)Energy-frontier muon collider (more cooling, lower beta) Muons, Inc.

3. LEMC Scenario Rol - July 21, 2009 NuFact09 3 Muons, Inc. Bogacz Dogbones Scheme

4. NF from MC front end While many aspects of MC and NF R&D are shared, muon beam cooling is an exception. In the present ISS NF scheme, relatively little transverse and no longitudinal muon cooling is required, while MC plans require at least 6 orders of magnitude 6-D cooling. MC front-ends (p-driver, target, collection, cooling, acceleration to 30 GeV) are well-suited to fill a NF storage ring, with good duty factor and high intensity. The smaller emittance due to muon cooling can reduce the cost and difficulty of the RF and magnet systems of the NF. The incorporation of more cooling into NF designs can lead to better cooperation and faster progress for both machines. A CW 8-GeV proton driver could provide sufficient beam power to do both simultaneously. Recent muon cooling progress is very encouraging. Yonehara slides from LEMC09 follow: Rol - July 21, 2009 NuFact09 4 Muons, Inc.

5. Progress of Helical Cooling Channel Design K. Yonehara APC, Fermilab Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 1

6. Work on HCC project Test high pressure RF cavity Study RF incorporating into helical magnet Improve cooling performance – Cooling factor & Transmission efficiency Phase space matching Design 6D cooling demo experiment A. Tollestrup, M. Chung M. Lopez, M. Popovic R. Abram, S. Kahn Speakers in this workshop Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 2

7. Optimization of HCC In past, mainly optimized helical magnet – Adjust dispersion function Cooling decrements Momentum slip factor In present, take into account RF parameters – Increase longitudinal acceptance Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 3

8. Clue: How to tune RF parameter HCC has sufficient size of transverse phase space acceptance HCC acceptance is limited by longitudinal phase space Increase longitudinal acceptance by increasing RF bucket Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 4

9. RF bucket dependence E = 31.4343 MV/m, ψ=160˚, L rf = 100 mm E = 16.0 MV/m, ψ=140˚, L rf = 50 mm v = 400 MHz, κ=1.0, λ=1.0 m GH2 pressure = 200 atm (at room temp) Transmission efficiency is improved by more than factor two Old designNew design Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 5 ΔE [GeV]

10. Transverse motion E = 31.4343 MV/m, ψ=160˚, L rf = 100 mm E = 16.0 MV/m, ψ=140˚, L rf = 50 mm Particle loss Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 6

11. Six-Dimensional emittance evolution in new HCC Old result v = 400 MHz, κ=1.0, λ=1.0 m GH2 pressure = 200 atm (at room temp) Cooling factor > 500 ~ 2 9 @ z = 100 m Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 7

12. Transverse vs Longitudinal phase space A 400 MHz HCC may be sufficient to accept the beam phase space after conventional frontend channel If Luminosity estimation is correct we can reach 10 34 even only HCC section (but reverse emittance exchange is still needed) 400 MHz 200 MHz 800 MHz 1600 MHz 400 MHz 800 MHz 1600 MHz 10 32 10 33 10 34 10 35 (E)PIC REMEX Hi Emit Lo Emit Muons, Inc. 8 equi. emit

13. Parameter list λ (m)κb (T)b’ (T/m)bz (T)E rf (MV/m)φ rf L rf (mm) 400 MHz HCC1.0 1.60-0.55-5.3031.46160100 800 MHz HCC0.61.02.67-1.53-8.8432.5816060 1600 MHz HCC0.31.05.33-6.10-17.732.5316030 Field parameter Average momentum = 0.25 GeV/c GH2 pressure = 200 atm @ room temp Dispersion factor = = 1.83 Length of each channel = 100 m RF cell RF length will be double to save RF power For instance, 400 MHz HCC, L rf = 200 mm, E rf = 40 MV/m HCC field can be produced with correction magnets (although it is not a final design) LEMC’09 @ Fermilab, K. Yonehara 9 Muons, Inc.

14. High Pressure RF for HCC HPRF can be operated in strong magnetic fields We do not know how HPRF works under high rad condition Dopant gas will reduce electron density in the cavity Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 10

15. HPRF simulation LEMC’09 @ Fermilab, K. Yonehara 11 Muons, Inc.

16. RF system in HCC Traveling wave RF system Lrf = 50 mm, 400 MHz helical RF Required RF power is ~2.5 GW/m!! The reason is that it has a coupling hole only at the center of cell window By putting a magnetic coupling holes on side of cell, required power is SIGNIFICANTLY reduced down to ~40 MW/m Field quality is also good (but it has a thin metallic window) First design Second design Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 12

17. Wedge shape RF system L. Thorndahl tried further challenge! He designs a wedge shape RF system Advantage: Reduce peak E field Probably, reduce number of cells Challenge: Asymmetric field distribution Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 13

18. Dielectric loaded RF Cu/Steel ceramics Vaccum/H/He Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 14

19. Possible way to put RF power RF power coupling port Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 15

20. Next-to-do More tuning up Design matching section Study RF power issue Push high pressurizing RF cavity test harder Propose dielectric loaded RF test Mechanical design of HCC Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 16

21. Conclusion A 400 MHz HCC can be a first cooling Achieve luminosity 10 34 even without extra cooling channel – but emittance exchange is still needed High pressure RF with dopant gas seems ok HPRF with beam is crucial Need to study RF power issue Dielectric loaded RF test Muons, Inc. LEMC’09 @ Fermilab, K. Yonehara 17