Ionization Cooling – neutrinos, colliders and beta-beams

1. Ionization Cooling – neutrinos, colliders and beta-beams David Neuffer July 2009

2. Outline • Front End and Cooling – IDS neutrino factory • Study 2A – ISS baseline example • Target-capture, Buncher, Rotator. Cooler • Shorter bunch train example(s) • nB= 10, Better for Collider; as good for ν-Factory • Variation – 88 MHz • Rf cavities in solenoids – major constraint? • up to 15MV/m, ~2T • Alternatives • Use lower fields (B, V’), use “magnetic insulation” ASOL lattice, use gas-filled rf cavities • Large Emittance Muon Collider option • Low-Energy Cooling discussion • ERIT results • Ion cooling for Beta-beams

3. Official IDS layout

4. Neutrino Factory-IDS For IDS need baseline for engineering

5. ISS Study 2B baseline • Base lattice has B=1.75T throughout buncher and rotator • rf cavities are pillbox • grouped in same-frequency clusters • 7 to 10 MV/m Buncher; 12.5 Rotator • with 200μ to 395μ Be “windows”, • 750μ windows in “Rotator” • Cooling Lattice is alternating-solenoid with 0.75 half-period • 0.5m pillbox rf cavity • 1cm LiH absorbers • 15.25MV/m cavities

6. IDS - Shorter Version • Reduce drift, buncher, rotator to get shorter bunch train: • 217m ⇒ 125m • 57m drift, 31m buncher, 36m rotator • Rf voltages up to 15MV/m (×2/3) • Obtains ~0.26 μ/p24 in ref. acceptance • Similar or better than Study 2B baseline • Better for Muon Collider • 80+ m bunchtrain reduced to < 50m • Δn: 18 -> 10 500MeV/c -30 40m

7. Shorter Buncher-Rotator settings • Buncher and Rotator have rf within ~2T fields • rf cavity/drift spacing same throughout (0.5m, 0.25) • rf gradient goes from 0 to 15 MV/m in buncher cavities • Cooling same as baseline • ASOL lattice • 1 cm LiH slabs (3.6MeV/cell) • ~15MV/m cavities • also considered H2 cooling • Simulated in G4Beamline • optimized to reduce # of frequencies • Has 20% higher gradient ASOL lattice

8. Baseline has up to 12 MV/m in B=1.75T (in 0.75m cells) short version has up to 15MV/m in B=2.0T Experiments have shown reduced gradient with magnetic field Results show close to needed ? 14MV/m at 0.75T on cavity wall half-full or half-empty ? Future experiments will explore these limits will not have 200 MHz in constant magnetic field until summer 2010 Open cell cavities in solenoids? did not show V’ /B limitation Rf in magnetic fields?

9. For IDS, we need an rf cavity + lattice that can work Potential strategies: Use lower fields (V’, B) Use Open-cell cavities? Use non-B = constant lattices alternating solenoid Magnetically insulated cavities Is it really better ??? Alternating solenoid is similar to magnetically insulated lattice Shielded rf lattices low B-field throughout rf -Rogers Use gas-filled rf cavities but electron effects? Solutions to possible rf cavity limitations

10. Lower-field (?) Variant • Use B=const for drift + buncher • Low-gradient rf ( < 6 MV/m) • B= 1.5 to 2.0 T ? • Use ASOL for rotator + Cooler (and/or H2 cavities) • 12 MV/m rf Rotator • 15 MV/m cooler • 0.75 half-cells • Simulation: fairly good acceptance • Lose some low energy mu’s • bunch train shortened • ~0.25 μ/24p after 60m H2 cooling • ~0.19 μ/24p after 60m LiH cooling

11. Be windows do not show damage at MTA no breakdown? Model: Energy deposition by electrons crossing the rf cavity causes reemission on the other side less energy deposition in Be higher rf gradient threshold ~2× gradient possible with Be cavities ?? calculated in model extrapolation to 200MHz ? Change cavity material-Palmer B electrons 2R

12. Variant: “88” MHz Front end p π→μ FE Target Solenoid Drift Buncher Rotator Cooler 10 m ~80 m ~60m 60m ~100 m • Drift ~90m • Buncher ~60m • 166→100 MHz, 0→6MV/m • Rotator ~58.5m • 100→86 MHz, 10.5 MV/m • Cooler ~100m • 85.8MHz, 10 MV/m • 1.4cm LiH/cell ASOL

13. 88 MHz example • Performance seems very good • ~0.2 μ/p24 • smaller number of bunches • > ~80% in best 10 bunches • Gradients used are not huge, but probably a bit larger than practical • up to ~10 MV/m • ~2T magnetic fields • With 10 MV/m (0.75m cells) probably not free of breakdown problems • redo with realistic gradients • 6MV/m ?

14. Plan for IDS • Need one design likely to work for Vrf/B-field • rf studies are likely to be inconclusive • Hold review to endorse a potential design for IDS • – likely to be acceptable (Vrf/B-field) • April 2010 ? • Use reviewed design as basis for IDS engineering study

15. Cooling for first muon collider • Important physics may be obtained at “small” initial luminosity μ+μ- Collider • μ+ +μ- -> Z* , HS • L > 1030 cm-2s-1 • Start with muons fron neutrino factory front end: • 3 × 1013 protons/bunch • 1.5× 1011μ/bunch • ~12 bunches – both signs! • εt,rms, normalized ≈ 0.003m εL,rms, normalized≈ 0.034m • Accelerate and store for collisions • Upgrade to high luminosity

16. Proton Source: X -> ν-Factory/μ-Collider 8GeV Linac Accumulator Buncher • Project X based proton driver • 8 GeV SRF linac , 15 Hz • 1.2×1014/cycle • H- inject full linac pulse into new “Accumulator” • “small” dp/p • Large εN6π=120π mm-mrad • Bunch in harmonic 4 • adiabatic OK !! (2kV) • Transfer into new “Buncher” • 100kV h=4 • 1250 turns (2ms) • short ~1 m bunches !! • 3×1013/bunch • BF = 0.005 • δν = 0.4

17. Large Emittance Muon Collider Use only initial “front-end” cooling Accelerate front-end bunch train; collide in ring Proton Linac 8 GeV Accumulator, Buncher Hg target Drift, Bunch, Cool 200m Linac RLAs Detector Collider Ring

18. Must be upgradeable to “high-luminosity” • MEMC Upgrades • reduce εt to 0.001m • initial part of HCC • 1300MHz rf • combine 12 -> 1bunch • L -> 3 1032 • High luminosity • Cool to 0.000025

19. Other cooling uses- not just high-energy muons! • . Stopping  beam • (for 2e, etc.) • C. Ankenbrandt, C. Yoshikawa et al., Muons, Inc. • For BCNT neutron source • Y. Mori - KURRI • For beta-beamsource • C. Rubbia et al • … (dE/ds)/E= gL(dp/ds)/p

20. Revisit Use of NF/MC Front End to Stop Muons with Momentum-dependent HCC … HCC μ± & π±from 100k POT MERIT-like targetry C Yoshikawa P(MeV/c) end of NF/MC drift region 170 μ−’s stopped Virtual detector 25 r = 3 m matching (not done) Mu-’s at end of HCC. Displayed is 5398/100k, but stopping rate is 3519/100k. 100k Mu-’s w/ Bent Sol Spread at start of HCC. Potential to enhance yield via P vs. y correlation in bent solenoid. Mu-’s midway to end of HCC (20,836/100,000)

21. Ionization cooling of protons/ ions is unattractive because nuclear reaction rate  energy-loss cooling rate But can work if the goal is beam storage to obtain nuclear reactions Absorber is beam target, add rf ERIT-P-storage ring to obtain neutron beam (Mori-Okabe, FFAG05) 10 MeV protons (β = v/c =0.145) 10Be target for neutrons 5µ Be absorber, wedge (possible) δEp=~36 keV/turn Ionization cooling effects increase beam lifetime to ~ 1000 turns not actually cooling FFAG-ERIT neutron source (Mori, KURRI)

22. Observations of “Cooling”-PAC09 • ERIT ring has been operated • Beam lifetime longer than without energy-recover rf • agrees with ICOOL simulation • Beam blowup is in agreement with simulation • multiple scattering heating in agreement with ICOOL

23. β-beam Scenario (Rubbia et al.) • β-beam – another e source • Produce accelerate, and store unstable nuclei for -decay • Example: 8B8Be + e++ν or 8Li8Be + e-+ ν* • Source production can use ionization cooling • Produce Li and inject at 25 MeV • nuclear interaction at gas jet target produces 8Li or 8B • 7Li + 2H  8Li + n • 6Li + 3He  8B + p • Multiturn storage with ionization “cooling” maximizes ion production • 8Li or 8B is ion source for β-beam accelerator • C. Rubbia, A. Ferrari, Y. Kadi, V. Vlachoudis, Nucl. Inst. and Meth. A 568, 475 (2006). • D. Neuffer, NIM A 583, p.109 (2008) e

24. β-beams example: 6Li + 3He  8B + n • Beam: 25MeV 6Li+++ • PLi =529.9 MeV/c Bρ = 0.59 T-m; v/c=0.094 Jz,0=-1.6 • Absorber:3He -gas jet ? • dE/ds = 110.6 MeV/cm , • If gx,y,z = 0.13 (Σg= 0.4), β┴=0.3m at absorber • Must mix both x and y with z • εN,eq= ~ 0.000046 m-rad, • σx,rms= ~2 cm at β┴=1m • σE,eq is ~ 0.4 MeV • Could use 3He as beam • 6Li target ( foil or liquid)

25. β-beams alternate: 6Li+3He 8B + n • Beam: 12.5MeV 3He++ • PLi =264 MeV/c Bρ = 0.44 T-m; v/c=0.094 • Absorber: 6Li - foil or liquid jet • dE/ds = 170 MeV/cm, LR=155cm • at (ρLi-6= 0.46 gm/cm3) • Space charge 2 smaller • If gx = 0.123 (Σg= 0.37), β┴=0.3m at absorber • εN,eq= ~ 0.000133m-rad • σx,rms= 2.0 cm at β┴=0.3m, • σx,rms= 5.3 cm at β┴=2.0m • σE,eq is ~ 0.3 MeV • ln[ ]=5.34

26. Cooling Ring for Beta-Beams • Assume He-3 beam • Bρ=0.44T-m, β=0.094 • Cooling ring parameters • C =12m (?) • Absorber • 0.01 cm Li wedge • βt = ~0.3m, η= ~0.3m • rf needed • 2 MV rf • Injection • charge strip He+ to He++ (?) • Extraction • kicker after wedge • NuFACT09 • miniworkshop: July27-29 rf Solenoid 1.38T-m Cooling wedge β=0.3m, η=0.3m

27. Summary • Rf in magnetic field problem must be addressed • Need rf configuration that can work with high confidence • Need to establish scenario • Use as basis for engineering study • Further meetings/studies • NuFACT 2009 • miniworkshop at Fermilab (July 27-28) • front end and beta-beam cooling • 9-11am WH3NE • 1:30-4PM • Front End Review • April 2010?

28. Future Funding … ??