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

2. 2Outline  Front End and Cooling – IDS neutrino factory  Study 2A – ISS baseline example Target-capture, Buncher, Rotator. Cooler  Shorter bunch train example(s) n B = 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. 3 Official IDS layout

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

5. 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. 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/p 24 in ref. acceptance  Similar or better than Study 2B baseline  Better for Muon Collider  80+ m bunchtrain reduced to < 50m  Δn: 18 -> 10 -3040m 500MeV/c

7. 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 H 2 cooling  Simulated in G4Beamline  optimized to reduce # of frequencies  Has 20% higher gradient ASOL lattice

8. 8 Rf in magnetic fields?  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

9. 9 Solutions to possible rf cavity limitations  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?

10. 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 H 2 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 H 2 cooling  ~0.19 μ/24p after 60m LiH cooling

11. 11 Change cavity material-Palmer  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 ? B electrons 2R

12. 12 Variant: “88” MHz Front end  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 10 m~80 m FE Targ et Solenoid DriftBuncherRotatorCooler ~60m60m ~100 m p π→μ

13. 13 88 MHz example  Performance seems very good  ~0.2 μ/p 24  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. 14 Plan for IDS  Need one design likely to work for V rf /B-field  rf studies are likely to be inconclusive  Hold review to endorse a potential design for IDS  – likely to be acceptable (V rf /B-field)  April 2010 ?  Use reviewed design as basis for IDS engineering study

15. 15 Cooling for first muon collider  Important physics may be obtained at “small” initial luminosity μ + μ - Collider  μ + + μ - -> Z *, H S  L > 10 30 cm -2 s -1  Start with muons fron neutrino factory front end:  3 × 10 13 protons/bunch  1.5× 10 11 μ/bunch ~12 bunches – both signs!  ε t,rms, normalized ≈ 0.003m ε L,rms, normalized ≈ 0.034m  Accelerate and store for collisions  Upgrade to high luminosity

16. 16 Proton Source: X -> ν-Factory/μ-Collider  Project X based proton driver  8 GeV SRF linac, 15 Hz  1.2×10 14 /cycle  H- inject full linac pulse into new “Accumulator”  “small” dp/p  Large ε N6π =120π mm-mrad  Bunch in harmonic 4  adiabatic OK !! (2kV)  Transfer into new “Buncher”  100kV h=4  1250 turns (2ms)  short ~1 m bunches !!  3×10 13 /bunch B F = 0.005 δν = 0.4 8GeV Linac Accumulator Buncher

17. 17 Large Emittance Muon Collider ParameterSymbolValue Proton Beam PowerPpPp 2.4 MW Bunch frequencyFpFp 60 Hz Protons per bunchNpNp 3×10 13 Proton beam energyEpEp 8 GeV Number of bunchesnBnB 12  +/- / bunch NN 10 11 Transverse emittance  t,N 0.003m Collision  * ** 0.05m Collision  max ** 10000m Beam size at collision  x,y 0.013cm Beam size (arcs)  x,y 0.55cm Beam size IR quad  max 5.4cm Collision Beam EnergyE  +,E  _ 1 TeV (2TeV total) Storage turnsNtNt 1000 LuminosityL0L0 4×10 30 Proton Linac 8 GeV Accumulator, Buncher Hg target Linac RLAs Collider Ring Drift, Bunch, Cool 200m Detector Use only initial “front-end” cooling Accelerate front-end bunch train; collide in ring

18. 18 Must be upgradeable to “high-luminosity”  MEMC Upgrades  reduce ε t to 0.001m initial part of HCC  1300MHz rf  combine 12 -> 1bunch  L -> 3 10 32  High luminosity  Cool to 0.000025 ParameterSymbolHEMCMEMCLEMC Value Proton Beam PowerPpPp 2.4 MW4MW Bunch frequencyFpFp 60 Hz 15Hz Protons per bunchNpNp 3×10 13 5×10 13 4×10 13 Proton beam energyEpEp 8 GeV 50 GeV Number of bunchesnBnB 1211  +/- / bunch NN 10 11 1.5×10 12 2×10 12 Transverse emittance  t,N 0.003m0.001m0.000025 Collision  * ** 0.06m0.040.01 Beam size at collision  x,y 0.013cm0.0063cm0.0005cm Beam size (arcs)  x,y 0.55cm0.32cm0.05cm Beam size IR quad  max 5.4cm3.2cm0.87cm Collision EnergyE  +,E  _ 1 TeV (2TeV total) 1 TeV Luminosity turnsntnt 1000 Luminosity cm -2 s -1 L0L0 4×10 30 2.7×10 32 1.5×10 34

19. 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-beam source  C. Rubbia et al  …  (dE/ds)/  E= g L (dp/ds)/p

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

21. 21 FFAG-ERIT neutron source (Mori, KURRI)  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)  10 Be target for neutrons  5µ Be absorber, wedge (possible)  δE p =~36 keV/turn  Ionization cooling effects increase beam lifetime to ~ 1000 turns  not actually cooling

22. 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. 23 β-beam Scenario (Rubbia et al.)  β -beam – another e source  Produce accelerate, and store unstable nuclei for  -decay  Example: 8 B  8 Be + e + + ν or 8 Li  8 Be + e - + ν *  Source production can use ionization cooling  Produce Li and inject at 25 MeV  nuclear interaction at gas jet target produces 8 Li or 8 B 7 Li + 2 H  8 Li + n 6 Li + 3 He  8 B + p  Multiturn storage with ionization “cooling” maximizes ion production  8 Li or 8 B 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. 24 β-beams example: 6 Li + 3 He  8 B + n  Beam: 25MeV 6 Li +++  P Li =529.9 MeV/c Bρ = 0.59 T-m; v/c=0.094 J z,0 =-1.6  Absorber: 3 He -gas jet ?  dE/ds = 110.6 MeV/cm,  If g x,y,z = 0.13 (Σ g = 0.4), β ┴ =0.3m at absorber  Must mix both x and y with z  ε N,eq = ~ 0.000046 m-rad,  σ x,rms = ~2 cm at β ┴ =1m  σ E,eq is ~ 0.4 MeV  Could use 3 He as beam  6 Li target ( foil or liquid)

25. 25 β-beams alternate: 6 Li+ 3 He  8 B + n  Beam: 12.5MeV 3 He ++  P Li =264 MeV/c Bρ = 0.44 T-m; v/c=0.094  Absorber: 6 Li - foil or liquid jet  dE/ds = 170 MeV/cm, L R =155cm at (ρ Li-6 = 0.46 gm/cm 3 )  Space charge 2  smaller  If g x = 0.123 (Σ g = 0.37), β ┴ =0.3m at absorber  ε N,eq = ~ 0.000133m-rad  σ x,rms = 2.0 cm at β ┴ =0.3m,  σ x,rms = 5.3 cm at β ┴ =2.0m  σ E,eq is ~ 0.3 MeV  ln[ ]=5.34

26. 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  β t = ~0.3m, η= ~0.3m  rf needed  2 MV rf  Injection  charge strip He + to He ++ (?)  Extraction  kicker after wedge  NuFACT09  miniworkshop: July27-29 Solenoid 1.38T-m Cooling wedge β=0.3m, η=0.3m rf

27. 27Summary  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. 28 Future Funding … ??