1. 1 Front End Capture/Phase Rotation & Cooling Studies David Neuffer Cary Yoshikawa December 2008

2. 20utline  Introduction  ν-Factory Front end  Capture and Φ-E rotation  High Frequency buncher/rotation Study 2B ν-Factory  Shorter version  ν-Factory →μ + -μ - Collider  Discussion

3. 3 Variations tried …  Study 2A – ISS baseline  Shorter bunch train example  n B = 10  Better for Collider; as good for ν-Factory  ICOOL/G4Beamline simulations  Study of “accepted” particles  Rf cavities in solenoids?  Use “magnetic insulation” ASOL lattice  Not too bad  Variations  Higher energy capture ??

4. 4 Study2B June 2004 scenario (ISS)  Drift –110.7m  Bunch -51m   (1/  ) =0.008  12 rf freq., 110MV  330 MHz  230MHz   -E Rotate – 54m – (416MV total)  15 rf freq. 230  202 MHz  P 1 = 280, P 2 = 154  N V = 18.032  Match and cool (80m)  0.75 m cells, 0.02m LiH  Captures both μ + and μ -  ~0.2 μ/(24 GeV p)

5. 5 Study 2B ICOOL simulation (N B =18) s = 1m s=109 m s=166m s= 216m -40 60 500 MeV/c 0 Drift Bunch Rotate 500 MeV/c 0

6. 6 Features/Flaws of Study 2B Front End  Fairly long system ~300m long (217 in B/R)  Produces long trains of ~200 MHz bunches  ~80m long (~50 bunches)  Transverse cooling is ~2½ in x and y, no longitudinal cooling  Initial Cooling is relatively weak ? -  Requires rf within magnetic fields  in current lattice, rf design; 12 MV/m at B = ~2T, 200MHz  MTA/MICE experiments to determine if practical  For Collider (Palmer)  Select peak 21 bunches  Recombine after cooling  ~1/2 lost -4060m 500 MeV/c

7. 7 Shorter Bunch train example  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  Slightly better ? ~0.24 μ/p for Study 2B baseline  80+ m bunchtrain reduced to < 50m  Δn: 18 -> 10 -3040m 500MeV/c

8. 8 Further iteration/optimization  Match to 201.25 MHz cooling channel  Reoptimize phase, frequency  f = 201.25 MHz, φ = 30º,  Obtain shorter bunch train  Choose ~best 12 bunches  ~ 21 bunch train for Collider at N B = 18 case ~12 bunches (~18m)  ~0.2 μ/p ref in best 12 bunches  Densest bunches are ~twice as dense as N B = 18 case

9. 9 Details of ICOOL model (N B =10)  Drift– 56.4m  B=2T  Bunch- 31.5m  P ref,1 =280MeV/c, P ref,2 =154 MeV/c,  n rf = 10  V rf 0 to 15MV/m (0.5m rf, 0.25m drift) cells  360 MHz  240MHz   -E Rotate – 36m –  V rf = 15MV/m (0.5m rf, 0.25m drift) cells   N V = 10.07 (240 -> 201.5 MHz)  Match and cool (80m)  Old ICOOL transverse match to ASOL (should redo)  P ref = 220MeV/c, f rf = 201.25 MHz 0.75 m cells, 0.02m LiH, 0.5m rf, 16.00MV/m, φ rf =30°  Better cooling possible (H 2, stronger focussing)

10. 10 Simulations (N B =10) -30m 30m 500 MeV/c 0 Drift and Bunch s = 89 m s = 1m Rotate s = 125 m s = 219 m Cool

11. 11 Front end simulations  Initial beam is 8GeV protons, 1ns bunch length

12. 12 Comparisons of ICOOL and G4BL  Simulations of front end and cooling agree  ICOOL and G4Beamline results can be matched  Buncher – rotator – cooler sequence can be developed in both codes  Method Captures both μ + and μ -  But some differences  dE/dx is larger in ICOOL  Phasing of rf cavities uses different model

13. 13 12.9 m43.5 m31.5 m36 m driftbuncher rotator capture MC Front End Layout in G4beamline “Cool and Match” 3 m (4x75 cm cells)“Cool” 90 m of 75 cm cells Rotator 36 m long 75 cm cell 1 cm LiH 23 cm vacuum 50 cm 201.25 MHz RF cavity

14. 14 G4BeamlineICOOL Pi+/Mu+ Pi-/Mu- Rotator End

15. 15 G4BeamlineICOOL Pi+/Mu+ Pi-/Mu- Cool End

16. 16 Reduce number of independent frequencies  Initial example had different rf frequency for each cavity  Buncher- 42 cavities -31.5m 360to 240 MHz  Rotator- 48 cavities -36m 240 to 202 MHz  Reduce # by 1/3  14 in buncher; 16 in rotator  Nearly as good capture (<5%less)  Similar to study 2B discreteness  Reduce by 1/6  7 in buncher, 8 in rotator  Significantly worse (~20%)

17. 17 Accepted particles  Accepted particles fit final beam cuts:  A X + A y < 0.03m  A L < 0.2m  Initial beam has momenta from ~75 to ~600 MeV/c  Final beam is ~200 to 300 MeV/c  Transverse emittance is cooled from ~0.014 to ~0.0036 600 MeV/c 0 MeV/c

18. 18 Accepted Longitudinal distros 1m 135m 196m -30m 40m 600 MeV/c 0 MeV/c

19. 19 “Accepted” Beam properties  For study 2A acceptance means several cuts:  A X + A y < 0.03m  A L < 0.2m  For beam within acceptances,  ε t, N,rms = 0.0036m (from ~0.007)  ε L, N,rms = ~0.04m (from ~0.09)  Emittances are much smaller than the full-beam emittances …  x rms = 6cm (all-beam)  x rms = 3.6cm (accepted-beam) -30cm +30cm -30cm +30cm

20. 20 Variations - focusing  Buncher and Rotator have rf within 2T fields  Field too strong for rf field ??  Axial field within “pill-box” cavities  Solutions ??  Open-cell cavities ??  “magnetically insulated” cavities Alternating Solenoid lattice is approximately magnetically insulated Use ASOL throughout buncher/rotator/cooler  Use gas-filled rf cavities ASOL lattice

21. 21 Use ASOL lattice rather than 2T  Study 2A ASOL  B max = 2.8T, β * =0.7m,  P min = 81MeV/c  2T for initial drift  Low energy beam is lost (P < 100MeV/c) Bunch train is truncated  OK for collider  Also tried weaker focusing ASOL  B max = 1.83T, β * =1.1m,  P max = 54 MeV/c  1.33 T for initial drift  Match scaled from 2A match + - B(z)

22. 22 2T -> ASOL

23. 23ASOL-1.33T 56m 62m 133m 193m

24. 24 First ASOL results  Simulation results  2.8T ASOL  0.18 μ/24 GeV p  0.059 μ/8 GeV p  Cools to 0.0075m  1.8T ASOL  0.198 μ/24 GeV p  0.064 μ/8 GeV p  ~10% more than stronger focussing  Cools to 0.0085m  Baseline (2T -> ASOL) had  ~0.25 μ/24 GeV p  ~0.08 μ/8 GeV p  Weaker-focusing ASOL has ~10% better acceptance than 2.8T lattice  Longer bunch train

25. 25 Variant-capture at 0.28 GeV/c 0.0 1.0GeV/c 0.0 2T → 2.8T ASOL -30m+40m-30m+40m 1.0GeV/c s=59m s=66m s=126m s=200m

26. 26 Capture at 280 MeV/c  Captures more muons than 220 MeV/c  For 2.T -> 2.8T lattice  But in larger phase space area  Less cooling for given dE/ds Δs  Better for collider  Shorter, more dense bunch train  If followed by longitudinal cooling 220 MeV/c 280 MeV/c

27. 27 Higher-Energy Simulation results  Higher energy capture improves capture for high- field lattice  Cooling is slower  Not as good for low-field lattice  Weaker focusing reduces cooling  For High field lattice:  2.8T ASOL  8GeV beam  0.065 μ/p in ε t <0.03, ε L <0.2  0.093 μ/p in ε t <0.045, ε L <0.3  24 GeV beam  0.19 μ/p in ε t <0.03, ε L <0.2  0.26 μ/p in ε t <0.045, ε L <0.3  For Low-field lattice 1.8T ASOL  8GeV beam 0.053 μ/p in ε t <0.03, ε L <0.2 0.083 μ/p in ε t <0.045, ε L <0.3 cools only to ~0.010m

28. 28Discussion  High frequency phase-energy rotation + cooling has been explored  Shorter system better for Collider  Shorter bunch train; denser bunches  “magnetic insulated” lattice could be used rather than B = 2 or 1.75 T lattice  Slightly worse performance (?) ~10 to 20% worse for neutrino factory  Ok for Collider Particles lost are at end of bunch train

29. 29 Any Questions?

30. 30 Project X Status

31. 31 High-frequency Buncher and φ-E Rotator  Form bunches first  Φ-E rotate bunches