Front End Capture/Phase Rotation & Cooling Studies

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

2. 0utline • Introduction • ν-Factory Front end • Capture and Φ-E rotation • High Frequencybuncher/rotation • Study 2B ν-Factory • Shorter version • ν-Factory→μ+-μ- Collider • Discussion

3. Variations tried … • Study 2A – ISS baseline • Shorter bunch train example • nB= 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. 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 • P1=280 , P2=154NV = 18.032 • Match and cool (80m) • 0.75 m cells, 0.02m LiH • Captures both μ+ and μ- • ~0.2μ/(24 GeV p)

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

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 500 MeV/c -40 60m

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/p24 in ref. acceptance • Slightly better ? • ~0.24 μ/p for Study 2B baseline • 80+ m bunchtrain reduced to < 50m • Δn: 18 -> 10 500MeV/c -30 40m

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 NB= 18 case ~12 bunches (~18m) • ~0.2 μ/pref in best 12 bunches • Densest bunches are ~twice as dense as NB = 18 case

9. Details of ICOOL model (NB=10) • Drift– 56.4m • B=2T • Bunch- 31.5m • Pref,1=280MeV/c, Pref,2 =154 MeV/c, nrf = 10 • Vrf 0 to 15MV/m (0.5m rf, 0.25m drift) cells • 360 MHz  240MHz • -E Rotate – 36m – • Vrf = 15MV/m (0.5m rf, 0.25m drift) cells • NV = 10.07 (240 -> 201.5 MHz) • Match and cool (80m) • Old ICOOL transverse match to ASOL (should redo) • Pref= 220MeV/c, frf = 201.25 MHz • 0.75 m cells, 0.02m LiH, 0.5m rf, 16.00MV/m, φrf =30° • Better cooling possible (H2, stronger focussing)

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

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

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. 50 cm 201.25 MHz RF cavity 1 cm LiH 75 cm cell 23 cm vacuum Rotator 36 m long “Cool and Match” 3 m (4x75 cm cells) “Cool” 90 m of 75 cm cells MC Front End Layout in G4beamline 12.9 m 43.5 m 31.5 m 36 m rotator capture drift buncher

14. Rotator End G4Beamline ICOOL Pi+/Mu+ Pi-/Mu-

15. Cool End G4Beamline ICOOL Pi+/Mu+ Pi-/Mu-

16. 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%) Reduce number of independent frequencies

17. Accepted particles • Accepted particles fit final beam cuts: • AX + Ay < 0.03m • AL < 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 600MeV/c 0 MeV/c

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

19. “Accepted” Beam properties • For study 2A acceptance means several cuts: • AX + Ay < 0.03m • AL < 0.2m • For beam within acceptances, • εt, N,rms = 0.0036m (from ~0.007) • εL, N,rms = ~0.04m (from ~0.09) • Emittances are much smaller than the full-beam emittances … • xrms = 6cm (all-beam) • xrms = 3.6cm (accepted-beam) +30cm -30cm -30cm +30cm

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. Study 2A ASOL Bmax= 2.8T, β*=0.7m, Pmin= 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 Bmax= 1.83T, β*=1.1m, Pmax = 54 MeV/c 1.33 T for initial drift Match scaled from 2A match Use ASOL lattice rather than 2T + - B(z)

22. 2T -> ASOL

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

24. 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 First ASOL results

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

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 280 MeV/c 220 MeV/c

27. 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 εt <0.03, εL <0.2 0.093 μ/p in εt <0.045, εL <0.3 24 GeV beam 0.19 μ/p in εt <0.03, εL <0.2 0.26 μ/p in εt <0.045, εL <0.3 For Low-field lattice 1.8T ASOL 8GeV beam 0.053 μ/p in εt <0.03, εL <0.2 0.083 μ/p in εt <0.045, εL <0.3 cools only to ~0.010m Higher-Energy Simulation results

28. Discussion • 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. Any Questions?

30. Project X Status

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