Front End Studies International Design Study & Muon Collider

1. Front End StudiesInternational Design Study &Muon Collider David Neuffer December 2009

2. Outline • Front End for the Neutrino Factory/MC • Concepts developed during study 2A • Concern on Vrf’ as function of Bsol • ~200MHz, 10+ MV/m B= ~2T • Variations • Need baseline design for IDS • need baseline for engineering study • updated version to match IDS • ~lower fields; medium bunch length

3. Plan for IDS • Need one design likely to work for Vrf/B-field • rf studies are likely to be inconclusive • B=1.25T; V’ = 10MV/m is very likely to work • B= 2T; V’ = 15 MV/m should work with Be • 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

4. Potential strategies: Use lower fields (V’, B) 10MV/m at 1.5T? 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 Use gas-filled rf cavities same gradient with/without fields but electron effects? Use Be Cavities should have better B/ V’rf Solutions for possible rf cavity limitations

5. Shielded rf cooling channel (C. Rogers) • Lattice that keeps B small within rf cavities • Iron placed around coils • B < 0.25T at rf • Problems • rf occupancy ~1/3 • larger β* (~1m) • tranverse acceptance • Still has fair cooling • increases μ/p by 1.7 3m rf cavity

6. Baseline IDS candidate p π→μ FE Target Solenoid Drift Buncher Rotator Cooler 10 m ~50 m ~32m 36m up to ~100m m • ISS study based on nB = 18 ( 280 MeV/c to 154 MeV/c) • 1.75T, 12MV/m • Reference -shorter has nB = 10 ( 280 MeV/c to 154 MeV/c) • slightly higher fields (2T, 15MV/m) • Looking for candidate variation for IDS • developing intermediate case, with a bit weaker fields

7. Recent Studies on Lower Fields • Adequate acceptance can be obtained by reducing magnetic fields and gradients • B -> 1.25T, V’ -> 10 MV/m ?? • (10MV/m is 7MV/m real estate gradient; could use 7MV/m if space is filled.) • Reduced B, V’ are relatively certain to work. • Cost optimum? • B=1.5T ?, 12MV/m 0.75T, 14MV/m

8. Look at performance if V’rf is reduced • Muons per 10 8-GeV protons B=2T (B=1.25T ~5% worse) - B= 1.5T ~5% better Variation is not strong; more rf still means more muons

9. Front End ReOptimization p π→μ FE Target Solenoid Drift Buncher Rotator Cooler 18.9 m ~60.7 m ~33m 42m up to ~100m m • Change reference B-field to 1.5T • constant B to end of rotator • Redoing nB =“12” example • A bit longer than nB = 10 • optimize with lower fields • V’rf < 12 MV/m • Will see if we can get “better” optimum

10. High-frequency Buncher and φ-E Rotator p π→μ FE Target Solenoid Drift Buncher Rotator Cooler 18.9 m ~60.7 m ~33m 42 m ~80 m • Drift (π→μ) • “Adiabatically” bunch beam first (weak 320 to 232 MHz rf) • Φ-E rotate bunches – align bunches to ~equal P (233MeV/c) • 232 to 202 MHz, 12MV/m • Cool beam201.25MHz

11. Parameters of candidate release • Initial drift from target to buncher is 79.6m • 18.9m (adiabatic ~20T to ~1.5T solenoid) • 60.7m (1.5T solenoid) • Buncher rf – 33m • 320  232 MHz • 0  9 MV/m (2/3 occupancy) • B=1.5T • Rotator rf -42m • 232  202 MHz • 12 MV/m (2/3 occupancy) • B=1.5T • Cooler (50 to 90m) • ASOL lattice, P0 = 232MeV/c, • Baseline has 15MV/m, 2 1.1 cm LiH absorbers /cell 0.08 μ/p cooling 0.00

12. progression through system z =1m 80m 156m 215m 112m

13. NF Release Candidate • Front End a bit longer than “short” example • ~50m shorter than ISS, however • gradients no greater than ISS baseline • slightly better “performance” 66m bunch window

14. How Long a Bunch Train for IDS? • ISS study alotted space for 80 bunches (120m long train) • 80m or 54 bunches is probably plenty Study 2A ~80m -20 100 nB =10 ~50m 40 -30

15. Bunch train length • Within IDS design could reduce bunch train to ~80m (52 bunches) • very little mu loss • With shorter front end, could reduce that to 50m or less • For Collider scenario ~12 best bunches, (18m) contains ~70% of muons • Reserving80m for bunch trains should be adequate for IDS Study 2A 20m

16. B0 = 1.5T, nB = 12 RC • Muons per 10 8-GeV protons (At< 0.03, AL<0.02) Black are old nB = 10 example; new version is Green

17. Varying Buncher/Rotator Voltage • Vary buncher/rotator gradients from baseline to explore sensitivity to gradient limits. • same baseline cooling channel (16MV/m, 1.15cm LiH) • 15 MV/m -> 1.1cm Li H • Somewhat less sensitive than previous

18. rf requirements • Buncher • 319.63, 305.56, 293.93,285.46, 278.59, 272.05, 265.80, 259.83, 254.13, 248.67, 243.44, 238.42, 233.61 (13 f) • ~100MV total • Rotator • 230.19, 226.13, 222.59, 219.48, 216.76, 214.37,212.28, 210.46,208.64, 206.90, 205.49,204.25, 203.26, 202.63,202.33 (15 f) • 336MV total • Cooler • 201.25MHz –up to 75m ~750MV

19. Plans etc. • Move toward “realistic” configuration • More realistic B-field • B= 1.5T -> coil-based fields • add Be windows • smaller number of rf frequencies • Set up design for cost algorithm • rf cavity design (pillbox, dielectric) • rf power requirements • Magnet design • Continuing front end IDS design study • C. Rogers, G. Prior, D. Neuffer, C. Yoshikawa, K. Yonehara, Y. Alexahin, M. Popovic, Y. Torun, S. Brooks, S. Berg, J. Gallardo … • Fermilab meeting (July) • ~Biweekly phone Conference • Meeting at RAL • December 14-18 • April at Fermilab (IDS meeting) dielectric

20. IDS - cost issues …

21. Study2B June 2004 scenario (ISS) • Drift –110.7m • Bunch -51m • 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)