1. WG2 (Proton FFAG) Summary G.H. Rees

2. Proton Driver Working Group  Participants: M. Yashimoto, S. Ohnuma, C.R. Prior, G.H. Rees, A.G. Ruggiero  Topics: FFAG or RCS proton driver for a Neutrino Factory 1 GeV, 10 MW Proton Driver:  1 kHz H  Linac + 1 kHz FFAG, or  50 Hz Proton Linac

3. Neutrino Factory Proton Driver Neutrino Factory Driver EnergyRep. rateBunches/cycle 5 GeV50 Hz4 8 GeV50 Hz6 15 GeV25 Hz8 30 GeV8 Hz8 RCS Designs: 4 MW, ~1 ns rms bunches Solutions found for: H  injection at 180 MeV Collimation Bunch Compression to 1 ns rms

4. Neutrino Factory Proton Driver FFAG  Short straights make difficulties for: H  injection Collimation  Spallation Neutron Sources favoured: Linac/compressor ring over FFAG, or RCS over FFAG (old, out-of fashion)

5. Neutrino Factory Proton Driver Possible 50 Hz Neutrino Factory Driver  180 MeV H  Linac  3 GeV Booster (  2)  8 GeV FFAG (  1) (An 8 GeV FFAG replaces two 8 GeV RCS)  If practical, would have some advantages: More rugged Able to hold bunches until needed  But: May need separate compressor ring.

6. 10 MW Proton Driver R/TFFAG 200-400 MeV H  S/CR/T 200 MeV protons 1 GeV, 50 Hz protons 1 GeV, 1 kHz protons Comparison: Capital cost + 20 year operating cost Total power levels involved are important, and Number of operating staff

7. 10 MW Proton Driver Comparison of R/T Linacs  Proton Linac has advantage: Structure power down by 1/3 May use fewer, higher peak power klystrons Requires no chopper Chopper for H  linac is beyond state of art  So, proton linac has head start over FFAG Proton Linac100 mADuty cycle 10%50 Hz H  Linac35 mADuty cycle 33%1 kHz

8. 10 MW Proton Driver 10 MW, 1 kHz FFAG  Will foil survive?  Compare with other designs, for example: 2.5 MW, 50 Hz (~20 ms cooling time)  T~1000  C,T 1000 to 2000  C (State of art injection system with H  through foil and on average 2 later traversals/proton) Particles/pulse 6.25  10 13 Injection interval0.33 ms Acceleration interval0.67 ms Foil cooling time between pulses0.67 ms

9. 10 MW Proton Driver H  Injection  Needs to be studied very carefully  State of art injection required  Programmed H and V bumps  Three free-edge corner foil  High power electron collector  Removal of unstripped beam from ring (H º )  To modify his design, A. Ruggiero has begun a study of insertions

10. 10 MW Proton Driver H  Injection (continued)  May be forced to  Or even: More compressors to solve foil heating problem E.g. 3 rings of 1/3 circumference of FFAG H  linac FFAG Compressor

11. 10 MW Proton Driver FFAG Collimation/Protection  Acceptable loss over most of ring ~ 500 Watts  Acceptable loss in dedicated collimators < 5 kW (5 parts in 10 5, 5 parts in 10 4 )  Studies at SNS, ORNL suggest  Q<0.2 for 1 part in 10 4 loss  Ruggiero design has  Q<0.35 at 200 MeV  So: injection energy 200  400 MeV?

12. 10 MW Proton Driver Collimation  No problem in designing collimators for the suggested compressor rings  Insertions may be needed for the FFAG  Note (also for an RCS): Bump magnets needed in the collimation straight insertions Vertical and horizontal bumpers needed Halo surviving to top energy may get lost on extraction elements  Note for FFAG: Beam lost longitudinally may survive at low energy  kick out before next pulse?

13. 10 MW Proton Driver Collimation  Resonance crossing may be a problem  Basic FFAG has high periodicity But if insertions are introduced, periodicity is reduced  Major effect probably space charge induced coupling at lower energies  Control of tunes likely to be needed over acceleration  Radiation hard magnets in collimation regions

14. 10 MW Proton Driver Other Thoughts  Advisable to guard against e-p instability Coating of vacuum chamber Effect of shape of vacuum chamber  Instabilities may be an issue at lower energies  Effect of stray fields of injection/extraction septa and rf cavities

15. Summary  The possible use of an FFAG in a Neutrino Factory Proton Driver has been outlined  For a 1 GeV, 10 MW proton driver, a detailed cost comparison is suggested between the two scenarios discussed  Note: In a 25 MW, 1 GeV proton driver study, the following were considered: a) 1 GeV proton linac, 50 Hz b) Three 8 MW cw cyclotrons c) Two 12.5 MW separated orbit cyclotrons It was found that a) was the cheapest option. The FFAG option was not considered.