1. FFAG’07 GrenobleJ. Pasternak, LPSC Grenoble Medical Spiral FFAG (RACCAM Ring) J. Pasternak, LPSC Grenoble 1.Motivations for medical FFAG. 2.Principle of energy variability for RACCAM. 3.Design constraints. 4.Working points under study. 5.Injection/extraction geometries. 6.Betatron stacking. 7.Towards vertical tune stabilization. 8.Summary.

2. FFAG’07 GrenobleJ. Pasternak, LPSC Grenoble Motivations for medical FFAGs 1.Variable extraction energy. 2.Limited (No) use of energy degraders. 3.Cost reduction. In additon FFAGs allow for: RF manipulations Accumulation Low losses at extraction

3. FFAG’07 GrenobleJ. Pasternak, LPSC Grenoble Principle of energy variability for RACCAM system Variable extraction energy from Injector – H - cyclotron (AIMA), 7-15 MeV-see J. Mandrillon’s talk Variable magnetic field in FFAG Variable extraction energy from FFAG within 1 s (70-180 MeV) + pulse by pulse variation with kicker system

4. FFAG’07 GrenobleJ. Pasternak, LPSC Grenoble Design constraints: 1.Scaling FFAG – to allow for slow acceleration with large DA. 2.Spiral type – smaller ring (no negative bending). 3.Maximal magnetic field 1.5 T. 4.Small number of cells (7-10…). 5.Small packing factor to avoid tilting RF cavity. 6.Spiral angle as small as possible. 7.Both injection and extraction in horizontal plane. 8.Multiturn injection (about 10 turns) – fractional tune close to 0.2 (0.8). 9.Good DA.

5. FFAG’07 GrenobleJ. Pasternak, LPSC Grenoble Working points under study 8 cell, difficult injection 8 cells, large orbit excursion 10 cell QHQH QVQV

6. FFAG’07 GrenobleJ. Pasternak, LPSC Grenoble 10 cell design parameter list N 10 k 5.2 spiral angle 47.7 degree R max 3.9 m R min 3.2 m (Qx, Qy) (2.82, 1.28) B max 1.5 T Packing factor 0.34 Extraction energy 70-180 MeV

7. FFAG’07 GrenobleJ. Pasternak, LPSC Grenoble Injection Magnetic Septum Electrostatic Septum (3 MV/m) Bumper Beam Direction Bumper m m

8. FFAG’07 GrenobleJ. Pasternak, LPSC Grenoble Extraction Septum Kicker (0.04 T max field, 100 ns)

9. FFAG’07 GrenobleJ. Pasternak, LPSC Grenoble Multiturn injection by horizontal betatron stacking m rad 1 turn3 turns 7 turnsEnd of injection

10. FFAG’07 GrenobleJ. Pasternak, LPSC Grenoble Towards vertical tune stabilization Vertical tune changes with momentum (see J. Fourrier, talk). Possible cures: Variable chamfer Spiral angle as a function of R Field clamp Combination of above. Example: Change of spiral angle with R for gap shaping and constant gap magnets for 8 cell machine in order to achieve constant Q v. Gap shaping Constant gap degree m

11. FFAG’07 GrenobleJ. Pasternak, LPSC Grenoble Summary: 8 and 10 cell designs for RACCAM ring were worked out and the search for other scenarios is going on. Preliminary geometries for both injection and extraction have been identified. Multiturn injection with 50 % efficiency looks visible. To be done soon: „Scaling” magnet design. Lattice design optimization.