1. Magnetic design of a superconducting magnet for the FFAG accelerator T.Obana, T.Ogitsu A,T.Nakamoto A,K.Sasaki A A.Yamamoto A, M.Yoshimoto A, Y.Mori A,T.Origasa B The Graduate University for Advanced Studies High Energy Accelerator Research Organization A Toshiba Corporation B

2. Contents 1.Background & Purpose 2.How to generate FFAG field 3.2D &3D Calculation Results 4.Conclusion

3. Background Downsizing the FFAG accelerator is essential so that the FFAG can be widely used. High energy physics Electric power High magnetic field is required. FFAG field is constant. Superconducting magnet is proposed for FFAG accelerator. Cancer therapy

4. Purpose The purpose of this study is to develop the superconducting magnet of the FFAG accelerator. 150MeV FFAG Conventional magnet of 150MeV FFAG accelerator at KEK

5. Magnetic Field for FFAG 0 Beam tube Beam area Center of the magnet Center of the accelerator r : Distance from the accelerator center [m] R 0 : Distance between the accelerator center and the magnet center [m] B o : Magnetic field at the magnet center [T] K : K value ( Geometrical field index)

6. How to generate the FFAG Field! Di-pole Quadru-pole Sextu-pole Realize FFAG magnetic field with mutipole combination ！

7. Current distribution ++ – – X Y + + + – – – X + – Y X Y It ’ s too difficult to make a multi layer coil ! n=3 n=2 n=1 Up to n=8 I=I 0 cos(nθ) Multi layer coil

8. Current distribution – ＋ X Y Simplify! – ＋ X Y Left-Right asymmetry & Ellipse ++ – – X Y + + + – – – X + – Y X Y Downsize! With single layer Left-Right asymmetry Up to n=8 n=1 n=2 n=3

9. Major axis0.8 m Minor axis0.6 m K value10 Ro5.0 m Excursion0.4 m Turn number Bo 120 1.2 T Excursion Coil Coil parameters of FFAG for cancer therapy – ＋ X Y Current distribution FFAG FFAG for cancer therapy Energy ～ 200Mev Current ～ Several 100μA FFAG for cancer therapy High Energy Beam Low Energy Beam Cross-Section + -

10. K value & Field distribution on mid-plane@ 2D K value Field distribution Excursion Local K is used to evaluate K value. K value By/By@x=0m Positions of the conductor can be optimized in 2D!

11. Single winding@3D coil In single winding, one coil makes one layer. Y X Z X Z Y Z Y Z-Y plane Z Y Straight section Superconducting wire

12. Single winding@3D coil Coil end is large. Demerit Merit Straight length is same in each turn with 2 layers. 2 layers with 2 coils Z Y Z Y Z-Y plane Y X Z X Z Y

13. Twin winding@3D coil In twin winding, two coils make one layer. X X Z Z Y Y Z X X Z Y Z Y Z-Y plane Straight section Superconducting wire

14. Twin winding@2D coil Straight length is different in each turn. Coil end is small. Merit Demerit 1 layer with 2 coils Z Y Z Y Z-Y plane X X Z Z Y Y

15. Field distribution on mid-plane@ ３ D Field distribution on mid-plane@ ３ D Single Winding Twin Winding Coil end X Z Z X Z-X plane By/By@x=0m Trajectory X=0 m 5.8° 10.0° 0°0° Coil Center of FFAG Top view θ

16. K value @ ３ D-Result θ= 0° Single Winding Coil end 0°0° θ X=0 m 5.8° Coil Center of FFAG Top view X X Z Z Z-X plane Twin Winding K value X[m]

17. K value @ ３ D-Result θ= 2° 0°0° θ X=0 m 5.8° Coil Center of FFAG Top view 2°2° Z Z X X Z-X plane Single winding Twin winding Coil end K value

18. K value @ ３ D-Result θ= 4° Single winding Twin winding Coil end Z-X plane XX Z Z 0°0° θ X=0 m 5.8° Coil Center of FFAG Top view 4°4° K value

19. K+1 value by BL @ ３ D-Result K+1 value by BL @ ３ D-Result X=0.0 m 5.8° 10.0° 0°0° Coil Center of FFAG BL= K+1 value

20. Conclusion 2D & 3D FFAG magnetic fields are calculated. The optimizing program of the conductor position in 2D is developed. Two types of 3D coil configuration are compared in terms of K value & BL. Future plan Tracking will be done with 3D magnetic filed. Prototype of single winding coil will be made from this October.

21. What ’ s FFAG accelerator ? Can be High repetition & High Intensity ! Strong focusing in horizontal and vertical Synchrotron Constant magnetic field strength in time Cyclotron FFAG 〔 Fixed Field Alternating Gradient 〕 accelerator Properties...

22. Various Accelerators FieldFixRampFix Closed Orbit Large MoveFixSmall Move FocusingWeakStrong Duty Factor LargeSmallLarge

23. Why ’ s SC magnet required? Normal Conducting Magnets –Low Current Density< 10 A/mm2 Field by Iron Pole –Iron Saturation 2 Tesla Superconducting Magnets –High Current Density< 500 A/mm2 Field by Current –Tevatron4.5 Tesla –LHC8.4 Tesla High magnetic field can be generated by SC magnet. Accelerator size can be downsized !

24. Accelerator Driven System (ADS) FFAG Proton Reactor Core neutron Target (Uranium )

25. Winding Technique Direct Winding Superconducting wire can adhere directly to the base. Reference http://www.bnl.gov/magnets/BioMed/BioMed.asp

26. Superconducting wire Nb-Ti Cu 1.0 mm

27. How to evaluate K value Total field Local field

28. Straight length with 2 layers Single winding Z Y Z Y First Second First Second Z-Y plane Z Y Y Z Straight length with 2layers Twin winding

29. 0° 90° 180° -90° -180° (-90°) (90°) θ Expansion plane θ X Y 0° 90° -90° Twin winding Single winding

30. How to evaluate K+1 value BL= X=0.0 m θ = 0° Coil Center of accelerator θ r

31. K value & K+1 value by BL Z B Z X X-Z plane Local evaluation of the field Beam traveling direction K value K+1 value by BL Total evaluation of the field

32. How to optimize the positions of the conductor Current angle 180° SS S S S S 1.Evaluate the current distribution 2.Divide the area so as to be same

33. How to adjust the target! How to adjust the target! X[m] K+1 value X[m] K+1 value Adjust the 2D target so that K+1 can reach 3D target Difference Target Adjust target! Calculation