April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries1 Non-Scaling FFAG Gantries Introduction: Motives: The most challenging problem in the carbon/proton cancer therapy facilities! What is scaling or non-scaling FFAG? Example of the non-scaling FFAG carbon gantry: Basic cell, orbits, betatron functions,  dependence Matching to the accelerator Scanning and focusing Magnet properties Summary

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries2 Introduction: motives The most challenging problem in the carbon/proton cancer therapy facilities: Constraints are very difficult to fulfill with the warm temperature magnets: Large B  for carbon ions requires large magnetic fields. The magnet size depends on the beam size – values of the betatron functions and dispersion are important. Matching has to be valid for any angle of the isocentric gantry. Beam scanning and choice of different spot size allows better patient treatment. Results are: very large magnets and large weight of the transfer line and the whole support.

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries3 Introduction: motives The top notch design today in Heidelberg: Heidelberg Carbon/proton gantry properties: weight of beam transport components: 135 tons total weight of rotating part 570 tons total weight of the system 630 tons diameter of rotating part 14 m length of rotating part 19 m overall length 22 m 14 meters

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries4 Introduction: Scaling FFAG B=B o (r/r o ) k (k~1500) 25 –150 cm - very large energy acceptance. - particles travel in orbits parallel to each other for different dp. - chromaticity is small. - tunes are constant. - orbit offsets are large. - magnets are large and heavy.

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries5 Introduction – Scaling FFAG: at KEK 150 MeV protons

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries6 Introduction: non-scaling FFAG Concept introduced 1999 at Montauk meeting – Trbojevic, Courant, Garren) - Extremely strong focusing with small dispersion function. - smaller energy acceptance. - tunes vary. - orbit offsets are small. - magnets are small.

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries7 Example of the non-scaling FFAG carbon gantry-cell

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries8 Example of the non-scaling FFAG carbon gantry: Submitted to The Phys. Rev. Special Topics (selected by the EPAC06 )

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries9 Example of the non-scaling FFAG carbon gantry: Example of the non-scaling FFAG carbon gantry:  functions dependence on  Goals: -Fixed field for all required energies -Small orbit offsets: small and “light” magnets. -Scanning and small spot size.

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries10 Example of the non-scaling FFAG carbon gantry: start with a design of the ring

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries11 Example of the non-scaling FFAG carbon gantry: B o = T

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries12 Example of the non-scaling FFAG carbon gantry: Example of the non-scaling FFAG carbon gantry: Betatron functions at the central energy

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries13 Initial conditions for tracking through the gantry:

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries14 Particles in x-x’ space at the end of the gantry in the energy range of 150 – 400 MeV/u for carbon ions

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries15 Particles in x-y space at the end of the gantry in the energy range of 150 – 400 MeV/u for carbon ions

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries16 Particles in y-y’ space at the end of the gantry in the energy range of 150 – 400 MeV/u for carbon ions

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries17 Matching to the accelerator: It is assumed that emittances are the same size  x =  y. (If the emittances are not equal then  x  x =  y  y.) At the point of junction to the gantry the betatron functions are equal and the dispersion function and its slope are equal to zero:  x =  y,  x =0,  y =0, D x =0, D x ’=0. These conditions are fulfilled by the matching cell. The combined function elements (dipole+quadrupole) allow the dispersion matching. The gantry rotates along the axis from the junction point (where  x =  y ).

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries18 Scanning and choosing the spot size: We have chosen:  x =  y =0.50 m. This makes the beam size of the beam with normalized emittance of  n  = 0.5 mm mrad at 150 MeV equal to  =0.265 mm or 98%= 3.29  = 0.87 mm Beam spot at the patient: The triplet has to be adjusted for each energy. The minimum spot size is obtained with setting:  x =  y =0.35 m The beam spot is scanned in both planes Properties of the new superconducting coil – it is combined with copper due to the eddy current problems. The speed of the current change - 30 A/s. It is possible to keep the voltage ~ 300 V to the ground potential (it is usually 1000 V) and this makes the current to be ~ 100 A.

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries19 Example of the non-scaling FFAG carbon gantry: Magnet properties Lengths, gradients, and bending fields: roro B max = G * r o = 52.6 T/m * 36 mm/2 ~ 1.9 T  ~2.5 m and  =0.5 mm mrad = 0.59 mm The total beam size 6  = 6 * 0.6 mm 3.6 mm Minimum aperture (mm):  36 mm

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries20 Example of the non-scaling FFAG carbon gantry:

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries21 Magnet properties Superconducting combined function magnet for the gantry

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries22 Magnet properties

April 17, Dejan TrbojevicFFAG07 -Non-Scaling FFAG gantries23Summary: Gantry made of non-scaling FFAG using superconducting combined function dipoles provides few advantages: The orbit offsets for the required energy range are very small allowing use of small magnets. Estimated weight and cost should be very small: total weight 1.5 tons with respect to 135 tons. It should be easier in operation due to fixed magnetic field in the transport elements. Similar superconducting magnets have already being built at BNL.