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Compact High Current FFAG for Radioisotope Production

This paper discusses the design and performance of a compact fixed field alternating gradient (FFAG) accelerator for radioisotope production. The study includes beam dynamics, machine components, and potential performance. The next steps and conclusions are also presented.

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Compact High Current FFAG for Radioisotope Production

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  1. Compact High Current FFAG for Radioisotope Production Rob Edgecock, Roger Barlow, David Bruton, Basil Gonsalves, Carol Johnstone & Jordan Taylor Industrial partners: GE & Tesla • Reminder about FFAGs • Status of radioisotope FFAG - results from beam dynamics - first look at machine components • Potential performance • Next Steps • Conclusions

  2. FFAGs Fixed Field Alternating Gradient accelerators: • Very similar to cyclotrons • Two types (sort of): scaling and non-scaling • Scaling invented in late 1950s 20 to 400 keV machine Operated at MURA in 1956 Sector focussed cyclotron but much larger flutter and field gradient Scaling for constant betatron tunes Chandrasekhar Bohr

  3. Scaling FFAGs Re-invented in Japan in late 1990s • For muon acceleration • Has resulted in the construction of >6 scaling machines

  4. Non-scaling FFAGs 27 Invented in US in late 1990s • For muon acceleration • First type: linear non-scaling FFAG • Large beam acceptance • Parabolic time of flight 14 8 Path length Travel time /p /p

  5. First (and only) non-scaling FFAG EMMA 20MeV electron proof of principle accelerator

  6. Carbon Therapy FFAG PAMELA – non-linear non-scaling FFAG

  7. Our FFAG • More cyclotron-like • Wedge-shaped magnets • Gradient focussing • Edge focussing • Weak focussing • Allows simultaneous tune and tof control • Flat(ish) tunes • Isochronous enough for fixed RF frequency • CW operation • Three designs done: • ~ 28 MeV for radioisotope production • 330 MeV for proton therapy and proton CT • 430MeV/n for therapy with ions up to neon

  8. Radioisotope machine • Four identical wedge-shaped magnets • No reverse bend, fields to sextupole • Assumed 2 RF cavities – 200 keV/turn • Plenty of space for: - injection - extraction - instrumentation - pumps • Studied using COSY Infinity & Opal • Injection energy: 75 keV • Extraction: 10 MeV – 102cm 14 MeV – 120cm 28 MeV – 170cm

  9. Performance from tracking Time of flight Protons to 28 MeV: isochronous to 0.3%

  10. Performance from tracking Tunes Protons to 28 MeV 250 keV – just over one turn

  11. Performance from tracking Acceptances 14 MeV 10 MeV 1 MeV 20 MeV 28 MeV

  12. Performance from tracking Acceptances Protons to 28 MeV – huge! In Opal, with space charge, 20mA to 28 MeV

  13. Performance from tracking From IAEA Tech Report 465 2008

  14. Flexibility Alphas: • 28 MeV protons = 28.2 MeV α • Acceleration to 28.2 MeV works with same field map • TOF ~twice - use 1st and 2nd RF harmonics? - but with small frequency change - needs to be studied Variable energy: • 10 MeV orbit moved to 28 MeV radius by simple field scaling • TOF a little worse • Fixed by a very small tweak • But RF frequency quite different?

  15. Injection • Use external ion sources: - high beam current - more flexibility - easier to replace • But beam capture more difficult • Usually, axial injection • Various methods used to steer vertical beam into horizontal plane

  16. Injection Left dee Spiral inflector • Problems: • Complicated 3D fields • Tends to be lossy Right dee

  17. Injection • Alternative: horizontal injection • Allows higher energy • Use septum, electrostatic deflector, etc to steer beam onto EO • Separation between first two orbits >7cm, plenty of space • Beam dynamics under investigation

  18. Magnet Concepts • Sector gradient magnets • Scaling FFAGs and AVF cyclotrons (higher energy cyclotrons have gradient magnets) • Several designs under study • Vary gap size as a function of energy to create increasing gradient • Coils - TRIUMF and PSI cyclotrons have coils to tune gradients • Hybrid designs exploiting permanent magnet yoke material with electromagnets High energy gradient magnet (left) and hybrid permanent magnet design (right) which can be scaled to achieve the correct radial gradient. Coils can be added to slots in poles in both designs.

  19. Cavities • Initial thoughts only • Use cyclotron Dee cavity designs: - 2 cavities - double gap(?) - 50 kV/gap - tunable for α’s • Main issue: gap at low energy - higher energy injection?- variable voltage with energy • Central region needs optimisation • Need expert input! PSI injector double gap cavity 400 kV/gap

  20. Target Options Two possibilities • Internal: - pass the beam through thin target many times - restore lost energy every turn - relies on large acceptance - similar to ERIT, but heavier target • External: - multiple targets

  21. Target Options Internal: 200keV energy loss ≈ 10μm 100Mo Yield/turn = 0.1mCi/μAh at 14 MeV External target yield = 4.74mCi/μAh → 48 turns Internal target issues: cooling outgasing processing

  22. Target Options External – two options: • Charge exchange extraction, as used in cyclotrons: - lossy - not possible for α’s - foil heating and lifetime can be a problem • Electrostatic deflector and septum

  23. Radioisotope Production Yields of various imaging isotopes – all identified of importance by IAEA - using Talys for 1 hr at 2mA

  24. Therapeutic Radioisotopes UK situation: • All reactor produced • None in the UK • Supplycan be a problem • Someisotopes need α: 211At, 67Cu, 47Sc, 161Tb • Recent review said: It is recommended that a national strategy for the use of radiotherapeutics for cancer treatment should be developed to address the supply of radiotherapeutics, projected costs of drugs and resources, the clinical introduction of new radioactive drugs, national equality of access to treatments and resource planning.

  25. Therapeutic Radioisotopes UK situation: • All reactor produced • None in the UK • Supplycan be a problem • Someisotopes need α: 211At, 67Cu, 47Sc, 161Tb • Recent review said: It is recommended that a national strategy for the use of radiotherapeutics for cancer treatment should be developed to address the supply of radiotherapeutics, projected costs of drugs and resources, the clinical introduction of new radioactive drugs, national equality of access to treatments and resource planning.

  26. Radioisotope Production

  27. Radioisotope Production

  28. Next steps • Continue to search for funding! • Continue modelling: - optimise lattice - study internal targets - study extraction and beam delivery - look at central region and beam capture • Engineering: - magnet design - RF design - injection and extraction - target design → Business case • Aim: - build it to make and sell radioisotopes - commercialise the FFAG - proof of principle of higher energy machines

  29. Next steps

  30. Conclusions • New type of FFAG/SFC looks very promising for: - radioisotope production - proton therapy & pCT - ion therapy • For radioisotopes, very large acceptance: - beam current up to 20mA - possibility of internal target • Main next step: engineering, especially magnets • Business case would open up opportunities for construction

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