FFAG 150 Mev acceleration

1. SHIRAZ PARAMEDICAL UNIVERSITY-2015 FFAG Fixed Field Alternating Gradient Accelerator What is an FFAG ? 150 Mev FFAG Designs for hadron therapy Siavash zare

3. What is an FFAG ? • A Fixed-Field Alternating Gradient accelerator (FFAG) is a circular particle accelerator concept on which development was started in the early 50s. • Alternating gradient is a focusing scheme with both sign of gradient magnets, focusing and defocusing elements. • Development is stopped in late 1960s because: • Magnet design was complicated. It was hard to get desired 3-D fields profile in practice. • No material for RF cavity. It requires high shunt impedance, high response time, and wide aperture. • Synchrotron was more compact and better choice for accelerator of high energy frontier. horizontal vertical

4. Revival in late 1990s • Technology becomes ready and enough reason to re-start development: • 3-D calculation code such as TOSCA becomes • available. Static fields can be modeled precisely. • RF cavity with Magnetic Alloy (FINEMET as an example) has most suitable properties for FFAG. • Growing demands for fast cycling, large acceptance, and high intensity in medium energy accelerator regime.

6. World First Proton FFAG Accelerator PoP(proof-of-principle) FFAG :KEK 2000

7. FFAG (Fixed Field Alternating Gradient) Advantages • Alternating gradient : Like synchrotron : strong focus accelerator • FFAGs rely on Alternating Gradient focusing so that the beam size can be much smaller. • Fixed field: like cyclotron :Zero chromaticity , Higher repetition rate : so higher average current • Fast acceleration • You can accelerate very quickly (as fast as your RF allows…) • flexibility, easy operation.

8. Classification of FFAG • Scaling FFAG: (Non-linear , Radial sector magnet , constant tune non-isochronous) • MURA (e-model) • PoP, 150 MeV (The project to construct the 150 MeV FFAG accelerator is under going at KEK) • PRISM • Muon acceleration ( Nufact-J, low frequency RF) • Non-Scaling FFAG: (Linear , spiral sector magnet , non-constant tune non isochronous, smaller magnet) • EMMA(U.K) ( Electron Machine with Many Applications ) advantage This gives them a large dynamic aperture and the ability to use higher rf frequencies than scaling FFAGs disadvantage Beam loss complex No resonances Very complex

9. 150 MeV FFAG

11. injectors Baby-cyclotron: proton beam is extracted from the cyclotron to the FFAG. After transportation line, with septum magnet, electrode and two bump magnet, beam will be put in the acceleration orbit.

12. injectors An injected beam is deflected by the magnetic septum and its angle is adjusted by the electrostatic septum. To observe beam position, two thin plates are installed near those septa.

13. injectors Tandem Accelerator (*Van de Graaff Accelerator*) The tandem accelerator employed as a heavy ions (10B 12C16O 19F 35Cl 72BR …) injector to the 150 MeV FFAG. Beams from the tandem accelerator will also be used for AMS, nuclear physics experiment, and so on.

14. injectors

15. injectors Tandem Accelerator The FN Tandem accelerator is a special type of Van de Graaff accelerator, in that it requires a negatively charged beam produced by an ion source external to the accelerator. The disadvantage to this system is that negatively charged beams are very difficult to produce.

16. Negatively charged beam is produced by an external ion source and is injected into the FN Tandem accelerator. • The ion source produces beams with one extra electron, so the charge state of the beam as it enters the FN Tandem accelerator is q = -1. • This beam accelerates towards the positive potential at the terminal, and gains an energy given by: • |qV| = (1) x Terminal Voltage Ion source (About 80kev)

17. For our FN Tandem, the “comfortable” operating range for the terminal voltage is: 2 MV – 10 MV Operating the FN Tandem above 10 MV is possible, but sparking (spontaneous discharging of the terminal voltage) is more likely and the entire system may be less stable. Control of HV breakdown World high energy: 20+ MV

19. injectors summary

20. injectors

21. RF cavity Requirements of RF cavity To achieve the rapid cycle acceleration in the proton FFAG, an RF cavity with high field gradient and broadband impedance is necessary. These requirements have been satisfied by using a high-permeability soft magnetic alloy (MA) core (FINEMET instead of Ferrite)and a high power broadband amplifier. voltage required to achieve the rapid acceleration of 100 Hz with two RF cavities • Broad band • Frequency sweep of a factor. • High gradient • Make it fast acceleration possible. • Large aperture • Especially in horizontal to • accommodate orbit excursion. The maximum shunt impedance is 200 Ω

22. RF cavity the cooling system for MA cores had a technical difficulty in terms of the thermo mechanical reliability. Since the efficiency of the heat cooling was low, the temperature on inner surface of the core reached over 150°C. To resolve this problem, a new type of the RF cavity with a high-efficiency cooling system has been developed. Developed RF cavity for 150 MeV FFAG

23. RF cavity The cavity consists of two MA cores, and the water-cooled plates are attached to one side of the cores. A thin thermally conductive spaceris inserted between the core and the cooling plate. the water cooling plate for the RF cavity. The blue area and arrows indicate the coolant passage and the direction of water follow, respectively.

24. F Sector Shunt D Sector FFAG main magnet Instead of using F (forces) and D (defocus) magnets separately, combine FDF together (triplet).We make a triplet sector magnet, Defocus, Forces ,Defocus magnet. Magnet for 150MeV FFA The design of the main magnet was carried out with 3-dimensional field calculation by a code TOSCA

25. FFAG main magnet Triplet type of the magnet The triplet type of the magnet has many advantages. The fringing field between focusing and defocusing fields can be easily cancelled. Long straight sections which gives sufficient space for installing the injection and extraction devices, and the beam diagnostics instruments, can be obtained. Another practical side benefit is the weight reduction. (a) OriginalRadial Sector (b) Triplet Radial Sector

26. Extraction Extraction is the process of ejecting a particle beam from an accelerator and into a transfer line or a beam dump. The extraction scheme is fast extraction commonly used in synchrotrons while a kickermagnet and a septummagnet should work at 100Hz. Proton beam bunch is accelerated with Rf voltage and extracted every 10msec. The layout of extraction devices and calculated extraction orbit in FFAG ring are shown below. With the magnet, it is possible to extract beam from the region of FFAG magnet. If the beam is extracted from the region of straight section, the extraction septum magnet should bend the beam in large angle

27. Extraction Kicker and septum magnet kicker magnet provides time selection of beam to be injected/extracted. The field produced by a kicker magnet must rise/fall within the time period between the beam Bunches. a septum is a device which separates two field regions. Important features of septa are an ideally homogeneous (electric or magnetic) field in one region, for deflecting beam, and a low fringe field (ideally zero magnetic and electric field) next to the septum so as not to affect the circulating beam.

28. Medical FFAG Design Studies Have been many and varied. I’ve chosen a few to highlight… but it is a wide topic

29. Goals of FFAG designs for Medical Accelerators • Synchrotron-like features • Variable extraction energy • Multiple extraction points – multiple treatment areas • Cyclotron-like features • High current output • Ease of operation

33. MORE? FFAG International Collaboration Workshop and Conference : http://hadron.kek.jp/FFAG/