NS-FFAGs for Hadron Therapy

Due to their fixed magnetic field and alternating gradient, or strong, focussing nature, FFAGs combine many of the positive properties of both cyclotrons and synchotrons for hadron therapy. In particular, they are:

Fast cycling: Due to the fixed field, they can be cycled much more rapidly than synchrotrons, up to perhaps 1kHz. This means they can accelerate a much bigger current than a synchrotron and one that is comparable to a cyclotron. This gives them the flexibility to use the most modern beam delivery techniques, such as spot scanning.
Easy operation: The fixed magnet field also means that FFAGs don't need constant adjustment during operation, similar to a cyclotron. This also means that operation should be stable, with a predictable intensity being delivered to the patient.
Carbon: Although cyclotrons are able to accelerate protons to the 230 MeV protons required therapy they are currently unable to accelerate carbon ions to the 430 MeV/nucleon required. As a result, all the existing carbon facilities and all those under construction use synchrotrons. They therefore suffer the intensity and operational problems noted above. FFAGs are able to accelerate protons, carbon and other ions.
Variable energy: In general, cyclotrons are able to deliver only a single energy, typically 230 MeV. To treat tumours at a shallower depth, this energy then needs to be degraded by passing the beam through an absorber. AS well as complicating operation, this also has the effect of bollowing up the beam somewhat and causing a spread in energy. It can also create a loss intensity which is difficult to predict accurately. NS-FFAGs can deliver a beam of essentially energy, like a synchrotron, and hence avoid these problems. This variable beam possibility is also easier to achieve with non-scaling FFAGs than it is with their scaling cousins.
Easy maintenance: As NS-FFAGs consist of a single compact ring, there is easy access to all the machine components and they are easy to maintain. For operation in a hospital environment, this, like easy operability, is another important feature.
Multi-port extraction: Like synchrotrons, it is possible to extract the beam from an FFAG into a number of different beamlines simultaneously. This makes beam handling before the gantries easier.
Low beam loss: FFAGs have very low beam loss during acceleration and extraction. Although this is more important for high intensity applications, it does reduce the risk of activation of the machine components and improve the knowledge of the beam delivered to patients.

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For more information, please contact: Rob Edgecock - Tel: +44 (0)1235 44 5089