F ixed F ield A lternating G radient Synchrotrons

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Fixed Field Alternating Gradient Synchrotrons A new type of particle accelerator - with a wide variety of applications Cancer Therapy and UK Activities EMMA FFAGs are ideal for cancer therapy FFAGs are a new type of accelerator with properties that lead to wide variety of possible applications, in particular cancer therapy:  they can be used to accelerate protons, electrons and ions they can be rapidly cycled, much faster than a synchrotron they have a large acceptance for a particle beam, much bigger than a synchrotron  they have very small beam loss and low activation, smaller than a cyclotron  they are easy to maintain they can have a very large intensity they consist of a magnetic ring and do not require the same large magnets as cyclotrons they do not have the same restrictions on energy as a cyclotron beam can be extracted at a number of energies  they are reliable  they are easy to operate To extend the use of proton and ion therapy, in particular into major hospitals, there are a number of requirements that must be satisfied: • Efficient treatment • at least 500 patients per year • High dose rate • at least 5Gy per minute to provide sufficient flexibility • Flexibility (for various types of cancer) • the ability to run in respiration mode to treat as many types of tumour as possible • the ability to use spot scanning • a variable beam energy to reduce the need for absorbers • the possibility of using carbon ions as well as protons • Easy operation • Easy maintainability • low activation of the accelerator components to enable easy access • Low cost • both during construction and operation • Synchrotron Cyclotron FFAG • Beam intensity Low Plenty Plenty • Maintenance Normal Hard Normal • Operation Not easy Easy Easy • Carbon ions possible Yes Expensive Yes • Variable energy possible Yes No Yes • Multiple beam extraction Difficult No Yes The three FFAG rings of the Chiba ion therapy facility. The KEK proton therapy prototype. What are we planning to do in the UK? Accelerator scientists from the UK started working on scaling FFAGs about 2 years ago and have been investigating the use of these machines for a variety of applications. More recently, we have become interested in non-scaling FFAGs and in particular the electron model non-scaling FFAG. It is now proposed to build this unique machine at the Daresbury Laboratory in Cheshire, in collaboration with colleagues from Europe, Japan and the US. Existing infrastructure at Daresbury will be used to provide the electron beam. In addition, we will continue to investigate the utility of both types of FFAGs for a variety of applications, in particular hadron therapy. Funding for these activities is being sought from a number of sources. If successful, the electron model FFAG will initiate a revolution in future accelerator design! The Energy Recovery Linac Prototype is being built in two of the experimental halls of the van der Graaf. This will provide beams for the FFAG model, which will also be in one of these halls. The old tandem van der Graaf at the Daresbury Laboratory. Benefits of FFAGs for Proton and Carbon Therapy Comparison between Accelerator Technologies for Proton and Ion Therapy Current FFAGs have excellent properties for Hadron Therapy but further improvements are still possible Current Cancer Therapy Projects The following projects are under development using FFAGs All but the last are in Japan. The last differs from the others in another respect as well: it is a different type of FFAG. See below……… A second type of FFAG There are two types of FFAG envisaged. All those built or under construction so far are so-called "scaling" FFAGs in which the orbits of particles around the machine are the same, except they scale with energy. The problem with this is the magnets required tend to be large and complex, and hence expensive. This may hamper their use in medicine and industry. The second type is a "non-scaling" FFAG, in which the orbit shapes change as a function of energy. This allows the apertures of the magnets to be up to 10 times smaller than for a scaling machine, making the FFAG much more compact. In addition, the non-scaling magnets are less complex. Taken together, these should make a non-scaling machine considerably cheaper than a scaling machine for the same performance, bringing a sea change in accelerator technology. A magnet for the prototype 150 MeV scaling FFAG built at KEK. The magnets for a non-scaling FFAG could have a 10 times smaller aperture, making them smaller and cheaper. The orbit shape in scaling FFAG cells is the same at each energy, but varies with non-scaling machines. This allows the apertures of the magnets to be much smaller in the latter, reducing the cost for the same performance. However, non-scaling FFAGs have three unique features which must be investigated before their wide-spread use can be envisaged. To do this, it is planned to build an electron “model” non-scaling FFAG, the first of this type ever built, and study these features in detail. We are seeking collaborators to work with us on the development of this novel form of accelerator for proton and carbon ion therapy!