Fixed-field alternating gradient accelerator

[4] The idea of fixed-field alternating-gradient synchrotrons was developed independently in Japan by Tihiro Ohkawa, in the United States by Keith Symon, and in Russia by Andrei Kolomensky.

The first prototype, built by Lawrence W. Jones and Kent M. Terwilliger at the University of Michigan used betatron acceleration and was operational in early 1956.

[10] This was one of the first colliding beam accelerators, although this feature was not used when it was put to practical use as the injector for the Tantalus storage ring at what would become the Synchrotron Radiation Center.

With the shutdown of MURA which began 1963 and ended 1967,[16] the FFA concept was not in use on an existing accelerator design and thus was not actively discussed for some time.

In the early 1980s, it was suggested by Phil Meads that an FFA was suitable and advantageous as a proton accelerator for an intense spallation neutron source,[18] starting off projects like the Argonne Tandem Linear Accelerator at Argonne National Laboratory[19] and the Cooler Synchrotron at Jülich Research Centre.

[21] There have also been numerous annual workshops focusing on FFA accelerators[22] at CERN, KEK, BNL, TRIUMF, Fermilab, and the Reactor Research Institute at Kyoto University.

[24][29] In 2010, after the workshop on FFA accelerators in Kyoto, the construction of the Electron Machine with Many Applications (EMMA) was completed at Daresbury Laboratory, UK.

The computation for the magnets used on the Michigan FFA Mark Ib, a radial sector 500 keV machine from 1956, were done by Frank Cole at the University of Illinois on a mechanical calculator built by Friden.

A proof-of-principle linear, non-scaling FFA called (EMMA) (Electron Machine with Many Applications) has been successfully operated at Daresbury Laboratory, UK.

FFA accelerators have potential medical applications in proton therapy for cancer, as proton sources for high intensity neutron production, for non-invasive security inspections of closed cargo containers, for the rapid acceleration of muons to high energies before they have time to decay, and as "energy amplifiers", for Accelerator-Driven Sub-critical Reactors (ADSRs) / Sub-critical Reactors in which a neutron beam derived from a FFA drives a slightly sub-critical fission reactor.

Such ADSRs would be inherently safe, having no danger of accidental exponential runaway, and relatively little production of transuranium waste, with its long life and potential for nuclear weapons proliferation.

Because of their quasi-continuous beam and the resulting minimal acceleration intervals for high energies, FFAs have also gained interest as possible parts of future muon collider facilities.

In the 1990s, researchers at the KEK particle physics laboratory near Tokyo began developing the FFA concept, culminating in a 150 MeV machine in 2003.