A mechanism for acceleration of protons is described, in which energy gain occurs near cyclotron resonance as protons drift through a sequence of rotating-mode ${\mathrm{TE}}_{111}$ cylindrical cavities in a strong nearly uniform axial magnetic field. Cavity resonance frequencies decrease in sequence from one another with a fixed frequency interval $\Delta f$ between cavities, so that synchronism can be maintained between the rf fields and proton bunches injected at intervals of $1/\Delta f$. An example is presented in which a 122 mA, 1 MeV proton beam is accelerated to 961 MeV using a cascade of eight cavities in an 8.1 T magnetic field, with the first cavity resonant at 120 MHz and with $\Delta f=8\mathrm{}\mathrm{MHz}$. Average acceleration gradient exceeds 40 MV/m, average effective shunt impedance is $223\mathrm{M}\Omega /\mathrm{m}$, but maximum surface field in the cavities does not exceed 7.2 MV/m. These features occur because protons make many orbital turns in each cavity and thus experience acceleration from each cavity field many times. Longitudinal and transverse stability appear to be intrinsic properties of the acceleration mechanism, and an example to illustrate this is presented. This acceleration concept could be developed into a proton accelerator for a high-power neutron spallation source, such as that required for transmutation of nuclear waste or driving a subcritical fission burner, provided a number of significant practical issues can be addressed.

• Received 28 January 2002

DOI:https://doi.org/10.1103/PhysRevSTAB.5.081301

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