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The Hybrid Ring with a superconducting-linac injector as a highly flexible synchrotron radiation source to enable new experimental techniques and enhance many existing ones is proposed. It is designed to be operated with the coexistence of the storage (SR) bunches characterized by the performance of the storage ring, and the single-pass (SP) bunches characterized by the performance of the superconducting linac. Unique experiments can be performed by simultaneous use of the SR and SP beams, in addition to research with various experimental techniques utilizing the versatile SR beam and research in the field of ultrafast dynamics utilizing the ultrashort pulse of the SP beam. The extendability of the Hybrid Ring will allow it to be developed into a synchrotron radiation complex., (open access.)

A novel scheme to reduce transverse beam emittance in a ring accelerator is proposed by using a pair of coupling cavities as a basic unit to control damping partition numbers. As indicated by Robinson in 1958, a simple rf electromagnetic field (e.g., a TM210 mode by a single coupling cavity) cannot control the damping partition of three eigenoscillation modes in a ring accelerator due to the cancellation between the contributions from the magnetic and electric fields. Based on both analytical and numerical studies, we show that a pair of coupling cavities that satisfy phase and optics matching conditions can overcome this cancellation. The results indicate that the horizontal emittance is reducible to the theoretical limit based on the steady state condition and also, the emittance is reducible below the reduction limit under a nonsteady state by driving the coupling cavities with gated signals.

We report an experimental demonstration of the induction synchrotron, the concept of which has been proposed as a future accelerator for the second generation of neutrino factory or hadron collider. The induction synchrotron supports a superbunch and a superbunch permits more charge to be accelerated while observing the constraints of the transverse space-charge limit. By using a newly developed induction acceleration system instead of radio-wave acceleration devices, a single proton bunch injected from the 500 MeV booster ring and captured by the barrier bucket created by the induction step voltages was accelerated to 6 GeV in the KEK proton synchrotron.

A quasiadiabatic nonfocusing transition-energy crossing is proposed for suppressing any nonadiabatic and undesired features in a longitudinally separated function-type accelerator, in which particles are confined by an radio-frequency voltage with an adiabatic reduction of the amplitude and accelerated by a step voltage. This new method has been examined, both theoretically and experimentally.

A single rf bunch in the KEK proton synchrotron was accelerated with an induction acceleration method from the injection energy of 500 MeV to 5 GeV.

Halo formation under a nonequilibrium state for a two-dimensional Gaussian beam in a FODO lattice, which is an array of magnets where F is focusing, D is defocusing, and O is the drift space between magnets, was examined in terms of a transition of time-varying nonlinear resonances. Nonlinear resonant-interactions between individual particles and intrinsic beam-core oscillations result in a beam halo. The location of the halo is analytically tractable using canonical equations derived from an isolated resonance Hamiltonian.

A novel concept of a high luminosity hadron collider is proposed. This would be a typical application of an induction synchrotron being newly developed. Extremely long bunches, referred to as superbunches, are generated by a multibunch stacking method employing barrier buckets at the injection into the collider and are accelerated with a step voltage induced in the induction gaps. Superbunches intersect with each other, yielding a luminosity of more than 10(35) cm(-2) sec(-1). A combination of vertical crossing and horizontal crossing must be employed in order to avoid any significant beam-beam tune shift.

The emittance growth and halo formation for a mismatched beam of a one-dimensional Gaussian distribution in a uniform focusing channel were examined by means of a macroparticle simulation. The results were analyzed by isolated nonlinear resonance theory. The second-harmonic resonance driven by beam-core oscillation was both numerically and analytically shown to assume a key role in forming a halo. An analytic estimation of the halo location was explored, and the halo location was proved to correspond to the outer edge of the resonance islands. Nonlinear fields in an actual particle distribution have been shown to significantly affect both the halo's location and size.