David Kelliher

Effects of alignment errors in proton non-scaling FFAG accelerators

Non-scaling FFAGs have gained interest in the past decade for their potential application to charged particle therapy using proton and ion beams. However, linear ns-FFAGs naturally cross betatron resonances throughout acceleration. With an acceleration cycle of thousands rather than tens of turns, we find that resonance crossing produces severe orbit distortion in a linear proton/ion ns-FFAG in the presence of alignment errors. To overcome this, the PAMELA (Particle Accelerator for MEdicaL Applications) lattice design avoids resonance crossing with a non-linear ns-FFAG design. This design is outlined and a comparative analysis of alignment tolerances presented.

Amplitude-dependent orbital period in alternating gradient accelerators

Orbital period in a ring accelerator and time of flight in a linear accelerator depend on the amplitude of betatron oscillations. The variation is negligible in ordinary particle accelerators with relatively small beam emittance. In an accelerator for large emittance beams like muons and unstable nuclei, however, this effect cannot be ignored. In this study, we measured orbital period in a linear non-scaling fixed-field alternating-gradient accelerator, which is a candidate for muon acceleration, and compared it with the theoretical prediction. The good agreement between them gives important ground for the design of particle accelerators for a new generation of particle and nuclear physics experiments.

Study of Resonance Crossing in Non-scaling FFAGs using the S-POD Linear Paul Trap

Experiments on EMMA have shown that with rapid acceleration a linear non-scaling FFAG can accelerate through several integer tunes without detrimental effects on the beam [1]. Proton and ion applications such as hadron therapy will necessarily have a slower acceleration rate, so their feasibility depends on how harmful resonance crossing is in this regime. A simple and useful tool to answer such fundamental questions is the Simulator of Particle Orbit Dynamics (S-POD) linear Paul trap (LPT) at Hiroshima University, which can be set up to simulate the dynamics of a beam in an FFAG. We report here results of experiments to explore different resonance crossing speeds, quantify beam loss and study nonlinear effects. We also discuss the implications of these experimental results in terms of limits on acceptable acceleration rates and alignment errors.

Recent developments on the muon Non-Scaling FFAG for the Neutrino Factory and its subsystems

The current status and recent developments on the muon non-scaling FFAG for the Neutrino Factory studied in the framework of the EUROnu/IDS-NF projects are presented. Beam dynamics studies, including the process of acceleration, are discussed. A first pass at engineering for the layout of the ring cell is described. Progress of studies on the main machine subsystems is discussed. The future plans for the study are described.

High-order dispersion suppression for FFAG-based optics

The resurgence of interest in FFAG type magnets has motivated the desire for high-order dispersion suppression to aid the development of dispersion-free straight sections to currently circular designs. In scaling FFAGs, dispersion suppression can only be achieved over a limited momentum range and breaks down as high-order chromatic aberration terms become significant. However by breaking the scaling law and varying the individual multipole components, these can be compensated for and a design for high-order dispersion suppression achieved. This paper presents a process for doing so and discusses the impact on beta functions, as well as the effect of magnet positioning errors.

INJECTION AND EXTRACTION SYSTEMS FOR THE MUON FFAG RING IN THE NEUTRINO FACTORY

Non-scaling FFAG (NS-FFAG) rings have been proposed as a solution for muon acceleration in the Neutrino Factory. In order to achieve small orbit excursion and small time of flight variation, lattices with a very compact cell structure and consequent short straight sections are required. The resulting geometry, combined with the large transverse emittance of the muon bunch, places very challenging constraints on the injection/extraction systems. The injection/extraction system requires a set of distributed kickers, a superconducting septum and increased aperture in some of the main ring magnets. A scheme for both injection and extraction for a FFAG with triplet geometry is presented. In addition, a solution for the required kicker magnets is proposed.