Dr Suzie Sheehy

Abstract:

Fixed-field alternating gradient accelerators are promising candidates for next-generation 10 MW-class high power proton drivers. Recent advances in lattice design of non-scaling FFAGs have progressed toward both isochronicity and chromatic correction. The resulting 1 GeV non-scaling FFAG design may be able to support a continuous (CW) beam with far lower peak current than the pulsed alternative. A 6-cell non-scaling FFAG design is described and recent work in modeling 3D space charge using the OPAL framework is presented, including fixed energy studies and beam dynamics with fast acceleration in the so-called serpentine channel.

Abstract:

The drive for high beam power, high duty cycle, and reliable beams at reasonable cost has focused world attention on fixed-field accelerators, notably Fixed-Field Alternating Gradient accelerators (FFAGs). High-intensity GeV proton drivers are of particular interest, as these encounter duty cycle and space-charge limits in the synchrotron and machine size concerns in the weaker-focusing cyclotron. Recently, the concept of isochronous orbits has been explored and developed for non-scaling FFAGs using powerful new methodologies in FFAG accelerator design. These new breeds of FFAGs have been identified by international collaborations for serious study thanks to their potential applications including Accelerator Driven Subcritical Reactors (ADS) and Accelerator Transmutation of Waste. The extreme reliability requirements for ADS mandate CW operation capability and the FFAGs strong focusing, particularly in the vertical, will serve to mitigate the effect of space charge (as compared with the weak-focusing cyclotron). This paper reports on these new advances in FFAG accelerator technology and presents a stable, 0.25- 1GeV isochronous FFAG for an accelerator driven subcritical reactor. Copyright © 2012 by IEEE.

Abstract:

High-power FFAG rings are under study to serve as drivers for neutron spallation, muon production, and accelerator-driven reactor systems. In this paper, which follows on from earlier work [1], a 20 - 70 MeV model for a high-power FFAG driver is described. This model would serve as a test bed to study topics such as space charge and injection in such rings. The design incorporates a long straight to facilitate H- charge exchange injection. The dynamic aperture is calculated in order to optimize the working point in tune space. The injection scheme is also described. A separate design for an ISIS injector, featuring a novel modification to the scaling law, was also studied. Copyright © 2012 by IEEE.

Abstract:

The non-scaling FFAG EMMA (Electron Model for Many Applications) is currently inoperation at Daresbury Laboratory, UK. Since the lattice is made up solely of linearelements, the betatron tune varies strongly over the momentum range according to thenatural chromaticity. Orbit correction is complicated by the resulting variation inresponse to corrector magnet settings. We consider a method to optimise correction over arange of fixed momenta and discuss experimental results. Measurements of the closed orbitand response matrix are included. Copyright © 2012 by IEEE.