ORBIT CORRECTION IN A NON-SCALING FFAG
EMMA the Electron Model of Many Applications is to be built at the STFC Daresbury Laboratory in the UK and will be the first non-scaling FFAG ever constructed. The purpose of EMMA is to study beam dynamics in such an accelerator. The EMMA orbit correction scheme must deal with two characteristics of a non-scaling FFAG: i.e. the lack of a well defined reference orbit and the variation with momentum of the phase advance. In this study we present a novel orbit correction scheme that avoids the former problem by instead aiming to maximise both the symmetry of the orbit and the physical aperture of the beam. The latter problem is dealt with by optimising the corrector strengths over the energy range.
ORBIT CORRECTION IN THE EMMA NON-SCALING FFAG SIMULATION AND EXPERIMENTAL RESULTS
The non-scaling FFAG EMMA (Electron Model for Many Applications) is currently in operation at Daresbury Laboratory, UK. Since the lattice is made up solely of linear elements, the betatron tune varies strongly over the momentum range according to the natural chromaticity. Orbit correction is complicated by the resulting variation in response to corrector magnet settings. We consider a method to optimise correction over a range of fixed momenta and discuss experimental results. Measurements of the closed orbit and response matrix are included. CLOSED ORBIT MEASUREMENTS
EMMA, THE WORLD'S FIRST NON-SCALING FFAG ACCELERATOR
EMMA, the Electron Model with Many Applications, was originally conceived as a model of a GeV-scale muon accelerator. The non-scaling (ns) properties of resonance crossing, small apertures, parabolic time of flight (ToF) and serpentine acceleration are novel, unproven accelerator physics and require "proof of principle". EMMA has metamorphosed from a simple "demonstration" objective to a sophisticated instrument for accelerator physics investigation with operational demands far in excess of the muon application that lead to technological challenges in magnet design, rf optimisation, injection and extraction, and beam diagnostics. Machine components procured in 2008-09 will be installed March-August 2009 leading to full system tests September-October and commissioning with electrons beginning November 2009. APPLICATIONS OF NS-FFAGS FFAGs are like cyclotrons in that they accelerate without increasing the magnetic fields however to reduce magnet apertures they implement alternating gradient focussing. They were first proposed in the middle of the last century and demonstrations were made at that time with electrons [1,2,3,4]. Recently renewed attention has been given to the application of this type of accelerator, with proton acceleration being achieved at KEK [5]. So far these machines have been based on the scaling principle where the betatron tunes and orbit shape are kept constant during acceleration. In the late 1990s, motivated by consideration of the very rapid acceleration requirements for muons, the non-scaling concept was proposed. This new configuration achieves a more compact orbit by allowing the betatron tunes to vary throughout the acceleration. Initial designs did this using simple cells with purely linear magnets [6,7]. Serpentine acceleration demonstrated a mode of operation which allowed acceleration with constant RF frequencies over more than a factor of 2 in momentum [8,9]. These properties make ns-FFAGs a very attractive option for muon acceleration and for a diverse range of other applications. The PAMELA (Particle Accelerator for MEdicaL Applications) project is evolving the concept to produce a design for a proton and light ion accelerator for cancer therapy [10]. A ns-FFAG has also been adopted as apart of the baseline design of a Neutrino Factory [11] and they are being investigated as a possible options for an accelerator driver for subcritical reactors [12]. The applications of ns-FFAGs are being pursued actively within the CONFORM project, which holds a multimillion pound grant funding the construction of EMMA, the design study for PAMELA [13,14] and the study of wider reaching potential applications.