In this work, we examine the beam correction requirements for the FFA@CEBAF energy upgrade. Both hardware and software diagnostic and corrector components are under investigation; in particular the relationship between hardware and software optimization will be developed. To generate a representative sample of errors---from the machine lattice and other beam properties---we construct a Markov Chain Monte Carlo (MCMC) sampler which considers different probability distributions for different types of errors. This sample is used to investigate the statistical sensitivity of the beam to various diagnostic and corrective schema. Once statistics are acquired, we plan to use a variety of optimization techniques to minimize correction time for the electron beam in the FFA arcs designed for the CEBAF upgrade.

We describe optics designs of the key components of proton and electron Recirculating Linear Accelerators (RLAs). They are presented in the context of a high-power hadron accelerator being considered at ORNL and a CEBAF electron energy doubling study, FFA@CEBAF, being developed at Jefferson Lab. Both concepts rely on the Fixed-Field Alternating gradient (FFA) arc optics designs where multiple beam passes are transported by a single beam line.

Extending the energy reach of CEBAF by increasing the number of recirculations, while using the existing linacs is explored. This energy upgrade is based on the multi-pass acceleration of electrons in a single non-scaling Fixed Field Alternating Gradient (FFA) beam line, using Halbach-style permanent magnets. Encouraged by the recent successful demonstration of CBETA, a proposal was formulated to nearly double the energy of CEBAF from 12 to 22~GeV by replacing the highest energy arcs with FFA transport. The new FFA arcs would support simultaneous transport of an additional 6 passes spanning roughly a factor of two in energy. One of the challenges of the multi-pass (11) linac optics is to assure uniform focusing over a wide range of energies. Here, we propose a triplet lattice that provides a stable periodic solution covering an energy ratio of 1:33. The current CEBAF injection at 123 MeV, makes optical matching in the first linac impossible due to the extremely high energy ratio (1:175). Replacement of the current injector with a 650 MeV recirculating injector will alleviate this issue. Orbital and optical matching from the FFA arcs to the linacs is implemented as a compact non-adiabatic insert. The design presented here is anticipated to deliver a 22 GeV beam with normalized emittance of 76 mm·mrad and a relative energy spread of 1×10^{-3}. Further recirculation beyond 22 GeV is limited by the large (974 MeV per electron) energy loss due to synchrotron radiation.

The FFA@CEBAF energy upgrade study aims to approximately double the final energy of the electron beam at the Continuous Electron Beam Accelerator Facility (CEBAF). It will do this by replacing the highest-energy recirculating arcs with fixed-field alternating gradient (FFA) arcs, allowing for several more passes to circulate through the machine. This upgrade necessitates the re-design of the vertical spreader sections, which separate each pass into different recirculation arcs. Additionally, the FFA arcs will need horizontal splitter lines to correct for time of flight and R56. This work will present the current state of the spreader re-design and splitter design.

Recent studies by Dejan Trbojevic have confirmed that Non-Scaling Fixed Field Accelerators (NS-FFAs) can have their tune dependence on momentum flattened by adding non-linear components to the magnet fields, although not necessarily for an unlimited momentum range. This paper presents such a cell suitable for the proposed 3-12MeV FETS-FFA proton R&D ring at RAL. The nonlinear magnetic field components are found automatically using an optimiser and settings covering a ring tune range of one unit in both planes independently are attainable. A fully configurable magnet with multiple windings across its horizontal aperture has been designed in 2D using Poisson, which can produce the required nonlinear fields without exceeding 5A/mm^2 current density.

Fixed field Alternating gradient (FFA) accelerator is an option as a proton driver for the next generation spallation neutron source (ISIS-II). To demonstrate FFA suitability for high intensity operation, a 3 to 12 MeV proton prototype ring is planned at RAL, called FETS-FFA. The main magnets are a critical part of the machine, and several characteristics of these magnets require development. First the doublet spiral structure has never been designed before, and the essential feature of operational flexibility in terms of machine optics requires a wide range of changes for the field gradient. Finally, control of the fringe field is a challenge both mechanically and from the nonlinear optics point of view. This paper will discuss the design of the prototype magnet for FETS-FFA ring.

The CEBAF energy upgrade will require magnets with high fields to bend electron beams of up to 22GeV in the 80.6m radius tunnel. A peak field in excess of 1.5T, together with a large gradient of 40T/m or more, are used in its fixed-field arc lattice to bend multiple recirculation energies in a single pipe. Additionally, the magnet must have an open midplane to allow synchrotron radiation to be absorbed by a cooling channel. A short 45mm section of NdFeB prototype has been designed and built as part of permanent magnet R&D at BNL. This satisfies all the above requirements and has had its integrated field tuned to better than 1 part in 10^3. This tuning process uses a technique with iron rods adapted from CBETA and miniaturised here, together with measurements at a new compact field-mapping stand that is accurate to 1 part in 10^4.