BNL, Upton, Long Island, New York, USA
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
CBETA is an Energy Recovery Linac (ERL) accelerating an electron beam to 150 MeV in four linac passes. Instead of having four separate return loops to the linac, it instead has a single fixed field alternating gradient (FFAG) beamline with nearly a factor of 4 energy acceptance. While ideally the FFAG would be circular with identical cells all around, space and cost considerations dictate that small radius of curvature FFAGs should be used near the linac, connected by a straight beamline. To ensure good orbit matching over the entire energy range, adiabatic transitions are inserted between the arcs and the straight. After briefly introducing basic principles of FFAG optics, we describe how we choose the parameters of the arc cell, the basic building block of the lattice. We then describe how the straight cell is chosen to work well with the arc. Finally we describe the design process for the transition that ensures orbits over the entire energy range end up very close to the axis of the straight. We discuss how the realization of this lattice design with physical magnets impacts the design process.
BNL, Upton, Long Island, New York, USA
JLab, Newport News, Virginia, USA
A multiple-pass, high energy Energy Recovery Linac experiment at the JLab CEBAF will be instrumental in providing necessary information and technology testing for a number of possible future applications and facilities such as Linac-Ring based colliders, which have been designed at BNL (eRHIC) and CERN (LHeC), and also drivers for high-energy FELs and 4th GLS. The project has been submitted to, and has received approval from, JLab Program Advisory Committee (PAC 44) in July 2016. Since it was launched 2+ years ago, it has progressed in defining the experimental goals, including for instance multiple-beam instrumentation, ER efficiency, BBU, and the necessary modifications to CEBAF lattice, including for instance a 4-dipole phase chicane in recirculation Arc A, a dump line, and new linac optics. End-to-end simulations have been undertaken and software tools are under development. A next major objective in demonstrating readiness is a technical review as mandated by PAC 44. This paper gives a status of the project and its context, and presents plans for the near future.