BNL, Upton, Long Island, New York, USA
The Cbeta project[1] is a prototype electron accelerator for the proposed eRHIC project[2]. The electron accelerator is based on the Energy Recovery Linac (ERL) and the Fixed Field Alternating Gradient (FFAG) principles. The FFAG arcs of the accelerator are comprised of one focusing and one defocusing quadrupoles which are designed as Halbach-type permanent magnet quadrupoles[3]. We propose window frame electro-magnets surrounding the Halbach magnets to be used as normal and skew dipoles correctors and quadrupole correctors. We will present results from OPERA-3D calculations of the effect of these corrector magnets on the magnetic field of the main quadrupole magnets and the results will be compared with experimental measurements. We will also discuss applications of permanent magnets with such correctors for hadron beam facilities.
[1] http://arxiv.org/abs/1504.00588
[2] http://arxiv.org/ftp/arxiv/papers/1409/1409.1633.pdf
[3] K. Halbach, NIM 169 (1980) pp. 1-10
BNL, Upton, Long Island, New York, USA
Understanding space charge effects in FFAG is crucial in order to assess their potential for high power applications. This paper shows that, to carry out parametric studies of these effects in FFAG, the average field index of the focusing and defocusing magnets are the natural parametrization. Using several classes of particle distribution functions, we investigate the effects of space charge forces on the non-linear beam dynamics of FFAG and provide stability diagrams for an FFAG-like lattice. The method developed in this study is mainly applicable to systems with slowly varying parameters, i.e slow acceleration.
