The idea of the fixed field alternating gradient (FFAG)
accelerator [11], and the non-scaling FFAG (NS-FFAG) [12]
are quite old, but the idea of using a NS-FFAG lattice in an
ERL is new [13]. The important feature of this approach is the
ability to contain multiple passes, extending over a wide
energy range, in a compact magnet transport system, thus
leading to cost reduction of the accelerator.