PAMELA - A model for an FFAG based hadron therapy machine - Peach, K; Cobb, J; Yokoi, T; Gardner, I; Edgecock, R; Poole, M; Pozimski, J; Cywinski, B; Jones, B; McKenna, G; Vojnovic, B; Fouwd, M; et al. (2007 IEEE PARTICLE ACCELERATOR CONFERENCE, VOLS 1-11, 2007)