Design of an interaction region with head-on collisions for the ILC by Appleby, R, Angal-Kalinin, D, Jackson, F, Alabau-Pons, M, Bambade, P, Brossard, J, Dadoun, O, Rimbault, C, Keller, L, Nosochkov, Y, Seryi, A, Payet, J, Napoly, O, Rippon, C, Uriot, D