Proposal for a new LEIR Slow Extraction Scheme dedicated to Biomedical Research

This report presents a proposal for a new slow extraction scheme for the Low Energy Ion Ring (LEIR) in the context of the feasibility study for a biomedical research facility at CERN. LEIR has to be maintained as a heavy ion accumulator ring for LHC and for fixed-target experiments with the SPS. In parallel to this on-going operation for physics experiments, an additional secondary use of LEIR for a biomedical research facility was proposed [Dosanjh2013, Holzscheiter2012, PHE2010]. This facility would complement the existing research beam-time available at other laboratories for studies related to ion beam therapy. The new slow extraction [Abler2013] is based on the third-integer resonance. The reference beam is composed of fully stripped carbon ions with extraction energies of 20-440 MeV/u, transverse physical emittances of 5-25 µm and momentum spreads of ±2-9•10-4. Two resonance driving mechanisms have been studied: the quadrupole-driven method and the RF-knockout technique. Both were made compatible with the tight aperture constraints imposed by operation as heavy ion accumulator. Tracking is performed with MADX-PTC [MADX, PTC]. The resonance is excited using an existing Pole-Face Winding. The dedicated devices to be installed in LEIR are an electrostatic septum (0.1 mm, 8.0 MV/m, 86 cm physical length), a thin magnetic septum (9 mm, 0.46 T, 90 cm physical length), a thick magnetic septum (22 mm, 0.7 T, 1.2 m physical length) and two new orbit correctors (0.2 T, 40 cm physical length).