The aim of this project is high-gradient conditioning and operation of the prototype 3 GHz medical linac accelerating structure, currently under fabrication. The project follows on from a previous successfully-delivered KT Fund project in 2012, whose objective was to design and fabricate the two high-power prototypes – one optimized for 76 MeV protons, the other for 213 MeV (corresponding to the lowest and highest energy for the main part of a proton-therapy linac). The field of application of this technology is generally medical linacs for proton and carbon-ion cancer therapy. The structures proposed are specifically optimized for use in gantry-mounted linacs for compact, single-room proton-therapy facilities such as TULIP, proposed by the TERA Foundation. Such a development would both significantly increase the flexibility and reduce the cost of particle therapy.