This thesis involves the development of two radio-frequency quadrupole particle accelerators (RFQ) operating at 750 MHz. The first part covers radio-frequency (RF) design studies of the proton PIXE-RFQ. RF measurement results and tuning procedure are presented, showing very good agreement with simulations. The second part reports the development of the Carbon-RFQ for cancer therapy. The Carbon-RFQ features trapezoidal vanes whose fields are described using a novel semi-analytic approach. Dipole modes were detuned by a novel cavity length adjustment technique.<eng>
