The PHERMEX accelerator is a three-cavity rf linac that operates at 50 MHz. Each cavity has a radius of 2.3 m and a length of 2.6 m. The accelerator produces an electron beam with a peak current of 500 A and energy of 30 MeV. The rf power is supplied by multiple 2.5-MW tetrodes feeding coaxial lines with loops in the cavity wall. To increase the fields, multiple tetrodes and coupling loops must be used in each cavity; the problems associated with multiple-loop coupling are investigated. 3 refs., 4 figs
