Abstract: A segmented radio-frequency quadrupole accelerator (10) having a top segment (12), a bottom segment (14), a first side segment (16) and a second side segment (18), each segment having an elongated vane portion (20) arranged in diametrically-opposed pairs along a common longitudinal axis. Mounting arms (30) are integrally formed in the outer walls (28) of the vane portion (20), each end of each mounting arm (30) having a mounting surface (32) formed of a projection (34) having a surface (36) and an end surface (38) oriented at substantially right angles to cooperate with a mounting portion on an adjacent minor segment having a surface (44) and an end surface (46) oriented at right angles. Seals (48) having a C-shaped, cross-sectional configuration are placed between the mounting surfaces to maintain electrical contact between the segments. Fasteners (54) are securely fastened through oversized holes (52) in the segments to adjustably fasten the segments together.