bearing surface 20 provided on the mount 18 the cylindrical bearing surface 20 comprises a tubular section whose exterior face provides the bearing surface from one end of which is suspended the main body 22 of the mount 18 this main body 22 consists of a box section body with a circular aperture 24 at the front thereof and a circular aperture 26 at the rear thereof with substantially flat top and side portions the interior of the body 22 is generally open thus allowing a clear passage through the interior of the mount 18 from the front aperture 24 to the rear aperture 26 and through the tubular section 20 the top face has an aperture 28 for reasons which will be explained later the same applies to the two side faces which have a left aperture 30 and a right aperture 32 the bottom face includes an aperture 34 which leads into a box section 36 that is suspended beneath the body 22 the box section 36 is open at the top face to permit communication through the bottom aperture 34 and is likewise open at a front section 38 fig3 shows a linear accelerator arm 40 for use in conjunction with the mount shown in fig1 and 2 an exterior casing 42 covers a magnetron accelerator 44 and associated elements which produce a high energy beam of electrons and deliver that beam to a beam bending system 46 which conveys the beam to a radiation head 48 carrying the usual collimator set 50 this arm 40 can be fitted to the upper face of the mount body 22 as shown in fig5 and 6.