with an opening 35 in processing chamber 14 and positioned so that the wafers 18 are rotatably scanned past the focal axis of an ion beam 36 from a suitable source not shown in a column 37 secured by a gland 38 to processing chamber 14 in the pivoted position the housing 3 is moved by lead screw 12a and motor 13 or by a double acting cylinder not shown into sealing relationship e g by o rings or the like about opening 35 of processing chamber 14 in position the assembly is roughed down via conduit 39 by a vacuum pump not shown and brought to final pressure via conduit 40 by a high vacuum pump not shown when operating vacuums are reached the ion beam 36 is directed through analyzing accelerating and focussing elements not shown onto the wafers 18 the wafers 18 may concurrently be radially traversed by motor 7 and lead screw 6 across beam 36 as described in the aforesaid u s pat no 3 778 626 to effect the desired ion implantation in wafers 18 in accordance with a prescribed pattern after implantation the assembly is pressurized to ambients housing 3 retracted from processing chamber and pivoted to the upright position where the scanning disc 17 is in the horizontal load unload position and decelerated to rest as scanning disc 17 decelerates the centrifugal effects on weight.