A target processing machine (100), such as a lithography or inspection machine, comprising a rigid base plate (150), a projection column (101) for projecting one or more optical or particle beams on to a target (130), a support frame (102) supporting the projection column, the support frame being supported by and fixed to the base plate, a stage comprising a movable part (128) for carrying the target and a fixed part (132, 133) being supported by and fixed to the base plate, a beam sensor (160) for detecting one or more of the beams projected by the column, the beam sensor at least in part being supported by and fixed to the base plate, and a vacuum chamber (110) enclosing the support frame and the column, for maintaining a vacuum environment in the interior space of the chamber, the vacuum chamber formed with the base plate forming part thereof and supporting a plurality of wall panels (171, 172) including a plurality of side wall panels (171) supported by and fixed thereto.