Fixed part of the Stand/Gantry assembly containing the Klystron, power converters, cooling water heat exchanger, microwave generator and other elements of the linear accelerator and similar components of the Ximatron. In the HET Clinac, the stationary structure at the back of the accelerator that houses the assemblies for the power distribution controller, the cooling system SF6 gas controller, gantry drive, treatment room signal interface, beam gating interface, motion disable switch panel, and the control keyboard, as well as the cabinet housing the lower couch controller and the Stand controller. Sometimes referred to as the gantry stand or drive stand.