A vacuum adapter for feeding-through vacuum-insulated coolant lines (11, 12, 22, 23) from the surrounding atmosphere into a vacuum processing installation has an intermediate volume (2) which is connected firstly to at least one insulation intermediate space (32, 33) of the vacuum-insulated feed lines and secondly to a vacuum pump. The pump capacity is available at least temporarily for evacuating the insulation intermediate space around the coolant lines (22, 23).