Thermal management system

A thermal management system 100, such as for a vacuum pumping system, comprises a plurality of connected conduits for a flow of cooling fluid. The conduits comprise a cooling fluid inlet 102 to receive a supply of cooling fluid and one or more valves 106a, 106b, 106c located along one or more of the conduits to control the flow of cooling fluid through the conduits. A restrictor 104 may be located along one or more of the conduits between the inlet and the one or more valves. The restrictor reduces a pressure of the cooling fluid such that its pressure at the one or more valves is less than at the inlet. For each of the one or more valves, a length of conduit between the inlet and an inlet of that valve may be less than or equal to about 60cm. The plurality of conduits may include multiple permanent cooling lines 141, 142, each being a conduit between the inlet and a cooling fluid outlet 122, wherein the one or more valves are not located along any of the permanent cooling lines.