Gasturbine engine performance requires effective and reliable internal cooling overthe duty cycle of the engine. Life predictions for rotatingcomponents subject to the main gas path temperatures are vital.This demands increased precision in the specification of the internalair system flows which provide turbine stator well cooling andsealing. This in turn requires detailed knowledge of the flowrates through rim seals and interstage labyrinth seals. Knowledge ofseal movement and clearances at operating temperatures is of greatimportance when prescribing these flows. A test facility has beendeveloped at the University of Sussex, incorporating a two stageturbine rated at 400 kW with an individual stage pressureratio of 1.7:1. The mechanical design of the test facilityallows internal cooling geometry to be rapidly reconfigured, while coolingflow rates of between 0.71 C W,ENT and 1.46 CW,ENT, maybe set to allow ingress or egress dominated cavity flows.The main annulus and cavity conditions correspond to in cavityrotational Reynolds numbers of 1.71 × 106< Reφ<1.93 × 106. Displacement sensors have been used to establish hot running seal clearances over a rangeof stator well flow conditions, allowing realistic flow rates tobe calculated. Additionally, gas seeding techniques have been developed, wherestator well and main annulus flow interactions are evaluated bymeasuring changes in gas concentration. Experiments have been performed whichallow rim seal and re-ingestion flows to be quantified. Itwill be shown that this work develops the measurement ofstator well cooling flows and provides data suitable for thevalidation of improved thermo-mechanical and CFD codes, beneficial to theengine design process.