To　obtain　higher　thermal　efficiency,　advanced　gas　turbines　operate　at　a　turbine　inlet　temperature　(TIT)　up　to　2000K,　which　causes　an　extremely　high　thermal　load　on　the　first　stage　vane　endwall.　Therefore,　it　is　critical　to　understand　the　complex　thermal　environment　near　the　endwall　and　develop　efficient　cooling　schemes.　In　this　study,　adiabatic　cooling　effectiveness　measurements　on　an　annular　cascade　endwall　with　purge　flow　were　conducted　using　a　high-resolution　infrared　thermography　technique.　Effects　of　profiles　and　locations　of　an　upstream　slot　on　endwall　film　cooling　behaviors　were　investigated　at　three　coolant-to-mainstream　mass　flow　ratios　and　an　engine-like　density　ratio.　Using　numerical　simulation,　the　flow　details　were　illustrated　to　support　the　measured　cooling　effectiveness.　Results　indicate　that　moving　the　slot　to　a　further　upstream　location　will　reduce　film　cooling　effectiveness　on　the　endwall.　However,　a　further　upstream　slot　can　improve　the　uniformity　of　the　film　cooling　effectiveness　distribution.　Compared　with　the　normal　slot,　the　convergent　slot　accelerates　the　coolant　ejection　to　a　higher　momentum　and　thus　inhibits　the　influence　of　secondary　flows　on　endwall　film　cooling.　Therefore,　the　convergent　slot　significantly　improves　both　the　coolant　coverage　and　local　film　cooling　effectiveness　for　all　mass　flow　ratios　and　slot　locations　investigated.　Quantitatively,　an　enhancement　of　approximately　25%　in　laterally　averaged　cooling　effectiveness　can　be　achieved　by　the　convergent　slot.　©　2020　Elsevier　Masson　SAS