A methodforestimatingthetemperatureinhighenergydensityfreeelectron laser experiments
Résumé
Presentandforthcomingfreeelectronlaser(FEL)largescalefacilitiesdeliverhighfluenceultrafastsoft and hardX-raypulsesabletocreateandprobewarmdensematter(WDM).Properdiagnosticforbasic physicalquantities,liketemperatureanddensity,isnecessary,buttheshortlifetimeoftheWDMstate (few ps)makestheirmeasurementsachallengingtask.Inthisworkweproposeamethodtoestimate the WDMtemperatureusingtheexperimentalinformationfromaslowtemperaturepyrometricprobe exploitingthepropertiesoftheheatdiffusionequation.Numericalsimulationsshowthatfortypical thin foilsamples,atemperaturemeasurementwith1210 ms temporalresolutionatthedistanceof about3002500 mm fromthebeamcentercontainssufficientinformationtoretrievetheinitialspatial temperaturedistributionwithsufficientaccuracyprovidinginformationonthetemperaturereachedin the WDMregime.TheinversionoftheexperimentalinformationisobtainedbymeansofaBayesian approachexploitingaMetropolisMonteCarlonumericalprocedure.Themodelandcalculations presentedinthisworkprovidethetheoreticalbackgroundforthedevelopmentofadevicefor temperaturediagnosticsoftheTIMEXend-stationattheFermi@ElettraFELfacility.