简介：1IntroductionEarlyattemptstocreateasoundabsorberwhichwouldfunctionwithouttheinvolvementofanyfibrousorporousdampingmaterialgofarbacktoK.A.Veliszhanina,S.N.RschevkinandothersaswasoutlinedinRef.[1].30yearsago,D.Y.MAA[2]wasfirstinproposingapracticabledesignconceptandcalculationmodelforMicro-PerforatedAbsorber(MPA)prototypeswhichstillformsthebasisforvariousapplications.Duringthepast12yearstheFraunhoferIBP

简介：Recentexperimentsontheimplosionsof15-mmlongand2-μmthickaluminumlinershavingadiameterof12.8mmhavebeenperformedontheprimaryteststand(PTS)facility.Thestratifiedstructuresareobservedasalternatingdarkandlighttransversestripesinthelasershadowgraphimages.Thesestriationsperpendiculartothecurrentflowareformedearlyintheimplosion,i.e.,atthestagewhenthebulkofthematerialmasswasalmostatrest.Atwo-dimensional(2D)magnetohydrodynamics(MHD)codeisemployedtosimulatethebehavioroflinerdynamicsintheearlyphases.Itisfoundthatthestriationsmaybeproducedbytheelectrothermalinstability(ETI)thatresultsfromnon-uniformJouleheatingduetothecharacteristicrelationbetweentheresistivityandthetemperature.In2Dsimulations,thestratifiedstructurescanbeseenobviouslyinbothdensityandtemperaturecontoursasthelinerexpandsrapidly.Byanalyzinginstabilityspectrum,thedominantwavelengthsoftheperturbationsare8.33μm–20.0μm,whichagreequalitativelywiththetheoreticalpredictions.ItisalsointerestingtoshowthatETIprovidesasignificantseedtothesubsequentmagnetoRayleigh–Taylor(MRT)instability.

简介：Room-temperaturetestwithhighpowerisanessentialstepbeforecouplersareinstalledonsuperconductingcavities.Anewroom-temperatureteststandisbeingdesignedatIMP.ThenewstandwillbeassembledwithaNC(normal-conducting)QWRcavity.Thepowerlossonthecavitywhencouplersareconditionedintraveling-wavemodehastobethoroughlyevaluated.Fig.1demonstratesthepowerflowintraveling-waveconditioningmode.Pe1andPe2representthepowerthatisextractedbycouplers.PfandPredenotetheforwardpowerandreflectedpower,respectively.