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FabricationandFlyerDrivingCapabilityCharacterisationofanIntegratedExplodingFoilInitiator 8 9 5
tionprocess,whileithasbeencaughtupbytheflyerfrom
#
sample2 atthe100nsfrom thestartpoint.Accordingtothe 4.3 InfluencesofBarrelLengthontheFlyerAcceleration
sameinputenergy,thethinnerfoilprovidesgreaterenergy Capability
densitywhilethethickfoilwouldcreatemoreplasmaforac Thevelocityattheimpactpointisoneofthekeyfactors
celerationrelatively.Thegreaterenergydensityproducesa fortheinitiation,andtheimpactpointofflyer′sflightisdeter
fasterelectricalburstandbetterinitialacceleration,whilethe minedbythelengthofbarrel.Anunusualphenomenonwas
largerquantityofplasmaprovidesamorecontinuousaccelera foundthatthemeanthresholdvoltageofEFIsincreasesabout
[9]
tion.Thecombinationofthesefactorscouldleadtothephe 18% asthebarrellengthextendsfrom 0.2mm to0.4mm .
nomenathatexhibitedintheFig.8. Fortheinvestigationofflyers′accelerationprocessinthesetwo
kindsofbarrel,we′vesetanothertestfortheflyervelocity
Table2 ThesampleparametersofEFIfoilthicknesstest PDVdiagnostic;theparametersarelistedinTable3.
foil barrel flyer
barrel flyer
sample thickness length thickness Table3 ThesampleparametersofEFIbarrellengthtest
material material
/ μ m /mm / μ m
foil barrel flyer
1 # 3 0.4 Su8 25 paryleneC sample thickness length barrel thickness flyer
2 # 4 0.4 Su8 25 paryleneC / μ m /mm material / μ m material
1 # 4 0.2 Su8 25 paryleneC
#
2 4 0.4 Su8 25 paryleneC
TheresultofthePDV diagnosticisillustratedinFig.10,
whichshowsthatthereisn′tanydistinctdivergencebetween
#
#
thevelocityprofileofsample1 and2.Theflyervelocityat
#
theflightdistanceof0.2mm couldreachto92% (1 )and
#
88%(2)oftheultimatevelocitydetected,whichisconsist
[10]
entwiththevelocityprofileofChow ,Thevelocityatthe
#
#
impactpointof1(0.2mm)and2(0.4mm)arerespectively
-1 # -1 #
Fig.8 Theacclerationprofileofflyersdrivenbyexplodingfoilwith 3790m· s (1 ) and4129 m· s (2 ).Withthebarrel
differentthickness lengthextendfrom 0.2mm to0.4mm;thevelocityatimpact
pointhasincreasedabout9%.
Toinvestigatethevelocityatimpactpoint(thevelocityat
thebarrelexit) during the flyers′flight,the flyervelocity
distanceprofilecouldbeobtainedfrom theintegralofvelocity
timehistoryinFig.8.
AsitillustratedinFig.9,Theflyers′velocityattheimpact
#
-1
point(0.4 mm) are respectively3906 m · s (1 ) and
#
-1
4129m·s (2 ),thedivergenceofthem ismerelyabout
5%,whichisconsistentwiththetestsconductedbyJunSik
Hwang,thatthemean firingenergystaysin acomparative
level,whenthefoilthicknessrangefrom 3μ m to6μ m [8] .
Fig.10 ThevelocitydisplacementprofileofEFIassembledwithdiffer
entbarrellength
AsitshowninFig.10thatthevelocityattheimpactpoint
indeedincreasedasthebarrellengthextended,whichcould
deduced thatthe increasing ofthe mean threshold voltage
shouldnotowntotheflyervelocity.
Actually,otherfactorsmayalsoassociatewiththeflyer
initiationenergy,suchasimpactangle,impactarea,andim
pactduration. Afterthe vaporization ofmetalbridge, the
Fig.9 ThevelocitydisplacementprofileofEFIassembledwithdiffer flyer′sdrivingpressuredecreasessharplyfrom thepeaktoa
entfoilthickness relativelylow level.Undertheinfluenceofthedrivingpres
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