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High Brightness Electron Beam Diagnostics and their ... - CASA

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Wire Scanner Readback (mV)<br />

1200<br />

1000<br />

Foil out<br />

800<br />

600<br />

400<br />

whichdependsonthemeanaverageofcollisionanelectronexperiencesasitpassthroughthe foil:simplescattering(1), beamismeasuredusingawirescannerlocateddownstreamthefoil. describingscatteringinsideverythintargetseachofthemhave<strong>their</strong>owndomainofapplicability Figure4.5:Anexampleoftheeectofa0:8mthickaluminumfoilonthebeamprole.The<br />

0.8 m Foil in<br />

200<br />

0<br />

0 10 20 30 40 50 60<br />

pluralscattering(1 20),<br />

Position (mm)<br />

thatdescribesmultiplescattering.ThedetailedstudyofKeilmodelisoutofthescopeofthis thesis.Inbrief,KeilusedtheFouriertransformofthescatteringdistributionderivedbyMoliere Inthecaseofaluminumfoilwiththicknessthinnerthan5m,themeannumberofcollisionbeing lessthen20weareinthepluralscatteringregime.Thistypeofscatteringiswelldescribedby thesemi-empiricalmodelelaboratedbyKeil[30]whichisanextrapolationoftheMolieremodel multiplescattering(20).<br />

<strong>and</strong>onlyconsideredthetworsttermsofthisseries,avalidapproximationifthemeannumber ofcollisionisbelow20.Hethenempiricallycalculatedthenumericalcoecientoftheseriesusing theexperimentalmeasurementsperformedbyLeisegang[31]ashewasexperimentallystudying scatteringthroughverythingoldfoils.Therelationthatgivestheangularscatteringdistribution

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