High Brightness Electron Beam Diagnostics and their ... - CASA
High Brightness Electron Beam Diagnostics and their ... - CASA
High Brightness Electron Beam Diagnostics and their ... - CASA
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Solenoidal Lens #2<br />
Accelerating Cavity #4 & #3<br />
Achromatic Chicane<br />
OTR viewer<br />
Figure6.1:SimpliedschematicoftheIRFELphotoinjector(seetextforexplanation).<br />
OTR viewer<br />
Linac Entrance<br />
<strong>High</strong> Voltage<br />
Buncher<br />
Power Supply<br />
GaAs Photocathode<br />
<strong>High</strong> Dispersion<br />
Multislit Mask #1<br />
particlepushingcodeisusedasskeletonforthesimulation[53],theelectrostaticeldinthegun Theinjectorhasbeensubjecttoextensiveintegratedmodelingusingseveralcodes.Theparmela 6.1.1Introduction Thenumericalmodel<br />
Solenoidal lens #2<br />
Multislit Mask #2 OTR viewer<br />
<strong>and</strong>inthesolenoidlensesarecomputedwiththepoissoncode,whereastheelectromagneticeld<br />
pickup cavity<br />
parametershavebeensetaftermanyiterativeoptimizationrunsusingparmela.Theresulting intheRFcavitiesareobtainedfroma3Dmodelusingthemafiafamilycode.Theinjector<br />
Matching Telescope<br />
rmsbeamtransverse<strong>and</strong>longitudinalenvelopesthroughouttheinjectortransport,optimizedfor<br />
betweenthephotocathode<strong>and</strong>theanodecanreach500kV.Ideallyonewouldliketomaintain ThebeamisgeneratedwithaDCphotocathodegunaforementioned.Theacceleratingvoltage agunvoltageof350keVarepresentedingure6.2.<br />
thehighestacceleratingvoltagetominimizethespace-charge-inducedemittancegrowthsincethis forceisproportionalto1=2.Unfortunatelybecauseweencounteredtechnicaldiculties(e.g.eld emissionofthecathodesupport)duringtheguncommissioning,wehadtooperatethegunwith 6.1.2The350keVregion<br />
modelingthatevenwiththisloweracceleratingvoltage,wecouldstillndadequatesettingsto acceleratedinthegun,itsrmstransverse(i.e.radial)beamsizeisstronglydiverging<strong>and</strong>the aloweracceleratingvoltageof350keV(<strong>and</strong>sometime330keV).Itwasassessedvianumerical providetherequiredbeamparametersattheundulatorlocation.Asabunchisemitted<strong>and</strong> bunchiselongatingaspicturedingure6.2.Tocorrectforthestrongdivergence<strong>and</strong>collectall particleofthebunch,asolenoidlenshasbeenlocatedimmediatelydownstreamtheanodeplate.
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