G4Beamline PbBi

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Development of a Positron source using a PbBi converter and a Solenoid

Converter target properties

Definition of Lead Bismuth


1cm diameter target 2 mm thick PbBi

0.5 Tesla solenoid


Desire to know

Emmittance (mrad * mm)

dispersion (Delta P/P) (mradian/1000th mm/1000th)

of electrons after the PbBi target.


pole face rotation in vertical plane.

G4BeamLine and MCNPX

Target thickness optimization

PbBi_THickness_GaussBeam

Dmitry's simulations showing transverse phase space portrait (left) and longitudinal phase space portrait (right). Phase space portraits show coordinate x or y vs diveregense=px/pz or py/pz (or time vs kinetic energy )with ellipse - geometric (not normalized) emittance (ellipse area divided by "pi") and Twiss parameters as well as sqrt(beta*emittance) and sqrt(gamma*emittance) - half sizes of the projection of the ellipse on the coordinate and divergence axes respectively.

Electrons - RMS Ed1.png Electrons - 68.2% core Ed1.png Positrons - RMS Ed1.png Positrons - 68.2% core Ed1.png

PbBi_THickness_CylinderBeam

PbBi_THickness_PntSource

Energy Deposition in Target system (Heat)

Layout.png

ElectronTracks.pngPhotonTracks.png

ElectronEnergy.pngPhotonEnergy.png

MCNPX simulations of energy deposition into different cells are below. There is a slight overestimate (they add up to about 120%). Positrons contribute less than 1% of electrons' contribution. No magnetic filed is assumed.

Model.png

Tablen1.png

Tablen2.png

2mm thick PbBi, 10 MeV, point source

G4beamline pencil beam 10 cm radius

beam ellipse particle=e- nEvents=1000000 beamZ=0.0 beamX=0. beamY=0. \
        sigmaX=10.0 sigmaY=10.0 sigmaXp=0.000 sigmaYp=0.000 \
      meanMomentum=10. sigmaE=0. maxR=10.
PbBi Thickness (mm) #positrons/million electrons (G4Beamline) #positrons/million electrons (MCNPX)
1 1091
1.5 1728
2 1902[math]\pm[/math] 43 1984
2.5 2062
3 [math]\pm[/math] 13 1986
3.5 1938
4 [math]\pm[/math] 39 1858
5 1646
6 [math] \pm[/math] 37 1541
10 1216

Solenoid

Inner Radiusu=

Outer Radius =

Length =

Current=

Magnetic Field Map in cylindrical coordinates (Z & R) from Niowave

Beam Line Design

PbBi_BeamLine_Elements

Positrons#Simulations