G4Beamline PbBi

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

2mm thick PbBi, 10 MeV, 1 cm cylindrical incident electron distribution

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.

Incident Electron spatial distribution and energy

Positron and Electron Momentum after the converter

PbBi Thickness (mm)	#positrons/million electrons (G4Beamline)	#positrons/million electrons (MCNPX)
1	1169,1083,1068,1090,1088 =1100[math]\pm[/math] 40	1091
1.5	1723, 1668,1671, 1687,1726=1695[math]\pm[/math] 28	1728
2	1902,1921,1886,1967,1922=1920[math]\pm[/math] 30	1984
3	1920,1880,1883,1864,1857=1881 [math]\pm[/math] 24	1986
4	1688, 1766, 1712, 1709, 1753=1726[math]\pm[/math] 33	1858
5	1569,1585,1509 ,1536,1551=1550[math]\pm[/math] 29	1646
7	1475,1450,1457,1428,1477 =1457[math] \pm[/math] 20	1541
10	1250,1180,1178,1186,1166=1192[math]\pm[/math] 33	1216

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.

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

Positrons#Simulations