PbBi THickness CylinderBeam

Initial rate study

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

Dmitry's processing of Tony's GEANT 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 ). Captions show:

1. geometric (not normalized) emittance for transverse and emittance for longitudinal phase space portraits (ellipse areas divided by "pi")

2. Twiss parameters

3. Ellipse centroid for longitudinal phase portrait

4. sqrt(beta*emittance) and sqrt(gamma*emittance) - half sizes of the projections of the ellipses on the coordinate and divergence axes respectively.

Electrons - RMS

Electrons - 68.2% core

Positrons - RMS

Positrons - 68.2% core

The plot below shows the energy deposited in MeV along the pipe. The Z axis is along the beam direction. The distance around the beam pipe is determine by taking the pipe radius (34.8 mm) and multiplying it by the Phi angle around the pipe. The bins are 1cm x 1cm.

A maximum of 450,000 MeV is deposited in a 1 cm[math]^2[/math] bin when 20 Million , 10 MeV electrons are incident on a 2 mm thick PbBi target located at Z=-902 mm.

Below is energy deposited contributions from from photons(AVSzWg), positrons (AVSzWpos), and electrons.

Why is the positron hotspot upstream of the target? Because beam was going from right to left.

root commands used

TH2D *AVSz=new TH2D("AVSz","AVSz",100,-1000,0,12,-60,60)
BeamPipeE->Draw("35.*atan(PosYmm/PosXmm):PosZmm>>AVSz","DepEmeV"); 
AVSz->Draw("colz");

Rate comparison with Energy and target thickness

Difference with above simulation are that GEANT4 has SS windows and all created positrons that leave the target are counted , not just those going through a Sensitive detector downstream

6MeV

PbBi Thickness (mm)	#positrons/million electrons (GEANT4.9.6.p02	#positrons/million electrons (G4Beamline)
1	465,449,457,454,472 =[math]\pm[/math]
1.5	=[math]\pm[/math]
2	396,418,394,415,395 =[math]\pm[/math]
3	= [math]\pm[/math]
4	338,327,332,341,336=
5	=[math]\pm[/math]
7	257,280,265,268,259 =[math] \pm[/math]
10	=[math]\pm[/math]

8 MeV

PbBi Thickness (mm)	#positrons/million electrons (GEANT4.9.6.p02	#positrons/million electrons (G4Beamline)
1	994,996,967,971,956=[math]\pm[/math]
1.5	=[math]\pm[/math]
2	1184,1212,1175,1194,1178=[math]\pm[/math]
3	= [math]\pm[/math]
4	989,1013,975,962,956= [math]\pm[/math]
5	=[math]\pm[/math]
7	815,765,829,806,817=[math] \pm[/math]
10	=[math]\pm[/math]

10 MeV

PbBi Thickness (mm)	#positrons/million electrons (GEANT4.9.6.p02	#positrons/million electrons (G4Beamline)
1	1524,1607,1565,1598,1581 =[math]\pm[/math]
1.5	=[math]\pm[/math]
2	2445,2386,2321,2359,2368 =[math]\pm[/math]
3	= [math]\pm[/math]
4	2087,2104,2121,2154,2118 = [math]\pm[/math]
5	=[math]\pm[/math]
7	1675,1697,1708,1720,1750=[math] \pm[/math]
10	=[math]\pm[/math]

G4Beamline_PbBi#PbBi_THickness_CylinderBeam