Niowave 10-2015

Niowave Positron Project Progress for October 2015

A comparison was made between MCNPX and GEANT4 using a cylindrical electron beam with a radius of 1 cm. The 10 MeV incident electrons impinged a 2 mm thick PbBi target. Positrons escape the surface of the PbBi target with a mean momentum of 2.3 MeV.

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");

I was unable to do anything other than a gaussian beam right now, I will try to do one later

For now I have a gaussian with an 8mm RMS and 10 MeV incident electrons as shown below.

The positron and electron momentum distributions after the PbBi converter are shown below

A comma delimited text file with the above events in the format of

x,y,z,Px,Py,Pz

in units of cm for distance and MeV for momentum is located at

for positrons

http://www2.cose.isu.edu/~foretony/Positrons_2mm10MeV.dat

and

http://www2.cose.isu.edu/~foretony/Electrons_2mm10MeV.dat

for electrons

For now I have a gaussian with an 1mm RMS and 10 MeV incident electrons as shown below.