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. The positron production efficiency predictions from MCNPX and GEANT4 are within uncertainties.
Incident Electron spatial distribution and energy
Positron and Electron Momentum after the converter
Text files were delivered to Niowave so Niowave could begin designing a beamline to transport the positrons using a solenoid immediately downstream of the PbBi target.
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
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.
 |
|
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");