Niowave 10-2015

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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

PbBi 5-1-15 X-Yposition.pngPbBi 5-1-15 Ein.png

Positron and Electron Momentum after the converter

PbBi 5-1-15 Ppositron.pngPbBi 5-1-15 Pelectron.png


G4Bl-vs-MCNPX 5-5-2015.png


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

Ed1.png

Electrons - 68.2% core

Ed2.png

Positrons - RMS

Pd1.png

Positrons - 68.2% core

Pd2.png


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

E1.png

Electrons - 68.2% core

E2.png

Positrons - RMS

P1.png

Positrons - 68.2% core

P2.png



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.



BeamPipeDepEPhi 34.8 082815.png BeamPipeDepE 34.8 082815.png
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.


BeamPipeDepE 34.8 082815 parttype.png

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");