Development of a Positron source using a PbBi converter and a Solenoid

Task List

1.) new electron and positron files for the case of two 0.25 mm thick SS windows around the PbBi target.

2.) Determine electron energy deposition in SS pipe per cm^2 of pipe surface area for pipes with a radius of 34.8, 47.5, 60.2, 72.9, and 97.4 mm and thickness of 5mm along the z-axis.

3.) Insert uniform B-field that can be scaled from 0 to 0.3 and 1 Telsa.

Beam Pipe Heating

A 10 MeV electron beam with a radius of 0.5 cm was incident on a 2mm thick PbBi target. The target is positioned at Z = -900 mm. The plot below shows the energy deposited in MeV along the pipe. The Z axis is along the beam direction. The arec lenc of 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.

About 25,000 MeV/cm^2 is deposited when 20 Million , 10 MeV electrons are incident on the 2mm PbBi target.

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

PbBi_THickness_GaussBeam

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

PbBi_THickness_CylinderBeam

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

PbBi_THickness_PntSource

Electrons and Positrons after 2mm of LBE:

Electrons:

Positrons:

Energy Deposition in Target system (Heat)

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.