Difference between revisions of "G4Beamline PbBi"

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Development of a Positron source using a PbBi converter and a Solenoid
 
Development of a Positron source using a PbBi converter and a Solenoid
  
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=Converter target properties=
+
=Conclusions=
  
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Definition of Lead Bismuth
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#A 0.3 (0.6)  Tesla Solenoid with a diameter to allow a 9.74 (3.94) cm diameter pipe would collect a positron per thousand incident electrons on a 2mm thick LBE target with 0.25 mm thick SS windows.
 +
# A 15 cm long, 0.2 Tesla solenoid with a 3.94 diameter beam pipe would collect a positron per two thousand electrons impinging a 2mm thick LBE target with 0.25 mm thick SS windows.
 +
#A 4 Tesla Solenoid will remove beam pipe heating from scattered electrons downstream of the target when using a 3.94 cm diameter beam pipe.
  
 +
=Reports=
  
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1cm diameter target
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[[Niowave_Report_11-30-2015]]
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2 mm thick PbBi
 
  
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0.5 Tesla solenoid
 
  
 +
deadline 4/12/16
  
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Desire to know
 
  
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Emmittance (mrad * mm)
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==[[Niowave_9-2015]]==
 +
==[[Niowave_10-2015]]==
 +
==[[Niowave_11-2015]]==
 +
==[[Niowave_12-2015]]==
 +
==[[Niowave_1-2016]]==
 +
==[[Niowave_2-2016]]==
 +
==[[Niowave_3-2016]]==
 +
==[[Niowave_4-2016]]==
 +
==[[Niowave_5-2016]]==
 +
==[[Niowave_6-2016]]==
  
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dispersion (Delta P/P)  (mradian/1000th  mm/1000th)
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=Task List=
  
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of electrons after the PbBi target.
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0.) 34.8 mm pipe, 0.0 -> 0.5 Tesla, E= 6,8,10 MeV.
  
  
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pole face rotation in vertical plane.
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1.)  Create a positron (10,000 positrons) and electron event file containing t,x,y,z,Px,Py,Pz  for positrons exiting the solenoid and an incident Gaussian beam 1cm in diameter and with a sigma of 1cm.
  
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=G4BeamLine and MCNPX=
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compare distributions with and without solenoid.
  
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+
2.) Determine the back ground when using a 3.48 diameter beam pipe and Solenoid field of 0.2 for a NaI detector placed at
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==Target thickness optimization==
 
  
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===[[PbBi_THickness_GaussBeam]]===
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3.) Experiment, install dipole and solenoid in the tunnel.
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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
 
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diveregense=px/pz or py/pz (or time vs kinetic energy ). Captions show:
 
  
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1. geometric (not normalized) emittance for transverse and emittance for longitudinal phase space portraits (ellipse areas divided by "pi")
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=Beam Pipe Heating=
  
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2. Twiss parameters
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[[PbBi_BeamPipeHeatin_2015]]
  
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3. Ellipse centroid for longitudinal phase portrait
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=Converter target properties=
  
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4. sqrt(beta*emittance) and sqrt(gamma*emittance) - half sizes of the projections of the ellipses on the coordinate and divergence axes respectively.
 
  
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Electrons - RMS
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[[PbBi_NioWave_TargetProperties_2015]]
  
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[[File:Ed1.png| 400 px]]
 
  
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Electrons - 68.2% core
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=Target thickness optimization=
  
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[[File:Ed2.png| 400 px]]
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==[[PbBi_THickness_CylinderBeam]]==
  
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Positrons - RMS
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==[[PbBi_THickness_GaussBeam]]==
  
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[[File:Pd1.png| 400 px]]
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== [[PbBi_THickness_PntSource]]==
  
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Positrons - 68.2% core
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=Solenoid=
  
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[[File:Pd2.png| 400 px]]
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==Uniform ideal Solenoid==
  
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=== [[PbBi_THickness_CylinderBeam]]===
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=== [[PbBi_BeamPipeHeating_w_Solenoid_2015]]===
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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")
+
===[[PbBi_60cmLong_Solenoid_Collection_Efficiency_2015]]===
  
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2. Twiss parameters
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==Positron & Electron event files==
  
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3. Ellipse centroid for longitudinal phase portrait
+
[[PbBi_PosEventFiles_VaccumGaps_2015]]
  
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4. sqrt(beta*emittance) and sqrt(gamma*emittance) - half sizes of the projections of the ellipses on the coordinate and divergence axes respectively.
+
[[PbBi_PosEventFiles_NoGaps_2016]]
  
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Electrons - RMS
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==Solenoid Map==
  
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[[File:E1.png| 400 px]]
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Inner Radiusu=
  
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Electrons - 68.2% core
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Outer Radius =
  
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[[File:E2.png| 400 px]]
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Length =
  
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Positrons - RMS
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Current=
  
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[[File:P1.png| 400 px]]
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Magnetic Field Map in cylindrical coordinates (Z & R) from Niowave
  
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Positrons - 68.2% core
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=Rear Window Thickness=
  
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[[File:P2.png| 400 px]]
 
  
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=== [[PbBi_THickness_PntSource]]===
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Question:  Will a thicker downstream exit window increase the positron production efficiency by providing more material for a brehm photon to pair produce in?
  
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Electrons and Positrons after 2mm of LBE:
 
  
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Electrons:
+
Positrons were counted exiting a ideal 0.2 Tesla solenoid that was 15 cm long.  A ten MeV electron beam with a 0.5 cm cylindrical radius impinged a 2mm thick PbBi liquid target that had a surface area of 2.54 cm x 2.54 cm.  A 0.25 mm thick stainless steel entrance window was used. 
  
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[[File:e1.png| 200 px]][[File:e2.png| 200 px]]
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Target is at -106 mm, entrance SS window is at -108.25 mm , exit SS window is at -103.75 mm, A sensitive detector for positron is placed at Z= +44mm.  The sensitive detector is a cylinder of radius 11.74 cm.
 +
 +
{| border="1"
 +
{| border="1"
 +
| SS Exit WIndow Thickness (mm) || Positrons/Million electrons
 +
|-
 +
|0.0  || 1142,1096,1149,1073,1083 = 1109 +/- 35
 +
|-
 +
| 0.25  || 774,836,800,785,798 = 798 +/- 23
 +
|-
 +
|  0.5    ||  693,704,713,697,715 = 704 +/- 10
 +
|-
 +
|  1.0    ||  587,606,548,592,550 =577 +/- 26
 +
|+
 +
|}
  
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Positrons:
 
  
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[[File:p1.png| 200 px]][[File:p2.png| 200 px]]
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;Conclusion 1: Positron production efficiency improves when the exit window is made thinner
  
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===Energy Deposition in Target system (Heat)===
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;Conclusion 2 : You loose about 28 +/- 4 % of the positrons in the 0.25 mm thick SS exit window.
  
 +
=Background studies=
  
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[[File:Layout.png| 400 px]]
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==Brem Spectrum==
  
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[[File:ElectronTracks.png| 200 px]][[File:PhotonTracks.png| 200 px]]
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Below is the photon energy distribution (from Brem & pair production) using a 2mm Pb target for two different incident electron energies; 6 and 10 MeV. The photons are 1 cm downstream of the target and intersection a large forward region.
  
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[[File:ElectronEnergy.png| 200 px]][[File:PhotonEnergy.png| 200 px]]
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[[File:PbBi_Brem_6-10MeV_4-7-16.png | 200 px]]
  
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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.
+
insert photon spacial distributions
  
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[[File:Model.png| 400 px]]
+
Now move the scoring region downstream to a position representing the location of a NaI detector.
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[[File:Tablen1.png| 200 px]]
 
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[[File:Tablen2.png| 200 px]]
 
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==Solenoid==
 
−
 
 
−
 
 
−
Inner Radiusu=
 
−
 
 
−
Outer Radius =
 
−
 
 
−
Length =
 
−
 
 
−
Current=
 
−
 
 
−
Magnetic Field Map in cylindrical coordinates (Z & R) from Niowave
 
  
 
=Beam Line Design=
 
=Beam Line Design=

Latest revision as of 21:39, 8 June 2016

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

Conclusions

  1. A 0.3 (0.6) Tesla Solenoid with a diameter to allow a 9.74 (3.94) cm diameter pipe would collect a positron per thousand incident electrons on a 2mm thick LBE target with 0.25 mm thick SS windows.
  2. A 15 cm long, 0.2 Tesla solenoid with a 3.94 diameter beam pipe would collect a positron per two thousand electrons impinging a 2mm thick LBE target with 0.25 mm thick SS windows.
  3. A 4 Tesla Solenoid will remove beam pipe heating from scattered electrons downstream of the target when using a 3.94 cm diameter beam pipe.

Reports

Niowave_Report_11-30-2015


deadline 4/12/16


Niowave_9-2015

Niowave_10-2015

Niowave_11-2015

Niowave_12-2015

Niowave_1-2016

Niowave_2-2016

Niowave_3-2016

Niowave_4-2016

Niowave_5-2016

Niowave_6-2016

Task List

0.) 34.8 mm pipe, 0.0 -> 0.5 Tesla, E= 6,8,10 MeV.


1.) Create a positron (10,000 positrons) and electron event file containing t,x,y,z,Px,Py,Pz for positrons exiting the solenoid and an incident Gaussian beam 1cm in diameter and with a sigma of 1cm.

compare distributions with and without solenoid.

2.) Determine the back ground when using a 3.48 diameter beam pipe and Solenoid field of 0.2 for a NaI detector placed at

3.) Experiment, install dipole and solenoid in the tunnel.

Beam Pipe Heating

PbBi_BeamPipeHeatin_2015

Converter target properties

PbBi_NioWave_TargetProperties_2015


Target thickness optimization

PbBi_THickness_CylinderBeam

PbBi_THickness_GaussBeam

PbBi_THickness_PntSource

Solenoid

Uniform ideal Solenoid

PbBi_BeamPipeHeating_w_Solenoid_2015

PbBi_60cmLong_Solenoid_Collection_Efficiency_2015

Positron & Electron event files

PbBi_PosEventFiles_VaccumGaps_2015

PbBi_PosEventFiles_NoGaps_2016

Solenoid Map

Inner Radiusu=

Outer Radius =

Length =

Current=

Magnetic Field Map in cylindrical coordinates (Z & R) from Niowave

Rear Window Thickness

Question: Will a thicker downstream exit window increase the positron production efficiency by providing more material for a brehm photon to pair produce in?


Positrons were counted exiting a ideal 0.2 Tesla solenoid that was 15 cm long. A ten MeV electron beam with a 0.5 cm cylindrical radius impinged a 2mm thick PbBi liquid target that had a surface area of 2.54 cm x 2.54 cm. A 0.25 mm thick stainless steel entrance window was used.

Target is at -106 mm, entrance SS window is at -108.25 mm , exit SS window is at -103.75 mm, A sensitive detector for positron is placed at Z= +44mm. The sensitive detector is a cylinder of radius 11.74 cm.

SS Exit WIndow Thickness (mm) Positrons/Million electrons
0.0 1142,1096,1149,1073,1083 = 1109 +/- 35
0.25 774,836,800,785,798 = 798 +/- 23
0.5 693,704,713,697,715 = 704 +/- 10
1.0 587,606,548,592,550 =577 +/- 26


Conclusion 1
Positron production efficiency improves when the exit window is made thinner
Conclusion 2
You loose about 28 +/- 4 % of the positrons in the 0.25 mm thick SS exit window.

Background studies

Brem Spectrum

Below is the photon energy distribution (from Brem & pair production) using a 2mm Pb target for two different incident electron energies; 6 and 10 MeV. The photons are 1 cm downstream of the target and intersection a large forward region.

PbBi Brem 6-10MeV 4-7-16.png 

insert photon spacial distributions

Now move the scoring region downstream to a position representing the location of a NaI detector.

Beam Line Design

PbBi_BeamLine_Elements

goals for JLab

Positrons#Simulations

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