Difference between revisions of "Niowave 9-2015"

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(Created page with "The energy deposited by electrons scattered into a 3.48 diameter stainless steel beam pipe (1.65 mm thick) from a PbBi target as a function of a uniform Solenoidal magnetic fiel…")
 
 
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The energy deposited by electrons scattered into a 3.48 diameter stainless steel beam pipe (1.65 mm thick) from a PbBi target as a function of a uniform Solenoidal magnetic field.
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Niowave Positron Project Progress for September 2015
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Simulations were performed to predict the efficiency of producing positrons using a Lead-Bismuth target and a 10 MeV incident electron. MCNPX and GEANT4 were used to predict this efficiency in an effort to benchmark the results.  Niowave performed a simulation using MCNPX and ISU used GEANT4.  A comparison of the positron production efficiency predictions made by MCNPX and G4beamline (GEANT4) is shown in the table below.  The two simulation packages appear to be consistent with each other for some thicknesses.
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{| border="1"
 
{| border="1"
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{| border="1"
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| PbBi Thickness (mm) || #positrons/million electrons (G4Beamline)|| #positrons/million electrons (MCNPX)
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| B-field (Tesla) || Hot Spot (<math>MeV/e^-</math>)
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| 1    ||1138,1154,1097,1159,1125 =1135<math>\pm</math>25 || 1091
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| 1.5    || 1668,1701,1639, 1644, 1628=1656<math>\pm</math>29 ||1728
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| 2    || 1937,1930,1851,1874,1945=1907<math>\pm</math>42  || 1984
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| 3|| 1889,1821,1852,1809,1859=1846<math>\pm</math>32 || 1986
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| 4||1726,1696,1673,1693,1681=1694<math>\pm</math> 20 ||  1858
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| 5|| 1566,1543,1546,1625,1566=1569<math>\pm</math>33 || 1646
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| 6|| 1549, 1486,1564,1545,1452=1520<math>\pm</math> 50 ||1541
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| 7|| 1462,1327, 1407,1489 ,1477=1432<math>\pm</math> 67  || 1541
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|8|| 1289, 1335,1280, 1271, 1280 = 1291<math>\pm</math> 25 ||
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| 10|| 1141,1241, 1199, 1202, 1148 =1186<math>\pm</math>42 || 1216
 
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| 0.0  || 0.35
 
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|  0.3    ||  0.35
 
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|  1.0  || 0.35
 
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|  1.5  || 0.22
 
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|  2.0  || 0.10
 
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|  4.0  || 0.002
 
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To convert this deposited energy per incident electron on the target to a heat load in the pipe you need to divide by the area of the pipe.
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Below are the momentum distributions observed for both electrons and electrons using MCNPX.  The 10 MeV electrons loose a mean energy of about 3 MeV traversing the 2mm thick PbBi target.  The incident 10 MeV electrons produce Brehsstrahlung photons as traverse the PbBi target.  These photon will produce electron-positron pairs within the PbBi target material.  The positrons below escape the PbBi target and have a momentum between one and two MeV.
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A histogram is filled with 1 cm bins along the Z axis.  The surface area becomes <math>1 cm \times 2 \pi 3.48/2 = 10.933 cm^2</math>.  The beam pipe diameter assumed is 3.48 cm.
 
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When filling the histogram binned 1 cm in Z, you should weight it by the amount of depositred energy divided by the circumference of the pipe and divided by the number of incident electrons on the target (5 million).  The energy units are converted to keV by multiplying the numberator by 100 or in this case dividing by 5000 instead of 5 million.
 
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  TH1F *T00N=new TH1F("T00N","T00N",100,-1000.5,-0.5)
 
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  Electrons->Draw("evt.EoutPosZ>>T00N","evt.DepE/10.088/5000")
 
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To convert From Mev/ e- to kW/cm^2 assuming a current of 1mA (10^-3 C/s) you 
 
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<math>\left( \frac{\mbox{MeV}}{\mbox{cm}^2 \mbox{e}^-}\right) \times \left( \frac{ \mbox{e}^-}{1.6 \times 10^{-19}\mbox{C}}  \right ) \times \left( \frac{1 \times 10^{-3} \mbox{C}}{\mbox{s}} \right )  \times \left( \frac{1.6 \times 10^{-13}\mbox{W} \cdot \mbox{ s}}{\mbox{MeV} }\right )</math>
 
  
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<math>\left( \frac{\mbox{keV}}{\mbox{cm}^2 \mbox{e}^-}\right) = \left( \frac{\mbox{W} }{\mbox{cm}^2 } \right )</math>
 
  
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Electrons:
  
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[[File:e01.png| 400 px]][[File:e02.png| 400 px]]
  
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Positrons:
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{| border="1"
 
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| [[File:BeamPipeDepEmev-vs-B.png |200px]] || [[File:BeamPipeDepPower-vs-B.png |200px]]|| [[File:BeamPipeDepPower-vs-lowB.png |200px]] 
 
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|+ Energy deposited (MeV) along a 1 m long beam pipe of stainless steel 1.65 mm thick.
 
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With SS windows
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[[File:p01.png| 400 px]][[File:p02.png| 400 px]]
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Positrons->Draw("sqrt(evt.BeamPosPosX*evt.BeamPosPosX+evt.BeamPosPosY*evt.BeamPosPosY)","evt.BeamPosMomZ>0 && evt.BeamPosPosZ>-500 && sqrt(evt.BeamPosPosX*evt.BeamPosPosX+evt.BeamPosPosY*evt.BeamPosPosY)<97.4/2");
 

Latest revision as of 14:39, 13 April 2016

Niowave Positron Project Progress for September 2015


Simulations were performed to predict the efficiency of producing positrons using a Lead-Bismuth target and a 10 MeV incident electron. MCNPX and GEANT4 were used to predict this efficiency in an effort to benchmark the results. Niowave performed a simulation using MCNPX and ISU used GEANT4. A comparison of the positron production efficiency predictions made by MCNPX and G4beamline (GEANT4) is shown in the table below. The two simulation packages appear to be consistent with each other for some thicknesses.


PbBi Thickness (mm) #positrons/million electrons (G4Beamline) #positrons/million electrons (MCNPX)
1 1138,1154,1097,1159,1125 =1135[math]\pm[/math]25 1091
1.5 1668,1701,1639, 1644, 1628=1656[math]\pm[/math]29 1728
2 1937,1930,1851,1874,1945=1907[math]\pm[/math]42 1984
3 1889,1821,1852,1809,1859=1846[math]\pm[/math]32 1986
4 1726,1696,1673,1693,1681=1694[math]\pm[/math] 20 1858
5 1566,1543,1546,1625,1566=1569[math]\pm[/math]33 1646
6 1549, 1486,1564,1545,1452=1520[math]\pm[/math] 50 1541
7 1462,1327, 1407,1489 ,1477=1432[math]\pm[/math] 67 1541
8 1289, 1335,1280, 1271, 1280 = 1291[math]\pm[/math] 25
10 1141,1241, 1199, 1202, 1148 =1186[math]\pm[/math]42 1216


Below are the momentum distributions observed for both electrons and electrons using MCNPX. The 10 MeV electrons loose a mean energy of about 3 MeV traversing the 2mm thick PbBi target. The incident 10 MeV electrons produce Brehsstrahlung photons as traverse the PbBi target. These photon will produce electron-positron pairs within the PbBi target material. The positrons below escape the PbBi target and have a momentum between one and two MeV.


Electrons:

E01.pngE02.png

Positrons:

P01.pngP02.png

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