Difference between revisions of "Niowave 1-2016"

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Niowave Positron Project Progress for January 2016
 
Niowave Positron Project Progress for January 2016
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The positron collection efficiency was investigated for several solenoidal magnetic field strengths and beam pipe radii to determine the impact of using a solenoidal field strength that was less than one Tesla.  The figure below shows the number of positrons that exit the solenoid for every million electrons that impinge a 2mm thick PbBi target sandwiched between 0.25 mm thick stainless steel windows.  If the solenoids field strength was limited to a maximum of 0.3 Tesla, then a 97.5 mm diameter beam pipe would have the same positron transport efficiency as a 1.0 Tesla field and a 34.8mm diameter beam pipe.  Otherwise, the positron transport efficiency can increase by a factor of two when using a 34.8 mm diameter beam pipe if the solenoidal field strength is increased from 0.3 Tesla to 1.0 Tesla.
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| [[File:PositronRates-vs-SolenoidField_10-1-15.png |600px]] 
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|+ Positron Rates -vs- Solenoid Field for 2mm thick PbBi target and several Beam pipe diameters
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Latest revision as of 15:23, 13 April 2016

Niowave Positron Project Progress for January 2016

The positron collection efficiency was investigated for several solenoidal magnetic field strengths and beam pipe radii to determine the impact of using a solenoidal field strength that was less than one Tesla. The figure below shows the number of positrons that exit the solenoid for every million electrons that impinge a 2mm thick PbBi target sandwiched between 0.25 mm thick stainless steel windows. If the solenoids field strength was limited to a maximum of 0.3 Tesla, then a 97.5 mm diameter beam pipe would have the same positron transport efficiency as a 1.0 Tesla field and a 34.8mm diameter beam pipe. Otherwise, the positron transport efficiency can increase by a factor of two when using a 34.8 mm diameter beam pipe if the solenoidal field strength is increased from 0.3 Tesla to 1.0 Tesla.


PositronRates-vs-SolenoidField 10-1-15.png
Positron Rates -vs- Solenoid Field for 2mm thick PbBi target and several Beam pipe diameters


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.