Niowave 2-2016

Niowave Positron Project Progress for February 2016

Event files were generated for Niowave's beam line designers assuming an ideal solenoid having an inner radius of 2.527 cm surrounding a beam pipe with a radius of 1.74 cm. Electrons impinge a 2mm thick PbBi liquid target that has a surface area of 2.54 cm x 2.54 cm. Stainless steel windows 0.25 mm thick sandwhich the PbBi target at locations Z= -90.325 and Z= -89.875 cm. The target is located at Z =-90.1 cm and the beam begins 20 cm upstream at Z = -110.1 cm. The incident electron beam is a 0.5 cm radius cylinder.

Below is a table illustrating the target and stainless steel window geometry as well as a rare event where positrons were produced in the stainless steel window instead of the PbBi target. The solenoid design uses a maximum uniform field of 0.20 Tesla and a length of 150 mm.

Apparatus

Closeup of Target Simulation Geometry. The center of the 0.25mm thick stainless steel windows are a distance of 2.25 mm from the center of the LBE target. [math]d_{USS} = d_{DSS} =[/math] 2.25 mm, [math]t_{LBE}=2[/math] mm, [math]t_{SS} =[/math] .25 mm.

An example positron production event. The yellow lines represents a sensitive detector used to record positron events. The red line represents the incident 10 MeV electron that produces two bremsstrahlung photons shown in green. The first photon has an energy of 2.151 MeV and pair produces in the stainless steel window. The second photon has an energy of 1.393 MeV and exits the system without interacting. The first photon is created at time t= 3.323 ns. The first photon produces a 234.6 keV electron and a 894.2 keV positron at time t=3.336 ns. Only the positron has enough energy to exit the stainless steel window.

In other words I should generate position and momentum files for positrons and electrons at the Z location 15 cm downstream from the middle of the LBE target and within a 3.48 cm diameter beam pipe.

/vis/viewer/zoom 2

/gps/pos/centre 0.0 0.0 -150.

/vis/viewer/panTo -90.1 0 cm

/vis/viewer/reset

Twenty (20) million incident electrons with an energy of 10 MeV and forming a cylindrical beam with a 0.5 cm radius cylinder impinged a 2mm thick LBE target located at Z = -106 mm. The Z location of positrons exiting the beam pipe at the end of the 15 cm long solenoid is 44 mm. The positrons are 150.00 mm from the middle of the LBE target (Z=44mm).

A space delimited text file with the above events in the format of

PID, x(mm),y,z,Px,Py,Pz(MeV),t(ns)

in units of cm for distance and MeV for momentum is located at

for positrons

http://www2.cose.isu.edu/~foretony/Positrons_2mm10MeVCyl.dat

and

http://www2.cose.isu.edu/~foretony/Electrons_2mm10MeVCyl.dat

The file below contains all the positrons that were created at the target

format

A space delimited text file with the above events in the format of

Initial electron (x,y,z,Px,Py,Pz), Final electron (t,x,y,z,Px,Py,Pz), Positron location after leaving LBE target (t,x,y,z,Px,Py,Pz),Location of positron as it exits a SS window (t,x,y,z,Px,Py,Pz). Units are ns, mm, MeV/c.

http://www2.cose.isu.edu/~foretony/AllPositrons_2mm10MeVCyl.dat

Positron Distributions

Particle flight times for 20 million incident electrons on a 0.2mm thick LBE target with 0.25 mm thick stainless steel windows (no material exists after the last stainless steel window, only vacuum). The time an electron brems in the target (EscatTime) is shown in black. The time a positron is created in the target (PosTime) is shown in blue. The time a positron has traveled 15 cm traversing a uniform 0.2 Tesla Solenoidal field (PosBeamTime) is shown in fuchsia. The field exists throughout the entire world. PosBeamTimeCuts are positrons that are constrained to a beam pipe diameter of 34.8 mm. Positrons are traveling about the speed of light (30 cm/ns) so after 15 cm they arrived 0.5 nsec after the initial electron beam impinges the target.

Positrons and Electrons after the SS Exit window

The same configuration as the previous subsection except that the 1mm thick sensitive detector is placed at Z = -100.5 mm. Most of the electrons exit at Z = -100.9 mm.

A space delimited text file with the above events in the format of

PID, x(mm),y,z,Px,Py,Pz(MeV),t(ns)

in units of cm for distance and MeV for momentum is located at

for positrons

23500  Positrons in the file below

http://www2.cose.isu.edu/~foretony/PositronsAtExitWindow.dat

and

297216 electrons in the file below

http://www2.cose.isu.edu/~foretony/ElectronsAtExitWindow.dat

G4Beamline_PbBi#Positron_.26_Electron_event_files