LB January Flux Simulations

Simulations were run using geant4 to try and see if the ratio of the flux between the nickel foil and the inner selenium pellet would explain why the ratios of the rates are not correct. A general particle source was used to fire electrons in a beam at a titanium beam window, which then proceeds to an aluminum/tungsten radiator. After that the particles will encounter a nickel foil followed by an aluminum sheet and finally a selenium pellet that is -0.75cm off of the beam axis (to try and replicate the location of the foil relative to the selenium pellet). The run.mac file is shown below

/gps/particle e-

/gps/position 0 0 -5 m

/gps/pos/type Plane

/gps/pos/shape Circle

/gps/pos/radius 0.5 cm

/tracking/verbose 2

/gps/direction 0 0 1

/gps/verbose 2

/gps/pos/sigma_r 0.5 cm

/gps/energy 32 MeV

/run/beamOn 50000

The dimensions of the pieces of interest are:

Se Pellet: 0.25cm radius Nickel Foil: 6cm in x, 2cm in y

A picture of the setup is shown below:

Below are the flux plots as a function of position for the nickel foil and the selenium pellet

Now try moving the target around until there is an area that has twice as much flux as the selenium pellet.

We can see here that the selenium pellet has 13620 counts in it, while the selected region of the nickel foil has 26980 counts. Taking the ratio gives 0.50.