Beam divergence, Beam characteristics in GPS

Hi guys,
I define a beam in GPS. I’m not sure if that is correct or not, especially beam divergence. please help me.
These are my beam characteristics:
it considers a Gaussian shape for the energy spectrum. irradiation configurations were created broad beam. Energy spreads of 0.1% MeV of total energy were simulated. A realistic beam divergence of 3 mrad was assumed. The dimensions of the beam source were 2 x 2 cm in the case of broad beam irradiation.

this is my macro

/gps/particle proton
/gps/direction 0 0 1
/gps/pos/type Beam
/gps/pos/shape Rectangle
/gps/pos/halfx 1 cm
/gps/pos/halfy 1 cm
/gps/pos/centre 0 0 -7 cm
/gps/ang/type planar
/gps/ene/type Gauss
/gps/ene/mono 400.0 MeV
/gps/ang/sigma_x 0.003 rad
/gps/ang/sigma_y 0.003 rad
/gps/ene/sigma 0.4 MeV