GPS Command Example 29:

/gps/particle geantino
/gps/pos/type Plane
/gps/pos/shape Annulus
/gps/pos/radius 3. cm
/gps/pos/inner_radius 1. cm
/gps/pos/centre 0.5 1. 0. cm
/gps/ang/type cos
/gps/ene/type Exp
/gps/ene/min 2. MeV
/gps/ene/max 10. MeV
/gps/ene/ezero 2.

Resulted Distribution Plots: