A spherical neutron field

Dear experts,
I want to define a spherical neutron field urgently, but I do not have the ability to write a “source.f” now, anyway can I achieve it by standard flair card?

Is BEAMPOS=SPHE-VOL with BEAMPOS=NEGTIVE and BEAM=isotropic correct?
By the way ,how to use geometry to see the source distribution?

Dear @xiongbp,

please have a look at the lecture: