How to use the results of this simulation as the source sampling for the next simulation

II want to simulate X-ray imaging. Want to realize: there are two steps of simulation. The first step is to simulate and record the Photon energy spectrum and angular distribution emitted by the X-ray tube, and then use it as the source sampling for subsequent simulation [SSR and SSW card in MCNP]。

I hope to receive everyone’s guidance!

Have you solved the problem? I have the same doubts.