Tally filter for first-flight collision probabilites

[smharper]

It would be handy if we could compute first-flight collision probabilities. I imagine we could do it by adding something like last_collision_material to the particle header which tells us in which material the particle had its last collision (or was born). Then we could filter it with a LastCollisionMaterialFilter that would be similar in implementation to a MaterialFilter.

@johnnyliu27, would you like to tackle this issue?

[johnnyliu27]

Sure I’d like to give a try on this. Regarding to the future implementation of CMM, a variable in the particle header recording the neutron’s birth place will be definitely more useful for CMM.
I’ll update here when I get into more details on this.

[EinKaiser]

Hi, can I have a go at this?

[paulromano]

@johnnyliu27 Did you ever work on this or is it ok for @EinKaiser to give it a shot?

[johnnyliu27]

Feel free to take this issue @EinKaiser since I didn't go too far on it. Thanks!

[maxtriano]

Is this still open? Can give it a try if so

[pshriwise]

Hi @maxtriano, I think this is all yours if you want to take a crack at it!

[maxtriano]

Would this last_collision_material be different from material_last_ which is currently stored in GeometryState? In that case, all that needs to be done is to add a LastCollisionMaterialFilter?