Pulse height tally in mixed neutron and photon fields. #3880
Description
Bug Description
Currently, openmc model secondary photons (from neutron interactions) without correct correlations.
This affect the results of pulse height tallies when secondary photons are important.
See https://openmc.discourse.group/t/pulse-height-tally-in-mixed-neutron-gamma-fields/6229
We might also want to warn the user when delayed_gamma_scaling is used in a simulation with pulse height tallies.
Solution
When using pulse height tallies, sample one photon producing reaction and then sample photons according to the reaction yield instead of sampling number of photons from all reactions.
Alternative Solution
Warn the user about incorrect results when using pulse height in simulation containing neutrons.