# Explicit simulation of delayed photons

**URL:** <https://openmc.discourse.group/t/explicit-simulation-of-delayed-photons/5679>\
**Category:** User Support\
**Created:** [July 14, 2025, 11:24pm UTC](https://openmc.discourse.group/t/explicit-simulation-of-delayed-photons/5679 "2025-07-14T23:24:09Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![oyardas2](https://avatars.discourse-cdn.com/v4/letter/o/8491ac/32.png) [@oyardas2](https://openmc.discourse.group/u/oyardas2)\
**Post date:** [July 14, 2025, 11:24pm UTC](https://openmc.discourse.group/t/explicit-simulation-of-delayed-photons/5679/1 "2025-07-14T23:24:09Z")

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## TL;DR: Does OpenMC explicitly simulate delayed photons that I can tally using a `ParticleFilter` and a `TimeFilter`?

I am trying to do some coupled neutron-photon simulations, and I am interested in counting the delayed photon population and comparing it to the prompt neutron population. I have been poking around the discourse and the documentation and haven’t found anything that suggests that OpenMC explicitly simulated delayed neutrons. I have found there is a special treatment for accounting for delayed photon energy deposition ([this](https://openmc.discourse.group/t/coupled-neutron-photon-transport-problem/942/4) discourse post was helpful), but outside of that there is no treatment of delayed photons. Is my understanding correct?