Delay full simulation until deposited energy is known#273
Merged
kvjmistry merged 6 commits intonext-exp:masterfrom Jan 21, 2026
Merged
Delay full simulation until deposited energy is known#273kvjmistry merged 6 commits intonext-exp:masterfrom
kvjmistry merged 6 commits intonext-exp:masterfrom
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Push also ionization electrons to the waiting stack
The event energy is determined when the primary particle interacts in the active volume. This is the metric used to determined if the event needs to be fully simulated or not. Once this is determined, optical photons and ionization electrons don't need to be delayed any further and all particles are simulated eagerly.
kvjmistry
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Jan 19, 2026
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This is a really nice upgrade to the nexus simulation!
Code has been tested and runs as expected.
Excellent job @gonzaponte!
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Full simulation is computationally very expensive. The main reason is light tracking, as a large number of optical photons can be produced per event. Moreover, nexus is capable of disregarding (not saving) events depending on their energy. However, this is criterion is only checked at the end of the full event simulation, which includes the propagation of photons. This can result in a long simulation that ends up being thrown away.
In this PR we introduce a stacking action that delays the propagation of photons (and ionization electrons, which turn will only produce more optical photons) until all particles that can deposit energy are tracked. The result is a two-stage simulation similar to what we have in what we call fast-sim:
with the second stage performed only when the event meets the deposited energy criterion.
Footnotes
S1 photons are actually produced in the first stage, but not tracked immediately. S2 photons are generated during the second stage, when the ionization electrons delayed from the first stage are tracked. ↩