The challenge
Effective UV-C disinfection requires delivering a minimum germicidal dose (fluence, in mJ/cm²) to every point of the target area — including zones located deep within a medium that absorbs and scatters UV-C (water, gel, film, biofilm). UV-C radiation is strongly absorbed, so the dose falls off rapidly with depth (Beer-Lambert law), and scattering further disturbs the distribution. Too low a dose at depth means surviving pathogens; too high a dose means wasted energy, shortened lamp life, and a risk of material damage. Measuring the dose at depth with physical methods (actinometry, biodosimetry) is labor-intensive and indirect.
The solution
The medium was modeled in TracePro as a solid with bulk absorption and bulk scattering, with optical properties matching a real material in the UV-C band, together with the source geometry. After ray tracing, the Volume Flux function calculates the flux absorbed in successive volume cells along the penetration axis — i.e. the dose profile as a function of depth. The volume is divided into cells (in the documentation example: 90 cells along the Z axis, spatial resolution 0.1 mm).
A key point is that TracePro's macro language lets you combine multiple traces while keeping the memory footprint of a single run: in the example, 18,000 runs of 1000 rays each were summed, giving 18,000,000 rays at the memory cost of a single 1000-ray trace. The result is an exceptionally smooth, noise-free distribution of absorbed flux — a trustworthy dose profile on which design decisions can be based.
Volume Flux cells overlaid on the model — the volume divided into segments along the penetration axis (Z).
Profile of absorbed flux and cumulative dose as a function of depth — smooth thanks to millions of rays.
Results
- Dose at every depth — the absorbed-flux profile (proportional to dose in mJ/cm²) read cell by cell along the penetration axis.
- Effective disinfection depth — immediately visible: the depth at which the dose falls below the germicidal threshold (dependent on the pathogen and the required log reduction).
- A smooth result with no noise — combining millions of rays at the memory cost of a single run produces a smoothed distribution, so variants are compared on data, not sampling artifacts.
- Fewer physical trials — choosing source power, geometry, and exposure time in the model reduces costly biodosimetric testing.
Why TracePro
Dlaczego to narzędzie. Volume Flux is a native TracePro function for calculating the flux absorbed within the volume of an absorbing and scattering medium — exactly the quantity from which UV-C dose is derived. It's part of the energy-balance and illumination domain, without needing diffraction or aberration analysis, which are the domain of other tools.
Want to check whether your UV-C dose reaches the required depth before you build a chamber? Request a TracePro trial or get in touch with us — we'll show you how to build this kind of Volume Flux analysis for your system.
Uwaga. An illustrative example, based on the Volume Flux functionality in TracePro (TracePro 2026 documentation, "Volume Flux Calculations Example"). The values given are for illustration only.