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Neutron fluence Φ is the number of neutrons incident on a unit area.
Unit conversions are applied internally using SI base units (m², s) and then reported in both m² and cm² forms.
Practical tip: For non-uniform beams, consider using the effective irradiated area that matches your detector response.
| Scenario | Inputs | Output (fluence) | Notes |
|---|---|---|---|
| Count ÷ Area | N = 2.0×108, A = 10 cm² | Φ = 2.0×107 n/cm² | Detector counted total neutrons over its active area. |
| Flux × Time | φ = 5.0×105 n/cm²/s, t = 120 s | Φ = 6.0×107 n/cm² | Assumes average flux remains steady during exposure. |
| Fluence ÷ Time | Φ = 1.2×109 n/cm², t = 10 min | φ = 2.0×106 n/cm²/s | Converts a specification into an average flux value. |
Neutron fluence (Φ) quantifies cumulative neutron exposure per unit area. It is widely used in radiation effects testing, shielding verification, activation planning, and detector calibration. Unlike dose, fluence tracks particle count, making it ideal for material damage or displacement metrics.
Fluence is reported as n/cm² or n/m². Many lab specifications and test reports use n/cm² because values are compact; 1 n/cm² = 1×104 n/m². It is common to express results using scientific notation, such as 3.5×108 n/cm² for short irradiation campaigns.
Flux (φ) is the rate form, typically in n/cm²/s. When the source is steady, fluence is found by integrating flux over time, which simplifies to Φ = φ·t. For time-varying beams, compute φ for each interval and sum the interval fluences.
The same neutron count produces different fluence values depending on the chosen area. A 2×108 neutron exposure over 10 cm² yields 2×107 n/cm², but over 1 cm² it becomes 2×108 n/cm². Use the effective irradiated area that matches your detector or sample footprint.
If your count comes from a detector, consider efficiency, dead time, and background. For example, correcting 1.9×108 raw counts with a 95% efficiency gives a higher estimate of incident neutrons. Apply corrections before using the N/A mode.
Many applications require energy-resolved fluence. A practical workflow is to compute fluence per energy bin and report both the integrated Φ and the bin table. This calculator focuses on integrated fluence, but it supports consistent unit conversions and clean export for reports.
Fluence derived from multiplication or division inherits uncertainty from each input. The optional uncertainty fields estimate a combined 1σ value using root-sum-square of relative uncertainties. This helps compare runs, evaluate stability, and communicate measurement confidence.
Confirm units, verify that time corresponds to the same interval as flux or counts, and review geometry assumptions. If results differ by a factor of 104, it often indicates a cm² versus m² mismatch. Export CSV for calculations and PDF for audits.
Fluence is the total neutrons per area accumulated over time. Flux is the rate, neutrons per area per second. For steady conditions, fluence equals flux multiplied by exposure time.
Use Count ÷ Area. Enter total neutrons (corrected for efficiency if available) and the effective irradiated area. The calculator returns fluence in both n/m² and n/cm².
Fluence is normalized to area. Smaller areas produce larger fluence for the same neutron count. Always use the actual beam footprint on the sample or the detector’s active area.
Yes. Inputs accept scientific notation such as 1.2e9 and values with decimals. This is helpful for large neutron fields where fluence and flux are commonly reported in powers of ten.
For products or ratios, the tool combines relative input uncertainties using root-sum-square and reports an estimated 1σ output uncertainty. It is a quick planning aid, not a substitute for a full uncertainty budget.
Use the unit requested by your procedure. Many test plans specify n/cm², while SI reporting may use n/m². This calculator provides both outputs to minimize transcription mistakes.
Compute fluence per pulse or per time interval and sum the contributions. If you only know an average flux over the full duration, you can still use Flux × Time as an approximation.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.