Calcolatore Energia Fusione Nucleare — Formula
## Nuclear Reaction Cross Section
The macroscopic cross section combines the probability of a single nucleus interacting (microscopic cross section) with the number of target nuclei per volume.
### Formulas
**N = rho × NA / A** (atom number density)
**Sigma = N × sigma** (macroscopic cross section)
**Lambda = 1 / Sigma** (mean free path)
where sigma is in barns (1 barn = 10⁻²⁴ cm²), NA = 6.022 × 10²³/mol.
The macroscopic cross section combines the probability of a single nucleus interacting (microscopic cross section) with the number of target nuclei per volume.
### Formulas
**N = rho × NA / A** (atom number density)
**Sigma = N × sigma** (macroscopic cross section)
**Lambda = 1 / Sigma** (mean free path)
where sigma is in barns (1 barn = 10⁻²⁴ cm²), NA = 6.022 × 10²³/mol.
Esempio Risolto
U-235 (sigma_f = 580 barns, density 19.1 g/cm³, A = 235).
- N = 19.1 × 6.022 × 10²³ / 235 = 4.89 × 10²² atoms/cm³
- Sigma = 4.89 × 10²² × 580 × 10⁻²⁴ = 28.38 cm⁻¹
- Mean free path = 1 / 28.38 = 0.0352 cm