Enter fission and fragment inputs
The page stays in a single vertical flow. The input controls below expand to three columns on large screens, two on medium screens, and one on mobile.
Example data table
| Case | A₁ / Z₁ | A₂ / Z₂ | TKE | Light energy | Heavy energy | Scission estimate |
|---|---|---|---|---|---|---|
| Thermal-like asymmetric split | 95 / 38 | 139 / 54 | 170.5 MeV | 101.280 MeV | 69.220 MeV | 163.052 MeV |
| More symmetric split | 116 / 46 | 118 / 46 | 165.0 MeV | 83.205 MeV | 81.795 MeV | 167.470 MeV |
| Heavy-fragment favored test | 90 / 36 | 144 / 56 | 175.0 MeV | 107.692 MeV | 67.308 MeV | 160.523 MeV |
These examples illustrate how kinetic energy shifts toward the lighter fragment when momentum is equal and the heavier fragment carries more mass.
Formula used
The model assumes a two-fragment split with equal and opposite recoil momentum, a standard first-pass approximation for fragment kinetic sharing. The Coulomb term is a benchmark, not a full microscopic scission model.
How to use this calculator
- Choose Known total kinetic energy when you already know the fragment TKE from experiment or literature.
- Choose Derive from energy balance when you want TKE from Q value, neutron input, gamma output, and residual excitation.
- Enter the light and heavy fragment mass numbers and charge numbers.
- Optionally enter the parent nucleus values and prompt neutron count to check conservation.
- Set the radius coefficient and scission factor for the Coulomb estimate.
- Press the calculate button. The result panel appears below the header and above the form.
- Review kinetic energies, velocities, momentum symmetry, Coulomb difference, and any model notes.
- Use the CSV or PDF buttons to export the current result table.
Key output meaning
A lighter fragment usually receives a larger kinetic-energy share because both fragments leave with nearly equal momentum. The heavier fragment usually moves slower, even when it carries substantial recoil energy.
FAQs
1) Why does the lighter fragment usually get more kinetic energy?
Two fragments recoil with nearly equal momentum. Since kinetic energy scales as p²/(2m), the smaller mass receives the larger energy share.
2) What does the Coulomb estimate represent?
It approximates the electrostatic repulsion energy at scission using fragment charges and separation distance. It is useful for comparison, not a full nuclear-structure prediction.
3) When should I use energy-balance mode?
Use it when you know the Q value and energy losses to prompt neutrons, gammas, or fragment excitation. It converts those terms into an estimated total kinetic energy.
4) Are the velocity values relativistic?
No. They are non-relativistic estimates from v = √(2E/m). For typical fragment speeds, the approximation is usually acceptable, but very precise work may need relativistic treatment.
5) Why include parent A, parent Z, and prompt neutrons?
Those inputs let the calculator test conservation. A mismatch warns that the fragment assignment, neutron count, or parent nucleus values may be inconsistent.
6) Can this replace detailed fission simulations?
No. It is a fast analytical tool for screening, teaching, and preliminary calculations. Detailed fragment yields, shell effects, and excitation partitioning require specialized models.
7) What scission factor should I choose?
Start near 1.4 to 1.7 for exploratory work. Higher values imply larger separation at scission and reduce the Coulomb-based kinetic-energy estimate.
8) What does a large TKE minus Coulomb difference mean?
It suggests your geometry, excitation assumption, or chosen fragment charges may not align with the selected TKE. It is a diagnostic flag, not necessarily an error.