Contents

Bethe–Feynman formula

• a = internal energy per gram
• b = growth rate
• c = sphere radius

${\displaystyle a\approx ($bc)^{2}f}

A numerical coefficient would then be included to create the Bethe–Feynman formula—increasing accuracy by more than an order of magnitude.^[3]

${\displaystyle E_{f}f=\left({\frac {E_{2}}{\gamma -1}}\right)\cdot \alpha _{max}^{2}\cdot R_{crit}^{2}\cdot \left({\frac {\delta }{1-\delta }}\right)\cdot \left({\frac {2+3\delta }{2}}\right)}$

where γ is the thermodynamic exponent of a photon gas, E₂ is the prompt energy density of the fuel, αisV_n (neutron velocity) / λ_mfptot (total reaction mean free path), R_crit is the critical radius and 𝛿 is the excess supercritical radius (R_core - R_crit) / R_crit.

See also[edit]

• Richard Feynman
• Hans Bethe
• Robert Serber

References[edit]

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