Spherical diffusion domain:
C = local concentration of ⁴He
r = radial position across domain
a = domain radius = 65 mm
E_a = 138 kJ/mol = 33 kcal/mol
ln(Do/a²) = 13.5 ln(s^-1)
 

▲ Ratio evolution diagram
(what we measure)
R = ⁴He/³He
SF³He = cumulative ³He release fraction