# Difference between revisions of "Using Gamma-ray Counts to Calculate Element Concentration"

###### Written and developed by Prof. Tor Bjørnstad (IFE/UiO)

In principle, it is possible to perform quantitative NAA by using the general formula for activation:

where
w = mass of unknown element in sample
Rx = measured count rate of unknown element (cps)
M = atomic weight of unknown element
λx = decay constant of the measured radionuclide of the unknown element = ln2/T1/2
Where T1/2 is the half-life of this radionuclide (s-1)
td = decay time = time between irradiation end and midpoint of counting period (s)
= counting efficiency of the detected gamma energy
σ= thermal neutron reaction cross section of the unknown element (barn = 10-24
cm2)
φ= neutron flux in irradiation position (ns-1cm-2).