⁶³Ni β-ray Source Used on Thickness Gauge

Abstract

The accumulation of the deposited soot is measured with⁶³Ni 0.067 MeV β-rays using an end-window type G-M tube. The X-rays produced from breaking of β-rays and the radiations from active impure atoms in a source have influence upon the accuracy of measurement of thickness. Those impure atoms are mainly long lived⁶⁰Co and⁵⁹Ni.
The⁶³Ni is electroplated on copper plates in industrial plating solution containing⁶³ NiCl₂. The radiations emitted from these sources are counted through filters of 5.4 mg/cm2² polyethylene or 540 mg/cm² Al foil. Then counting rates of β-ray, X-ray and γ-ray components are obtained. The counting rates of β-rays and backgrounds fit respectively to the relation I∞ (1-e^-μT) with differentt absorption coefficients, μ, as function of thickness of source, T (see Fig. 6) .
The β-ray counting rate saturates at thinner thickness of the source layer because of higher self-absorption, At thicker thickness, the counting rates of background components are more dominant than that of β-rays. When thin source was prepared from the plating solution of low activity and the counting rate of β-rays is too low, the accuracy of the gauge is bad under the influence of natural background. From Eq. (17) and (18), the suitable thickness (at minimum Δx/x) of the source is obtained with the best accuracy. It is concluded that the method could be in the practical measurement of the concentration of soot-dust in a furnace.