| 摘要 |
PURPOSE:To measure easily the thickness of metallic foil by radiating beta rays to the front side of a laminate plate having metallic foil laminated on both surfaces while bringing metallic foil of the same material with the metallic foil into contact with the rear-surface metallic foil, and then measuring the dosage of beta rays scattered backward by a Geiger-tube. CONSTITUTION:When beta rays are incident to a metallic body, the beta rays are scattered in the metallic body and travel backward in the direction opposite to the incidence direction. When the metallic body consists of two layers and the upper layer is very thin, the intensity I of the scattered-back rays is as shown by an equation (where Is1 and Is2 are saturation values from the scattered rays from the thin upper layer and thick lower layer, d1 is the thickness of the upper layer, and mu2 is the coefficient of absorption of the material of the lower layer). When the thickness of the metallic foil of the laminate plate 4 is measured, the lower-side metallic foil 3b is brought into contact with the metallic foil 5 of the same material which has a >=100mum and is saturated with the scattered rays and the top surface of the upper-side metallic foil 3a to be measured is irradiated with the beta rays. Then, the scattered rays are incident to the Geiger-tube 7 of a radiation Geiger counter and the dosage of the beta rays is measured. The thickness d1 is calculated on the basis of the dosage from the expression. |
